21) You have isolated a cell that unable to produce : 1380732.
21) You have isolated a cell that is unable to produce cholesterol for its cell membranes. Which of the following defects is this cell most likely to have?
A) The cell membrane will not have the correct fluidity.
B) The cell will not be able to communicate with other cells.
C) The cell will be unable to transport nutrients.
D) The cell will burst as a result of osmosis.
E) The cell will not be able to regulate the transportation of substances into and out of the cell.
22) If you transferred a phospholipid bilayer from water to oil, what effect would this have on the membrane?
A) The membrane would become very rigid.
B) The membrane would form four layers instead of its normal two.
C) The membrane would be unaffected by the oil.
D) The membrane would invert its normal structure by positioning the heads on the inside of the bilayer and the fatty-acid tails outside.
E) The phospholipid bilayer would split into two separate layers, which each would be maintained in the oil.
23) Peripheral proteins:
A) usually span the entire membrane.
B) have no known functions in membranes.
C) act as channels through which materials can pass.
D) are defective in cystic fibrosis.
E) usually attach to integral proteins.
24) If you could add a colored label to one phospholipid in the cell’s plasma membrane to observe this molecule, what kind of movement of the molecule would you see?
A) The molecule would move rapidly back and forth across the surface of the membrane.
B) The molecule would be locked in place by its tightly packed neighbors in the plasma membrane.
C) The molecule would be converted back and forth between a receptor protein and a phospholipid.
D) The molecule would move back and forth between the membrane and the surrounding watery solution.
E) The molecule would flip back and forth from one layer of the membrane to the other.
25) The plasma membrane is a semipermeable membrane. This means that it is:
A) permeable to small molecules except water.
B) permeable to small and uncharged molecules but not to larger or charged substances.
C) only permeable to cholesterol.
D) permeable to large charged molecules but not to small uncharged molecules.
26) Diffusing molecules move ________ until they are ________.
A) down their concentration gradients; evenly distributed
B) up their concentration gradients; evenly distributed
C) through channels of active transport proteins; evenly distributed
D) up their concentration gradients; unevenly distributed
E) down their concentration gradients; unevenly distributed
27) Red blood cells placed in pure water will swell and burst. What process is causing this to happen?
A) Water is diffusing across the plasma membrane from a region of high (outside the cell) to low (inside the cell) “free” water concentration.
B) Water is being pulled into the cell by the cell’s solutes.
C) Water is diffusing across the plasma membrane from a region of low (outside the cell) to high (inside the cell) “free” water concentration.
D) Solutes are being drawn into the cell across the plasma membrane.
E) Ions are diffusing across the plasma membrane and destabilizing the phospholipids.
28) The central vacuoles of some plant cells you are studying fill with water and press the cell contents against their cell walls because of osmosis. What can you predict about the concentration of solutes in the solution that bathes the turgid plant cells?
A) The concentration of solutes outside the cell must be significantly lower than the concentration within the cell.
B) The concentration of solutes outside the cell must be significantly higher than the concentration within the cell.
C) There must be no solutes either outside or inside the cell.
D) The concentration of solutes outside the cell must be about the same as that of seawater.
E) The concentration of solutes outside the cell can’t be predicted, because it’s the concentration inside the cell that’s important.
29) It seems that bacteria and molds should grow well in jam. It’s extremely high in sugar, a substance many cells can use for energy, and contains enough other nutrients to support cell growth. Yet jam can be left unrefrigerated for a very long time without contamination by microorganisms. How can this be?
A) Bacteria and molds cannot grow on fruit products.
B) The high sugar concentration causes bacterial and mold cells to swell and rupture.
C) The high sugar concentration damages cell membranes.
D) Bacteria and molds cannot get into the jam because its high concentration of sugar makes it so sticky.
E) The high sugar concentration causes bacterial and mold cells to shrink and die.
30) Oxygen moving through the plasma membrane down its concentration gradient is an example of:
A) simple diffusion.
B) active transport.
C) facilitated diffusion.