Animal Physiology Objectives Answers Unit 1

Answers Objectives-1, BIO 3360

INTRODUCTION

  1. The study of functions of animal systems at all levels of organization.
  2. Animal Physiology is studied from the atomic and chemical levels, through cellular, tissue, organ and system levels. Finally, populations of organisms, their communities, the ecosystem and the entire biosphere are studied.
  3. Teleological is why something works and mechanistic is how something works. Evolutionary physiology examines the significance of a mechanism and how that mechanism has responded to natural selection through numerous generations.
  4. Balance or equilibrium that allows internal constancy.  Temperature regulation is an example.
  5. In multicellular organisms, most cells are in an internal environment which just means inside of the animal.  ECF is extracellular fluid which “bathes” the cells and ICF is intracellular fluid that is inside of the cell.
  6. Negative feedback lends itself towards homeostasis because in has the opposite effect that corrects a value outside of its set point.  The variable being regulated moves in the direction opposite the original value.  If you have too much of a substance, negative feedback decreases the production of that substance.
  7. Conformers change their internal body as variables in their environment changes and regulators keep internal constancy over a range of environmental changes.

MEMBRANES

  1. Membranes are a selectively permeable and protective barrier between extra- and intracellular portions.  It provides chemical and physical stability as well as isolation of the cell.
  2. This is a double layer of phospholipids with the hydrophobic portions facing each other and the hydrophilic heads facing outward.  (Amphipathic refers to the fact that the two ends of the fat differ, in that one end is water soluble or polar, and one end is lipid soluble or nonpolar.)
  3. Phosphoglycerides (glycerol), sphingolipids (sphingosine), cholesterol.
  4. The arrangement of the phospholipids actually allows for a semi-fluid membrane as the phospholipids move since there are no bonds between the lipids.  This is referred to as the fluid mosaic model. Regulation of fluidity can come from the number of unsaturated and saturated chains, the length of the fatty acid chains and the amount of cholesterol in the environment.   (shorter fatty acid chains, unsaturated chains and more cholesterol increase fluidity) The fluidity depends on the lipids in that there are no chemical bonds between the lipids and they can move easily.  The fluidity also allows for repair.
  5. Integral proteins are embedded across the phospholipid bilayer and peripheral proteins are located at one of the surfaces of the phospholipid bilayer.
  6. Membrane proteins serve to be receptors, carriers, ion channels, messengers, and enzymes.

CELL SIGNALING

  1. The building blocks are amino acids, and they connect to each other via peptide bonds.  Primary is linear sequence of amino acids, secondary is the folding because of the hydrogen bonds, tertiary is the folding due to interaction with surroundings, quaternary is non-covalent forces between polypeptide subunits.
  2. A ligand is a molecule binding to a protein receptor by a weak van der Wall force.
  3. Receptor specificity refers to a lock and key fit for a ligand with its receptor.  Saturation is when all of the receptors have ligand attached.  Affinity is the degree of attraction between ligand and receptor.  Modulation is changing the receptor via a regulatory site such that a ligand can bind.
  4. Gap junctions are water filled channels between 2 adjacent cell membranes.  Only small molecules can pass, and it is excellent for current flow (ions).
  5. Autocrine is when the chemical produced by a cell acts on the same cell; paracrine is when the chemical produced by a cell acts on a neighboring cell; endocrine is when the chemical produced by a cell travels through the bloodstream to another tissue.
  6. Cell surface or intracellular are the locations of hormone receptors. Lipid soluble ligands bind to intracellular receptors. Lipid-insoluble ligands and ions bind to surface receptors.
  7. The first messenger is the ligand that binds to the receptor protein; a hormone is an example. The first messenger may activate another molecule that leads to a cell change which is a second messenger. Common examples of second messengers include cAMP, cGMP, IP3, DAG, calcium ions.
  8. The cell with the matching receptor to the ligand or hormone is a target cell. A kinase adds a phosphorous group to a molecule, called phosphorylation.
  9. Extracellular ligand-binding domain is a receptor on cell membrane surface and ligand binds a ligand present in ECF. Transmembrane domain is across the cell membrane, and transmits a change of shape of the receptor across the membrane, and thus activating the last domain of the receptor. The catalytic intracellular domain is inside of the cell membrane and when activated, it is an enzyme which leads to a cascade of phosphorylation of proteins causing a response in the target cell.
  10. Signal amplification is when a small stimulus yields a huge response. For example, 1 molecule of glucagon hormone may result in 1000 molecules of cAMP which activate protein kinases. Each protein kinase activates 1000 molecules of other enzymes and leads to the mobilization of 10,000 molecules of glucose!
  11. Recognition of the signal by its receptor. • 2. Transduction of extracellular message into an intracellular (second) messenger. • 3. Transmission of the second messenger signal to the effector . • 4. Activation of protein kinases or phosphatases ). • 5. Response of the cell. 6. Termination of the response.

