BMS 595 Physiology Exam 1 | Complete Solutions (Verified Answers)

BMS 595 Physiology Exam 1 | Complete Solutions (Verified Answers) What is the basic unit of life? The cell What does the Cell Theory state? All organisms are made of cells, cells are the basic unit of life, and all cells come from pre-existing cells What are membranous organelles? Plasma membrane, ER, Golgi, lysosomes, mitochondria, peroxisomes What are non-membranous organelles? Ribosomes, centrioles, microtubules, filaments, proteasomes What is the main role of the plasma membrane? Selectively controls entry and exit of substances What model explains the plasma membrane? Fluid Mosaic Model What is the main function of mitochondria? ATP (energy) production What is the main function of the Rough ER? Protein synthesis and modification What is the main function of the Smooth ER? Lipid/steroid synthesis, detoxification, calcium storage What is the main function of the Golgi apparatus? Packages and distributes proteins What is the main function of lysosomes? Digest and recycle cellular material What is homeostasis? Maintaining a stable internal environment What are the three parts of a homeostatic system? Sensor, control center, effector What type of feedback returns a variable to normal? Negative feedback What type of feedback amplifies a change until an endpoint? Positive feedback What type of regulation anticipates a change before it happens? Feedforward What does "set point" mean in homeostasis? The normal range of a variable Do homeostatic systems act like on/off switches? No, they continuously adjust Example: Low blood sugar triggers glucagon release. What type of feedback? Negative feedback Example: Childbirth contractions releasing more oxytocin. What type of feedback? Positive feedback Example: Sweating begins before body temp rises too much. What regulation? Feedforward Which variables are homeostatically regulated? Ions, glucose, blood pressure, blood volume, osmolarity, body temperature What is interdependence of organ systems? Systems work together to maintain life What causes disease? Genetics, infection, toxins, poor nutrition, environment What is the difference between signs and symptoms? Signs are measurable; symptoms are subjective When homeostasis fails, what occurs? Disease Which organelle is the site of protein synthesis? Ribosomes The cell membrane functions to: maintain integrity, regulate transport, and act as a barrier. True or False? True Which hormone increases blood glucose during hypoglycemia? Glucagon Which of the following is positive feedback: blood clotting, blood sugar regulation, thermoregulation? Blood clotting What are the main body fluid compartments? Intracellular fluid and extracellular fluid (plasma + interstitial fluid) What type of membrane transport requires no ATP? Passive transport What drives simple diffusion? Movement down a concentration gradient Which molecules can cross membranes by simple diffusion? Oxygen, carbon dioxide, lipids What is facilitated diffusion? Transport using carrier or channel proteins without ATP What is osmosis? Diffusion of water across a semipermeable membrane What happens to cells in a hypertonic solution? They shrink What happens to cells in a hypotonic solution? They swell and may burst What is the sodium-potassium pump? An ATP-driven pump that moves Na⁺ out and K⁺ in What is secondary active transport? Uses ion gradients to move other substances What is an antiporter? A protein that moves substances in opposite directions If a compartment is in steady state, what happens to the amount of substance in it? It stays constant over time What is the central dogma of molecular biology? DNA → RNA → Protein What process copies DNA for cell division? Replication What process makes RNA from DNA? Transcription What process makes protein from mRNA? Translation What is gene expression? The process from DNA transcription to protein formation What percentage of DNA codes for traits? About 2-3% What are genes? DNA segments that code for traits, proteins, and enzymes What is a chromosome? DNA coiled with proteins (histones) What is the role of histones? Keep DNA tightly coiled and organized What are chromatids? Identical copies of a chromosome joined at the centromere What are nucleotides made of? Sugar, phosphate, nitrogenous base Which bases are purines? Adenine and guanine Which bases are pyrimidines? Thymine and cytosine What is base pairing? A bonds with T, C bonds with G What are nucleosomes? DNA wrapped around histones What are telomeres? Protective ends of DNA that shorten with replication What enzyme maintains telomeres? Telomerase What is the model of DNA replication? Semi-conservative (each new strand has one old and one new) What enzyme unzips DNA? DNA helicase What enzyme adds new nucleotides during replication? DNA polymerase What are codons? Three-base sequences in DNA or mRNA that code for amino acids What base replaces thymine in RNA? Uracil What enzyme carries out transcription? RNA polymerase What are the 3 stages of transcription? Initiation, elongation, termination What is mRNA's role? Carries genetic code to ribosomes What is tRNA's role? Brings amino acids to ribosomes What is rRNA's role? Forms ribosomes and catalyzes protein assembly What is miRNA's role? Regulates gene transcription and translation Where does transcription occur? Nucleus Where does translation occur? Ribosomes in cytoplasm How many codons are there? 64 codons What determines which genes are active in a cell? Selective gene expression What phase is most of the cell cycle spent in? Interphase What are the phases of interphase? G1, S, G2 What happens in G1 phase? Growth and protein synthesis What happens in S phase? DNA replication What happens in G2 phase? Preparation for mitosis What is G0 phase? Resting or differentiated state What is mitosis? Division of a cell into two identical daughter cells What are the stages of mitosis? Prophase, metaphase, anaphase, telophase What is cytokinesis? Division of the cytoplasm into two cells What is cell differentiation? Cells specialize by selective gene expression What causes cancer at the genetic level? Mutations in genes that control growth and division What is a proto-oncogene? A normal gene that regulates growth What is an oncogene? A mutated gene causing uncontrolled growth What is an anti-oncogene (tumor suppressor)? A gene that suppresses oncogene activation Is cancer usually inherited? No, it arises from somatic