ATI TEAS CRASH COURSE BOOK

ATI TEAS CRASH COURSE BOOK SCIENCE The third section of the TEAS exam covers Science and features 47 scored items. There are three categories of Science objectives for the TEAS. The test items are divided among the Science objectives as follows: S.1 HUMAN ANATOMY AND PHYSIOLOGY — 32 QUESTIONS S.1.1 Describe the general anatomy and physiology of a human. S.1.2. Describe the anatomy and physiology of the respiratory system. S.1.3 Describe the anatomy and physiology of the cardiovascular system. S.1.4 Describe the anatomy and physiology of the gastrointestinal system. S.1.5 Describe the anatomy and physiology of the neuromuscular system. S.1.6 Describe the anatomy and physiology of the reproductive system. S.1.7 Describe the anatomy and physiology of the integumentary system. S.1.8 Describe the anatomy and physiology of the endocrine system. S.1.9 Describe the anatomy and physiology of the genitourinary system. S.1.10 Describe the anatomy and physiology of the immune system. S.1.11 Describe the anatomy and physiology of the skeletal system. S.2 LIFE AND PHYSICAL SCIENCES — 8 QUESTIONS S.2.1 Describe the basic macromolecules in a biological system. S.2.2 Compare and contrast chromosomes, genes, and DNA. Chapter 4 S.2.3 Explain Mendel’s laws of heredity. S.2.4 Recognize basic atomic structure. S.2.5 Explain characteristic properties of substances. S.2.6 Compare and contrast changes in states of matter. S.2.7 Describe chemical reactions. S.3 SCIENTIFIC REASONING — 7 QUESTIONS S.3.1 Identify basic scientific measurements using laboratory tools. S.3.2 Critique a scientific explanation using logic and evidence. S.3.3 Explain relationships among events, objects, and processes. S.3.4 Analyze the design of a scientific investigation. In addition, the TEAS Science section features six unscored items as a pretest. These items can address objectives from any of the above categories. 134 Science S.1 HUMAN ANATOMY AND PHYSIOLOGY S.1.1 DESCRIBE THE GENERAL ANATOMY AND PHYSIOLOGY OF A HUMAN Anatomy is the structure of the body, while physiology includes the normal functions of a living creature. The human body features a hierarchy (system of levels) of structures and functions that go from the smallest part of a cell to organ systems that nourish or protect the entire body. On the Science portion of the TEAS exam, you must be able to describe each of these structures and functions. You must also use correct terminology about anatomical structures and their precise location. Know the basic tenets of cell theory. • All living organisms are composed of cells. • The cell is the basic unit of structure and organization in organisms. • All cells come from preexisting cells. Describe how cells carry out the basic processes of life. • Take in food and metabolize it for energy • Respond to the environment • Grow • Reproduce • Dispose of waste Distinguish between the two main types of cells: prokaryotes and eukaryotes. (For the purposes of this book, archaea and bacteria are grouped together as prokaryotes.) 135 Chapter 4 Prokaryotes Eukaryotes Single-celled Single-celled and multicelled Bacteria, algae Plants, animals, fungi, and protists Extremely small cells Large cells (10 times as large as prokaryotes) No nucleus or organelles Nucleus and organelles Single, usually circular chromosome Multiple chromosomes Reproduces by fission (budding) Mitosis and meiosis for reproduction and growth Identify organelles, which are the parts of a cell. These membrane- bound structures carry out a cell’s basic functions, such as processing food and disposing of waste. Look at the organelles labeled in the cell diagram below. (Eukaryotic cells have organelles, but prokaryotic cells do not.) The diagram is followed by a chart describing the function of organelles. A Generalized Animal Cell Structure Lysosome Flagellum Golgi apparatus Vesicles Cytoplasm Ribosome Nuclear envelope Nucleus Rough endoplasmic reticulum Nucleolus Plasma membrane Nuclear pore Smooth endoplasmic reticulum Mitochondrion Cytoskeleton 136 Science Organelles and Their Functions Structure What It Does What Has It Chloroplast Site of photosynthesis Eukaryotic plant cells Nucleus Regulates all cell activity, including cell replication; does this through DNA, which codes for enzymes that carry out all important cell “jobs” All eukaryotes Ribosomes Use RNA to transcribe the original DNA code into proteins Eukaryotes and prokaryotes Mitochondria Cell powerhouses; use oxygen to burn glucose and produce ATP for cell’s energy All eukaryotes Cytoplasm Watery medium inside of cell All eukaryotes and prokaryotes Cytoskeleton Provides structure for cell and allows for transport All eukaryotes Endoplasmic reticulum (ER) Rough ER has ribosomes and produces proteins; smooth ER used in synthesis of fats All eukaryotes Cell membrane Phospholipid bilayer that acts as a highly selective barrier for passive and active transport. All eukaryotes and prokaryotes Cell wall Stiff outer cell structure Plants, fungi, and prokaryotes Golgi bodies Package proteins; secrete materials outside of cell All eukaryotes Vacuoles Storage containers All eukaryotes Flagellum Locomotion Prokaryotes and some eukaryotes Remember that, in multicellular organisms such as humans, cells are used as building blocks to form more complex body parts. 137 Chapter 4 Organ system Cells that have a specialized function join together to form tissues. The four main types of tissue are: • Connective tissue (bone and cartilage) • Muscle tissue (skeletal and cardiac muscles) • Nervous tissue (brain cells and spinal nerves) • Epithelial tissue (organ surfaces, mouth lining, and skin) Recognize that tissues join together to form organs. Examples of organs include the heart, brain, stomach, and kidneys. 138 Science Organs and tissues join together to form organ systems. The ten major organ systems in the human body are: • Respiratory system • Cardiovascular system • Gastrointestinal system • Neuromuscular system • Reproductive system • Integumentary system • Endocrine system • Genitourinary system • Immune system • Skeletal system These systems work together in a coordinated way to maintain homeostasis — a stable environment inside the human body. When preparing for the TEAS, become familiar with the standard anatomical position for human anatomy: the body is upright and faces forward; the feet are flat and directed forward; and the upper limbs are held at the body’s side with palms facing forward. Remember the anatomical planes for human anatomy. • Coronal plane: divides body into front and back portions. (Anterior—front, Posterior—back; Ventral—front, Dorsal—back) • Sagittal Plane: divides body into left and right portions. • Transverse Plane: divides body into top and bottom portions. (Superior—head; Inferior—feet) 139 Chapter 4 S.1.1 PROBLEM A patient has a cellular problem that involves protein synthesis. Which organelle is NOT likely to be faulty? (A) mitochondria (C) ribosomes (B) endoplasmic reticulum (D) nucleus STRATEGY To answer this question, think about where proteins are made in the cell. THINK • Protein production is orchestrated in the nucleus (D) and carried out in the ribosomes (C), Golgi bodies, and endoplasmic reticulum (B). All these organelles could be involved in a cellular problem involving protein synthesis. Thus all these answer choices are incorrect. • The mitochondria are involved in metabolism, not protein synthesis, so answer (A) is correct. S.1.2 DESCRIBE THE ANATOMY AND PHYSIOLOGY OF THE RESPIRATORY SYSTEM On average, a person breathes about 20,000 times a day. Breathing involves taking in oxygen from the surrounding air and releasing carbon dioxide as a waste gas. The respiratory system manages this process, which the body’s cells require for energy and growth. On the TEAS exam, you must be able to describe the parts of the respiratory system and how they work together to keep the cells healthy and provided with energy. The function of respiration is to provide oxygen to the body cells for use in creating energy. This is accomplished through gas exchange to the cells, delivering oxygen and removing carbon dioxide as waste. The lungs and the respiratory system perform the gas exchange process automatically. 