Genetics and Molecular Biology - Chapter 2

Proteins are polymers of how many different amino acids? 36 16 24 20

20

The mitochondrial inner membrane is about _______ protein. 10% 0% 42% 75%

75%

Fully folded proteins typically have polar side chains on their surfaces, where electrostatic attractions and hydrogen bonds can form between the polar group on the amino acid and the polar molecules in the solvent. In contrast, some proteins have a polar side chain in their hydrophobic interior. Which of the following would not occur to help accommodate an internal, polar side chain? Hydrogen bonds form between polar side chains and a buried water molecule. A hydrogen bond forms between a polar side chain and an aromatic side chain. A hydrogen bond forms between a polar side chain and the protein backbone. A hydrogen bond forms between two polar side chains.

A hydrogen bond forms between a polar side chain and an aromatic side chain.

Common factors affecting membrane fluidity include temperature. All of the above number of double bonds in the fatty acid chains. length of phospholipid fatty acid chains.

All of the above

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

All of the above

RNA in cells can serve as a regulator of gene expression. All of the above catalyst or enzyme. carrier of information from the nucleus to the cytoplasm.

All of the above

Which of the following are involved in forming the tertiary structure of proteins? Ionic bonds Hydrophobic interactions All of the above H bonds

All of the above

Proteins can be covalently modified by the addition of phosphate groups to all but which of the following amino acids? Serine Arginine Threonine All of the above

Arginine

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

Both a and b

Like other catalysts, enzymes shift the chemical equilibrium from more reactants to more products. do not alter the chemical equilibrium between reactants and products. Both a and c increase the rate of reactions without being consumed in reactions.

Both a and c

shift the chemical equilibrium from more reactants to more products. Both a and c do not alter the chemical equilibrium between reactants and products. increase the rate of reactions without being consumed in reactions.

Both a and c

Which of the following is not a way in which DNA differs from RNA? DNA contains deoxyribose sugars. DNA is usually a double-stranded molecule. DNA contains thymine as one of its bases. DNA can form hydrogen bonds with complementary sequences.

DNA can form hydrogen bonds with complementary sequences.

Approximately 50% of the chemical reactions in cells are catalyzed by enzymes. False True

False

Each membrane phospholipid contains 3 fatty acid chains. False True

False

Each membrane phospholipid contains 3 fatty acid chains. True False

False

Enzymes accelerate reactions and affect the end equilibrium concentration of reactants and products. False True

False

Most proteins interact with other proteins through covalent protein-protein interactions. False True

False

Most proteins interact with other proteins through covalent protein-protein interactions. True False

False

One conclusion derived from the Singer and Nicolson fluid mosaic model of membrane structure is that integral membrane proteins are freely soluble in water. False True

False

The function of glycogen, starch, and cellulose is to store glucose. True False

False

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

Frederick Sanger

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

Frederick Sanger.

In DNA, G pairs with A and C pairs with T. G pairs with C and U pairs with A. G pairs with T and A pairs with C. G pairs with C and A pairs with T.

G pairs with C and A pairs with T.

Which of the following is not a basic amino acid? Arginine All of the above are basic amino acids. Histidine Glutamine

Glutamine

Which of the following molecules stores the most chemical energy per unit of weight? Carbohydrates Nucleic acids Proteins Lipids

Lipids

The trypsin substrate binding site contains an aspartate residue, which is able to form an ionic bond with which amino acids in its polypeptide substrates? Lysine or arginine Glutamate or glutamine Leucine or phenylalanine Serine or threonine

Lysine or arginine

The fluid mosaic model of cell membranes was proposed by Singer and Nicolson. Watson and Crick. Gorter and Grendel. Frye and Edidin.

Singer and Nicolson.

Which statement describes the most common relationship of the inhibitor molecule to the allosteric enzyme in feedback inhibition of enzyme activity? The inhibitor is the final product of the metabolic pathway. The inhibitor is a metabolically unrelated signal molecule. The inhibitor is the product of the enzyme-catalyzed reaction. The inhibitor is the substrate of the enzyme.

The inhibitor is the final product of the metabolic pathway.

Cholesterol is an amphipathic molecule. True False

True

Christian Anfinsen and colleagues showed in the 1950s that proteins contain all the information to spontaneous fold into an active enzyme. Yet sixty years later, we can still not predict the three-dimension shape of a protein from its amino acid sequence. True False

True

Coenzymes function in conjunction with enzymes to carry chemical groups between substrates. False True

True

RNAs can be enzymes. True False

True

Some enzymes participate directly in the chemical reactions they catalyze. True False

True

Sphingomyelin is a serine-based phospholipid. True False

True

The activity of enzymes can be controlled by the binding of small molecules, by interaction with other proteins, and by covalent modifications. True False

True

The glucose molecules in cellulose are joined by β(1→4) bonds. True False

True

The sugar groups of glycolipids and glycoproteins are found on the outer surface of the plasma membrane. False True

True

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

active

Passive transport molecules can transport against a concentration gradient. are peripheral proteins. use the energy of ATP to transport molecules. allow small molecules across membranes.

allow small molecules across membranes.

A reaction in which the substrate glucose binds to the enzyme hexokinase and the configuration of both molecules changes is an example of allosteric inhibition. competitive inhibition. an induced fit mechanism. a lock-and-key mechanism.

an induced fit mechanism.

