Chapter 3 - Proteins, Carbohydrates, and Lipids (HOMEWORK & QUIZ)

By how much did removal of the cysteines in bridge 1 reduce enzyme activity? A) About 77 percent B) About 43 percent C) About 90 percent D) About 23 percent

A) About 77 percent

In some cases, a single amino acid substitution can cause a protein to lose its biological activity. In other cases, a single amino acid substitution causes no change to a protein's biological activity. Which statement can best be used as evidence to support an explanation for these observations? A) Each amino acid side chain has properties that are very different from those of some side chains and very similar to those of others. B) Amino acids occur as optical isomers, but only one isomer of each is found in the proteins of most of the organisms on Earth. C) Noncovalent interactions between atoms in a polypeptide chain stabilize the secondary, tertiary, and quaternary levels of its structure. D) Amino acids are covalently linked through peptide bonds to form the primary structure of a protein. E) Amino acids found in the proteins of living organisms have many similarities, including an alpha-amino group and an alpha-carboxyl group.

A) Each amino acid side chain has properties that are very different from those of some side chains and very similar to those of others.

A question was raised during a class discussion about whether it was possible for two isomers to have different biological properties. A student from the class responded, stating that only optical isomers met this requirement. Which statement provides the best evaluation of this student's assertion? A) It is only partially correct, because structural isomers and cis-trans isomers can also meet the requirement. B) It is completely correct. C) It is only partially correct, because structural isomers can also meet the requirement. D) It is incorrect, because no isomers meet the requirement. E) It is only partially correct, because cis-trans isomers can also meet the requirement.

A) It is only partially correct, because structural isomers and cis-trans isomers can also meet the requirement.

Bring up the unsaturated triglyceride option in the simulation. After you build the molecule, answer the following question: Which bond(s) on this molecule distinguish(es) this molecule from a saturated triglyceride? A) The double bonds in the fatty acid tails B) The ester bonds linking fatty acids to glycerol C) The single bonds between carbons in the glycerol backbone D) The single bonds in the fatty acid tails

A) The double bonds in the fatty acid tails

Cellulose is A) a structural organic compound. B) made up of α-glycosidic linkages. C) highly unstable. D) readily soluble in water. E) a form of energy storage.

A) a structural organic compound.

All of the following contribute to the three-dimensional shape of a protein except A) ester linkages. B) hydrophobic interactions. C) van der Waals forces. D) hydrogen bonds. E) salt bridges.

A) ester linkages.

An essential functional group involved in cellular energy reactions is the _______ group A) phosphate B) amino C) sulfhydryl D) saccharide E) hydroxyl

A) phosphate

Based on its structure, a triglyceride is most closely related to a A) phospholipid. B) carotenoid. C) trans fat. D) steroid. E) lipoprotein.

A) phospholipid.

Bring up the DNA adenine nucleotide option in the simulation. After you build the molecule, answer the following question: Which two atoms on this molecule form covalent bonds with atoms of two other nucleotides to form a chain? A) 2'-C of deoxyribose and N-7 of adenine B) 3'-OH of deoxyribose and a-P bonded to 5'-OH of deoxyribose C) α-P bonded to 5'-OH of deoxyribose and N-3 of adenine D) β -P bonded to 5'-OH of deoxyribose and 3'-OH of deoxyribose

B) 3'-OH of deoxyribose and a-P bonded to 5'-OH of deoxyribose

Which statement best describes the properties of the GFP-composite silk? A) It was about as thick as silkworm silk but could not be stretched as much. B) It was about as thick as silkworm silk but could be stretched much more. C) It was about as thick as spider silk but could be stretched much more. D) It was about as thick as spider silk but could not be stretched as much.

B) It was about as thick as silkworm silk but could be stretched much more.

Cis-butene and trans-butene have the same functional groups but cis-butene binds to a particular biological receptor and elicits a biological response in a cell, while trans-butene does not. Which statement about these two compounds explains this difference? A) They do not have the same mass. B) They are not the same shape. C) Neither is an organic compound. D) They are optical isomers. E) They differ in chemical composition.

B) They are not the same shape.

Chemical modification of carbohydrates A) affects structure, not function. B) affects structure and function. C) affects function, not structure. D) occurs only in animals, not plants. E) occurs only in plants, not animals.

B) affects structure and function.