140 Science Nasal cavity Oral cavity Tongue Trachea Pleura Right lung Diaphragm Pharynx Epiglottis Larynx Bronchus Left lung The gas exchange process takes place as follows: • Air is inhaled from the atmosphere and enters the nose. Air passes through the nasal cavity, pharynx, and larynx. • From the larynx, air enters a cartilage-lined tube called the trachea. The epiglottis is a flap that covers the trachea and prevents solid and liquid material from entering it when the person swallows. • The trachea divides into two bronchi that go to the lungs. Inside the lungs the bronchi branch out into narrower tubes called bronchioles. At the end of the bronchioles are small sacs called alveoli. As a person inhales and exhales, the alveoli inflate and deflate like clusters of tiny balloons. This is the main site of gas exchange. • The thin walls of the alveoli have an enormous surface area to facilitate gas exchange. If pressed flat and spread out, the alveoli would encompass a football field. • Gas exchange takes place by diffusion between the alveoli and blood. Oxygen diffuses through the surfactant, or fluid 141 Chapter 4 coating the membranes of the alveoli. The surfactant reduces the pressure required to inflate the alveoli by lowering surface tension. Oxygen passes through the alveoli wall into the surrounding blood capillaries and into red blood cells. • When a person exhales, the process is reversed. Oxygen and carbon dioxide are exchanged in the alveoli. Carbon dioxide is released as a waste gas. • The diaphragm is a domelike muscle located below the lungs. The diaphragm flattens to draw air into the lungs and expands to force air out. The respiratory and the cardiovascular systems interact by way of the heart and lungs. (The cardiovascular system is also called the circulatory system.) The heart delivers deoxygenated blood through the pulmonary arteries to the lungs. There the gas exchange occurs, with the blood taking in oxygen from the alveolar sacs and releasing its store of carbon dioxide. The oxygenated blood returns to the heart and is circulated to the rest of the body. S.1.2 PROBLEM What symptoms would you expect in a patient with low blood oxygen? (A) joint pain (C) excessive bleeding (B) weakness and low energy (D) nausea STRATEGY Refer to the process of respiration to determine how low oxygen would affect a person. THINK • Remember that the purpose of respiration is to supply oxygen to cells. This oxygen is used to “burn” food and create energy. • Therefore, a person with low oxygen would be energy depleted and feel weak. Answer (B) is correct. 142 Science S.1.3 DESCRIBE THE ANATOMY AND PHYSIOLOGY OF THE CARDIOVASCULAR SYSTEM Heart health is a major concern because the heart plays such a vital role in the body’s various systems — delivering nutrients, removing wastes, regulating hormones, and fighting infections. On the TEAS exam, you must be able to describe the parts of the cardiovascular system and how they work together to circulate blood and lymph throughout the body. The function of the cardiovascular system (also called the circulatory system) is to transport materials to and from the body’s cells. Blood is the major carrier of these materials. The materials the cardiovascular system carries to the body cells include: • Nutrients from the digestive system • Oxygen from the respiratory system • Hormones, such as insulin, that are secreted by glands and nerve cells • Immune cells and products that fight infections The materials that the cardiovascular system carries away from the body cells include: • Waste products that eventually gets excreted as urine • Carbon dioxide that eventually is exhaled • Excess salts and other materials that are often retained by the body Arteries are thick-walled vessels that carry oxygenated blood away from the heart. Arteries branch into smaller vessels called arterioles and then into even smaller vessels called capillaries. Veins are thinner-walled vessels that carry deoxygenated blood from body cells back to the heart. The blood first diffuses in the lungs into tiny capillaries and then returns to the heart through venules that merge to create larger veins. The human heart has four chambers — the left atrium and right atrium on top and the left ventricle and right ventricle on the bottom. (Right and left indicate the right and left sides of the body.) 143 Chapter 4 Pulmonary valve Right atrium Tricuspid valve Right ventricle Pulmonary artery Pulmonary vein Left atrium Aortic valve Mitral valve Left ventricle Inferior vena cava Blood is transported through the body on a system of two loops, or circuits. The pulmonary loop transports deoxygenated blood from the right ventricle to the lungs and carries oxygenated blood back to the left atrium. The systemic loop transports oxygenated blood from the left ventricle to the body and carries deoxygenated blood back to the right atrium. The rhythmic contraction and relaxation of heart muscles is called the heart cycle. Systole is the contraction of heart muscles. Diastole is the relaxation of heart muscles. The sinoatrial node — also called the pacemaker — is located in the upper wall of the right atrium and controls heart muscle contractions by sending out electrical signals. Blood has four main components: plasma, red blood cells, white blood cells, and platelets. Plasma is the liquid component of blood and moves blood cells through the body. Red blood cells, or erythrocytes, carry oxygen (held in a protein called hemoglobin) 144 Science from the lungs to the rest of the body and return carbon dioxide to the lungs. White blood cells, or leukocytes, are made up of five major types of cells that fight infection in the body. Platelets are fragments of cells that facilitate blood clotting. The lymphatic system is a network of capillaries and veins that carry interstitial fluids and wastes through a fluid called lymph. S.1.3 PROBLEM The systemic loop carries oxygenated blood to the body from which chamber of the heart? (A) left atrium (C) left ventricle (B) right atrium (D) right ventricle STRATEGY Refer to the descriptions of the pulmonary and systemic loops in which blood is transported to and from the heart and makes its way through- out the body. THINK • In the systemic loop, oxygenated blood travels from the left ventricle to the body. Answer (C) is correct. S.1.4 DESCRIBE THE ANATOMY AND PHYSIOLOGY OF THE GASTROINTESTINAL SYSTEM The gastrointestinal system — also called the digestive system — serves to break down food both physically and chemically. Digestion is the process of breaking down food into its molecular components. Essential nutrients in the food are then absorbed into blood vessels and sent on to individual cells. On the Science section of the exam, you must be able to describe the organs of the gastrointestinal system and how they work together to break down food. You must also know the enzymes and hormones that regulate the digestive process. 