Chapter 03 - The Macromolecules of the Cell

Based on the principle of complementary base pairing, you would expect the percentage of __________ to be equal to the percentage of __________. T; G T; C A; T A; C

A; T

Many cell biologists claim that monosaccharides are older (chronologically and evolutionarily) than nucleotides. Which of the following observations supports this hypothesis? All nucleotides contain monosaccharides. Monosaccharides are metabolized by cells to make nucleotides (i.e., glucose is metabolized by the enzymes of glycolysis to make ATP). Nucleotides have more chemically complicated structures than monosaccharides. All of the other answer choices support this hypothesis.

All of the other answer choices support this hypothesis

The primary structure of a protein is the linear sequence of amino acids that are linked together by peptide bonds. is important both genetically and structurally. is important for determining the secondary and tertiary structure of a protein. is simply the order of amino acids from one end of the protein to another. All of these statements are true.

All of these statements are true.

Trans fats are unsaturated fatty acids. resemble saturated fatty acids in shape. are associated with an increased risk of heart disease. are present in small amounts in meat and dairy products. All of these statements are true.

All of these statements are true.

Which of the following is true of purines? Purines have a double-ringed structure. Purines bind readily to deoxyribose but not to ribose. Cytosine is a purine. Both adenine and thymine are purines. Adenine's bonding to thymine is stronger than is guanine's to cytosine.

Purines have a double-ringed structure.

The chemical nature of each amino acid is determined by which of the following groups? amino hydrogen R carboxyl hydroxyl

R

Which of the following statements is the most accurate reflection of native protein tertiary structure? Protein tertiary structure is present only to allow for the formation of multiple functional domains. The protein tertiary structure results from all amino acids in a protein adopting secondary structure. Protein tertiary structure is present only to allow for the formation of protein quaternary structure. Tertiary structure is the overall three-dimensional shape of a protein. It is determined by hydrogen bonds, interactions between hydrophobic R groups, ionic bonds between R groups, van der Waals interactions, and disulfide bridges.

Tertiary structure is the overall three-dimensional shape of a protein. It is determined by hydrogen bonds, interactions between hydrophobic R groups, ionic bonds between R groups, van der Waals interactions, and disulfide bridges.

Cellulose, chitin, and the polysaccharide that makes up the cell walls of many bacteria are the structural polysaccharides, whereas starch and glycogen are the main storage polysaccharides. What must be true about these two classes of polysaccharides? The beta-glycosidic bonds of storage polysaccharides are more stable than the alpha-glycosidic bonds of structural polysaccharides. In addition, chemical stability correlates with permanence or nonreactivity. Which of the two types of polysaccharides would be expected to remain the same for longer? The beta-glycosidic bonds of storage polysaccharides are less stable than the alpha-glycosidic bonds of structural polysaccharides. The alpha-glycosidic bonds of storage polysaccharides are less stable than the beta-glycosidic bonds of structural polysaccharides. The alpha-glycosidic bonds of storage polysaccharides are more stable than the beta-glycosidic bonds of structural polysaccharides.

The alpha-glycosidic bonds of storage polysaccharides are less stable than the beta-glycosidic bonds of structural polysaccharides.

Sickle-cell anemia is a striking example of the drastic effect a single amino acid substitution can have on the structure and function of a protein. Given the chemical nature of glutamate and valine, can you suggest why substitution of valine for glutamate at position 6 of the β chain would be especially deleterious? The amino acid glutamate is hydrophobic and ionizes at cellular pH, whereas valine is hydrophilic and nonionic. The amino acid glutamate is hydrophobic and nonionic, whereas valine is hydrophilic and ionizes at cellular pH. The amino acid glutamate is hydrophilic and nonionic, whereas valine is hydrophobic and ionizes at cellular pH. The amino acid glutamate is hydrophilic and ionizes at cellular pH, whereas valine is hydrophobic and nonionic.

The amino acid glutamate is hydrophilic and ionizes at cellular pH, whereas valine is hydrophobic and nonionic.