Due to the six hydroxyl groups bonded to its six-carbon backbone, the carbohydrate compound inositol can be classified as a(n) A) carboxylic acid. B) alcohol. C) ketone. D) aldehyde. E) thiol.

B) alcohol.

Lipids differ from polysaccharides in that they A) contain carbon. B) are nonpolar. C) have important structural roles. D) can aggregate. E) store energy.

B) are nonpolar.

Fatty acids are A) large polymers of monosaccharides. B) carboxylic acids with long hydrocarbon tails. C) saturated hydrocarbons. D) linked to glycerol in fats by phosphodiester bonds. E) generally present in water-soluble proteins.

B) carboxylic acids with long hydrocarbon tails.

All of the following are examples of lipids except A) steroids. B) glucosamine. C) chlorophylls. D) wax. E) oil.

B) glucosamine.

Starch and glycogen, which are both polysaccharides, differ structurally in that glycogen _______, whereas starch _______. A) is moderately branched; consists of parallel strands B) is highly branched; is moderately branched C) consists of parallel strands; is highly branched D) consists of a combination of branching and parallel strands; is moderately branched E) is highly branched; consists of parallel strands

B) is highly branched; is moderately branched

All of the following statements about wax are true except A) made by animals and plants. B) it is a pigment. C) it provides waterproofing. D) it is a barrier to pathogens. E) it is a hydrocarbon.

B) it is a pigment.

A structural isomer for the molecule NaOCH2CH3 would be expected to have _______ carbon atoms. A) one B) two C) three D) five E) nine

B) two

Bring up the sucrose option in the simulation. After you build the molecule, answer the following question: Which two carbon atoms in this molecule are aldehyde carbons that participated in the reactions leading to ring formation in the monosaccharide monomers? A) Carbon-1 of glucose and carbon-5 of fructose B) Carbon-2 of glucose and carbon-2 of fructose C) Carbon-1 of glucose and carbon-2 of fructose D) Carbon-5 of glucose and carbon-5 of fructose

C) Carbon-1 of glucose and carbon-2 of fructose

Which amino acid substitution for alanine would least likely affect the three-dimensional shape of the resulting protein? A) Tyrosine B) Cysteine C) Isoleucine D) Histidine E) Aspartic acid

C) Isoleucine

This compound is soluble in chloroform, a nonpolar organic solvent, but it is not soluble in water. Based on this information, to which class of biological macromolecules does this compound belong? A) Enzymes B) Oligosaccharides C) Lipids D) Carbohydrates E) Proteins

C) Lipids

Two polypeptide chains have the same amino acid composition and molecular weight, yet only one binds to a cell membrane receptor. Several possible scenarios have been listed to explain these observations. Which is the only plausible one? A) One chain was synthesized in a laboratory, while the other was synthesized in a bacterium, causing differences in the final structures of the proteins. B) The two chains fold into different three-dimensional shapes because the polypeptides were made by two different organisms. C) The two chains fold into different three-dimensional shapes because the sequences of amino acids differ in the chains. D) One chain is longer than the other chain, causing the polypeptides to fold into different shapes. E) One chain has bond linkages connecting amino acids that differ from the bond linkages in the other chain.

C) The two chains fold into different three-dimensional shapes because the sequences of amino acids differ in the chains.

Cis and trans isomers A) have the same structure but the trans form has an extra double bond. B) have similar properties despite opposite orientations in structure. C) are centered around a double bond with atoms on either side in different orientations with respect to each other. D) are mirror images of each other in structure. E) have the same structure, but the cis form has an extra double bond.

C) are centered around a double bond with atoms on either side in different orientations with respect to each other.

Lipids can to perform all of the following functions except A) color the leaves of a tree. B) store energy. C) dissolve polar substances. D) prevent feathers from getting wet. E) provide a signal from one part of the body to the other.

C) dissolve polar substances.

Olive oil melts at a lower temperature than beef fat because A) fats contain more unsaturated fatty acids than oils do. B) oils contain glycerol, whereas fats do not. C) fats contain more saturated fatty acids than oils do. D) oils are made by plants, whereas fats are made by animals. E) olive trees naturally occur in warmer climates than beef cattle do.

C) fats contain more saturated fatty acids than oils do.

Salt bridges are a part of a protein's tertiary structure and can occur between A) serine and threonine. B) tryptophan and valine. C) glutamic acid and arginine. D) histidine and lysine. E) two cysteines.