145 Chapter 4 The gastrointestinal system begins at the mouth and ends with the anus. In between, food passes through the esophagus, stomach, small intestine, large intestine, and rectum. Oral cavity Salivary glands Mouth Tongue Pharynx Esophagus Liver Pancreas Small intestine Large intestine Anus Stomach Gallbladder Rectum Digestion begins when mechanical chewing and enzymes begin to break down food in the mouth. Saliva moistens the food and begins to digest it chemically with enzymes. Food is shaped into a bolus, or ball, before it is swallowed. After being swallowed, food passes into the pharynx, or throat. A tissue flap called the epiglottis closes the trachea so that food passes into the esophagus. Food then goes through the esophagus to the stomach. The stomach secretes gastric juice, consisting of hydrochloric acid of pH 1 to 2 (highly acidic), the enzyme pepsin, and mucus. Gastric juice serves two main purposes. The acid kills bacteria in the food, and the pepsin digests food proteins. With its folding structure like an accordion, the stomach can store as much as four liters of material. Food mixes with water and gastric juice to make a creamy substance called chyme. Food moves through the digestive system by the muscular squeezing action of peristalsis. 146 Science The chyme passes through a valve at the stomach’s end called the pyloric sphincter. This valve regulates passage into the duodenum, which is the first part of the small intestine. In the small intestine, food is broken down further. Proteins are broken down into amino acids. Starches are broken down into simple sugars. When broken down to the molecular level, food nutrients (sugars, amino acids, and small fats) get absorbed through the walls of the small intestine into the blood. The blood carries these nutrients to the body cells. Undigested food stays in the small intestine and gets passed on to the cecum and into the large intestine or colon. Water and salt are reabsorbed to create solid waste, called feces. This waste is stored in the rectum, and is eliminated from the body through the anus. S.1.4 PROBLEM Where is food broken down in the digestive system so it can ultimately enter the bloodstream? (A) in the stomach only (B) in the stomach, small intestine, and large intestine (C) in the mouth, stomach, and large intestine (D) in the mouth, stomach, and small intestine STRATEGY To answer this question, identify parts of the digestive system that break down food. 147 Chapter 4 THINK • You should recognize at once that the food that enters the large intestine is not digestible and therefore is no longer broken down for absorption through the small intestine. This eliminates answer (B) and answer (C) because both include the large intestine. • Enzymes in the mouth begin the process of digestion. Digestion continues in the stomach, and food is broken down to its final molecular level in the small intestine. This means that answer (D) is correct. S.1.5 DESCRIBE THE ANATOMY AND PHYSIOLOGY OF THE NEUROMUSCULAR SYSTEM The Central Nervous System The central nervous system (CNS), which includes the brain and the spinal cord, controls thought and muscle movement in a human being. This enormously complex system transmits signals and impulses that affect every part of the body. On the Science portion of the TEAS exam, you must describe the parts of the neuromuscular system and how the nervous system exerts control over the muscles. Neurons, or basic nerve cells, conduct information electrically along incoming axon fibers and outgoing dendrites. The axon is usually a long extension of the nerve cell body that sends impulses. The dendrite is usually a shorter branched extension that receives stimuli. These stimuli can come from sources such as light (for nerve cells in the eye) or touch (for nerve cells in the hand). Communication between axon terminals and neurons is done chemically using neurotransmitters that are released into the synapse, or junction, between neurons. 148 Science Dendrite Information is conveyed along the nervous system both electrically and chemically. Axons and dendrites work like electrical wires. Synapses transmit information using chemicals called neurotransmitters. A voluntary movement occurs in the following manner: • An electrical signal is sent from the brain to a motor neuron in the spinal cord. • The motor neuron relays the signal to the muscle. • At the muscle, the electrical signal gets transformed into release of the common chemical neurotransmitter acetylcholine. • Acetylcholine stimulates excitable muscle tissue to contract. The peripheral nervous system, a network of sensory nerves that connect to the CNS, is divided into somatic (voluntary) and automatic (involuntary) nerves. Different regions of the brain are specialized for different functions. 149 Chapter 4 Frontal lobe Executive functions, thinking, planning, organizing and problem solving, emotions and behavioral control, personality Motor cortex Movement Sensory cortex Sensations Parietal lobe Perception, making sense of the world, arithmetic, spelling Occipital lobe Vision Temporal lobe Memory, understanding, language The cortex, or outer rind, of the brain, is a layer of tissue about the thickness of three dimes. The cortex performs the brain’s most sophisticated functions. Visual information enters the back of the brain in the occipital lobe. Note that the sensory cortex is near the motor cortex for quick action. The planning-reasoning-imagining area of the brain is in the frontal lobe. This is where executive function and decision making largely occur. The Muscular System The muscular system enables body movement and maintains posture. There are three kinds of muscle tissue: skeletal muscle, cardiac muscle, and smooth muscle. 150 Science Muscles Sternocleidomastoid Pectoralis Biceps Brachioradialis External oblique Rectus abdominis Rectus femoris Sartorius Quadriceps Extensor digitorum longus Tibialis Skeletal muscles, which are attached to bones, are the only one of the three types that can be consciously controlled. Smooth muscles move substances through organs. The digestive system has smooth muscles. Muscles can only contract; they cannot extend. Muscles are arranged in antagonistic pairs such as the biceps and triceps. When the biceps contracts, the triceps relaxes and bends the limb. When the triceps contracts, the biceps relaxes and extends the limb. Bones are connected to other structures by tendons and ligaments. Tendons connect bones to muscles, and ligaments connect bones to other bones, usually at joints. 151 Chapter 4 S.1.5 PROBLEM A patient has been diagnosed with a chemical imbalance in his brain. Which part of his neurons is likely to be affected by this imbalance? (A) dendrites (C) synapses (B) axons (D) lateral STRATEGY To answer this question, identify the part of the neuron that is most closely related to chemical transmission of information. THINK • In a neuron, the impulse travels electrically along the axon and dendrite, making answers (B) and (A) incorrect choices. • When the electrical impulse reaches the synapse, it causes the release of chemical neurotransmitters that transmit the information to the next neuron in the sequence. This makes answer (C) correct. S.1.6 DESCRIBE THE ANATOMY AND PHYSIOLOGY OF THE REPRODUCTIVE SYSTEM The complex system for human reproduction actually consists of two systems: male and female. Overall, these systems work along with the endocrine system to affect various parts of the body and facilitate reproduction. On the Science portion of the TEAS, you must identify parts of the male and female reproductive systems and show knowledge of how they function and how they interact with the endocrine system. The female reproductive system includes the following: • The ovaries (singular: ovary) are the organs where ova, or eggs, are produced. • The oviduct, or fallopian tube, is the tube through which eggs move from the ovary to the uterus. Each of the two ovaries has an oviduct. 