Cell+Membrane+AG

Allie Gruber Human Bio Field Period 1 September 15, 2008

(1) p. 31 Describe the structure of a phospholipids. Indicate the parts that are hydrophilic and the parts that are hydrophobic. Phospholipids are structured like fats, but one fatty acid is replaced by a polar phosphate group. Therefore, the head is polar while the tails are nonpolar.

(2) p. 31 How do phospholipids arrange themselves in water? Phosholipids are the primary componets of celluar membrans; they spontaneously forma bilayer in which the hydrophilic heads face outward toward watery solutions and the tails form the hydrophobic interior.

(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 fluid-mosaic model, a working description of membrane structure, shows that protein molecules form a shifting pattern within the fluid phospholipids bilayer. The hydrophilic heads of phospholipids are a part of the outside surface and the inside surface of the membrane. At body temperature, the phospholipid bilayer is a liquid and the proteins are able to change their position by moving.

(4) p. 46 What is the function of the membrane? How does the structure of the membrane suit that structure? The plasma membrane marks the boundary between the outside and the inside of the cell. The plasma membrane keeps a cell intact. It allows only certain molecules and ions to enter and exit the cytoplasm freely. Its structure is said to be “selectively permeable that only lets the specifically sized molecules in and out.

(5) p. 46 Why is the membrane considered selectively permeable? Macromolecules and charged molecules are substances that cannot diffuse across the plasma membrane. H20 and non-charged molecules are substances that can diffuse across the plasma membrane.

(6) p. 46 What is diffusion? Give an example. Diffusion is the random movement of moleucules from the area of higher concentration to the area of lower concentration until they are equally distributed. Baking things such as cookies is an example of the diffusion that is given off when the gaseous molecules move from where they were concentrated to all the rooms in the house.

(7) p. 46 What is osmosis? Osmosis is the diffusion of water across a plasma membrane.

(8) p.46 How do isotonic, hyptonic, and hypertonic solutions differ and how does each affect cells? (insert an image) In an isotonic solution, there is the same amount of solute concentration as in the cell where the cell remains the same. Hypotonic solutions have lower solute concentration than in a cell, the cells gain water and may burst. In a hypertonic solution there is a higher solute concentration than in the cell and cells lose water and shrink.

(9) pp. 46-47 What is the difference between passive and active transport? Passive transport is when 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 means the cell does not need to expend energy to move a substance down its concentration gradient. In active transport, a molecules is moving conrarty to the normal direction (from lower to higher concentration). Active transport 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? Substances can enter and exit cells through diffusion; the movement of molecules from a higher to lower concentration, facilitated transport; a passive transportation where molecules are transported at a rate from lower to higher concentration, endocytosis; an active transportation where a portion of the plasma membrane forms a pouch to envelop a substance fluid, exocytosis; a passive act of transport where a vesicle fuses with the plasma membrane as secretion occurs.

(11) p. 47 What is the difference between exocytosis and phagocytosis? Phagocytosis is the special name given to endocytosis which is when white blood cells are able to take up pathogens, where as exocytosis is the process of vesicles fusing with the plasma membrane during secretion.

(12) p. 54 What is the overall formula of cellular respiration? What are the reactants and what are the products? Cellular respiration is 6C6H12 + O2 → 6CO2 + 6H2O. This formula is the process in which glucose and oxygen breaks down the carbon dioxide waste and the water waste and allows the body to dispose of those wastes in the lungs and kidneys.

(13) pp. 54-55 Which molecule captures the energy released from glucose? How many molecules are produced per glucose? ATP is a triphosphate molecule that captures the energy between glucose breakdowns in cellular respiration and produces 32 molecules per glucose.

(14) p. 55 What is the role of oxygen in cellular respiration? Oxygen is electronegative during cellular respiration and is essential to the energy and breakdown process. Its purpose is to receive the electrons at the end of the electron transport chain.

(15) p. 55 Where does carbon dioxide come from in cellular respiration? The carbon dioxide in our bodies comes from the glucose in our system.

(16) p. 56 What is fermentation? How many ATP are produced per glucose molecule? Fermentation is an anaerobic process (doesn’t require oxygen). When oxygen is not present, cells have a safety valve so that some ATP can still be produced. In this case only 2 ATP molecules are produced per glucose molecule.

(17) p.56 What is the waste product of yeast fermentation? Yeast fermentation produces alcohol and carbon dioxide instead of lactate and produces the waste product in carbon dioxide wastes in the lungs.