Cell membrane structure and function

1. The structure of the plasma membrane is best described as
a. a single layer of phospholipids, in which the phosphate groups face the interior of the cell
b. a single layer of phospholipids, in which the phosphate groups face the extracellular space
c. lipid bilayer, in which the phosphate groups on the phospholipids face the interior of the bilayer
d. a lipid bilayer, in which the phosphate groups on the phospholipids face the exterior of the bilayers

2. The role of cholesterol in cellular membranes is to
a. help keep the membrane fluid
b. transport ions across the membrane
c. transport proteins across the membrane
d. regulate the shape of the cell

3. Which of the following is true concerning active transport?
a. The cell uses energy to move substances against a concentration gradient.
b. Membrane proteins can move more than one molecule or ion across the membrane at a time.
c. The cell can move larger proteins across a membrane than can be moved by facilitated diffusion.
d. It allows cells to select what molecules cross into the cell.
e. All of the above are correct.

4. The difference between facilitated diffusion and passive transport is that facilitated diffusion
a. requires energy from a source such as the hydrolysis of ATP
b. can only occur in one direction across a membrane from the extracellular to the cytoplasmic surface
c. can only move molecules from areas of high to lower concentration
d. requires the participation of a carrier protein in the movement of the substance across the membrane

5. The function of mitochondria is to
a. synthesize hormones for secretion from the cell
b. modify and repackage newly synthesized lipids and proteins
c. extract energy from sugar molecules and store it in the high-energy bonds of ATP
d. serve as a recycling and digestive center for the cell
e. use solar energy to generate high energy bonds in sugar molecules

6. Which of the following is NOT a general characteristic of a prokaryotic cell?
a. They contain multiple molecules of DNA.
b. They are enclosed by a cell wall.
c. Their enzymes are not organized into organelles.
d. Their nuclear material is found in a nucleoid.
e. They contain ribosomes.

7. The cell theory states that __________.
a. single cells can assemble into multicellular organisms
b. cells synthesize their own proteins on cytoplasmic ribosomes
c. all cells are either prokaryotes or eukaryotes
d. all living things are composed of cells
e. all cells contain genetic material in the form of DNA

8. Which of the following structures are NOT common to all eukaryotic cells?
a. cell wall
b. plasma membrane
c. nucleus
d. cytoplasm
e. ribosomes