C) glutamic acid and arginine.

In an α helix, the coiling is stabilized by A) the hydrophobic nature of the R chains, which causes the chain to coil with the R groups inward. B) disulfide bond formation between cysteines that are regularly spaced along peptide chains. C) hydrogen bonding of the N-H groups on one amino acid and the C=O groups on another. D) repulsion of the R chains from each other, causing the coil to form with the R groups on the outside. E) the N-C-C repeat of the polypeptide chain, allowing for regularly spaced peptide bonds between chain segments.

C) hydrogen bonding of the N-H groups on one amino acid and the C=O groups on another.

Glucose A) has six hydrogens. B) is a pentose. C) is broken down for energy. D) is a disaccharide. E) is a polysaccharide.

C) is broken down for energy.

Within a polypeptide chain is the following amino acid sequence, which reads in the N terminus to C terminus direction from left to right: Glycine-Tyrosine-Serine. Which statement about this polypeptide is true? A) The side chains or R groups of the amino acids in the sequence are covalently bonded to one another through peptide bonds. B) A hydrolysis reaction occurred during peptide bond formation between the carboxyl group of glycine and the carboxyl group of tyrosine. C) The polypeptide can become branched if the side chain of tyrosine reacts with a free amino acid to form a peptide bond. D) A molecule of water was released when the amino group of tyrosine formed a peptide bond with the carboxyl group of serine. E) A condensation reaction formed a peptide bond between the amino group of glycine and the carboxyl group of tyrosine.

D) A molecule of water was released when the amino group of tyrosine formed a peptide bond with the carboxyl group of serine

Which amino acid would, when incorporated into a polypeptide chain (not at the N or C terminus), make the charge of the polypeptide more positive? A) Serine B) Aspartic acid C) Alanine D) Arginine E) Cysteine

D) Arginine

Which of the following would be expected as the result of polymerization reactions in which four monomers are linked to form a straight chain polymer? A)Energy is released and four water molecules are produced. B) Energy is consumed and four water molecules are consumed. C) Energy is released and three water molecules are produced. D) Energy is consumed and three water molecules are produced. E) Energy is released and three water molecules are consumed.

D) Energy is consumed and three water molecules are produced.

Bring up the option to build a protein with the sequence alanine, glycine, isoleucine, arginine in the simulation. After you build the molecule, answer the following question: Which parts of this molecule are the same in every protein, and which parts differ from one protein to the next? A) The peptide bonds are the same in every protein, but the peptide backbone differs. B) The R groups along the peptide backbone are the same in every protein, but the peptide bonds differ. C) The peptide backbone is the same in every protein, but the peptide bonds differ. D) The peptide backbone is the same in every protein, but the R groups along the peptide backbone differ.

D) The peptide backbone is the same in every protein, but the R groups along the peptide backbone differ.

How many isomers of which type can be drawn to represent the chemical formula C5H12? A) Four structural isomers B) Three cis-trans isomers C) Two optical isomers D) Three structural isomers E) Four cis-trans isomers

D) Three structural isomers

The primary structure of proteins is the _______. The primary structure contains the information necessary for the formation of a secondary structure, including the _______ and the _______. Secondary structure of proteins is stabilized by the formation of _______ bonds. A) amino acid sequence; β pleated sheet; α helix; disulfide B) β pleated sheet; α helix; amino acid sequence; hydrogen C) α helix; amino acid sequence; β pleated sheet; hydrophobic D) amino acid sequence; α helix; β pleated sheet; hydrogen E) amino acid sequence; α helix; β pleated sheet; peptide

D) amino acid sequence; α helix; β pleated sheet; hydrogen

Monomers are joined together by _______ and broken down by _______. A) acids; bases B) hydrogen; oxygen C) phosphorylation; dephosphorylation D) condensation; hydrolysis E) proteins; lipids

D) condensation; hydrolysis

Triglycerides are composed of A) phosphatidylcholine and linoleic acid. B) steroids and saturated fats. C) aggregates of glycerol. D) glycerol and fatty acids. E) carotenoids and palmitic acid.

D) glycerol and fatty acids.

Tertiary and quaternary structures share all of the following properties except A) disulfide bridges. B) ionic interactions. C) van der Waals interactions. D) multiple subunits. E) hydrogen bonding.

