Membrane+and+Cellular+Respiration+HW1+MC

1. p. 31 Describe the structure of a phospholipid (insert an image). Indicate the parts that hydrophillic and the parts that are hydrophobic. They have a phosphate group. They are contructed like fats, except that in place of the third fatty acid, there is a phosphate group of a grouping that contains both phosphate and nitrogen. The phosphate and nitrogen containing groups are ionized. They form the polar head of the molecule, while the rest of the molecules becomes the hydrophobic tails. The picture indicates which parts are hydrophobic. 2. p. 31 How do phospholipids arrange themselves in water? The head is polar, while the tails are nonpolar which causes the molecules to arrange themselves like they are when exposed to water inside and outside the cell. 3. p. 46 Describe the fluid-mosaic model of a membrane. (insert an image) Which components are the fluid, and why? Which components are the mosaic, and why? The membrane is composed of a phospholipid bilayer in which proteins are embedded. The hydrophobic heads of the phospholipids are part of the outside surface of the membrane. The hydrophobic tails make up the interior of the membrane. The plasma membrane’s asymmetry –carbohydrate chains are attached to the outside surface, and cytoskeleton filaments are attached to the inside surface. At body temperature, the phospholipid bilayer is a liquid because it has the consistency of olive oil; and the proteins are able to change their position by moving laterally. The fluid-mosaic model says that the protein molecules form a shifting pattern within the fluid phospholipid bilayer. 4. p. 46 What is the function of the membrane? How does the structure of the membrane suit that structure? It keeps the cell intact and allows only certain molecules and ions to enter and exit the cytoplasm freely. Small molecules can pass through the membrane easily. The small size of water molecules allows them to freely cross the membrane by utilizing protein channels called aquaporins. 5. p. 46 Why is the membrane considered selectively permeable? Because it allows only certain molecules and ions to enter and exit the cytoplasm freely. 6. p. 46 What is diffusion? Give an example. Diffusion is the random movement of molecules from the area of higher concentration to the area of lower concentration, until they are equally distributed. An example is the aroma of chocolate chip cookies permeated the house and that wonderful smell greeted Calvin when he opened the front door. The smell filled the house because the cookies gave off a gaseous molecules that moved from the kitchen to all rooms of the house. When they were equally distributed, the molecules will still be moving randomly in all directions. 7. p. 46 What is osmosis? Osmosis is the diffusion of water across a plasma membrane. Osmosis involves water and a solute that cannot readily cross the plasma membrane. 8. p.46 How do isotonic, hyptonic, and hypertonic solutions differ and how does each affect cells? (insert an image). Intravenous solutions medically administrated are usually Isotonic. Normally, body fluids are isotonic to cells; the same concentration of non-diffusible solutes and water on both sides of the plasma membrane. Solutions that cause cells to swell or even to burst due to an intake of water are said to be hypotonic. If red blood cells are placed in a hypotonic solution, which has a lower concentration of solute and a higher concentration of water than do the cells, water enters the cells and they swell to bursting. Solutions that cause cells to shrink and shrivel due to a loss of water are said to be Hypertonic. If red blood cells are placed in a hypertonic solution, which has a higher concentration of solute and a lower concentration of water than do the cells, water leaves the cells and they shrink.

9. pp. 46-47 What is the difference between facilitated and active transport? During facilitated transport, a molecule is transported at a rate higher than usual across the plasma membrane from the side of higher concentration to the side of lower concentration. This is passive because the cell does not need to expend energy to move a substance down to its concentration gradient. During active transport, a molecule is moving contrary to the normal direction from lower to higher concentration. It requires a protein carrier and the use of cellular energy obtained from the breakdown of ATP. 10. pp. 46-47 What are the various ways substances can enter and exit cells? (diffusion, facilitated transport, active transport, endocytosis, exocytosis) Which are passive and which are active ways of crossing the cell? Various ways that substances can enter and exit cells is through diffusion, facilitated transport, and active transport. Diffusion and facilitated transport are both passive ways of crossing the cell. Active transport is obviously active ways of crossing the cell. 11. p. 47 What is the difference between exocytosis and phagocytosis? During exocytosis, a vesicle fuses with the plasma membrane as secretion occurs. Phagocytosis is a process by which amoeboid-type cells engulf large substances, forming an intracellular vacuole. 12. p. 54 What is the overall formula of cellular respiration? What are the reactants and what are the products? With E=enzymes, S=substrate, ES=enzyme-substrate complex, and P=product the overall formula is E+S→ES→E+P. 13. pp. 54-55 Which molecule captures the energy released from glucose? How many molecules are produced per glucose? The molecule that captures the energy released from glucose is ATP. 32 ATP molecules are produced per glucose. 14. p. 55 What is the role of oxygen in cellular respiration? It serves as the final acceptor of the electrons at the end of the chain. After Oxygen receives the electrons, it combines with hydrogens and becomes water. The sole purpose of oxygen is to receive electrons at the end of the electron transport chain. 15. p. 55 Where does carbon dioxide come from in cellular respiration? Yeast fermentation produces alcohol and carbon dioxide instead of lactate. When yeast is used to leaven bread, carbon dioxide production makes the bread rise. 16. p. 56 What is fermentation? How many ATP are produced per glucose molecule? Fermentation is an anaerobic process, meaning that it does not require oxygen. Only 2 ATP molecules are produced per glucose molecule. 17. p.56 What is the waste product of yeast fermentation? The waste product of yeast fermentation is alcohol and carbon dioxide instead of lactate.