mutations Sequences of DNA nucleotides that carry protein instructions are called what? Genes The correct pathway from transcription to translation is? DNA → mRNA → Protein The mRNA is the result of which process? Transcription Which phase is actual cell division? M phase What are the two main types of transport across cell membranes? Passive (no ATP, with gradient) and Active (requires ATP, against gradient) What are examples of passive transport? Diffusion, facilitated diffusion, filtration, osmosis What are examples of active transport? Carrier transport, Na⁺/K⁺ pump, bulk transport (endocytosis, exocytosis, phagocytosis, pinocytosis) What is the fluid mosaic model? The membrane is a phospholipid bilayer with embedded proteins, fluid and dynamic in nature What role does cholesterol play in membranes? Improves stability and reduces fluidity What are the main body fluid compartments? Intracellular fluid and extracellular fluid (interstitial fluid + plasma) How are ICF and ECF related? They are in osmotic equilibrium but have different chemical compositions What fraction of body water is intracellular fluid? About two-thirds What fraction of ECF is plasma vs interstitial fluid? Plasma is 25%, interstitial fluid is 75% What is simple diffusion? Passive movement of molecules down a concentration gradient through membranes or channels What factors affect diffusion rate? Concentration gradient, surface area, membrane permeability, thickness, temperature, molecule size What law describes diffusion rate? Fick's Law What molecules move by simple diffusion? Oxygen, carbon dioxide, lipids What is facilitated diffusion? Passive transport with the help of carrier or channel proteins What is osmosis? Diffusion of water across a semipermeable membrane What happens to a cell in a hypertonic solution? It shrinks What happens to a cell in a hypotonic solution? It swells and may burst What is filtration? Movement of fluid and solutes due to pressure differences What is active transport? Transport of molecules against a gradient using ATP What is transport maximum? The limit to how fast carriers can move substances What is the sodium-potassium pump? An ATPase pump that moves 3 Na⁺ out and 2 K⁺ in against their gradients Why is the sodium-potassium pump important? Maintains gradients, resting potential, and drives secondary active transport What is secondary active transport? Uses energy from ion gradients to move other molecules What is a symporter? Moves substances in the same direction (e.g., Na⁺-glucose symporter) What is an antiporter? Moves substances in opposite directions (e.g., Na⁺-H⁺ antiporter) What is endocytosis? Process of bringing substances into the cell What is phagocytosis? Cell engulfs solids What is pinocytosis? Cell engulfs liquids What is exocytosis? Release of substances from the cell What is resting membrane potential? The steady negative potential across the cell membrane due to ion gradients Which ion primarily determines resting membrane potential? Potassium (K⁺) Why is the resting potential negative? More K⁺ leaks out than Na⁺ comes in, and large negative proteins remain inside What is the typical resting membrane potential of neurons? Around -70 mV What is threshold potential? The critical depolarization needed to trigger an action potential What are the three main stages of an action potential? Depolarization, repolarization, hyperpolarization What causes depolarization? Opening of voltage-gated Na⁺ channels, Na⁺ rushes in What causes repolarization? Closing of Na⁺ channels, opening of K⁺ channels, K⁺ leaves the cell What causes hyperpolarization? Excess K⁺ efflux before channels close What is the all-or-none principle of action potentials? Once threshold is reached, an action potential fires fully What are graded potentials? Small changes in membrane potential that vary in size and decrease with distance How are graded potentials different from action potentials? Graded are variable and local, action potentials are all-or-none and travel long distances What is the equilibrium potential? The membrane voltage at which ion movement by gradient and electrical forces are balanced What equation calculates equilibrium potential? Nernst equation What contributes to the -90 mV resting potential? K⁺ diffusion (-86 mV) and Na⁺/K⁺ pump (-4 mV) How do neurons transmit signals? By propagating action potentials along the axon How do axon diameter and myelin affect conduction speed? Larger axons and myelinated axons conduct faster What is saltatory conduction? Action potentials jumping between nodes of Ranvier in myelinated axons How do neurons communicate with each other? At synapses (electrical or chemical) What is an electrical synapse? Direct ion flow through gap junctions Where are electrical synapses found? Heart, retina, gut, hypothalamus What is a chemical synapse? Neurotransmitters cross a synaptic cleft to stimulate the next cell Give an example of a chemical synapse. Neuromuscular junction with acetylcholine What are the steps of neurotransmission? Dendrites receive, cell body integrates, axon conducts, terminals release neurotransmitters What is the latent period of a muscle twitch? Time between stimulus and contraction while Ca²⁺ is released What is the contraction phase of a twitch? Ca²⁺ binds troponin, actin sites exposed, muscle contracts What is the relaxation phase of a twitch? Ca²⁺ removed, muscle relaxes What is a motor unit? A motor neuron and the muscle fibers it innervates How does recruitment increase muscle force? Activating more motor units What is asynchronous recruitment? Motor units take turns to delay fatigue What are isotonic contractions? Muscle shortens or lengthens while generating force and moving a load What are isometric contractions? Muscle generates force without changing length What are the main functions of muscle tissue? Movement, posture, regulating organ volume, moving substances, heat production What are the properties of muscle tissue? Excitability, contractility, extensibility, elasticity What connects muscle to bone? Tendons What connects muscle to muscle? Aponeuroses What is the structural unit of a muscle? Muscle fiber (cell) What is a myofibril made of? Thick (myosin) and thin (actin) filaments What is the functional unit of muscle contraction? The sarcomere What are the three types of proteins in muscle? Contractile, regulatory, structural What are the contractile proteins? Actin and myosin What are the regulatory proteins?