BIOL 122 Ch 7 Membrane Q's!

What is the fluid mosaic model? What does it refer to?
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What is the fluid mosaic model? What does it refer to?
The fluid mosaic model describes a model of the plasma membrane. The fluid mosaic model describes the cell membrane as a tapestry of several types of molecules (phospholipids, cholesterols, and proteins) that are constantly moving.
What function does cholesterol have in the plasma membrane?
Cholesterol helps maintain the plasma membrane's fluidity- at warm temps, it restricts the movement and reduces fluidity. At cold temps, it prevents tight packing.
What molecules cannot easily pass through the plasma membrane, polar or nonpolar? Why?
Polar molecules pass through with difficulty, nonpolar molecules can cross easily. Polar molecules do not pass as easily because of the hydrophobic region.
How is an integral protein different from a peripheral protein?
An integral protein span the hydrophobic center. The peripheral protein do not penetrate the hydrophobic center.
What structure is required in an integral/ transmembrane protein that is not necessary in a peripheral protein?
Integral proteins have a nonpolar section.
What part of the membrane is more likely connected to the cytoskeleton?
Protein fibers
What are the components of a glycoprotein? A glycolipid?
A glycoprotein is a compound containing carbohydrate (or glycan) covalently linked to protein (amino acids). The basic structure of a glycolipid consists of a mono- or oligosaccharide group attached to a sphingolipid or a glycerol group (can be acetylated or alkylated) with one or two fatty acids.
What is the function of the glycocalyx? On what side of the membrane is it found (intracellular or extracellular)?
The glycocalyx is composed of sugars protruding from lipids and proteins. Functions include lubricating cells, sticking cells down, and serving as a binding site for proteins for communication and recognition. It is found outside of the cell (extracellular).
How are animal cells joined together? How do the types of cells vary? Can plant cells be joined together?
Animal cells communicate via their extracellular matrices and are connected to each other via tight junctions, desmosomes, and gap junctions.
What is the fundamental difference between passive and active transport across the membrane?
Passive: does not require ATP, but does require molecules moving down concentration gradients
Active: requires ATP, molecules must pass across the membrane up the concentration gradient
How would you classify (active/passive transport) diffusion? What causes diffusion (simple diffusion)?Passive transport Simple diffusion is caused by random motion of moleculesHow is diffusion (simple diffusion) different from facilitated diffusion?Facilitated diffusion is when larger polar molecules need help transporting across the membrane (transport protein helps)What is the concentration gradient of a molecule? Would a molecule diffuse up (from low to high conc.) or down (from high to low conc) its concentration gradient?A concentration gradient is the difference in concentration of a substance from one location to another. A substance will diffuse from where it is more concentrated where it is less concentrated, down the concentration gradientAs molecules diffuse across a semipermeable membrane they will reach a dynamic equilibrium. What does this mean? How is it different from a static equilibrium?Dynamic equilibrium means as many molecules pass one way as the other direction. Static equilibrium means there is no movement between the reactants/productsWhat is osmosis?Osmosis is the net movement of water molecules over a slightly permeable membrane down its concentration gradient2 solutions are separated by a semipermeable barrier that allows the flow of water molecules, but not the solutes. Solution A is hypertonic to solution B. A | B. How would you classify solution B. Which way will water molecules flow? (from A B or from B A)?Solution B is hypotonic, the water molecules will flow from B to A (more water --> to less water) water wants to be hypertonic.A blood cell is placed into distilled water. How would you classify the distilled water (hypo, hyper, isotonic compared to the cell)? How would you classify the solution in the cell in comparison to the distilled water? Which direction would the water molecules flow (into the cell / out of the cell)?The DI water is hypotonic (has more water) The soln in the cell is hypertonic (has less water) The water molecules will flow into the cellA piece of celery is placed into salt water. Would you expect the cells to celery to become more flaccid or more turgid? Why?Flaccid- the water from the celery will go out of those cells into the salt water because salt water is hypertonic compared to the celeryWhat is osmoregulation? What organisms need to do this?Osmoregulation is the regulation of osmosis to maintain the internal environment (maintains homeostasis). Many vertebrates, including humans, are osmoregulatory.What is an electrochemical gradient? Which side of the plasma membrane is electronegative? What forms this gradient?An electrochemical gradient is created actively so the passive transport of cations into the cell and anions out of the cell will be favored by passive diffusion. The inside is more electronegative. Electrogenic pumps form the gradient (active transport)How does the Sodium-Potassium pump work? Is this active or passive transport? Why?The sodium-potassium pump system moves sodium and potassium ions against large concentration gradients. It moves two potassium ions into the cell where potassium levels are high, and pumps three sodium ions out of the cell and into the extracellular fluid. It is active transport (uses ATP)How does cotransport work?A transport protein couples the diffusion of a solute down its concentration gradient with the "uphill" transport of a different solute against its gradient.The transfer of materials out of a cell using vesicles is called _______ExocytosisHow do the three major types of endocytosis differ from one another?1. phagocytosis- "cell eating" 2. receptor mediated- grabbing specific things 3. pinocytosis- "cell drinking"