Chapter 2 Composition of a Cell

What mole percent of cholesterol is found in the plasma membrane of E. coli and related bacteria? a. 0% b. 10% c. 18% d. 45%

a. 0%

The major bonds in glycogen are _______ glycosidic bonds. a. α(1→4) b. α(1→6) c. β(1→4) d. β(1→6)

a. α(1→4)

Proteins are polymers of how many different amino acids? a. 16 b. 20 c. 24 d. 64

b. 20

Which of the following is not a basic amino acid? a. Arginine b. Glutamine c. Histidine d. Lysine

b. Glutamine

Sugars can cyclize if they contain _______ or more carbons. a. four b. five c. six d. eight

b. five

How many common amino acids are there? a. 5 b. 10 c. 20 d. 25

c. 20

Transmembrane proteins can span the lipid bilayer as a. α-helices. b. β-barrels. c. Both a and b d. None of the above

c. Both a and b

In DNA, a. G pairs with T and A pairs with C. b. G pairs with A and C pairs with T. c. G pairs with C and A pairs with T. d. G pairs with C and U pairs with A.

c. G pairs with C and A pairs with T.

Which of the following is not a common analytical instrument approach in proteomics? a. Atomic absorption analysis of the metal content of plant tissues b. High-throughput microscope analysis of the distribution of GFP fusion proteins in cells c. Mass spectrometry d. Two-dimensional gel electrophoresis

c. Mass spectrometry

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

c. polypeptide chain

Sela, White, and Anfinsen's experiments on denatured ribonuclease showed that a. protein denaturation is irreversible. b. proteins can renature to regain their activity only with the assistance of specialized enzymes. c. proteins can renature and regain their enzymatic activity. d. proteins can fold in a new structure that lacks enzyme activity.

c. proteins can renature and regain their enzymatic activity.

Lipid bilayers are permeable only to molecules that are _______ and _______. a. large; uncharged b. large; charged c. small; uncharged d. small; charged

c. small; uncharged

Active transporter proteins can a. transport a molecule against its concentration gradient. b. use the energy of ATP hydrolysis to undergo a configurational change. c. transport H+ across a membrane against a pH gradient. d. All of the above

d. All of the above

Cholesterol affects the fluidity of membranes into which it inserts by a. increasing membrane fluidity at all temperatures. b. decreasing membrane fluidity at all temperatures. c. decreasing membrane fluidity at high temperatures and increasing membrane fluidity at low temperatures. d. increasing membrane fluidity at high temperatures and decreasing membrane fluidity at low temperatures.

d. increasing membrane fluidity at high temperatures and decreasing membrane fluidity at low temperatures.

The unique properties of different membranes are primarily a function of their a. glycolipids. b. phospholipids. c. cholesterol molecules. d. proteins.

d. proteins

The interaction of the α and β subunits to form the hemoglobin molecule is an example of _______ structure. a. primary b. secondary c. tertiary d. quaternary

d. quaternary

The most abundant molecules in cells are a. proteins. b. carbohydrates. c. minerals. d. water.

d. water.

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

a. Starch

Molecules that traverse a membrane against their concentration gradient do so by _______ transport. a. active b. passive c. carrier-mediated d. channel-mediated

a. active

Steroid hormones are derivatives of a. cholesterol. b. phospholipids. c. amino acids. d. sugars.

a. cholesterol.

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

a. cysteine

Integral membrane proteins are those that are a. directly associated with membrane lipids. b. associated with the membrane indirectly. c. never span the membrane bilayer. d. None of the above

a. directly associated with membrane lipids.

In the fluid mosaic model of biological membrane structure, transmembrane proteins are a. embedded nearly randomly in the lipid bilayer. b. nearly 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.

Complementary base pairs form _______ bonds to direct replication of DNA. a. hydrogen b. phosphodiester c. glycosidic d. peptide

a. hydrogen

Phospholipids in a membrane commonly a. move laterally in the plane of the bilayer. b. rotate within the bilayer. c. move from one bilayer to the other. d. Both a and b

a. move laterally in the plane of the bilayer.

In the primary structure of a protein, amino acids are joined together by _______ bonds. a. peptide b. phosphodiester c. glycosidic d. hydrophobic

a. peptide

Fatty acids are stored in fat droplets in the form of a. triacylglycerols. b. phospholipids. c. cholesterol. d. glycolipids.

a. triacylglycerols.

What is the effect of a β-barrel on the permeability of a membrane? a. It decreases permeability. b. It increases permeability. c. It has no effect. d. β-barrels are never found in membranes.

b. It increases permeability.

Which of the following store most energy per unit weight? a. Carbohydrates b. Lipids c. Proteins d. Nucleic acids

b. Lipids

The fluid mosaic model of cell membranes was proposed by a. Frye and Edidin. b. Singer and Nicolson. c. Gorter and Grendel. d. Avery and McLeod.

b. Singer and Nicolson.

What kind of molecules can readily cross the lipid bilayer? a. Small, charged b. Small, uncharged c. Large or small, uncharged d. Small, charged or uncharged

b. Small, uncharged

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

b. amphipathic.

