Bio-chemistry Test bank, All chapters (answered) | A+ Solutions

Bio-chemistry Test bank, All chapters (answered) | A+ Solutions-1) Which elements account for more than 97% of the weight of most organisms? A) C, H, N, Mg, O, S B) C, H, N, O, P, S C) C, H, N D) Fe, C, H, O, P E) Ca2+, K+, Na+, Mg2+, Cl- Answer: B Page Ref: Section 2 2) Proteins in biological membranes may be A) porous. B) attached to the membrane surface. C) span the membrane. D) All of the above E) B and C only Answer: D Page Ref: Section 3 3) Which statement about cellulose is false? A) It is the most abundant polysaccharide in nature. B) Its monomers are joined by glycosidic bonds. C) It is present in the stems of flowering plants. D) The hydroxyl groups of neighboring cellulose molecules interact to form strong, insoluble fibers. E) It is a branched polymer of glucose. Answer: E Page Ref: Section 3 4) When Keq of a reaction = 1, then A) the forward reaction is faster than the reverse reaction. B) the reverse reaction is faster than the forward reaction. C) the forward and reverse reaction rate constants are equal. D) more products are formed than reactants. E) fewer products are formed than reactants. Answer: C Page Ref: Section 4 5) Which statement is true about a reaction with an equilibrium constant, Keq, equal to 1000? A) The forward rate constant is 1000 times greater than the reverse rate constant. B) The forward rate constant is 3 times greater than reverse rate constant. C) The forward rate constant is 1000 times smaller than the reverse rate constant. D) The forward rate constant is 3 times smaller than the reverse rate constant. E) There is not enough information given to compare the forward and reverse rate constants. Answer: A Page Ref: Section 4 6) The study of the energy changes during metabolic reactions is called . A) bioinformatics B) metabodynamics C) thermometrics D) bioenergetics E) biological heat dynamics Answer: D Page Ref: Section 4 7) A spontaneous chemical reaction always has a change. A) positive Gibbʹs free energy B) negative Gibbʹs free energy C) positive enthalpy D) negative enthalpy E) positive entropy Answer: B Page Ref: Section 4 8) Prokaryotes are valuable tools for biochemists because A) E. coli is well-studied and typical of prokaryotes. B) they contain as many genes as eukaryotic cells. C) many of their chromosomes are sequenced. D) they are not very diverse organisms. E) All of the above Answer: C Page Ref: Section 6 9) Which cellular component carries out oxidation reactions, some of which produce hydrogen peroxide? A) peroxisomes B) mitochondria C) chloroplasts D) lysosomes E) vacuoles Answer: A Page Ref: Section 8 10) Why is it important that the enzymes in lysosomes are more active at acidic pH than at neutral pH? A) Since lysosomes are primarily found in the stomach acid of mammals, their pH dependence allows for maximum efficiency for the digestion of foodstuffs. B) It prevents their diffusion out of the lysosomes. C) It maximizes the interaction with their substrates which are always bases. D) It prevents them from accidentally degrading the macromolecules in the cytosol. E) It allows for regulation of their uptake by the mitochondria. Answer: D Page Ref: Section 8 11) Molecules from living cells cannot be synthesized outside of living cells. Answer: FALSE Page Ref: Section 1 12) Fermentation in the absence of cells demonstrated that metabolic processes were chemical in nature. Answer: TRUE Page Ref: Section 1 13) Enzymes are protein catalysts that form an intermediate with a substrate that fits into it. Answer: TRUE Page Ref: Section 1 14) The modified lock-and-key theory of enzyme action proposed by Emil Fischer has been completely replaced by more modern ideas of catalysis. Answer: FALSE Page Ref: Section 1 15) Enzymes are not as efficient as most catalysts used in organic chemistry, since they must function at body temperature. Answer: FALSE Page Ref: Section 1 16) Bioinformatics has permitted rapid advances in our understanding of structural macromolecules from living cells. Answer: TRUE Page Ref: Section 1 17) The role of DNA as the genetic material was confirmed by transforming Streptococci in experiments performed several years after the famous Watson and Crick description of DNA structure. Answer: FALSE Page Ref: Section 1 18) Crick referred to the flow of information from nucleic acid to protein as the Central Dogma. Answer: TRUE Page Ref: Section 1 19) Functional groups describe one or more portions of organic compounds found in living cells. Answer: TRUE Page Ref: Section 2 20) A phosphate ester contains a phosphate functional group. Answer: TRUE Page Ref: Section 2 21) Under most biological conditions, acid groups and amino groups are fully protonated. Answer: FALSE Page Ref: Section 2 22) Removal of water from residues of a macromolecule results in the formation of that macromolecule. Answer: TRUE Page Ref: Section 3 23) Mr is the mass of a molecule relative to 1/12 the mass of an atom of the most common isotope of carbon. Answer: TRUE Page Ref: Section 3 24) Biochemists describing the molecular weight of a protein really mean the atomic weight in grams. Answer: FALSE Page Ref: Section 3 25) The absolute molecular mass of macromolecules is given in daltons, where 1 dalton = 1 atomic mass unit. Answer: TRUE Page Ref: Section 3 26) A peptide bond is formed by the condensation of different functional groups from two amino acids. Answer: TRUE Page Ref: Section 3 27) The conformation of a protein enzyme determines whether it is functional or not. Answer: TRUE Page Ref: Section 3 28) Lysozyme is an enzyme with a cleft or depression at its active site. Answer: TRUE Page Ref: Section 3 29) The Haworth projection of the ring form of a monosaccharide always shows a flat plane with one edge projecting out of the page (using thicker lines). Answer: TRUE Page Ref: Section 3 30) Sugars with six carbons are the only ones capable of forming a ring structure as shown in a Haworth projection. Answer: FALSE Page Ref: Section 3 31) ATP contains both phosphoester and phosphoanhydride linkages. Answer: TRUE Page Ref: Section 3 32) A phosphodiester linkage in DNA contains two phosphorous atoms. Answer: FALSE Page Ref: Section 3 33) Lipids aggregate to form bilayers because some lipid molecules are hydrophobic and other lipid molecules are hydrophilic. Answer: FALSE Page Ref: Section 3 34) Thermodynamics and its laws are obeyed by living cells. Answer: TRUE Page Ref: Section 4 35) The tendency of a metabolic reaction to proceed is due to the free energy of both the reactants and products as well as the change in randomness of that reaction. Answer: TRUE Page Ref: Section 4 36) Biochemical reactions are more likely to proceed if the reaction has an increase in enthalpy ( △H) and a decrease in entropy (△S). Answer: FALSE Page Ref: Section 4 37) All prokaryotic cells are about 1/10 the size of an average eukaryotic cell or smaller. Answer: FALSE Page Ref: Section 5 38) All cells have kept the same general patterns of metabolism, a very similar genetic code and the same monomers or residues. Answer: TRUE Page Ref: Section 5 39) Eukaryotes include plants, animals and bacteria. Answer: FALSE Page Ref: Section 5