Porth's Pathophysiology Chapter 2 Cell and Tissue Characteristics Exam Questions and Complete Solutions

Porth's Pathophysiology Chapter 2 Cell and Tissue Characteristics Exam Questions and Complete Solutions Nucleus - Ans: - Control center of the cell - Contains most of the hereditary material, DNA - DNA's genes encode information necessary for the synthesis of essential proteins - Site for synthesis of the three types of RNA Three types of RNA (ribonucleic acid) - Ans: 1. Messenger RNA (mRNA) - (transcription) travels to ribosomes in cytoplasm so these instructions can be used to make proteins 2. Ribosomal RNA (rRNA) - site of protein production 3. Transfer RNA (tRNA) - (translation) transports amino acids to ribosomes so that mRNA can be turned into a sequence of amino acids Prokaryote cells - Ans: - Lack a nucleus - Do not have compartments - Reproduce through simple fission (e.g., bacteria) Eukaryote cells - Ans: - Any cell that has a defined nucleus - Cells are larger and have more specific parts in compartments divided by membranes, called organelles 3 distinct compartments of the eukaryote cell - Ans: 1. Nucleus 2. Cytoplasm 3. Cell membrane Cytoplasm - Ans: - Surrounds the nucleus and is where the work of the cell takes place - Colloidal solution containing water, electrolytes, suspended proteins, neutral fats, and glycogen molecules -Pigments also accumulate but do not contribute to the cell's function Organelles - Ans: Embedded in the cytoplasm and function as the organs of the cell. They include: - Ribosomes - ER (Endoplasmic Reticulum) - Golgi complex - Mitochondria - Lysosomes Ribosomes - Ans: - Sites of protein synthesis: needed for cell function - rRNA and proteins held together by a strand of mRNA to form polyribosomes (also called polysomes) ER (Endoplasmic Reticulum) - Ans: - Extensive system of paired membranes and flat vesicles that connect various parts of the inner cell - Two forms of ER exist in cells: rough and smooth Rough Endoplasmic Reticulum - Ans: - Studded with ribosomes attached to specific binding sites on the membrane - Proteins usually become components of lysosomes or other organelles, are incorporated into cell membranes, or leave the cell as secretory proteins Smooth Endoplasmic Reticulum - Ans: - Free of ribosomes and is continuous with the rough ER - Does not participate in protein synthesis - Site of lipid, lipoprotein, and steroid hormone synthesis Golgi Complex (Golgi apparatus) - Ans: - Consists of four or more stacks of thin flattened vesicles or sacs - Found near the nucleus and function in association with the ER - Modifies substances that are larger than the active product and packages them into secretory granules or vesicles - Thought to produce large carbohydrate molecules that combine with proteins produced by the ER to form glycoproteins - May receive proteins and other substances form the cell surface by a retrograde transport mechanism Lysosomes - Ans: - The cell's digestive system - Small, membrane-enclosed sacs containing powerful hydrolytic enzymes which break down excess and worn-out cell parts, and foreign substances taken into the cell - Primary lysosomes - Ans: Membrane-bound intracellular organelles that contain a variety of hydrolytic enzymes that have not yet entered the digestive process --> receives enzymes and their membranes from Golgi Secondary lysosomes - Ans: The aftermath of primary lysosomes fusing with membrane-bound vacuoles that contain material to be digested Peroxisomes - Ans: Break down fatty acids and produce hydrogen peroxide Proteasomes - Ans: - Small organelles composed of protein complexes that are thought to be present in both the cytoplasm and the nucleus - Recognize misformed and misfolded proteins that have been targeted for degradation Mitochondria - Ans: - Cell "power plants" - Found near the site of energy consumption in the cell - Do not make energy - Extract energy from organic compounds - Transform organic compounds into energy that is easily accessible to the cell - Participate in cellular respiration: multi-step process whereby most of the energy in foodstuffs is converted into energy through the use of the mitochondria's enzymes - Most of the energy is stored by the cells as high-energy phosphate bonds in compounds such as adenosine triphosphate (ATP) to power cellular activities - Contain their own DNA and ribosomes - Self-replicating - Function as key regulators of apoptosis 2 Membranes of the Mitochondria - Ans: 1. Outer membrane: encloses the periphery of the mitochondrion --> large number of transmembrane porins 2. Inner membrane: forms a shelf-like projection, cristae --> contains enzymes & proteins to make ATP Cytoskleton - Ans: -network of microtubules, microfilaments, intermediate filaments, and thick filaments -controls cell shape and movement -microtubules = maintain the position of organelles -microfilaments = aid in cell motility Four functions of the cell membrane - Ans: 1. Acts as a semipermeable structure that separates the intracellular and extracellular environments 2. Provides receptors for hormones and other biologically active substances 3. Participates in the electrical events that occur in nerve and muscle cells 4. Aids in the regulation of cell growth and proliferation Pathogenesis of Polycystic Kidney Disease - Ans: Genetic defect in the cilia of the renal tubular cells Pathway for cell communication?? - Ans: - Extracellular signals or first messengers activate receptors (include neurotransmitters, protein hormones and growth factors, steroids, and other chemical messengers) - G-Protein-Linked Receptors: > 1000 in number ~ convert external signals (first messengers) into internal signals (second messengers) - Enzyme-Linked Receptors: interact with certain peptide hormones (e.g., insulin and growth factors) and directly initiate the activity of the intracellular enzyme - Ion-Channel-Linked Receptors: signaling is mediated by neurotransmitters that transiently open or close ion channels formed by integral proteins in the cell membrane --> can change local charges or voltages - Signaling systems may also include transducers and effectors primarily involved in conversion of the signal into a physiological response - Intracellular signaling mechanisms are second messengers Many molecules involved in signal transduction are proteins ~ these proteins accomplish conformational changes (ability to change their shape or conformation) through enzymes, protein kinases Autocrine signaling - Ans: Cell releases a chemical into the extracellular fluid that affects its own activity Paracrine signaling - Ans: Acts mainly on nearby cells; enzymes rapidly metabolize the chemical mediators Endocrine signaling (transmission of information by hormones) - Ans: Relies on hormones carried in the bloodstream to cells throughout the body Synaptic signaling (transmission of information by neurotransmitters) - Ans: Occurs in the nervous system; act only on adjacent nerve cells through special contact areas, synapses Cell cycle - Ans: G0 - cell cycle begins G1 - cell grows and performs its cellular functions S - replication of DNA G2 - cell prepares to divide Mitosis - cell division Mitosis - Ans: Dynamic and continuous process divided into four stages: 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase Prophase - Ans: - Chromosomes become visible secondary to an increase in DNA coiling - The two centrioles replicate; and a pair moves to each side of the cell - The microtubules of the mitotic spindle appear between two pairs of centrioles - In the later part, the nuclear envelope and nucleolus disappear Metaphase - Ans: Organization of the chromosome pairs in the midline of the cell and the formation of a mitotic spindle composed of microtubules Anaphase - Ans: Separation of the chromosome pairs occurs with the microtubules pulling one member of each pair of 46 chromosomes toward the opposite pole Telophase - Ans: - Mitotic spindle vanishes - A new nuclear membrane develops and encloses each new set of chromosomes - Cell division or cytokinesis is complete Interphase - Ans: The phase in which the cell is not undergoing division Adenosine Triphosphate (ATP) - Ans: - The special carrier for cellular energy - Large amounts of free energy are released when ATP is hydrolyzed to form adenosine diphosphate (ADP) - Energy from foodstuffs is used to convert ADP back to ATP Diffusion - Ans: - Process whereby molecules and other particles in a solution become widely dispersed, and reach a uniform concentration because of energy created by their spontaneous kinetic movements - Electrolytes and other substances move from an area of higher concentration to an area of lower concentration facilitated diffusion - Ans: process of diffusion in which molecules pass across the membrane through cell membrane channels -these cells cannot pass through the cell of their own Osmosis - Ans: - Process whereby water moves through water channels (aquaporins) in a semipermeable membrane (most membranes) along a concentration gradient - Moving from an area of higher to one of lower concentration - Regulated by the concentration of nondiffusible particles on either side of a semipermeable membrane - When there is a difference in the concentration of particles, the water moves from the side with the lower concentration of particles and higher concentration of water to the side