Module 1 Flashcards
homeostasis
Homeostasis is the dynamic response to maintain a stable internal environment w/in a physiologically tolerable range
NOT the same as equilibrium. Life only works when there is an imbalance in chemical rxns
positive feedback in physiological systems
PROMOTES A CHANGE IN ONE DIRECTION (instability, disease, but sometimes a good thing). bolsters stimulus/amplifies output signal
ex: action potential, hemorrhage, blood clotting, progression of labor to childbirth
negative feedback in physiological systems
PROMOTES STABILITY. inhibits process/ decreases effect of stimulus
stimulus sensed by a receptor. Error signal released toward integrator, which collects signals from different receptors. Integrator releases message known as a correcting signal to effector that ultimately corrects the initial change in the controlled variable.
**NOT in isolation
ex: Baroreceptor Reflex, body temp
Describe the composition of a cell membrane
Bilayer of phospholipids w/ proteins
glycocalyx- surface carbohydrates
glycolipids (10%)
glycoproteins(majority)
proteoglycans (heavily glycosylated glycoproteins)
Diagram A CELL MEMBRANE cross section
extracellular fluid
phospholipid bilaryer w/ proteins
cytoplasm
explain how the distribution of phospholipids and proteins influences the cell membrane permeability of ions, hydrophilic and hydrophobic compounds.
cholesterol
Saturation/longer FA side chains:
Cholesterol: increases stability and flexibilility. decreases fluidity and permeability
Saturation/longer FA side chains: decreases fluidity
Differentiate between the terms osmole, osmolarity, osmolality and tonicity
osmole- osmotic pressure equivalent to the amount of solute that dissociates in solution to form one mole (Avogadro’s number) of particles
osmolarity- # of particles in soln
tonicity- osmolarity but factoring in permeability of membrane
List the typical value and normal range for plasma osmolality
300mOsm
Define the term “steady state,” and differentiate it from “equilibrium.”
equilibrium- equal # of positive and negative ions moving in and out of cell
steady state-
Relate the pump-leak model of steady-state ion content to cell solute gradients and cell volume maintenance.
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Explain the differences between structure and functions of four main classes of membrane proteins.
Transporters- transport ions and nurtrients; pores, channels, carriers, pumps;
Enzymes- Catalyze rxns
Anchors- anchor membrane to macromolecules/other cells
Receptors- Detect signals and relay to interior
Compare and contrast the ultrastructure and function of three main components of the cytoskeleton
actin filaments- smallest and most flexible, provide shape and movement, cell cortex, microvilli, contractile bundles, contractile ring (cell division), lamallipodia &filopodia, amoeboid locomotion (endocytosis and exocytosis), Cytochalasin prevents polymerization, Phalloidin prevents depolymerization– both mean no cell movement
intermediate filaments- rope-like, mechanical strength, (keratin, vimentin, neurofilaments, nuclear lamin), span from desmosome to desmosome, epidermolysis bullosa simplex (keratin), ALS (neurofilaments)
microtubules- thickest, most rigid, organize the cellular interior, cilia and flagella (permanant), mitotic spindles (transient) from centrosomes; Colchicine prevents polymerization (needed in PROPHASE), Taxol prevents depolymerization (needied in ANAPHASE).
ALL- non-covalently linked subunits
Write Fick’s Law of diffusion
how fast (flux) diffusion of an ion will occur using simple diffusion
Jx=Px([X]o-[X]i)
permeability coefficient times the concentration difference across the membrane.
explain how changes in the concentration gradient, surface area, time, and distance will influence the diffusional movement of a compound.
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Based on the principle of ionic attraction, explain how a potential difference across a membrane will influence the distribution of a cation and an anion
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Using a cell membrane as an example, explain how the relative permeability of a cell to water and solutes will generate an osmotic pressure
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Contrast the osmotic pressure generated across a cell membrane by a solution of particles that freely cross the membrane with that of a solution with the same osmolality, but particles that cannot cross the cell membrane.
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Differentiate the following terms based on the source of energy driving the process and the molecular pathway for: diffusion, facilitated diffusion, secondary active transport, and primary active transport.
diffusion- concentration difference, electric potential (EMF), hydrostatic pressure difference
facilitated diffusion-
secondary active transport-
primary active transport-
Describe how transport rates of certain molecules and ions are accelerated by specific membrane transport proteins (“transporter” and “channel” molecules).
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Transporters and channels needed to move polar and charged molecules through phospholipid bilayer (facilitated diffusion)
Diffusion rate limited by Vmax of carrier protein. When Vmax is reached, all carrier proteins occupied
Channels- continuous flow (open or gated)
Carrier Proteins/Transporters- (2 gates, never open at same time, non-continuous)
Describe how energy from ATP hydrolysis is used to transport ions such as Na+, K+, Ca2+, and H+ against their electrochemical differences (e.g., via the Na+ pump, sarcoplasmic reticulum Ca2+ pump, and gastric H+ pump).
Na+-K+ ATPase pump- pumps 3Na out, 2 K in. Cytoplasmic Mg and ATP
sarcoplasmic reticulum Ca2+ pump- sequester cytosolic Ca w/in intracellular organelles for signal transduction.
gastric H+ pump- concentrates H+ ions for acid secretion
Understand the role of ATP-binding cassette transporters in, for example, multidrug resistance and its significance for cancer chemotherapy.
Cytoplasmic ATP binding domain, ATP hydrolysis, Ion movement
cystic fibrosis transmembrane conductance regulator- chloride ion channel
multidrug resistance- MDR1 P-glycoprotein. pumps medicine out of cell. increased expression on cancer cells
Explain how energy from the Na+ and K+ electrochemical gradients across the plasma membrane can be used to drive the net “uphill” (against a gradient) movement of other solutes (e.g., Na+/glucose co-transport; Na+/Ca2+ exchange or counter-transport). Apply this principle to understand oral rehydration procedures.
(Secondary Active Transport)
Symporters- Movement of sodium down its gradient–>energy for the uphill movement of glucose
in the same direction
Antiporters- NCX (Na-Ca exchanger). sodium down it’s gradient kicks Ca2+ out of cell
Describe the role of water channels (aquaporins) in facilitating the movement of water across biological membranes.
3 main features
- size restriction (pore narrows to 2.8A (diameter of water)
- electrostatic repulsion. (arginine at position 195, narrowest point of pore, barrier to cations, including protonated water)
- Water dipole Reorientation- disrupting H bonding among water molecules (prevents proton conductance and restricts only to water)
Understand how regulation of the concentrations of K+, Cl- , and other Na+ solutes influence cell volume.
if Na-K pump is inhibited–> net Na+ inwards–>depolarization–> Cl- can enter–> cell swells due to osmosis