152 Science • The uterus, or womb, is where the embryo develops until birth. The fertilized ovum attaches to the endometrium, or inside wall, of the uterus. • The vagina is also called the birth canal. During birth, the fetus passes through the cervix (the mouth of the uterus) into the vagina, and then emerges from the body. Uterus Fallopian tubes Vagina The male reproductive system includes the following: • Testicles (or testes; singular: testis) are the male gonads. Sperm production in the testes takes place in seminiferous tubules. The two testes are contained in the scrotum, a sac that hangs outside the abdominal cavity. • Epididymis is the coiled tube in each testis where sperm are stored and develop mobility. • The vas deferens is one of two muscular ducts carrying ejaculated sperm from the epididymis to the urethra. The urethra, a tube located in the penis, carries semen and urine. • Seminal vesicles are two glands that during ejaculation secrete mucus, fructose, and the hormone prostaglandin. • The prostate gland is a large gland that secretes semen, a milky alkaline fluid containing sperm and other secretions, into the urethra. 153 Chapter 4 Sexual reproduction and development takes place as follows: • Sperm are made in the testes, whose processes are controlled by the hormone testosterone. • Eggs are produced in the ovaries. Each month a single follicle matures and releases an egg from the ovary. The mature egg, or ovum, enters the fallopian tube. • Fertilization occurs when the sperm penetrates the egg, the sperm and ovum nuclei fuse, and a zygote is formed. • The zygote moves to the uterus, where it implants (in the endometrium) and begins to grow. The growing cells undergo rapid mitosis and become an embryo. • If it fails to be fertilized, the egg will eventually dissolve within the fallopian tube. On the following month, a new egg will descend, and the process will begin again. The endocrine system creates and releases hormones. These chemical messengers regulate most of the systems in the body including the reproductive system. The sex hormones testosterone, estrogen, and progesterone govern the release of gametes, or reproductive germ cells. In females, they prepare the uterus for supporting the developing fetus and help produce milk for feeding the newborn. Thus the endocrine system interacts with the reproductive system in many important ways. S.1.6 PROBLEM An ovum stays in the fallopian tube for several days without moving. What can you assume? (A) The ovum is not mature. (B) The ovum has been fertilized. (C) The ovum has not been fertilized. (D) The ovum may be twins. 154 Science STRATEGY To answer this question, refer to the steps involved in sexual reproduction. THINK • During the first stage of the cycle, the egg matures and moves to the fallopian tube. • In the fallopian tube, the egg may or may not be fertilized. If it is fertilized, the egg will move on to the uterus. If it is not fertilized, it will stay in the fallopian tube and eventually disintegrate. • The egg described is not moving, so it must not have been fertilized. Answer (C) is correct. S.1.7 DESCRIBE THE ANATOMY AND PHYSIOLOGY OF THE INTEGUMENTARY SYSTEM Human skin, hair, and nails receive enormous attention every day related to grooming and personal care products. But the organs and glands that make up the integumentary system actually play a vital role in protecting the body and regulating body temperature. On the TEAS exam, you must demonstrate familiarity with the parts of this system and how it works with other systems of the body to maintain healthy function. The integumentary system is an organ system that consists of skin, hair, nails, glands, and nerves. Skin is the human body’s outer covering and its largest organ. On average, a person’s skin weighs ten pounds and encompasses a surface area of about twenty square feet, yet its thickness is only a few millimeters. Skin makes up a barrier that protects the body from physical damage, ultraviolet light, chemicals, and disease. Skin also helps dispose of bodily waste by sloughing off dead skin cells. Skin has three main layers. • The epidermis is the outermost layer and is only a tenth of a millimeter thick. About ninety percent of the epidermis consists of cells called keratinocytes. The protein keratin makes these cells tough, scaly, and resistant to water. Less than ten percent of epidermal cells are melanocytes, producing the pigment 155 Chapter 4 melanin. This pigment protects from ultraviolet rays and sunburn. • The dermis is the middle layer, consisting of dense connective tissue, nervous tissue, and blood vessels. • The hypodermis is the inner layer of loose flexible tissues that connect the skin to underlying muscles and bones. The hypodermis is also called subcutaneous tissue. Hair is an organ of the skin consisting of columns of densely packed dead keratinocytes. Structurally it has three main parts: the follicle, root, and shaft. Hair is found in most areas of the body. It serves to protect the body from ultraviolet radiation and to insulate the body from cold. Nails are organs of the skin found on the distal ends of fingers and toes. Nails are formed of hardened keratinocytes in sheets. They protect the ends of digits and are useful for scraping or scratching. Glands in the integumentary system include exocrine glands that secrete products through ducts. • Sudoriferous glands, or sweat glands, secrete water and sodium chloride and serve to lower the body’s temperature. Sweat glands also help remove trace amounts of waste products such as ammonia. • Sebaceous glands produce sebum, an oily secretion that lubricates the skin and makes it more elastic. • Ceruminous glands are found in the skin of the ear canals. They secrete a waxy substance called cerumen to protect the ear canal and lubricate the eardrum. The integumentary system works with other body systems in various ways. • The skin works with the immune system by forming a barrier or defense mechanism against infection and disease. Oils 156 Science secreted by tiny glands in the skin contribute to this function. Immune cells in the skin form a vital first line of defense against infection. • Surface capillaries on the skin interact with the circulatory system, enabling certain substances to enter the bloodstream through capillary networks. Patches that deliver medications (such as nicotine patches for smokers) make use of surface capillaries. • Capillary networks also work with the digestive system by helping to synthesize and absorb vitamin D and promote absorption of calcium in the intestines. Digestion of fats and oils help produce the oils that protect the skin and hair. • Neurons embedded in the skin work with the nervous system to enhance the sense of touch. Inputs from these neurons — such as signals when a hammer strikes your finger — travel to nerve cell connections in the brain that interpret the signals as pain. S.1.7 PROBLEM The secretions from sudoriferous glands mainly serve what function? (A) lubricate the skin for elasticity (B) cool the body’s temperature (C) protect the ear canal (D) provide a first line of defense against infection STRATEGY To answer this question, refer to the functions of the exocrine glands in the integumentary system. THINK • Note that sudoriferous glands are also called sweat glands. • Sweat glands secrete water and sodium chloride to cool the body. Answer (B) is correct. 