with the higher concentration of particles and lower concentration of water Endocytosis (cell eating) - Ans: Process whereby cells engulf materials from their surroundings ~ includes pinocytosis and phagocytosis Pinocytosis - Ans: - "Cell Drinking" - Ingestion of small solid or fluids particles - Particles are engulfed into small, membrane-surrounded vesicles for movement into the cytoplasm - Important in the transport of proteins and strong electrolyte solutions Phagocytosis - Ans: - "Cell Eating" - Involves the engulfment and subsequent killing of degradation of microorganisms or other particulate matter - Macrophages and neutrophils are adept at engulfing and disposing of invading organisms, damaged cells, and unneeded extracellular constituents Exocytosis (exit) - Ans: - Mechanism for the secretion of intracellular substances into the extracellular spaces - Essentially the opposite of endocytosis - Involves the removal of large particles from the cell - Important in the removal of cellular debris and releasing of substances (e.g., hormones) synthetized in the cell Active Transport - Ans: - Requires the cell to expend energy in moving ions against a concentration gradient (low to high) - The sodium-potassium-ATPase pump is the best known mechanism for active transport: moves 3 sodium from inside the cell to the extracellular region; and returns 2 potassium to the inside of the cell Two Types of Active Transport - Ans: - Primary Active Transport - Secondary Active Transport Primary Active Transport - Ans: The source of energy (e.g., ATP) is used directly to transport the substance Secondary Active Transport - Ans: Mechanisms harness the energy derived from the primary active transport of one substance (usually sodium) for the co-transport of another substance -cotransport/symport = same direction -countertransport/anitport = opposite Ex. when sodium ions diffuse into cells, the energy of this movement is used to drive the transport of a second substance against its concentration gradient Generation of Membrane Potentials relies on - Ans: 1) Diffusion of current-carrying ions; 2) Development of an electrochemical equilibrium; 3) Establishment of RMP (resting membrane potential); and 4) Triggering of action potentials membrane potential - Ans: -cell said to be polarized at RMP b/c two sides of membrane have different voltages -depolarization - more positive charge inside than cell (sodium or calcium entering the cell) -hyperpolarization - more negative charge inside the cell (chloride entering cell) -repolarization - if cells are first depolarized and then potassium diffuses out of cells, removing the positive charge of potassium from the inside of the cell graded potential - Ans: Ex. if sodium or calcium channels are opened, then the dendrites and cell body are depolarized, because this would result in positive change traveling into the cell action potential - Ans: Ex. opening of Na channels allows large amounts of positively charged Na to diffuse to the interior of the cell, causing the membrane potential to undergo depolarization or a rapid change to positive on the inside and negative on the outside --> close Na channels and open K channels = removes it from the cell and reestablishes RMP Diffusion Potentials - Ans: - Potential difference generated across a membrane when a current-carrying ion (such as the potassium ion), diffuses down its concentration gradient - Two conditions are necessary 1. The membrane must be selectively permeable to a particular ion 2. The concentration of the diffusible ion must be greater on one side of the membrane than the other Equilibrium Potentials - Ans: - Membrane potential that exactly balances and opposes the net diffusion of an ion down its concentration gradient - An electrochemical equilibrium is one in which the chemical forces driving diffusion and the repelling forces are exactly balanced so that no further diffusion occurs Resting Membrane Potential (RMP) - Ans: - Necessary for electrical excitability - Present when the cell is not transmitting impulses - Because the resting membrane is permeable to potassium, RMP is essentially a potassium equilibrium potential Action Potential - Ans: - Involve rapid changes in the membrane potential - Each action potential begins with a sudden change from the negative RMP to a positive threshold potential causing an opening of the membrane channels for sodium (or other ions of the action potential) Cell differentiation - Ans: - Formation of different types of cells and the disposition of these cells into tissue types - Embryonic cells must differentiate to become all the various organ systems - Involves the sequential activation of multiple