Chapter 9-13 Reading Quizzes

4. Consider the structure of sucrose with labeled carbon atoms below. Identify the anomeric carbon atoms of sucrose.

A. 1 and 2' B. 6 and 6' C. 1 and 5' D. 1' and 5'

9. What statement is consistent with the structure of biological membranes?

A. All membrane proteins are integral and associate with the hydrophobic region of the membrane. B. Both proteins and lipids readily undergo transverse ("flip-flop") diffusion. C. The membrane lipids self-assemble to form the lipid bilayer. D. A biological membrane consists of proteins sandwiched between two layers of lipids.

8. Predict which fatty of the following fatty acids has the highest melting point.

A. CH3(CH2)4(CH=CHCH2)2(CH2)6COOH B. CH3(CH2)14COOH C. CH3(CH2)5CH=CH(CH2)7COOH D. CH3(CH2)2COOH

9. Which of the following is TRUE?

A. Cellulose is a storage form of fuel in plant cells B. Glycogen provides structural support for animals such as arthropods C. Glycogen functions in fuel storage in animal cells D. Starch provides structural support for plants

5. Cellulose could provide an abundant and cheap form of glucose for humans. Why is cellulose not a source of nutrients for humans?

A. Humans cannot absorb the hydrolyzed form of cellulose. B. Humans, and most vertebrates, lack the enzyme cellulase. C. Animals use starch and glycogen as an energy source, whereas plants use cellulose for energy. D. Human gut bacteria break down cellulose in the large intestine, after nutrient absorption occurs.

10. Determine which statements about glycosaminoglycans are true.

A. Hyaluronan (hyaluronate) and keratan sulfate are examples of glycosaminoglycans. B. Glycosaminoglycans are homopolysaccharides composed of repeating glucosamine or galactosamine residues. C. Because glycosaminoglycans consist of only two residues, they generally have low molecular weights. D. Cellulose is an example of a glycosaminoglycan.

11. Choose the CORRECT statement.

A. Lipid bilayer membranes have a very low permeability for ions and most polar molecules. B. There are electrostatic and hydrogen-bonding attractions between the hydrocarbon tails and water molecules. C. The favored structure for most phospholipids and glycolipids in aqueous media is a micelle. D. Hydrophilic interactions are the major driving force for the formation of lipid bilayers.

1. Which of the following statements does NOT describe a dimeric allosteric enzyme following the concerted model?

A. The enzyme can exist as an RR dimer. B. The RR form of the enzyme is the most active. C. The enzyme can exist as an RT dimer. D. In absence of substrate, the equilibrium between the T state and R state favors the T state.

5. How do the melting points of saturated fatty acids change with the length of the hydrocarbon tail?

A. The melting point of a fatty acid is independent of the length of the hydrocarbon tail. B. As the length of the hydrocarbon tail in the fatty acid increases, the melting point decreases. C. As the length of the hydrocarbon tail in the fatty acid decreases, the melting point increases. D. As the length of the hydrocarbon tail in the fatty acid decreases, the melting point decreases.

10. For fatty acids with the same number of carbon atoms, how does the melting point change as the number of double bonds in the fatty acid changes?

A. The melting point of the fatty acid increases as the number of double bonds decreases. B. The melting point of the fatty acid is unchanged as the number of double bonds changes. C. There is no relationship between the melting point of a fatty acid and the number of double bonds. D. The melting point of the fatty acid increases as the number of double bonds increases.

8. How are the allosteric properties of ATCase and hemoglobin similar?

A. The quaternary structure of both proteins is altered by binding small molecules. B. Both are regulated by feedback inhibition. C. The allostery of both proteins involves regulation by competitive inhibitors. D. Both proteins' allosteric properties manifest when their subunits dissociate.

6. Which of the following is NOT true of serine proteases?

A. a covalent intermediate is formed as part of the enzyme's mechanism B. there is a catalytic triad of serine, histidine, and aspartic acid in their active site C. a tetrahedral intermediate is formed as part of the enzyme's mechanism D. there are two aspartic acid residues in their active site

6. A phosphoglyceride molecule is composed of

A. a glycerol backbone, two fatty acids, a phosphate group and an alcohol B. a glycerol backbone with ester links to three fatty acids. C. a glycerol backbone with ether-linked fatty acids. D. a sphingosine backbone, two fatty acids, a phosphate group and an alcohol

10. The dependence of the reaction velocity on the substrate concentration for an allosteric enzyme is shown in the figure below as curve A. Which of the following would be expected to cause a shift to curve B?