D) multiple subunits.

A substance that is soluble in water and turns sweet in the presence of amylase, an enzyme that hydrolyzes glycosidic linkages, is most likely A) hemoglobin. B) collagen. C) glycogen. D) starch. E) glycerol.

D) starch.

Which protein is predicted to be most resistant to denaturation by heat? A) A protein with no proline residues in its primary structure B) A protein with a very short polypeptide chain C) A protein with no quaternary structure D) A protein with many internal hydrogen bonds E) A protein with many internal disulfide bonds

E) A protein with many internal disulfide bonds

Where would the leucine side chain most likely be found in a protein dissolved in water? A) On either the interior or the exterior of the protein B) In the interior of the protein in contact with polar side chains C) On the exterior of the protein D) In the interior of the protein in contact with water E) In the interior of the protein in contact with nonpolar side chains

E) In the interior of the protein in contact with nonpolar side chains

People born with the genetic disorder known as glycogen storage disease have impaired glycogen synthase. Glycogen synthase is the protein that catalyzes the polymerization of glucose to form glycogen. Affected people exhibit extreme tiredness and poor muscle function upon developing very low blood sugar levels when they have not eaten in a while. They show improvements soon after taking in food, which boosts their blood sugar concentrations. If the cells of these patients cannot polymerize glucose into glycogen, why don't the cells simply store excess glucose monomers for use during times between meals? A) The cells would immediately metabolize all of the glucose monomers, creating very large amounts of heat that would destroy the cells. B) The large number of glucose monomers would begin reacting with other molecules in the cell, causing disruption of normal metabolic reactions. C) Glucose monomers would have no way to move back across the cell membrane once they entered a cell. D) A large number of glucose monomers would take up much more space inside cells than glycogen made from an equivalent number of monomers. E) The accumulation of large numbers of glucose monomers would upset the osmotic balance of cells in a way that glycogen does not.

E) The accumulation of large numbers of glucose monomers would upset the osmotic balance of cells in a way that glycogen does not.

A peptide linkage forms between A) a phosphate group and a hydroxyl group. B) the two peptide chains of a protein dimer. C) R groups. D) sulfhydryl groups. E) an amino group and a carboxyl group.

E) an amino group and a carboxyl group.

The functional group written as -COOH is called the _______ group. A) keto B) carbonyl C) amino D) sulfhydryl E) carboxyl

E) carboxyl

All starches are A) aggregates in the presence of water. B) linear polymers. C) the principal energy storage for all organisms. D) insoluble in water. E) composed of only glucose monomers.

E) composed of only glucose monomers.

All carbohydrates A) are more soluble in nonpolar solvents than in water. B) are simple sugars. C) are polymers. D) are found in biological membranes. E) have the general structure (C1H2O1)n or CnH2nOn.

E) have the general structure (C1H2O1)n or CnH2nOn.

Methyl groups are nonpolar, and thus a molecule that contains multiple methyl groups will be A) acidic. B) soluble in water. C) easily hydrolyzed. D) involved in reactions forming more complex molecules. E) hydrophobic.

E) hydrophobic.

The three-dimensional structure of protein A) is not related to its function. B) will be different in different organisms, even when the amino acid sequence is the same. C) cannot be altered once folded by chaperone proteins. D) always contains multiple polypeptide chains. E) is determined by the sequence of amino acids in the polypeptide chain.

E) is determined by the sequence of amino acids in the polypeptide chain.

Cholesterol A) is classified as a carbohydrate. B) must be taken up in an animal's diet. C) is a carotenoid. D) is hydrophilic. E) is involved in membrane integrity.

E) is involved in membrane integrity.

A hydrolysis reaction requires A) a carboxyl group. B) a hydroxyl group. C) hydrogen. D) oxygen. E) water.

E) water.

Which bridge (if any) is essential to having any function of the enzyme? A) All of the bridges are essential. B) Only bridge 1 is essential. C) Only bridge 2 is essential. D) Only bridge 3 is essential. E) Only bridge 4 is essential. F) None of the bridges are essential.

F) None of the bridges are essential.

A polar _______ contributes to the ability of aldehydes and ketones to be involved in energy reactions. A) nitrogen atom B) phosphate group C) carbonyl group D) sulfur atom E) R group

nitrogen atom phosphate group carbonyl group sulfur atom R group