Because water _______, it is ideal as the most abundant molecule in cells. a. has low heat of vaporization b. is a polar molecule that can form hydrogen bonds with itself and with other polar molecules c. dissolves nonpolar molecules d. expands when it freezes

b. is a polar molecule that can form hydrogen bonds with itself and with other polar molecules

Introducing a double bond into a fatty acid has the effect of putting a(n) _______ into the conformation of the molecule. a. amino acid bulge b. kink c. reverse spiral d. reinforcing rod

b. kink

A few sugars joined together are called a(n) a. glycoside. b. oligosaccharide. c. polysaccharide. d. starch

b. oligosaccharide.

Polymerization of nucleotides to form nucleic acids involves the formation of _______ bonds. a. peptide b. phosphodiester c. glycosidic d. hydrogen

b. phosphodiester

The most common molecules in cellular membranes are the a. glycolipids. b. phospholipids. c. cholesterol molecules. d. proteins.

b. phospholipids

Channels form pores through which molecules of appropriate size and charge can cross a membrane, whereas carrier proteins a. actively transport molecules. b. selectively bind the molecule to be transported, change configuration, and release it on the other side. c. require ATP. d. transport a molecule against its concentration gradient.

b. selectively bind the molecule to be transported, change configuration, and release it on the other side.

Sphingomyelin contains two hydrocarbon chains linked to _______ rather than to glycerol. a. choline b. serine c. glycine d. tyrosine

b. serine

Protein interaction networks may be characterized by all of the following approaches except a. gentle isolation followed by mass spectrometry. b. shotgun sequencing of random DNA clones. c. screening for protein interactions in vitro. d. the yeast two-hybrid method.

b. shotgun sequencing of random DNA clones.

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

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

c. Secondary

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

c. Water

The pyrimidine bases in DNA are a. adenine and guanine. b. adenine and cytosine. c. cytosine and thymidine. d. cytosine and guanine.

c. cytosine and thymidine.

Phospholipids consist of a 3-carbon core to which 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.

In polysaccharides, sugars are linked together with _______ bonds. a. phosphodiester b. peptide c. glycosidic d. hydrophobic

c. glycosidic

The role of double bonds in the fatty acid tails of membrane phospholipids is to a. help stabilize the membrane. b. react with adjacent double bonds. c. increase membrane fluidity. d. interact with membrane proteins.

c. increase membrane fluidity.

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

c. increase the fluidity of membranes.

Transmembrane proteins that span the membrane are a. peripheral membrane proteins. b. covalently linked to membrane lipids. c. integral membrane proteins. d. ion transporters.

c. integral membrane proteins.

The principal components of cell membranes are a. carbohydrates. b. nucleic acids. c. lipids. d. proteins.

c. lipids.

An amphipathic molecule is a. water-soluble. b. water-insoluble. c. part water-soluble and part water-insoluble. d. hydrophilic.

c. part water-soluble and part water-insoluble.

Serine, threonine, asparagine, and glutamine are all _______ amino acids. a. basic b. acidic c. polar d. nonpolar

c. polar

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.

Nucleotides have important function in cells as a. building blocks for nucleic acids. b. carriers of chemical energy. c. intracellular signal molecules. d All of the above

d All of the above

Fluidity of a membrane depends on the a. length of the phospholipid fatty acid chains. b. temperature. c. number of double bonds in the fatty acid chains. d. All of the above

d. All of the above

In the most complete sense, "proteomics" refers to the large-scale analysis of a. cell proteins. b. protein localization c. large-scale construction of protein interaction networks. d. All of the above

d. All of the above

Lipids play a major role in cells as a. a form of energy storage. b. components of cell membranes. c. part of the cell signaling function. d. All of the above

d. All of the above

Membrane proteins can be anchored to the cytosolic face of the plasma membrane by a. prenyl groups. b. sugar groups of glycolipids. c. sugar groups of glycoproteins. d. All of the above

d. All of the above

Which of the following is involved in forming the tertiary structure of proteins? a. H bonds b. Hydrophobic interactions c. Ionic bonds d. All of the above

d. All of the above

RNA in cells can serve as a a. storage form of genetic information in nuclei. b. carrier of information from the nucleus to the cytoplasm. c. catalyst or enzyme. d. Both b and c

d. Both b and c

DNA differs from RNA in every way but which of the following? a. DNA contains deoxyribose sugars. b. DNA is usually a double-stranded molecule. c. DNA contains thymine as one of its bases. d. DNA can form hydrogen bonds with complementary sequences.

d. DNA can form hydrogen bonds with complementary sequences.

The scientist who first determined the complete amino acid sequence of a protein (insulin) was a. Christian Anfinsen. b. John Kendrew. c. Linus Pauling. d. Frederick Sanger.

d. Frederick Sanger.

Transport across biological membranes is speeded by what class of biological molecules? 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

The currently accepted model of membrane structure is called the _______ model. a. lipid bilayer b. unit membrane c. lipoprotein d. fluid mosaic

d. fluid mosaic

Which of the following bases is not found in DNA? a. Adenine b. Cytosine c. Guanine d. Thymine e. Uracil

e. Uracil