8. Which of the following molecules or ions would normally need to cell membrane
ID: 276019 • Letter: 8
Question
8. Which of the following molecules or ions would normally need to cell membrane? use a membrane protein to move through the a. O2 b. Na c. CO d. steroid hormones 9. Why are the head grou ps of the phospholipids found on the exterior and the cytoplasmic side of the membrane? a. b. c. They are non-polar. They are hydrophilic. They are hydrophobic. 10. What role does cholesterol play in the plasma membrane? a. It allows small molecules to pass through the membrane. b. It is necessary for active transport. c.It maintains optimal fluidity in the membrane. d. It is the major component of the lipid bilayer 11. What role does the glycocalyx play in the plasma membrane? a. b. c. signaling, lubrication, and cell adhesion assisting in the transport of molecules across the membrane maintaining membrane fluidity 12. In general, which of the following is largely responsible for moving substances across the plasma membrane, communicating with other cells, and identifying the celi? a. proteins c. cholesterol d. cytoskeleton 13. Why are ions UNABLE to move freely through the membrane? a. lons are charged, so they cannot diffuse through the hydrophobic core of the membrane b. lons are hydrophobic, so they cannot move through the hydrophobic core of the membrane. c. ions are non-polar, so they cannot move through the hydrophilic core of the membrane. d. lons are hydrophilic, so they cannot move through the hydrophilic core of the membrane. Chapter 5: Section 5.2 14. Why do we think of the plasma membrane as a semipermeable membrane? a. b. c. The plasma membrane does not allow any substances to cross it at all. The plasma membrane permits some substances to pass through and while others cannot The plasma membrane does not discriminate between substances that can pass through it. 15. In the process of diffusion, a. b. c. d. directed motion of the molecules causes them to migrate away from each other molecules move from an area of greater concentration to an area of lesser concentration molecules move from an area of lesser concentration to an area of greater concentration random motion of the molecules causes them to migrate toward each other 16. What is the fundamental property of molecules in solution that causes diffusion? a. random motion b. ionic charge c. hydrogen bonds d. attraction to areas of low concentrationExplanation / Answer
8. b
Na+ is a charged molecule. It cannot diffuse as such across the plasma membrane so it needs a membrane protein for movement.
9. b
The interior of the plasma membrane is hydrophobic due to fatty acids so the polar head groups are located in the exterior ant the cytoplasmic sides of the cell.
10. C
Cholesterol maintains the fluidity of the membrane by regulating phase transition temperature.
11. a
12. a
Proteins act as channels or transporters to transport materials across the cell membrane. They also help in cell adhesion like desmoglein, cadherins, etc.
13. a
Due to charge, the ions are not able to diffuse easily through membrane because of the hydrophobicity of the membrane.
14. b
The plasma membrane allows only selective molecules to pass through it.
15. b
Diffusion is a passive transport in which movement occurs from higher concentration to lower concentration.
16. a
Random motion in solution causes diffusion of molecules.
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