genes and their protein products - After differentiation, the tissue type does not revert to an earlier differentiation stage - Cell Memory controls the process of cell differentiation - maintained through regulatory proteins contained in the individual members of a particular cell type Epithelial tissue characteristics - Ans: 1) three distinct surfaces (free or apical surface, a lateral surface, and a basal surface); 2) closely opposed and joined by cell-to-cell adhesion molecules (CAMs) which form a specialized cell junction; and 3) basal surface is attached to an underlying basement membrane shapes of epithelial tissue - Ans: squamous - thin & flat (blood vessels) cuboidal - cube shaped (ovary & thyroid) columnar - resembling a column (intestines) Number of Layers of Epithelial Tissue - Ans: simple - single layer (blood vessels) stratified - more than one layer - deepest layer resting on basement membrane (skin) pseudostratified - all cells in contact with the underlying intercellular matrix, but some do not extend to the surface (upper respiratory tract) transitional epithelium - Ans: a stratified epithelium in which the shape of the surface cells changes (undergoes transitions) depending on the degree of stretch (urinary bladder) glandular epithelium - Ans: Composed of cells that are specialized to produce and secrete substances. secretory glands, exocrine glands, endocrine glands Connective Tissue Characteristics - Ans: - Cell produce the extracellular matrix that supports and holds tissues together - Derived from the embryonic mesoderm, but some is derived from the neural crest, a derivative of the ectoderm - Mesenchymal cells arise from the mesodermal cells to form mesenchyme ~ tissues derived from embryonic mesenchymal cells include bone, cartilage, and adipose - Include fibroblasts, chondroblasts, osteoblasts, hematopoietic stem cells, blood cells, macrophages, mast cells, and adipocytes - The matrix in the umbilical cord is composed of a second type of embryonic mesoderm, mucous connective tissue or Wharton jelly types of connective tissue - Ans: adipose, reticular, bone, cartilage, dense connective tissue, loose connective tissue, blood Muscle Tissue Characteristics - Ans: - Primary function: contraction - Responsible for movement of the body and its parts; and for changes in the size and shape of internal organs - Two types of fibers that are responsible for contraction: thin (primarily composed of actin); and thick filaments (primarily composed of myosin) - Actin and myosin filaments interact to produce muscle shortening ~ process activated in the presence of calcium - Three types: cardiac, skeletal, and smooth cardiac muscle - Ans: -Involuntary muscle tissue found only in the heart. -striated skletal muscle - Ans: -striated -voluntary -multinucleated fibers -attached to bone -contractions are responsible for movements of the skeleton smooth muscle - Ans: -not striated -involuntary -can divide -found in the iris of the eye, the walls of the blood vessels, surrounding hollow organs (stomach & urinary bladder), and hollow tubes (ureters & common bile ducts Nervous Tissue - Ans: - Distributed throughout the body as an integrated communication system - Develop from the embryonic ectoderm ~ are highly differentiated and therefore incapable of regeneration in postnatal life - Consists of two cell types: nerve cells or neurons; and glial or supporting cells - Consist of three parts: the soma or cell body; dendrites; and axon Extracellular Tissue Components - Ans: - Composed of a variety of proteins and polysaccharides ~ proteins and polysaccharides are secreted locally; and organized into a supporting meshwork in close association with the cells that produce them - Amount and composition of the extracellular matrix varies with the different tissues and their function - Extracellular fibers include: collagen fibers (comprise tendons and ligaments); elastic fibers (found in large arteries and some ligaments); and thin reticular fibers (abundant in organs that are subject to a change in volume such as the spleen and liver) - Three types of fibers are found in the extracellular space: collagen, elastin, and reticular fibers Collagen - Ans: - The most common protein in the body - A tough, nonliving, white fiber that serves as the structural framework for skin, ligaments, and tendons Elastin - Ans: Abundant in structures subjected to frequent stretching (e.g., aorta and some ligaments) ~ can be stretched and then returns to its original form Reticular fibers - Ans: Extremely thin fibers that create a flexible network in organs subjected to changes in form and volume (e.g., spleen, liver, uterus, or intestinal muscle layer)