The Cell: A Molecular Approach Chapters 2 Quiz Questions

Lipids with unsaturated fatty acids a. decrease fluidity of membranes. b. increase the charge associated with the inner face of a membrane. c. increase fluidity of membranes. d. are present only on the inner side of the plasma membrane.

c. increase fluidity of membranes

Proteins must have more than one _______ to have a quaternary structure. a. helix b. sheet c. polypeptide chain d. transmembrane segment

c. polypeptide chain

The (alpha) helix is an example of which level of protein structure? a. Primary b. Quaternary c. Secondary d. Tertiary

c. secondary

About 50% of the mass of most biological membranes consists of lipids and about 50% consists of proteins. Therefore, a. the membranes contain fewer molecules of lipid than of protein. b. the membranes contain equal numbers of lipid and protein molecules. c. the membranes contain more molecules of lipid than of protein. d. only a few membrane proteins are exposed at the cell surface.

c. the membranes contain more molecules of lipid than of protein

Passive transport across a membrane refers to a. transport into the interior of a cell. b. transport out of a cell. c. transport in the energetically favorable direction. d. simple diffusion across membranes, without the help of proteins such as channels or carriers.

c. transport in the energetically favorable direction.

Chymotrypsin, trypsin, elastase, and thrombin are all members of the serine protease family because each a. has similar charge and shape properties in its substrate insertion pockets. b. can form a heptahedral complex with its substrate. c. uses the same catalytic mechanism involving the same key amino acids. d. can be modified by the cell-wall degrading enzyme chitinase.

c. uses the same catalytic mechanism involving the same key amino acids

Which of the following is not one of the four major classes of organic molecules in the cell? a. Carbohydrates b. Lipids c. Water d. Proteins

c. water

Enzymes affect the transition state of a chemical reaction by a. binding to substrate(s). b. providing a surface on which reactions converting substrate to product can occur more rapidly. c. altering the conformation of substrate(s) to approach that of the transition state. d. All of the above

d. All of the above

Which class of molecule accelerates transport across biological membranes? a. Carbohydrates b. Lipids c. Nucleic acids d. Proteins

d. Proteins

The three-dimensional structure of a protein is analyzed most definitively by a. electron microscopy. b. light microscopy. c. subcellular fractionation. d. X-ray crystallography.

d. X-ray crystallography

While small, uncharged molecules can diffuse through the hydrophobic core of a phospholipid bilayer, larger polar molecules such as glucose must enter cells by binding to a. a nonphospholipid such as cholesterol. b. the carbohydrate portion of glycolipids. c. peripheral membrane proteins located on the inner side of the membrane. d. carrier proteins that facilitate the passage of specific molecules across membranes.

d. carrier proteins that facilitate the passage of specific molecules across membranes

Enzymes act by a. lowering the overall change in free energy of a reaction. b. decreasing the distance that reactants must diffuse to find one another. c. increasing activation energy. d. decreasing activation energy.

d. decreasing activation energy

Coenzymes are chemically related to a. amino acids. b. inorganic phosphate. c. glucose. d. vitamins.

d. vitamins

The most abundant molecule in cells is a. aspartic acid. b. DNA. c. sucrose. d. water.

d. water

Which of the following is not true of coenzymes? a. They are branched amino acids. b. They serve as carriers of chemical groups. c. They transfer specific chemical groups among a wide range of substrates. d. They work together with enzymes to enhance chemical reactions without being irreversibly altered.

a. They are branched amino acids.

A disulfide bond is formed between _______ residues. a. cysteine b. glycine c. methionine d. tyrosine

a. cysteine

In the fluid mosaic model of biological membrane structure, transmembrane proteins are a. embedded nearly randomly in the lipid bilayer. b. almost completely surrounded by membrane lipid. c. segregated into large protein clusters or rafts. d. weakly held in place on the surface of the lipid bilayer.

a. embedded nearly randomly in the lipid bilayer

Cholesterol, a membrane lipid in animals, has a chemical structure similar to a. estradiol. b. phosphatidylinositol. c. thymine. d. triacylglycerol.

a. estradiol

What is the major carbohydrate-storage molecule in plants? a. Starch b. Cellulose c. Glycogen d. Deoxyribonucleic acid

a. starch

Molecules that are partly water-soluble and partly water-insoluble are a. hydrophilic. b. amphipathic. c. hydrophobic. d. allosteric.

b. amphipathic

What is the effect of a barrel on the permeability of a membrane? a. It decreases permeability. b. It increases permeability. c. It has no effect. d. barrels are peripheral membrane proteins.

b. it increases permeability

Introducing a double bond into a fatty acid puts a(n) _______ into the conformation of the molecule. a. amino acid bulge b. kink c. reverse spiral d. branch

b. kink

The coenzymes NAD+ and NADP+ are structurally related to the vitamin a. riboflavin (B2). b. niacin. c. pantothenate. d. pyridoxal (B6).

b. niacin

How many amino acids are commonly incorporated into proteins? a. 5 b. 10 c. 20 d. 25

c. 20

Which of the following classes of amino acids is buried within the folded structure of the protein? a. Acidic b. Basic c. Nonpolar d. Polar

c. Nonpolar

All of the following are ways in which enzyme activity can be regulated except a. by binding to an allosteric site. b. through feedback inhibition. c. by modulation of intracellular sucrose concentrations. d. through phosphorylation.

c. by modulation of intracellular sucrose concentrations.

Phospholipids consist of a 3-carbon core to which two fatty acids and a phosphate group are linked. The most common 3-carbon core is a. dihydroxyacetone. b. glyceraldehyde. c. glycerol. d. serine.

c. glycerol