(Test Bank) Biochemistry- Complete Exam Test Bank - Exam Questions & Answers

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Chemistry

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1 Biochemistry - Complete Exam Test Bank - Exam Q uestions & Answers Chapter 1 : Introduction to Biochemistry 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 2 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 3 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 4 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 5 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 6 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 7 40) The only reason phages are not considered to be cells is because they do not contain a plasma membrane. Answer: FALSE Page Ref: Section 6 41) Diffusion is an adequate means of distributing nutrients in prokaryotic cytoplasm because they have more surface area than volume compared to most eukaryotes. Answer: TRUE Page Ref: Section 7 42) Eukaryotic cells are distinguished from prokaryotes by their usually larger size, a complex cytoskeleton and membrane -bounded organelles. Answer: TRUE Page Ref: Section 7 43) Chloroplasts are organelles found in plants, algae and some protists and are the site of photosynthesis. Answer: TRUE Page Ref: Section 7 44) The endoplasmic reticulum is the major site of RNA synthesis and the site of assembly of ribosomes. Answer: FALSE Page Ref: Section 8 45) The nuclear envelope is a membrane that surrounds the nucleus and is continuous with the endoplasmic reticulum. Answer: TRUE Page Ref: Section 8 46) Ribosomes on the surface of rough endoplasmic reticulum are the site of ATP synthesis. Answer: FALSE Page Ref: Section 8 47) The Golgi apparatus consists of flattened, fluid-filled, membranous sacs and is responsible for chemical modification and sorting of some biomolecules. Answer: TRUE Page Ref: Section 8 48) Mitochondria are the main sites of energy transduction in aerobic eukaryotic cells. Answer: TRUE Page Ref: Section 8 8 49) The mitochondria and Golgi apparatus are two organelles which originated from bacteria and were incorporated into eukaryotic cells via symbiosis. Answer: FALSE Page Ref: Section 8 50) In an animal cell, DNA can be found only in the nucleus. Answer: FALSE Page Ref: Section 8 51) Actin has been shown to be one of the most evolutionarily conserved proteins. It is present in all eukaryotic cells and frequently is the most abundant protein in the cell. Answer: TRUE Page Ref: Section 8 52) The mitotic spindles are formed from microtubule proteins. Answer: TRUE Page Ref: Section 8 53) The filament fibers in the cytoskeleton are composed primarily of carbohydrate molecules. Answer: FALSE Page Ref: Section 8 54) The diffusion of large molecules such as enzymes is significantly slowed by the presence of the cytoskeleton. Answer: TRUE Page Ref: Section 8 55) In eukaryotic cells lysosomes are specialized digestive vesicles with a highly acidic interior. Answer: TRUE Page Ref: Section 8 56) The process of cell division that occurs in the tissues is called mitosis. Answer: TRUE Page Ref: Section 8 57) Photosynthesis involves capturing energy from light that is then used to drive the formation of carbohydrates from carbon dioxide and water. Answer: TRUE Page Ref: Section 8 9 58) The chemical name for ATP is alanine triphosphate. Answer: FALSE Page Ref: Section 8 59) Absolute zero is equal to 0 °C. Answer: FALSE Page Ref: Appendix 60) One Angstrom is equal to 1 × 10-10 meters. Answer: TRUE Page Ref: Appendix 10 Chapter 2 Water 1) Which is not a proper way to form a hydrogen bond? (The symbol ʺRʺ represents a general organic group. The hydrogen bonding is represented by dashed lines.) A) I B) II C) III D) IV Answer: B Page Ref: Section 1 2) Which statement does not explain the polarity of water? A) Oxygen is more electronegative than hydrogen. B) Water molecules have a bent geometry (V-shaped). C) The oxygen in water has sp2 hybrid orbitals. D) In water the hydrogen carries a partial positive charge (δ+). Answer: C Page Ref: Section 1 3) Which substance do you expect to be most soluble in water? A) ammonia, NH3 B) methane, CH4 C) carbon dioxide, CO2 D) nitrogen, N2 Answer: A Page Ref: Section 1 11 4) What is the maximum number of hydrogen bonds that one water molecule can have with neighboring water molecules? A) 1 B) 2 C) 3 D) 4 Answer: D Page Ref: Section 2 5) The abundance of water in the cells and tissues helps to minimize temperature fluctuations. This is due to what property of water? A) density B) viscosity C) specific heat D) boiling