The term amphipathic describes the characteristic of some molecules that have ________. two nonpolar regions both a polar and a nonpolar region no polar regions two polar regions only a single polar region

both a polar and a nonpolar region

Cellulose belongs to which of the following groups of macromolecules? proteins nucleic acids lipids carbohydrates none of these

carbohydrates

Which of the following is not a major functional class of proteins? enzymes hereditary proteins motility proteins structural proteins regulatory proteins

hereditary proteins

To which of the following classes of sugars does glucose belong? heptose tetrose triose pentose hexose

hexose

The secondary structure of a protein results from _____. hydrophobic interactions hydrogen bonds peptide bonds bonds between sulfur atoms ionic bonds

hydrogen bonds

The two strands of DNA are held together by ________; thus ________. hydrogen bonds; double-stranded DNA separates into two separate strands at high temperatures antiparallel bonds; double-stranded DNA is amphipathic covalent bonds; double-stranded DNA is very stable at a range of temperatures ionic bonds; double-stranded DNA separates into two separate strands in water hydrophobic interactions; double-stranded DNA separates into two separate strands when dissolved in a hydrocarbon (hydrophobic) solvent

hydrogen bonds; double-stranded DNA separates into two separate strands at high temperatures

Several different kinds of bonds or interactions are involved in generating and maintaining the structure of proteins. List five such bonds or interactions. Select the five correct answers. hydrophobic bond glycosidic bond metallic bond disulfide bond peptide bond coordination bond hydrogen bond ionic bond phosphodiester bond

hydrophobic bond disulfide bond peptide bond hydrogen bond ionic bond

Which of the following contributes to the stability of the DNA double helix? hydrophobic interactions between aromatic bases at the center of the double helix ionic bonds between the negatively charged phosphate groups and the positively charged pyrimidine bases. covalent bonding between complementary purine and pyrimidine bases. hydrophobic interactions between aromatic bases at the center of the double helix and ionic bonds between the negatively charged phosphate groups and the positively charged pyrimidine bases hydrogen bonding between the phosphate and sugar groups in the backbone of the double helix

hydrophobic interactions between aromatic bases at the center of the double helix

What are the three general types of amino acids? acidic, basic, and neutral hydrophobic, polar (noncharged), polar (charged) covalent, noncovalent, and van der Waals forces α helices, β sheets, and looped segments positive, negative, and noncharged

hydrophobic, polar (noncharged), polar (charged)

RNA and DNA differ in that RNA contains ribose and DNA contains deoxyribose. in that RNA contains nucleosides and DNA contains nucleotides. in that RNA contains uracil and DNA contains thymine. in that RNA contains ribose and uracil, and DNA contains deoxyribose and thymine. All of these are correct.

in that RNA contains ribose and uracil, and DNA contains deoxyribose and thymine.

A peptide bond is a covalent bond between the NH group of one polypeptide and the CO group of an adjacent polypeptide that holds together multimeric proteins. is a covalent bond between the functional R groups of adjacent amino acids. is a noncovalent bond that dictates the tertiary structure of a protein. is a covalent bond between adjacent glucose molecules in a peptide. is a covalent bond between the carboxyl carbon of one amino acid and the amino nitrogen of a second amino acid.

is a covalent bond between the carboxyl carbon of one amino acid and the amino nitrogen of a second amino acid.

Hydrogen bonding is most important in stabilizing the ________ structure of many proteins. primary tertiary quaternary primary, secondary, tertiary, and quaternary secondary

secondary

Choose amino acids that would be much less likely than valine to cause impairment of hemoglobin function if substituted for the glutamate at position 6 of the β chain. serine, threonine, tyrosine, isoleucine tyrosine, cysteine, aspartate, isoleucine threonine, tyrosine, cysteine, isoleucine serine, threonine, tyrosine, cysteine, aspartate

serine, threonine, tyrosine, cysteine, aspartate

Cholesterol is a ________, which ________. steroid; is the basis for many animal and plant hormones terpene; is the basis for many animal and plant vitamins fatty acid; functions in energy storage steroid; is a component of eukaryotic membranes and is the basis for many animal and plant hormones steroid; is a component of eukaryotic membranes

steroid; is a component of eukaryotic membranes and is the basis for many animal and plant hormones

Disulfide bonds are often found to stabilize which of the following levels of protein structure? primary secondary primary, secondary, and tertiary tertiary None of these structures involve disulfide bonds.

tertiary

A general trend in the structure of many biomolecules is that each class of biomolecule can form either fibrous or globular conformations depending on the chemical conditions inside the cell. that they are all soluble in water independent of the size of the polymer. that the order and bonding of monomers form the basis for the secondary and tertiary structure of the polymer. that four different monomers form the basis for the functional and structural properties of each polymer. that each class of biomolecule forms one type of secondary structure independent of the order of the monomers in the polymer.

that the order and bonding of monomers form the basis for the secondary and tertiary structure of the polymer.