157 Chapter 4 S.1.8 DESCRIBE THE ANATOMY AND PHYSIOLOGY OF THE ENDOCRINE SYSTEM The endocrine system consists of the body’s hormone-producing glands and the hormones they make. (Endocrine glands secrete hormones internally while exocrine glands secrete products outside the body through ducts.) On the TEAS exam, you must demonstrate knowledge of the endocrine system and how the hormones it produces help regulate certain processes in the body. The endocrine system is made up of a network of glands that produce hormones, or chemical messengers, whose functions include the following. • Controlling growth — for example, growth hormone (GH) proceeds from the action of the hypothalamus, an almond- sized portion of the brain located below the thalamus, and the anterior pituitary. The hypothalamus plays a crucial role in bridging the endocrine system and the nervous system. • Controlling sexual development — for example, estrogen made in the ovaries helps the female reproductive system develop and controls the menstrual cycle. • Controlling metabolism — thyroxin from the thyroid gland regulates basic metabolic rate, or how fast your body’s “motor” runs. Hormone Gland Function Growth hormone Hypothalamus and pituitary Growth Oxytocin and vasopressin Hypothalamus Uterine contractions Thyroxin Thyroid gland Metabolism Insulin and glucagon Pancreas Blood sugar Cortisol Adrenal cortex Stress and metabolism Estrogen and testosterone Ovaries and testes Sex 158 Science Hormones typically are secreted from a gland and travel through the bloodstream. When a hormone reaches its target, it changes activity, structure, or behavior. Hormones in the endocrine system regulate the body’s healthy function. Hormone imbalance occurs when glands produce an incorrect amount of hormones. This results in endocrine-related diseases, which are quite common. A good example is the hormone insulin, which is made by the pancreas and regulates the body’s use of glucose (sugar) from carbohydrates. • When food is eaten and glucose enters the blood, the pancreas releases insulin into the blood. • Insulin allows cells to take in glucose. Without insulin, the body’s cells cannot take in glucose. • Normally, blood sugar levels rise after eating and then drop as insulin is released and glucose is taken into cells and metabolized. • A person with diabetes is unable to make insulin. Without insulin, the cells of a person with diabetes are starved for glucose. As a result, the person feels weak even though blood sugar levels remain high. • People with diabetes must carefully control when and how much insulin to take so they can maintain healthy blood sugar levels. S.1.8 PROBLEM Which of the following acts as a vital connection between the endocrine system and the nervous system? (A) the thyroid (C) the pancreas (B) the pineal gland (D) the hypothalamus 159 Chapter 4 STRATEGY To answer this question, refer to the functions of the endocrine system and its various parts. THINK • The hypothalamus acts as a bridge between the endocrine system of hormone-producing glands and the nervous system. Answer (D) is correct. S.1.9 DESCRIBE THE ANATOMY AND PHYSIOLOGY OF THE GENITOURINARY SYSTEM The genitourinary system — also called the urogenital system — consists of organs involved in excretion, or the process of eliminating bodily wastes. Some of the same structures form part of the reproductive system. On the TEAS exam, you must identify the parts of the genitourinary system and be able to explain how they work together in the excretion process and the maintenance of homeostasis. The genitourinary system includes the following major structures: kidneys, ureters, bladder, and urethra. The key organs for excretion are the kidneys. Each kidney is divided into two major parts called the cortex and the medulla. • Normal metabolism in cells produces waste products that enter the blood along with carbon dioxide. Before it returns to the lungs for oxygen and the small intestine for food, this blood must be filtered and cleaned. • Toxins are taken out of the blood in the liver. Blood then goes through the renal arteries to the kidneys. (Renal means “related to the kidneys.”) Filtering of waste occurs in the kidneys. • Each kidney has about one million tiny filtering tubes, or nephrons. Each nephron tube features a glomerulus, a cluster of capillaries that acts like a filter. 160 Science Clean blood • The nephron actually performs three processes: filtration, secretion, and reabsorption. • The glomerulus keeps proteins, key ions such as sodium and potassium, and other valuable substances in the body. It allows waste and excess fluid to collect in a tubule. Waste fluid, called urine, passes through ureters to the bladder, where it is stored temporarily. From the bladder, urine exits through the urethra and out of the body. 161 Chapter 4 Homeostasis is a self-regulating process for maintaining equilibrium in the human body. The genitourinary system maintains homeostasis by eliminating wastes, regulating acidity in the blood, and controlling blood levels for metabolites and electrolytes, including sodium, potassium, and calcium. Kidneys play a vital role in maintaining homeostasis. The genitourinary system shares ducts and tubules with the reproductive system. The extent of this sharing is greater for males than females. For example, the urethra, which passes through the penis, conducts urine in the excretory process and semen in the reproductive process. S.1.9 PROBLEM The cause of advanced kidney disease in a person is most likely which of the following? (A) The bladder has a bacterial infection. (B) The nephrons have lost their capacity to filter wastes out of the blood. (C) The kidneys have lost their elasticity. (D) Renal arteries no longer supply sufficient blood supply to the kidneys. STRATEGY To answer this question, refer to the structures of the genitourinary system. THINK • A bacterial infection is not related to advanced kidney disease. Answer (A) is incorrect. • Kidneys’ loss of elasticity is caused by aging or hypertension, so answer (C) is incorrect. 162 Science • Renal artery stenosis is more often the result of chronic kidney disease rather than the cause of it, so answer (D) is incorrect. • Kidney disease is usually caused by damaged nephrons that do not filter the blood. Answer (B) is correct. S.1.10 DESCRIBE THE ANATOMY AND PHYSIOLOGY OF THE IMMUNE SYSTEM Like an army that rallies together and closes ranks when faced with an invading force, the immune system provides three lines of defense against disease-causing microorganisms. On the TEAS exam, you must demonstrate knowledge about the parts of the immune system and how the system interacts with the body’s other systems. The human immune system is a network of cells, tissues, and organs that work in concert to protect the body from attack by tiny organisms that cause infections. The immune system consists of three major lines of defense against infections and antigens and pathogens (agents that cause disease). The first line of defense is nonspecific and forms a barrier that keeps pathogens from entering the body. The skin and assorted body fluids — tears, mucus, saliva, waxes, and stomach acid — keep infections out and can expel them if they enter. The second line of defense is also nonspecific and comes into play when microbes invade the body. This second line attempts to limit the spread of invading microbes before any specific immune response begins. The swelling and redness of inflammation signal that the body has called in white blood cells and natural killer (NK) cells to consume bacteria and destroy body cells infected with a virus. 