A. addition of an irreversible inhibitor B. addition of an allosteric activator C. addition of an allosteric inhibitor D. dissociation of the enzyme into subunits

7. Protein kinases generally regulate the activity of target proteins by transferring a phosphate group from ATP to the target protein. To what amino acid functional groups are these phosphates transferred?

A. amino groups B. hydrophobic groups C. carboxyl groups D. hydroxyl groups

4. What term describes molecules that have both hydrophilic and hydrophobic characteristics?

A. amphipathic B. amphiprotic C. amphibian D. amphoteric

8. Compared to simple glycoproteins, proteoglycans

A. are predominantly made of carbohydrates B. are used as a source of energy C. contain a VNTR region D. are predominantly made of protein

5. What is NOT a catalytic strategy?

A. covalent catalysis B. approximation of substrates C. lock and key mechanism D. acid-base reactions

11. What type of sugar is ribose?

A. hexose B. heptose C. pentose D. triose

2. Hydropathy plots are useful to

A. identify possible membrane‑spanning a-helices. B. identify regions of peripheral membrane proteins capable of interacting with the membrane surface. C. identify lipid anchors. D. identify amphipathic regions in the protein.

11. The inhibition of aspartate transcarbamoylase by cytidine triphosphate (CTP) is an example of

A. inactivation by phosphorylation. B. uncompetitive inhibition. C. feedback inhibition. D. competitive inhibition.

7. Which of the following correctly describes a lectin?

A. it's a lysosomal enzyme B. recognizes and binds to carbohydrates C. it's a protein conjugated with a carbohydrate D. It determines the blood type

3. Consider the monosaccharide shown below: Identify whether it is and aldose or a ketose.

A. ketose B. aldose

3. What membrane components contain carbohydrates?

A. lipid-linked proteins B. phosphatidylserine C. cholesterol D. glycolipids

1. Which type of chemical linkage is used to join fatty acids to glycerol?

A. peptide bond B. ester linkage C. ether linkage D. double bond

2. Glycoproteins are proteins to which carbohydrates have been covalently attached.The amino acid R group that serves as site for N‑linkages in glycoproteins include

A. positively charged amino acid R groups. B. cysteine. C. asparagine. D. hydroxyl‑containing R groups.

9. Which of the following CANNOT be used by enzymes to catalyze specific reactions?

A. proximity between substrates B. covalent enzyme-substrate complexes C. temperature changes D. metal ions

7. Whereas salts of fatty acids readily form micelles, phospholipids and glycolipids tend to form molecular bilayers instead because of

A. the amphipathic nature of phospholipids and glycolipids. B. the presence of two fatty acid chains. C. differing interactions between polar head groups. D. interactions between the different polar head groups and water.

1. Formation of pyranose and furanose forms of a sugar generates a new asymmetric carbon.If the anomeric alcohol group in a cyclic sugar molecule is on the opposite side as the C‑6, the sugar is described as

A. the epimeric form. B. the α anomer. C. the β anomer. D. the enantiomer.

3. In addition to the three histidine residues coordinated with Zn(II) in carbonic anhydrase, a fourth histidine residue is also important for the enzyme's function.The role of this fourth histidine residue (His 64) is

A. to neutralize the negative charge on the hydroxide ion bound to the Zn(II). B. to provide a fourth ligand for the Zn(II) when the hydroxide reacts with carbon dioxide. C. to shuttle protons to and from the active site. D. to enhance binding of the three histidine residues to the Zn(II).

4. The alkoxide group on chymotrypsin that attacks the carbonyl oxygen of the peptide bond of the substrate arises from which amino acid side chain?

A. tyrosine B. histidine C. serine D. aspartate

6. Select the amino acids that attach carbohydrates to proteins. SELECT ALL THAT APPLY.

A. valine B. phenylalanine C. threonine D. arginine E. serine

2. Enzymes that catalyze the same reaction but differ in amino acid sequence are called

A. zymogens. B. isozymes. C. heterozymes. D. allozymes.