In a DNA double helix an adenine of one strand always pairs with a(n) _____ of the complementary strand, and a guanine of one strand always pairs with a(n) _____ of the complementary strand. uracil ... cytosine cytosine ... uracil cytosine ... thymine guanine ... adenine thymine ... cytosine

thymine ... cytosine

The function of triglycerides is to store energy. to form semipermeable membranes. to transport substances in and out of cells. store information. to form semipermeable membranes and to transport substances in and out of cells.

to store energy.

Which of the following is found exclusively in RNA? cytosine adenine guanine thymine uracil

uracil

Two proteins associated with a rare neurodegenerative disorder have been sequenced. Protein A contains many polar amino acids with small regions containing nonpolar, hydrophobic amino acids. Protein B is rich in nonpolar, hydrophobic amino acids with only two small regions containing polar amino acids. What might this suggest about the two proteins? Protein A is fibrous and Protein B is globular. Protein A may be a cytoplasmic protein and Protein B may be a membrane associate protein. The two proteins may have different secondary structures. Protein A is most likely and enzyme and Protein B is most likely a storage protein. Protein A and Protein B are complementary parts of a supramolecular structure.

*Protein A* may be a *cytoplasmic* protein and Protein *B* may be a *membrane associate protein.*

The "permanent" wave that your local beauty parlor offers depends critically on rearrangements in the extensive disulfide bonds of keratin that give your hair its characteristic shape. To change the shape of your hair (that is, to give it a wave or curl), the beautician first treats your hair with a sulfhydryl reducing agent, then uses curlers or rollers to impose the desired artificial shape, and follows this by treatment with an oxidizing agent. Why do you suppose a permanent isn't permanent? Select all that apply. Disulfide bonds occasionally break and re-form spontaneously, allowing the hair proteins to return gradually to their original, thermodynamically more favorable shape. Hair continues to grow, and the new α-keratin molecules will have the natural disulfide bonds. Peptide bonds occasionally break and re-form spontaneously, allowing the hair proteins to return gradually to their original, thermodynamically more favorable shape. Hair continues to grow, and the new α-keratin molecules will not have any disulfide bonds.

Disulfide bonds occasionally break and re-form spontaneously, allowing the hair proteins to return gradually to their original, thermodynamically more favorable shape. Hair continues to grow, and the new α-keratin molecules will have the natural (correct) disulfide bonds.

Which of the following accurately describes the structure of fibrous proteins? Fibrous proteins have a simple primary structure and very little secondary structure, resulting in long, thin fibers. Fibrous proteins are usually composed of either α helices or β sheets throughout the molecule, giving them a highly ordered, repetitive structure. Fibrous proteins have an extensive tertiary and quaternary structure that affects the strength and elasticity of each fiber. Fibrous proteins usually contain a number of different domains with different structural motifs. Fibrous proteins are composed of an equal mixture of α helices and β sheets with interconnecting looped segments

Fibrous proteins are usually composed of either α helices or β sheets throughout the molecule, giving them a highly ordered, repetitive structure.

You are researching a cytoplasmic protein associated with a nerve disorder. The native form of the enzyme appears to be globular protein; however, when a sample of the purified protein is treated with a chemical that reduces disulfide bonds, the enzymatic activity decreases dramatically and multiple globular proteins can be detected in the sample. What does this tell you about the protein? The primary and secondary structure of the protein depends on disulfide bonds. The protein is most likely composed of \alpha helices that are held together by disulfide bonds. The protein is most likely composed of \betha sheets that are held together by disulfide bonds. The primary structure of the protein contains multiple cysteine residues that are hydrolyzed by the chemical reductant. The protein is most likely composed of multiple polypeptide chains that are held together by disulfide bonds.

The protein is most likely composed of multiple polypeptide chains that are held together by disulfide bonds.

You are investigating the structure of the seeds of a newly discovered tropical plant. There is storage material inside the seed. You treat the seed with peptidase (an enzyme that breaks peptide bonds), glycoside hydrolases (an enzyme that breaks β glycosidic bonds), and amylase (an enzyme that breaks α glycosidic bonds). Only the amylase appears to dissolve the storage material in the seed. What does this tell you about the identity of the storage material? The seed contains lipids to store carbon and energy. The seed contains cellulose to store carbon and energy. The seed contains fibrous proteins to store carbon and energy. The seed contains starch to store carbon and energy. The seed contains globular proteins to store carbon and energy.

The seed contains starch to store carbon and energy.