163 Chapter 4 White blood cells, or phagocytes, “swallow” bacteria that have been identified by helper T cells. Interferons combat virus invaders and block cell-to-cell infections. The third line of defense is specific. In other words, its defenses are “custom made” to fight off specific infections. The third line relies on two types of cells that originate in the bone marrow: B lymphocytes and T lymphocytes. Antigens (foreign proteins) bind to B lymphocytes or B cells, which produce antibodies specific to that infection. Antibodies are produced at the rate of 2,000 per second. This is called the humoral response or antibody-mediated response. The immune system keeps a certain number of lymphocytes, called memory cells, around to “remember” a specific infection. If the infection appears again — even years later — antibody production is quickly ramped up to fight off the invader. With a vaccine, a weakened form of an antigen is introduced into the body to activate B cells to produce antibodies. If the non-weakened antigen then arrives, the premade antibodies attack it. T lymphocytes originate in the bone marrow but mature in the thymus gland. They attack pathogens by the cell-mediated response. Killer T cells, or cytotoxic T cells, rove the body seeking out “nonself” cells and mounting a campaign to kill them off. Helper T cells help both B cells and killer T cells recognize invaders. The lymphatic system is largely responsible for bringing antibodies and white blood cells to different parts of the body. S.1.10 PROBLEM The humoral response fights infection by doing which of the following? (A) producing antibodies (B) ingesting microbes (C) forming a barrier consisting of various body fluids (D) creating “memory cells” that remember a specific infection 164 Science STRATEGY To answer this question, refer to the three lines of defense of the im- mune system. THINK • You should remember that the humoral response is part of the third line of defense in the immune system. • Phagocytes swallow, or ingest, bacteria in the second line of defense, so answer (B) is incorrect. • A barrier of body fluids to prevent infection is part of the first line of defense, so answer (C) is incorrect. • Creating “memory cells” that remember a specific infection is part of the cell-mediated response, so answer (D) is incorrect. • In the humoral response, lymphocytes that originate in the bone marrow are activated by specific antigens to produce antibodies that fight the infection. Answer (A) is correct. S.1.11 DESCRIBE THE ANATOMY AND PHYSIOLOGY OF THE SKELETAL SYSTEM The skeletal system is made up of bones that support and protect the body’s soft tissues and, along with tendons and ligaments, facilitate movement. It can be thought of as the body’s scaffold. On the Science section of the TEAS exam, you must demonstrate knowledge of what the skeletal system is and the vital functions it performs. The skeletal system of an adult human is made up of 206 bones and a connective network of tendons, ligaments, and cartilage. Tendons connect bones to muscles, and ligaments connect bones to other bones, usually at joints. 165 Chapter 4 is There are four main types of bones: long, short, flat, irregular. Bone is light but very strong. Calcium compounds (such as hydroxyapatite) provide bones with their strength. The protein collagen makes bone flexible. Bones serve to synthesize blood and immune cells, thus forming a vital connection to the human immune system. Bones consist of two types of tissue. Compact bone is the dense, hard tissue that forms the outer layer of most bones and the main shaft of long bones. Inside the hard tissue of compact bone are nerves and blood vessels. Spongy bone (also called cancellous bone) is a network of irregularly-shaped sheets making up the inner 166 Science part of bones. Spongy bone is located at the ends of long bones. It is found in the center of other bones, such as pelvic bones, skull, ribs, and vertebrae. Spongy bone is filled with red bone marrow. Red bone marrow consists of blood stem cells and blood cells in various stages of development. It creates most of the body’s blood cells, including red blood cells, white blood cells, and platelets. It also helps to eliminate old blood cells. Yellow bone marrow is found in the center of long bones. It mostly consists of fat. Even healthy bones are subject to fracture in accidents or injuries. Diseases of the bones include the following. • Osteoporosis is a disease that causes the bones to become fragile and susceptible to fracture. • Leukemia is a fast-growing cancer of the blood and bone marrow. • Arthritis is a rheumatic disease that can cause pain and stiffness in the joints and progressive loss of bone. • Scoliosis is a bone abnormality that leads to curvature of the spine. S.1.11 PROBLEM Which of the following helps to make bones very hard? (A) red blood cells (C) calcium (B) collagen (D) white blood cells 167 Chapter 4 STRATEGY To answer this question, refer to details about bones and the skeletal system. THINK • A calcium compound called hydroxyapatite is responsible for the strength and hardness of bones. Answer (C) is correct. S.2 LIFE AND PHYSICAL SCIENCES S.2.1 DESCRIBE THE BASIC MACROMOLECULES IN A BIOLOGICAL SYSTEM Macromolecules are essential for the human body to carry out life processes. These molecules are based on carbon and contain hundreds or even thousands of atoms. On the Science portion of the TEAS exam, you must show understanding of the structure and function of macromolecules and how these molecules correlate with familiar food groups. Macromolecules (macro- means large) are large organic molecules, or molecules that contain carbon atoms. Four of the six electrons in a carbon atom are available to bond with other atoms, allowing for the long chains or rings of atoms in macromolecules. Most macromolecules are polymers. This means that they consist of a monomer (single unit or building block) repeated many times, like a series of beads strung together in a necklace. Monomers join together by covalent bonds resulting from the removal of a water molecule. This is called dehydration reaction or condensation. The bonds are broken by adding water, a process called hydrolysis. Organic molecules have properties in common because they share similar clusters of atoms. These clusters are called functional groups. Each functional group lends a molecule a particular property, such as acidity or alkalinity. Four types of macromolecules make up all living matter. They are carbohydrates, lipids, proteins, and nucleic acids. 168 Science Macromolecules Molecule What It Does Composed of Examples Carbohydrates Energy source Carbon, hydrogen, and oxygen Sugars and starches Lipids Fats; form cell membranes; used as an energy source Carbon, hydrogen, and oxygen Glycerol and triglycerides Proteins As enzymes, proteins facilitate chemical reactions that are critical for life processes; structural proteins form muscles, connective tissue Amino acid chains made of carbon, hydrogen, oxygen, and nitrogen Pepsin (digestive enzyme), hemoglobin (in red blood cells), and myosin (in muscle cells) Nucleic acids DNA makes up chromosomes that code for all proteins Carbon, hydrogen, oxygen, nitrogen, and phosphorus DNA and RNA Macromolecules are taken in as food and are essential to nutrition. They correlate to basic food groups as follows: • Carbohydrates: sugars, starches, grains • Lipids: fats, oils, butter, lard • Proteins: meat, beans, leafy green vegetables • Nucleic acids: fish, nuts, fruit 169 Chapter 4 Carbohydrates such as sugars and starches are broken down and “burned” for energy. They are grouped into three categories keyed to the number of saccharide (sugar) molecules. • A monosaccharide (chemical formula C6H12O6) is the simplest carbohydrate, consisting of a single molecule of sugar. Examples are glucose, fructose, and galactose. • A disaccharide (chemical formula C12H22O11) consists of two sugar molecules joined together with a glycosidic linkage. The process of linkage causes one water molecule to be lost (resulting in O11 not O12). Examples are sucrose and lactose. • A polysaccharide consists of monosaccharides connected in a series. Thus a polysaccharide is a polymer of carbohydrates. Examples are starch, cellulose, and glycogen. Lipids are hydrophobic, meaning they are not attracted to water and not soluble in water. They are grouped into three main categories. • Triglycerides consist of fatty acids linked to a glycerol molecule. Examples include fats (saturated and unsaturated) and oils. • Phospholipids are the main ingredient in cell membranes. • Steroids include cholesterol and hormones such as testosterone and estrogen. Proteins are macromolecules that carry out many important functions in the body. Proteins in food are broken down into amino acids and re-formed into new proteins for muscle and other functions. Proteins are also involved in genetic expression (DNA proteins), structure (keratin in hair, collagen in connective tissue), transport (hemoglobin), digestion (pepsin), immune defense (antibodies), and catalyzing chemical reactions (various enzymes). Nucleic acids, which include DNA and RNA, are formed from monomers called nucleotides. 