Biochemistry Questions

Sickle cell anemia is caused by a mutation in the beta globin gene resulting in a glutamic acid to valine substitution at position 6 (Glu6Val) of the hemoglobin beta subunit. Under conditions of low oxygen concentrations in the blood, hemoglobin in the patient's red blood cells assemble together to form long fibers that "sickle" the cells leading to occlusion of capillaries.A. People with sickle cell anemia inherit the mutation from both parents and so the mutation is present in the genome of every cell of the body. Why are only the red blood cells affected by the mutation?B. Based on the chemical properties of the Glu and Val side chains, where are these amino acids normally found in the folded structure of a water soluble protein?C. How then do you think the presence of valine at position 6 contributes to the aggregation of hemoglobin when oxygen levels are low?

This disease is thought to result from the accumulation of protein fragments, called Ab, that improperly oligomerize to form amyloid fibers.A. Alzheimer's disease B. Tay-Sachs disease C. Creutzfeldt-Jakob disease D. Hemophilia E. Scrapie

Synthesis of a macromolecule from monomer building blocks is an energy demanding process that often requires "activation" of the monomer by attachment to a carrier prior to assembly. What carrier is used during translation to link amino acids into a polypeptide?A. ATP B. UTP C. mRNA D. tRNA E. 16S rRNA

The level of structure involving the 3D conformation of a polypeptide chain involving the interactions of the side chains (R groups) is ____ ?TertiaryQuaternaryPrimarySecondary

You treat a partially purified preparation of protein with a reagent that breaks hydrogen bonds. Which level(s) of protein structure are likely to be affected?Secondary, Tertiary, and QuaternaryTertiary and QuaternaryPrimary, Secondary, and TertiaryPrimary, Secondary, Tertiary, and QuaternaryPrimaryPrimary and Secondary

Which of the following tri-peptides would be most soluble in water?A. Leu-Ala-Lys B. Phe-Ala-Ile C. Arg-Trp-LeuD. Glu-Asn-Ser E. Pro-Gly-Val

Key forces that stabilize double stranded DNA include:A. Hydrogen bonding between bases on complementary strandsB. Electrostatic interactions across the helixC. The presence of water in the interior of the helixD. Hydrogen bonding between bases on the same strandE. Histones

Within a beta-sheet, H-bonds form between carbonyl and NH groups in:polar side chainscharged side chainshydrophobic side chainsthe peptide backbone

For elements of biological importance, two atoms will exert an attractive force on each other (van der Waals force) when they are approximately _______ apartA. 3 Å B. 3 nm C. 3 mm D. 3 mm E. 3 m

Which of the following statements about glucose and fructose is false?A. Glucose primarily forms a 6-membered ring and fructose a 5-membered ring.B. Glucose and fructose are mirror image stereoisomers of each other.C. Glucose and fructose are joined together to form sucrose.D. In the linear forms, a carbonyl is at carbon 1 of glucose and carbon 2 of fructose.E. Glucose and fructose are important sugars in human metabolism.

If we mix a protein (P) and its ligand (L) and allow the binding reaction to come to equilibrium (P+LßàPL), the formula [P][L]/[PL] = Kd can be used to determine the dissociation constant. Several weak, noncovalent bonds form between the protein and ligand when they bind. What would be the consequence of a mutation in the protein that did not disrupt its normal structure but prevented its ability to form one hydrogen bond with the ligand?No binding would occur and the Kd would be very low[P] and [L] would increase at equilibrium and the Kd would increase[P] and [L] would increase at equilibrium and the Kd would decrease[PL] would increase at equilibrium and the Kd would decrease

Reducing agents used in the laboratory can break disulfide bonds between two residues. For a single polypeptide chain, which level of protein structure would potentially be most directly affected by the reducing agent?QuaternaryPrimarySecondaryTertiary

Alzheimer's disease may be caused by the accumulation of __________ in the brain.

The effect of a competitive inhibitor can be reversed by _______.increasing inhibitor concentrationheating the reaction mixtureincreasing substrate concentrationchanging the pH

When numbering the carbons on nucleotides, which carbons are labeled with a "prime" sign?A. The carbons on the nitrogenous baseB. The carbons on the sugarC. The carbons that participate in H-bondingD. The carbons that make up the backboneE. The carbons that are used for energy during DNA synthesis

Which of the following statements about allostery is TRUE?Binding of allosteric molecules usually locks an enzyme in its current conformation, such that the enzyme cannot adopt a different conformation.Enzymes are the only types of proteins that are subject to allosteric regulation.Allosteric regulation is always used for negative regulation of enzyme activity.Allosteric regulators are often products of other chemical reactions in the same biochemical pathway.

Which of the following list of the components of DNA is accurate?A. Nitrogenous bases, phosphates, phosphodiester bonds, H-bonds, sulfatesB. Amino groups, nitrogenous bases, 2'-OH groups, H-bondsC. Nitrogenous bases, phosphodiester bonds, amino groups, H-bondsD. Phosphodiester bonds, nitrogenous bases, disulfide bonds, sugarsE. Phosphates, 2'-H groups, disulfide bonds, H-bonds

Noncompetitive inhibitors of enzymes typically _______.act by mimicking the natural substrate and occluding the active site.are covalently attached to the active site.use an allosteric mechanism where binding to a regulatory site alters the conformation of the active site so substrate cannot bind.use an induced fit mechanism where binding to a regulatory site improves the "fit" of the substrate in the active site.

The Km of an enzyme for its substrate is defined the concentration of the substrate that is required to produce the _________ velocity of the enzyme1/maximalinitialhalf-maximalmaximal

Which two amino acids are most likely to form an electrostatic interaction?Lysine and ArginineAspartic acid and LysineSerine and PhenylalanineNa+ and Cl-Methionine and Proline