Biochem Module 1 - KM Exam Questions and Answers Latest Update 2025 Already Passed

Biochem Module 1 - KM Exam Questions and Answers Latest Update 2025 Already Passed The water content in the human body is approximately: A) 90%. B) 80%. C) 70%. D) 60%. E) 50%. - Answers C) 70% The four most abundant chemical elements in living systems are: A) hydrogen, oxygen, sulfur and phosphorus. B) hydrogen, carbon, nitrogen and oxygen. C) sodium, potassium, carbon and oxygen. D) sodium, potassium, nitrogen and sulfur. E) carbon, nitrogen, oxygen and potassium. - Answers B) Hydrogen, carbon, nutrogen, and oxygen Nearly all proteins contain: A) cobalt. B) phosphorus. C) selenium. D) sulfur. E) none of the above. - Answers D) sulfur. Which of the following statements is FALSE? A) Proteins can be structural components of cells. B) Proteins can transmit signals between cells. C) Proteins can transport molecules within cells and between cells. D) Proteins can be both hormones and hormone receptors. E) Proteins are the only biological polymer that can catalyze biochemical reactions. - Answers E) Proteins are the only biological polymer that can catalyze biochemical reactions. Which of the following is NOT classed as a lipid? A) Cholesterol B) Palmitic acid C) Glycerol D) Phosphatidyl serine E) Triacylglycerol - Answers C) Glycerol Amino acids and simple organic compounds like carbon dioxide and hydrogen cyanide cannot be produced without the use of enzymes. - Answers False Oxidation-reduction reactions, which are the basis of many biochemical reactions and pathways, cannot take place in the absence of oxygen. - Answers False Many biochemical reactions that form biopolymers from monomeric units involve the removal of water. - Answers True The principle component of a biological membrane is a triglyceride. - Answers False The chemical element ________ has a role in both transfer of energy as well as in the structure of nucleic acids. - Answers Phosphorous List the four major classes of biological macromolecules. - Answers lipids, carbohydrates, proteins, nucleic acids An amphipathic molecule provides the foundation for biological membranes because they have both ________ and ________ functional groups. - Answers hydrophilic, hydrophobic Genomics is concerned with the entire ________, while ________ is focused on identifying all of the proteins of a cell. - Answers genome, proteomics Each of the following is a noncovalent interaction EXCEPT: A) a hydrogen bond. B) a carbon-hydrogen bond. C) the interaction between an amino and a carboxylate group. D) a van der Waals interaction. E) an interaction between —NH3+ and a water molecule. - Answers B) a carbon-hydrogen bond. The most important noncovalent interaction in biochemistry is the ________ bond. - Answers hydrogen Which of the following is FALSE when considering van der Waals interactions? A) The van der Waals radius represents the most stable distance between two interacting centers. B) Van der Waals radii can determine molecular surfaces. C) Molecules that interact by van der Waals forces do not interpenetrate. D) The total interaction energy is the sum of the attractive and repulsive forces. E) They are not important in determining the stability of three-dimensional structures of proteins - Answers E) They are not important in determining the stability of three-dimensional structures of proteins Which of the following in biological compounds are sufficiently electronegative to serve as strong donors in a hydrogen bond? A) Hydrogen and oxygen B) Oxygen and nitrogen C) Nitrogen and hydrogen D) Hydrogen and carbon E) Nitrogen and carbon - Answers B) Oxygen and nitrogen Hydrogen bonds share features of both covalent and noncovalent bonds. - Answers True Which of the following is TRUE of hydrophobic molecules? A) They have limited solubility in water. B) Water forms a cage-like structure around them. C) Dissolving in water decreases the entropy of the mixture. D) They self-associate by releasing some of the surrounding water molecules. E) All of the above - Answers E) All of the above Water is both a hydrogen bond donor and acceptor - Answers True Amphipathic molecules are not able to interact via van der Waals forces - Answers False Ionic compounds can be readily dissolved in water because the high dielectric constant of water screens and decreases the ________ force between the oppositely charged ions. - Answers electrostatic The ________ describes the tendency for hydrophobic molecules to aggregate because of the exclusion of water with the consequent increase of entropy of the solvent. - Answers hydrophobic effect Glycine cannot serve as a buffer because it has two ionizable groups. - Answers False The average charge on an amino acid below its pI will be positive - Answers True Calculate the acid dissociation constant Ka of a 0.2 M solution of weak acid that is 0.1% ionized. - Answers 2 × 10-7 Calculate the pH of a 0.1 M phosphate buffer (pKa = 6.86) that contains equal amounts of acid and conjugate base - Answers 6.86 Calculate the pH of a 0.2 M acetate buffer (pKa = 4.77) that contains twice as much acid as conjugate base - Answers 4.47 The pKa of each amino acid residue in a protein will not be influenced by the adjacent residue. - Answers False Calculate the pH at the end of an enzyme-catalyzed reaction if it were carried out in a 0.1 M phosphate buffer, pH 6.86 and 0.005 M of acid was produced during the reaction? - Answers 6.77 If hydroxide is added to an amino acid it will become increasingly ________ charged. - Answers negatively Calculate the pH of a weak acid that is 0.2% ionized in a 0.2 M solution - Answers 3.39 The net charge on an amino acid at its isoelectric point (pI) is ________. - Answers zero Many proteins interact with DNA at physiological pH because: A) proteins are naturally attracted to DNA regardless of the pH. B) the negatively charged DNA is electrostatically attracted to positively charged regions on proteins. C) the positively charged DNA is electrostatically attracted to negatively charged regions on proteins. D) proteins and DNA interact using mainly hydrophobic interactions. E) both proteins and DNA are at their isoelectric points at physiological pH and tend to aggregate. - Answers B) the negatively charged DNA is electrostatically attracted to positively charged regions on proteins. Small ions in biological fluids: A) encourage strong electrostatic interactions between oppositely charged macroions at low ionic strengths. B) encourage strong electrostatic interactions between oppositely charged macroions at high ionic strengths. C) have no effect on the interactions between oppositely charged macroions. D) tend to cluster around macroions of the same charge.