170 Science S.2.1 PROBLEM Changing disaccharides to monosaccharides involves which of the following processes? (A) dehydration (C) hydration (B) hydrolysis (D) condensation STRATEGY Think about macromolecules and the relationship of polymers and monomers. THINK • To change disaccharides to monosaccharides, you must break the chemical bond by adding water. • This process is called hydrolysis. Answer (B) is correct. S.2.2 COMPARE AND CONTRAST CHROMOSOMES, GENES, AND DNA In 2003 scientists from around the world completed an effort to map all the genes of the human genome — the complete set of genetic instructions. Their work has enabled everything from genetic testing for cancer risks to designs for gene-based medicines. On the TEAS exam, you must demonstrate knowledge of what genes, chromosomes, and DNA are and how proteins are produced from DNA. DNA is a nucleic acid. The letters DNA stand for deoxyribonucleic acid. DNA is the hereditary material in all living things. DNA is located on chromosomes in the cell nucleus. Chromosomes are primarily composed of DNA. Each gene is a section on a chromosome that codes for a protein. DNA forms a double helix, or two-stranded spiral, like a corkscrew. It is composed of four alphabet-like bases, or nucleotides: A (adenine), T (thymine), C (cytosine), and G (guanine). A base pair is one of the pairs A-T or C-G. 171 Chapter 4 A T C G The sequence of bases in a gene code for a particular protein looks like letters in an alphabet. To make a protein, the “alphabet” base pair code of DNA is unzipped and transcribed into RNA, or ribonucleic acid. The bases in RNA are C, G, A, and U (uracil). U replaces T (thymine) in RNA. The RNA is sent out of the nucleus to the ribosomes, where proteins are made. The letters (bases) of RNA code for amino acids, the building blocks of proteins. Proteins as enzymes help cells carry out all of their important chemical reactions. For example, one enzyme helps a cell break down a sugar molecule in the mitochondria so it can be burned in a combustion reaction for energy. The cellular process by which DNA makes proteins is shown below. The DNA triplet code is transcribed into a codon sequence in messenger-RNA (mRNA) in the nucleus. This new strand undergoes processing in the nucleus. The codon sequence translates into a 172 Science polypeptide, or amino acid sequence, in the cytoplasm on the ribosome. These proteins carry out all important cell functions. Mutations are mistakes in copying DNA. Examples of mutations that cause disorders are hemophilia and Down syndrome. A single mistake such as the one shown can cause the production of a faulty protein. Original DNA code Normal DNA strand 1: T A C T G G T G T T A DNA strand 2: A T G A C C A C A A T DNA mutation Mutation DNA strand 1: T A C G G G T G T T A DNA strand 2: A T G C C C A C A A T S.2.2 PROBLEM A scientist analyzed a sample from cells and found it to contain equal amounts of cytosine, guanine, uracil, and adenine. From which part of the cell did the sample come? (A) Ribosomes (C) Chromosomes (B) Nucleus (D) Genes STRATEGY To answer this question, be aware of the difference between RNA and DNA. 173 Chapter 4 THINK • Remember, cytosine, guanine, uracil, and adenine are all bases for nucleic acids. • Because uracil rather than thymine is included, the sample must be RNA rather than DNA. • RNA is located primarily in the ribosomes, not in the nucleus. Chromosomes and genes are both part of the nucleus, so answers (B), (C), and (D) are all incorrect. • Answer (A) is correct. S.2.3 EXPLAIN MENDEL’S LAWS OF HEREDITY In the mid-nineteenth century an Austrian monk named Gregor Mendel conducted experiments on pea plants that led him to describe many of the laws of heredity. The importance of Mendel’s work was not recognized until thirty years later. It remains a crucial contribution to the science of genetics. On the TEAS Science exam, you must be able to explain the important points of Mendel’s laws of heredity and the use of a Punnett square. Review the basic elements of Mendel’s work. He crossed purebred tall (TT) pea plants with purebred short plants (tt). The result for the F1 (first) generation was all tall plants. 3 F1 Mendel explained these results by suggesting that the plants had dominant and recessive genes. In the F1 generation, all individuals had a dominant T (tall) gene, so they all had the tall phenotype (actual form). 3 F1 Crossing the F1 generation with itself in a Tt 3 Tt pairing produces an F2 generation that does have short individuals. This Punnett square that follows shows the above cross. 174 Science Punnett Square F2 T t T 3 t F2 The genotypes (genetic form) and phenotypes (actual form) expected from this Tt 3 Tt cross would be 3 tall and 1 short.* Genotype: Phenotype: 3 4 tall 1 4 4 4 tt short For sex determination, organisms have X and Y chromosomes. An XX genotype creates a female; XY is male. A sex-linked trait such as color-blindness is carried only on X chromosomes and marked by XC. Y chromosomes are “blank” for sex-linked traits — they are not expressed. When a non-color-blind mother who carries the recessive color-blind XC allele (XCX) marries a normal XY father, the following genotypes result: X Y XC X As you can see, the female XCX is not color-blind because the XC allele is recessive. The male XCY is color-blind because the Y chromosome is not expressed for the color-blind gene. * Fractions/percentages are approximate, as they are predicted ratios. The actual numbers of offspring can differ. 175 Chapter 4 S.2.3 PROBLEM What fraction of offspring will be short in a cross of Tt and tt parents? (A) 1 2 (B) 1 4 (C) 3 4 (D) All STRATEGY To answer this question, create a Punnett square and use it to find the phenotypes. THINK • The Punnett square shows 2 of the 4 offspring as tt: t t T t • This means that half of the offspring will be short, making answer (A) the correct choice. S.2.4 RECOGNIZE BASIC ATOMIC STRUCTURE An atom is the fundamental building block of all matter. Different elements consist of different kinds of atoms. On the TEAS Science exam, you must recognize basic atomic structure, including the subatomic particles that make up an atom. You should also review the ways in which atoms bond together by losing, gaining, or sharing electrons. All matter is made up of atoms. An atom is composed of a central nucleus with positively charged protons and neutrally charged neutrons. Negatively charged electrons surround the nucleus. Elements are composed of a single kind of atom with a particular form, mass, and structure. Each element has its own characteristic atomic number and atomic mass. 176 Science The atomic number tells how many protons are in the nucleus of an atom. This determines the total positive charge of the atom. It also determines the atom’s chemical properties and its place in the periodic table of elements. Because atoms are electrically neutral, the atom must have the same number of negatively charged electrons to balance the number of protons. For example, sodium (abbreviated Na) has atomic number 11, meaning that