MEMBRANE TRANSPORT

  1. Diffusion is the movement of molecules as a result of continuous random movement from high concentration to low concentration; e.g. sugar cube in cup of coffee. Osmosis is movement of water from high to low concentration across semipermeable membrane. Osmotic pressure is a pulling pressure of water towards the solutes. Aquaporins are membrane proteins that are water channels. Facilitated diffusion is movement along a concentration gradient but facilitated diffusion can only occur along protein carriers. Voltage channels are sensitive to voltage levels and that determines if they open/close; ligand channels depend on a molecule binding to them and are therefore chemically regulated; mechanical channels open/close according to physical changes such as pressure. Channel gating is the opening and closing of ion channels. A solution is a combination of solute (the substance being dissolved) and solvent (the substance doing the dissolving). Symport has both items of cotransport traveling the same direction while antiport has one molecule going into the cell and one going out
  2. Diffusion rate influencing factors are temperature and mass of molecule.
  3. Osmosis is movement of water from high to low concentration across semipermeable membrane. Osmotic pressure is a pulling pressure of water towards the solutes. Water would move into a tissue with high osmotic pressure.
  4. Nothing happens to the cell in an isotonic solution, it swells in a hypotonic solution, it shrinks in a hypertonic solution.
  5. Ions diffuse through small selective protein channels; the cell’s permeability to that ion depends on the density of those channels and whether or not the channels are open.
  6. Voltage channels are sensitive to voltage levels and that determines if they open/close; ligand depend on a molecule binding to them and are therefore chemically regulated; mechanical channels open/close according to physical changes such as pressure.
  7. Primary active transport uses ATP as energy source and secondary uses concentration gradients (cotransport) as source of energy.

MEMBRANE POTENTIALS

  1. Close to the membrane opposite charged ions can accumulate on either side of the membrane because the bilayers keep the charges apart; farther away the positive and negatives mix randomly so that the net charge is zero, and there is no electrical potential
  2. All cells have a resting membrane potential.
  3. -65-80 mV with the negative meaning it is more negative inside of the cell
  4. Nernst equation allows you to calculate the equilibrium potential (inward and outward fluxes that end up balancing each other). NERNST EQUATION SIMPLIFIED: Ex in millivolts = +/- 60 log [X]in / [X]out. Therefore, if a cell with .1M concentration of KCl inside of the cell and .01M concentration of KCl outside of the cell, the equilibrium potential would be -60 mV; potassium wants to diffuse out of the cell making the cell more negative inside.
  5. No difference in resting membrane potential; and equilibrium potential if only potassium ions are involved.
  6. Chemical gradient and membrane permeability contribute to membrane potential. Since most sodium is outside of the cell and most potassium is inside the cell and the fact that the membrane is not permeable to sodium is the biggest role.
  7. Na/K pump moves three positive Na ions out of the cell while bringing in only 2 positive K ions.

EPITHELIAL TRANSPORT

  1. Histology is the study of tissues (groups of cells working together). Tight junctions are selectively permeable barriers for water, ions & other molecules on either side of the epithelium and allow an uninterrupted sheet of cells which contributes to their protection and covering functions. A basement membrane is at the base of the epithelium, which is also attached to underlying connective tissue. Transcellular goes through the cell while paracellular goes between cells.
  2. Epithelium nervous, muscular, connective.
  3. Protective, barrier, secretory, absorptive and is found as a covering (skin) and lining (mucosa of mouth). Glands are also epithelium.
  4. It is avascular and has continuous regeneration.
  5. Asymmetrical distribution of membrane proteins • Tight junctions which govern movement between cells • Diversity of cell types depending on the role • High density of mitochondria for ion transport energy demands.
  6. Leaky permit passage through tight junctions frequently while tight conducts minimal paracellular transport. Water movement depends on the leaky vs. tight epithelia.