Steroid hormones are derivatives of cholesterol. phospholipids. amino acids. sugars.

cholesterol.

The pyrimidine bases in DNA are cytosine and guanine. adenine and cytosine. cytosine and thymine. adenine and guanine.

cytosine and thymine.

Enzymes act by increasing activation energy. lowering the overall free energy change of a reaction. decreasing activation energy. decreasing the distance reactants must diffuse to find each other.

decreasing activation energy.

Cholesterol affects membrane fluidity by increasing membrane fluidity at all temperatures. decreasing membrane fluidity at high temperatures and increasing membrane fluidity at low temperatures. decreasing membrane fluidity at all temperatures. increasing membrane fluidity at high temperatures and decreasing membrane fluidity at low temperatures.

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

Nucleotides function in cells as all of the following except intracellular signal molecules. building blocks of nucleic acids. carriers of chemical energy. defenders against infection.

defenders against infection.

Integral membrane proteins are those that do not span the lipid bilayer. directly associate with membrane lipids. None of the above associate with the membrane indirectly.

directly associate with membrane lipids.

The main difference between double-stranded DNA (dsDNA) and single-stranded DNA (ssDNA) is that dsDNA has strands oriented in an antiparallel fashion, while ssDNA does not. dsDNA has bases that include thymine (T), while ssDNA has bases including uracil (U). dsDNA has 5' to 3' polarity while ssDNA does not. dsDNA cannot undergo translation while ssDNA can leave the nucleus to undergo translation.

dsDNA has bases that include thymine (T), while ssDNA has bases including uracil (U). dsDNA cannot undergo translation while ssDNA can leave the nucleus to undergo translation.

Sugars can cyclize if they contain _______ or more carbons. four six five seven

five

The currently accepted model of membrane structure is called the _______ model. lipid raft fluid mosaic unit membrane lipid bilayer

fluid mosaic

In polysaccharides, sugars are linked together by means of _______ bonds.

glycosidic

Complementary base pairs form _______ bonds to direct replication of DNA. hydrogen glycosidic covalent phosphodiester

hydrogen

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

increase membrane fluidity.

Transmembrane proteins that span the membrane are integral membrane proteins. peripheral membrane proteins. active transporters. covalently linked to membrane lipids.

integral membrane proteins.

Transmembrane proteins that span the membrane are peripheral membrane proteins. active transporters. covalently linked to membrane lipids. integral membrane proteins.

integral membrane proteins.

Water is an ideal solvent in cells because it has low heat of vaporization. dissolves nonpolar molecules. is a polar molecule that can form hydrogen bonds with itself and with other polar molecules. contracts when it freezes.

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

In allosteric regulation, binding of a small regulatory molecule to an enzyme _______ enzyme activity. may stimulate or inhibit neither stimulates nor inhibits inhibits stimulates

may stimulate or inhibit

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

oligosaccharide.

An amphipathic molecule is water-insoluble. hydrophilic. water-soluble. part water-soluble and part water-insoluble.

part water-soluble and part water-insoluble.

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

peptide

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

phosphodiester

Cell membranes are composed principally of phospholipids. nucleic acids. carbohydrates. proteins.

phospholipids.

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

polar

Membrane proteins can be anchored to the cytosolic face of the plasma membrane by None of the above prenyl groups. sugar groups of glycolipids. sugar groups of glycoproteins.

prenyl groups.

The unique functions of different membranes are primarily due to their glycolipids. cholesterol molecules. proteins. phospholipids.

proteins.

The interaction of two α and two β subunits to form a functional hemoglobin molecule is an example of _______ structure. tertiary secondary quaternary primary

quaternary

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

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

Because of the central role that one amino acid plays in the mechanism by which proteins are cleaved by the enzymes trypsin and chymotrypsin, these enzymes are called _______ proteases. histidine arginine serine lysine

serine

Sphingomyelin contains two hydrocarbon chains linked to glycerol. serine. choline. glycine.

serine.

A researcher is trying to determine the contents of a viral genome. Upon chemical analysis, the nucleic acid is found to contain 27% cytosine, 27% adenine, 23% uracil, and 23% guanine. Based on this data, the viral genome most likely consists of single-stranded RNA. single-stranded DNA. double-stranded RNA. double-stranded DNA.

single-stranded RNA.

Coenzymes are enzymes in the same pathway. proteins that form dimeric enzymes. small molecules that allosterically regulate enzymes. small molecules that work with an enzyme to enhance reaction rate.

small molecules that work with an enzyme to enhance reaction rate.

Phospholipid bilayers are permeable only to molecules that are _______ and _______. small; uncharged large; charged small; charged large; uncharged

small;uncharged

Anfinsen's experiments on denatured ribonuclease showed that proteins can renature to regain their activity only with the assistance of specialized enzymes. the conformation of the folded protein is determined by its amino acid sequence. protein denaturation is irreversible. proteins have unique amino acid sequences.

the conformation of the folded protein is determined by its amino acid sequence.

The fundamental building block of cellular membranes is cholesterol. protein. the phospholipid. the glycolipid.

the phospholipid

Fatty acids are stored in fat droplets in the form of cholesterol. triacylglycerols. glycolipids. phospholipids.

triacylglycerols.

The most abundant molecules in cells are water. carbohydrates. proteins. lipids.

water.

Transmembrane proteins can span the lipid bilayer as β turns. unstructured chains. Both a and c α helices.

α helices.

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

α(1→4)