Intro to Biochemistry (Murphy 301) CH 1 – 4 Solutions

Intro to Biochemistry (Murphy 301) CH 1 – 4 Solutions The side chain of histidine has a typical pKa value in the range of 6.5-7.4. However, when analyzing the pKa values in a particular protein, scientists determined that one particular His residue has an unusually low pKa value of 4.8. Which of the following statements correctly explain this anomaly? 1) The microenvironment around a residue can impact its pKa value. 2) A positively charged amino acid must be in close proximity to this residue. 3) A negatively charged amino acid must be in close proximity to this residue. 4) This residue must be located on the surface of the protein. - AnswersStatement 1 and 2 The side chain of ________ has a pKa in the physiological pH range and is therefore often involved in proton transfer during enzymatic catalysis. - AnswersHistidine All amino acids have a chiral α-carbon EXCEPT ________. - Answersglycine Which of the following statements regarding Anfinsen's denaturing experiments with ribonuclease A are valid? 1) Exposing the denatured protein to air oxidation and then dialysis to remove urea restored the protein to its original functionality. 2) Removing urea by dialysis and then allowing air oxidation of the denatured protein restored the protein to its original functionality. 3) Denaturing the protein with both urea and β-mercaptoethanol yielded an inactive protein. 4) Protein folding is determined by its primary sequence. - AnswersOnly statements 2, 3, and 4 are valid. Which of the following statements about protein quaternary structure are correct? 1) It involves a complex of two or more proteins interacting with each other. 2) The subunits of the structure can be either identical or different. 3) The interactions between subunits can give rise to indefinite growth of polymeric complexes. 4) Most assemblies of protein subunits have one or more defined axis of rotation. - AnswersAll statements are correct. In general, enzymes are what kinds of molecules? proteins minerals carbohydrates lipids nucleic acids - Answersproteins The basic building blocks of proteins are _______ - Answersamino acids All amino acids are composed what three things attached to it? - Answerscentral α-carbon that has an amine group a carboxylic acid group and an R group All amino acids except _______ are chiral with the two isomer forms known as the L-isomer and the D-isomer. - Answersglycine The ____ is the only isomer known to be incorporated into proteins. - AnswersL-isomer This ionic state, where the carboxylic acid is negative and the amine group is positive, is known as the __________ state - Answerszwitterionic state What are the N-terminal and C-terminal residues for the following peptide sequence? Peptide sequence: EASY - AnswersE is the N-terminal residue; Y is the C-terminal residue. Ultimate source of energy for life on earth is: A. Sun B. Geothermal heat C. Carbohydrates D. Fats E. Other organisms - AnswersSun Which is not a common component of biomolecules? A. Carbon B. Hydrogen C. Oxygen D. Nitrogen E. Chlorine - AnswersChlorine Which is a basic structural unit of living organisms? A. Nucleus B. Cell membrane C. Tissue D. Cell E. Cytoskeleton - AnswersCell Which of the following is not an organelle? A. Mitochondria B. Chloroplast C. Nucleus D. Plasma Membrane E. Golgi Complex - AnswersPlasma Membrane Which of the following is not a role played by carbohydrates in living cells? A. Energy source B. Structural support C. Intercellular communication D. Both A and B E. All roles are played - AnswersAll roles are played by carbohydrates in living cells Metabolism is best defined as the... A. Reactions of living cells B. Reactions that synthesize large molecules in living cells C. Reactions that degrade molecules in living cells D. Conversion of food molecules to energy E. Reactions that synthesize and degrade molecules in living cells - AnswersE. Reactions that synthesize and degrade molecules in living cells The average life span of a species is about ________years A) One million B) Ten million C) Five hundred thousand D) Five million E) One hundred thousand - AnswersA. One million