sodium has 11 protons and 11 electrons. Atomic mass is the number of protons plus the number of neutrons in an atom. Atomic mass is computed in atomic mass units (amu): 1 amu for each proton and each neutron. (Electrons have almost no mass.) Sodium’s atomic mass is 11 protons + 12 neutrons = 23 amu. The periodic table is shown on the next page. In it, atoms are arranged by atomic number (number of protons) in increasing order. The periodic table also shows atomic masses in decimal form. Atoms of the same element with different numbers of neutrons are isotopes. For example, the most common isotope of chlorine has 17 protons + 18 neutrons = 35 amu. A rare isotope has 17 protons + 20 neutrons = 37 amu. A compound is a substance composed of two or more elements, or different kinds of atoms, that are bonded together. Elements in a compound are always in fixed ratios. Sodium chloride, or table salt, is a compound. On the atomic level, compounds are composed of molecules. Water and sugar are compounds that are composed from molecules. A water molecule is composed of hydrogen and oxygen. It is represented as H2O — 2 hydrogen atoms bonded to 1 oxygen atom. A sugar (glucose) molecule is composed of 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms: C6H12O6. 177 Chapter 4 178 Science S.2.4 PROBLEM 1 How many neutrons does the average phosphorus atom (P) have? (A) 15 (C) 31 (B) 16 (D) 46 STRATEGY To answer this question, use the information on the periodic table. (Note that the atomic mass posted on the periodic table is the average mass of all isotopes for that element.) THINK • Remember that the number of protons (and electrons) for an element is equal to its atomic number. So phosphorus (P) has 15 protons. • The atomic mass for P is 30.9, which rounds to 31. • Remember that atomic mass = Protons + Neutrons. So if you write an equation for n neutrons it would be: 31 = 15 + n • Solving for n gives n = 16. Phosphorus has 16 neutrons. Answer (B) is correct. S.2.4 PROBLEM 2 Is hydrogen gas, H2, an element or a compound? (A) H2 is a compound because it has 2 atoms. (B) H2 is an element because it has 2 atoms. (C) H2 is an element because it has only one kind of atom. (D) H2 is an element because it has two kinds of atoms. 179 Chapter 4 STRATEGY Consider the definitions of both elements and compounds. THINK • A compound is defined as being composed of molecules having more than one kind of atom. H2 has only one kind of atom — hydrogen — that is bonded to itself. Thus, H2 cannot be a compound, meaning that answer (A) is incorrect. • An element is defined as having only one kind of atom, making answer (C) the correct choice. S.2.5 EXPLAIN CHARACTERISTIC PROPERTIES OF SUBSTANCES Substances can be distinguished from each other by their unique properties. These include both physical and chemical properties. On the Science portion of the TEAS, you will show that you understand the characteristic properties of different substances. All substances have both physical and chemical properties. Physical properties can be measured without altering the essential nature of the substance. They include such properties as melting point, boiling point, freezing point, volume, viscosity, and density. • Melting point is the temperature at which a substance in solid form becomes liquid. • Boiling point is the temperature at which a substance in liquid form boils and turns to vapor. • Freezing point is the temperature at which a substance in liquid form becomes solid. Like melting point and boiling point, freezing point is scientifically measured in units called degrees Kelvin (K). • Volume measures the amount of space that a substance occupies. 180 Science • Viscosity measures a substance’s resistance to motion when subjected to an applied force. • Density measures the amount of mass a substance has per unit volume. Density is measured in units of mass or weight per volume (example: g/cm3). Chemical properties may only be measured by altering the substance being measured. They include such properties as water- reactivity, ionization, solubility, pH (power of hydrogen), and heat of combustion. • Water-reactive substances are hazardous when wet due to their chemical reaction with water. • Ionization energy is the measure of the energy required to remove an electron from an atom or molecule. (First ionization energy measures removal of the first, or most loosely held, electron.) Ionization energy is measured in joules (also called electron volts). • The measure of the acidity and alkalinity of a solution is called pH. A pH less than 7 is an acid. A pH of more than 7 is alkaline. A pH of 7 is considered neutral. • Heat of combustion is the heat produced when 1 mole of a substance undergoes combustion with oxygen at constant pressure. Solubility is a chemical property that measures the ability of a substance to dissolve in a solvent. The graph shows that solubility for sugar (glucose) increases significantly with temperature. Solubility for salt increases very slightly as temperatures rise. 181 Chapter 4 500 450 400 350 300 250 200 150 100 50 0 Solubility of salt and sugar 0 20 40 60 80 100 Temperature (8C) Concentration, or the amount of solute dissolved per liter, can be computed by finding the ratio of solute to solvent. It is important to know the physical and chemical properties of water. A water molecule (H2O) is asymmetrical and thus very polar. Strong attractions of hydrogen atoms for each other give water its special qualities. • Water has a very high heat capacity. This is the degree to which the temperature of water changes when it gains or loses heat. In other words, water temperature tends to remain stable in response to temperature changes in the air surrounding it. It takes a significant amount of energy to boil water. A significant amount of energy must be removed for it to freeze. Water also has a high heat of vaporization, meaning it takes a relatively large amount of heat to vaporize. • Water is an effective solvent. With its highly polar structure, water dissolves polar and ionic substances. • The solid form of water floats on its liquid form. This is because ice is less dense than water. In its solid form, water’s molecules, with their weak hydrogen bonds, crystallize and become rigid, maintaining separation between them. • Water has strong cohesion that results in a high level of surface tension. Hydrogen bonds between molecules of water 182 Science means that water sticks to itself. This accounts for the fact that insects can walk on water without sinking. • Water has strong adhesion, based on attraction of unlike molecules. This is shown when a person wets her finger to pick up a pin. • A combination of cohesion and adhesion results in capillary action, as when spilled water clings onto an absorbent paper towel. Two important properties to remember are osmosis and diffusion. Both are examples of movement at the cellular level called passive transport. • Osmosis occurs when two solutions of unequal concentration are separated by a semipermeable membrane. This generally means there is a higher concentration of water surrounding the cell than inside the cell. Water tends to move across the membrane from an area of low solute concentration to the more concentrated solution. This serves to equalize the concentrations on each side of the membrane. Osmotic potential refers to the tendency of water to move across a permeable membrane. • Diffusion occurs when particles from an area of high concentration move spontaneously to an area of low concentration to produce a state of equilibrium. S.2.5 PROBLEM 20 ml of olive oil weighs 18.36 g. Will an 8-g chunk of plastic that has a volume of 11 cm3 float in olive oil? (A) Yes, because the plastic’s density is greater than that of the oil. (B) Yes, because the plastic’