02a-cell membranes (study guide) PDF

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Dr. Michael Lague Study Guide with Answers...

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BIOL 1270: ANATOMY & PHYSIOLOGY STUDY GUIDE: Cell Membranes The Plasma Membrane 1) What lipid molecule is the major structural component of cell membranes? How is it physically arranged? What qualities of this molecule cause it to be so arranged? Are the molecules of the plasma membrane static or dynamic? -glycolipids 2) What other lipid is common in membranes? What role does it play? -Phospholipids are also common and they play the role of structure 3) What is the glycocalyx? -The sugar coating around the cell that is comprised of glycolipids and glycoproteins that is important in cell to cell recognition 4) What role to membrane carbohydrates play? What is a glycolipid? A glycoprotein? -They bond with glycolipids and glycoproteins 5) What 2 types of proteins are associated with cell membranes? How do they differ? -Integral and peripheral proteins are also associated with cell membranes. They act to receive and transport information and they move side to side in the cell membrane, the peripheral proteins are on the inside of the cell and they help stabilize the cell 6) What is the difference between active processes and passive processes of membrane transport? What are examples of each type? -Active processes are when the materials need energy to flow into the cell, and passive does not require energy because things flow freely within the membrane. Membrane Permeability 7) What is diffusion? What does “movement down a concentration gradient” mean? -Diffusion is the movement of a solute down its concentration gradient meaning that it flows to areas with lower concentrations of the solute i.e. NaCl to water 8) What’s the difference between simple diffusion and facilitated diffusion? By which process can lipid-insoluble, polar substances cross a membrane? Does facilitated diffusion require energy? Why or why not? -Simple diffusion is unassisted diffusion where the things go right through the phospholipid bilayer and does not require an energy source; facilitated diffusion is carrier mediated meaning that the proteins can only pass through the membrane via carrier protiens that are made for certain shapes. Lipid insoluble substances pass via facilitated diffusion and this process DOES NOT REQUIRE ENERGY 9) What 2 kinds of membrane transport proteins are involved in facilitated diffusion? How do they differ? Which one allows transport of larger molecules (e.g., sugars, amino acids)? Which one allows transport of small ions? -There is channel mediated proteins and membrane transport proteins, channel mediated brings solutes through based on the ion shape and size and membrane proteins bring substances all the way through the membrane 10) What limits the rate at which solutes may pass through the membrane via carrier proteins? -The number of membrane transport proteins and the concentration so higher concentrations flow faster 11) What is osmosis? Does water diffuse to areas of higher or lower solute concentration? Does osmosis occur if the membrane is permeable to all solutes? -Osmosis is the diffusion of water and water goes to areas of higher concentration to reach equilibrium; yes but only water flows 12) What is osmotic pressure?

Osmotic pressure is the force of the osmotic flow which is the pressure exerted on the semi permeable membrane 13) What is osmolarity? How is it mathematically related to molarity? If a glucose solution and a saline (NaCl) solution both have the same molarity, why is the osmolarity of the saline solution higher? By how much? -Osmolarity is the total solute concentration in a solution and is important in determining the osmotic pressure, it contributes because it is based off the molarity of the solution to begin and its higher bc NaCl dissociates in solution into ions and glucose does not 14) What is tonicity? How do isotonic, hypotonic, and hypertonic solutions differ? -Tonicity is the effect that a solution will have on a cell- isotonic, they are at equilibrium; hypotonic- draws water into the cell bc it’s a higer concentration; hypertonic, water flows out of the cell and shrivels 15) Tonicity is determined by the difference in the concentration of nonpenetrating solutes inside vs. outside the cell. With respect to this difference, under what conditions will a solution cause lysis? Under what conditions will a solution cause crenation? -Lysis will occur if the solution and cell are hypotonic and the cell fills with to much water and explodes; crenation will occur if the solution is placed in a hypertonic solution and all the water leaves the cell 16) The osmolarity of both intracellular and extracellular fluid is 0.3 Osm/L. A living cell is placed into a 0.3 Osm/L solution which contains a penetrating solute that is not found inside the cell. Why does this solution cause the cell to swell? -Because they want to reach equilibrium 17) What are the 2 types of active transport? How do they differ? Which one drives sugars (e.g., glucose) and amino acids against their concentration gradient? -There is primary and secondary active transport and secondary is driven by the concentration difference formed from primary transport; primary uses ATP directly and changes the shape of carrier proteins, secondary transport drives substances against their concentration gradient 18) Active transport processes may be countertransport or cotransport systems. What does this mean? -Counter is when the solutes are flowing in different directions of of the cell (in and out) whereas co is when they flow in the same (either in or out) 19) Under normal conditions, how do the relative concentrations of Na+ and K+ inside/outside of cells differ? Which ion leaks into the cell? Out of the cell? How? Na+ is higher outside the cell and potassium is more inside. The potassium leaks into the cell while sodium leaks out in a ratio of 2 in 3 out via the sodium potassium pump 20) Unchecked leakage of Na+ and K+ ions would eventually eliminate their concentration gradients as the ions reach equilibrium across the membrane. How is the ionic imbalance maintained by the cell? -Sodium Potassium pump 21) What’s the difference between exocytosis and endocytosis? -Endocytosis is used to bring things into the cell by ligands binding to ligand receptor and then evelops into a coated vesicle where as exocytosis is used to bring things out via a vesicle and the vesicle then attaches to the cell membrane and ejects waste and debris out of the cell

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