A cotton fiber consists almost exclusively of cellulose, whereas a potato tuber contains mainly starch. Cotton is tough, fibrous, and virtually insoluble in water. The starch present in a potato tuber, on the other hand, is neither tough nor fibrous and can be dispersed in hot water to form a turbid solution. Yet both the cotton fiber and the potato tuber consist primarily of polymers of D-glucose in (1→4) linkage. How can two polymers consisting of the same repeating subunit have such different properties? The two polymers have very different properties because they differ in structure as a result of differing 1→4 linkages between glucose monomers. The α(1→4) linkage of cellulose gives it a rigid, fibrous structure not seen in starch, which has an β(1→4) linkage between fructose monomers. The two polymers have very different properties because they differ in structure as a result of different molecular mass. Low molecular mass of cellulose gives it a rigid, fibrous structure not seen in starch, which has high molecular mass. The two polymers have very different properties because they differ in structure as a result of differing 1→4 linkages between glucose monomers. The β(1→4) linkage of cellulose gives it a rigid, fibrous structure not seen in starch, which has an α(1→4) linkage between glucose monomers. The two polymers have very different properties because they differ in structure as a result of different molecular mass. High molecular mass of cellulose gives it a rigid, fibrous structure not seen in starch, which has low molecular mass.

The two polymers have very different properties because they differ in structure as a result of differing 1→4 linkages between glucose monomers. The *β(1→4)* linkage of cellulose gives it a rigid, fibrous structure not seen in starch, which has an *α(1→4)* linkage between glucose monomers.

Can you suggest an explanation for naturally curly hair? There is probably a genetic difference in the positioning of serine groups and hence in the formation of disulfide bonds. There are probably no disulfide bonds in α-keratin molecules. There are probably no disulfide bonds in β-keratin molecules. There is probably a genetic difference in the positioning of cysteine groups and hence in the formation of disulfide bonds.

There is probably a genetic difference in the positioning of c*ysteine groups* and hence in the formation of disulfide bonds.

Is it possible that two proteins could differ at several points in their amino acid sequence and still be very similar in structure and function? No, the substitutions always essentialy change chemical properties of proteins. Yes, if the substitutions are always of like-for-like amino acids in terms of chemical properties. No, the substitutions always essentialy change elemental composition of proteins. Yes, if the substitutions are always of like-for-like amino acids in terms of elemental composition.

Yes, if the substitutions are always of like-for-like amino acids in terms of chemical properties.

A discrete, locally folded unit of protein tertiary structure usually having a specific function best describes __________. quaternary structure a complex a domain a motif

a domain

The components of a nucleotide are a five-carbon sugar, a phosphate group, and a nitrogen-containing aromatic base. a six-carbon sugar, an ester linkage, and a four-ringed hydrocarbon. a three-carbon alcohol with a hydroxyl group on each carbon and three fatty acids. two six-carbon sugars attached with an α(1→4) glycosidic bond. a carboxyl group, an amine group, and a variable R group.

a five-carbon sugar, a phosphate group, and a nitrogen-containing aromatic base.

Which of the following is not a polymer of numerous monomer units? cellulose a phospholipid an RNA molecule starch a polypeptide

a phospholipid

Proteins are polymers of _____. nucleotides amino acids CH2O units hydrocarbons glycerol

amino acids

Which of the following has the greatest number of glycosidic bonds? vitamin A triacylglycerol amylose glucose DNA

amylose

In eukaryotic cells DNA has the appearance of a _____. single strand letter U double helix triple helix circle

double helix

Fatty acids are ________; they function in the cell as ________. short chains of double-bonded carbon molecules; vitamins, cofactors, and storage lipids four-ringed hydrocarbon molecules; key components of membranes short chains of double-bonded carbon molecules; vitamins and cofactors short chains of double-bonded carbon molecules; storage lipids long, unbranched hydrocarbon chains with a carboxyl group at one end; building blocks for other lipids

long, *unbranched hydrocarbon chains* with a carboxyl group at one end; *building blocks for other lipids*

DNA is composed of building blocks called _____. nucleic acids Gs nucleotides adenines amino acids

nucleotides

Which of the following pairs correctly matches the monomer with its polymer? peptides; proteins terpenes; nucleic acids glucose; proteins amino acids; polysaccharides nucleotides; nucleic acids

nucleotides; nucleic acids

What type of bond joins the monomers in a protein's primary structure? peptide ionic S - S hydrogen hydrophobic

peptide

Tertiary structure is NOT directly dependent on _____. peptide bonds hydrophobic interactions bonds between sulfur atoms hydrogen bonds ionic bonds

peptide bonds

Which of the following is not a steroid? phenylalanine aldosterone estradiol testosterone cortisol

phenylalanine

The nucleoside triphosphate molecules in DNA are linked together in the 5'→3' by a(n) ________ bridge. phosphodiester phosphatidyl covalent peptide phosphate

phosphodiester