point Answer: C Page Ref: Section 2 6) Compounds that ionize when dissolved in water are called . A) electrolytes B) polar compounds C) hydrophobic compounds D) amphipathic compounds Answer: A Page Ref: Section 3 7) Electrolytes dissolve readily in water because A) they are held together by electrostatic forces. B) they are hydrophobic. C) water molecules can cluster about cations. D) water molecules can cluster about anions. E) water molecules can cluster about cations and anions. Answer: E Page Ref: Section 3 8) A molecule or ion is said to be hydrated when it . A) is neutralized by water B) is surrounded by water molecules C) reacts and forms a covalent bond to water D) aggregates with other molecules or ions to form a micelle in water Answer: B Page Ref: Section 3 12 9) Which would you expect to be most soluble in water? A) I B) II C) III D) IV Answer: A Page Ref: Section 3 10) Solutes diffuse more slowly in cytoplasm than in water because of A) the higher viscosity of water. B) the higher heat of vaporization of water. C) the presence of many crowded molecules in the cytoplasm. D) the absence of charged molecules inside cells. Answer: C Page Ref: Section 3 11) The pressure is the pressure required to prevent the flow of solvent through a solvent -permeable membrane that separates two solutions of different solute concentration. A) hydrostatic B) electromotive C) osmotic D) partial Answer: C Page Ref: Section 3 13 12) Which is true about the solubility of electrolytes in water? A) They are all insoluble in water. B) They are usually only sparingly soluble in water. C) They often form super -saturated aqueous solutions. D) They readily dissolve and ionize in water. Answer: D Page Ref: Section 3 13) What is the difference between a particle being hydrated versus being solvated ? A) A hydrated particle is surrounded by a shell of water. A solvated molecule is surrounded by a shell of solvent molecules, not necessarily water. B) The terms hydrated and solvated mean exactly the same thing. C) A hydrated particle has reacted with hydrogen. A solvated particle is dissolved in a solvent. D) The word hydrated is used only when the solute is an electrolyte. Answer: A Page Ref: Section 3 14) The osmotic pressure of an aqueous solution depends on A) the chemical nature of the solute. B) the molar concentration of solute. C) the hydrophobic effect of the solute. D) All of the above. E) None of the above. Answer: B Page Ref: Section 3 15) The osmotic pressure of a 0.010 M sucrose (C 12H22O11) solution at 25 °C is 0.24 atm. How does the osmotic pressure of a 0.010 M glucose (C6H12O6) solution at 25 °C compare to this? Note that neither solute is volatile or ionizable. A) The glucose solution has a lower osmotic pressure because its molar mass is lower than sucrose. B) The glucose solution has a higher osmotic pressure because its molar mass is lower than sucrose. C) The osmotic pressures are equal because the solutions have the same molar concentration. D) Nothing can be said about the osmotic pressure of the glucose solution without more information. Answer: C Page Ref: Section 3 14 16) Oil and water do not form a solution due to . A) the hydrophobic effect B) the inability of oil to hydrogen bond with water C) the nonpolarity of oil D) All of the above (A-C) E) A and C only Answer: D Page Ref: Section 4 17) Molecules that are both hydrophobic and hydrophilic are . A) amphipathic B) amphoteric C) bipolar D) not possible Answer: A Page Ref: Section 4 18) Which molecule or ion below is amphipathic? A) H2NCH 2COOH (glycine) B) H2O C) CH3(CH2)14COO- D) CH3CH2CH2CH2CH3 Answer: C Page Ref: Section 4 19) Which statement explains the cleaning action of soap on greasy dishes? A) The soap changes the water -solubility of the grease so that it is easily dissolved by the water. B) The grease is trapped inside the hydrophobic interior of micelles made of soap molecules. C) The soap chemically breaks down the grease into smaller, more water -soluble molecules. D) The soap hydrates the grease with its polar head groups and holds it in suspension. Answer: B Page Ref: Section 4 20) Some ions such as thiocyanate that are poorly solvated in water and can enhance the solubility of nonpolar compounds in water by disordering the water molecules are called . A) azeotropes B) hydrophobic ions C) zeolytes D) chaotropes Answer: D Page Ref: Section 4 15 21) Which of the following is NOT a ʺweakʺ interaction? A) hydrogen bonds B) van der Waals forces C) disulfide bonds D) ionic interactions E) hydrophobic interactions Answer: C Page Ref: Section 5 22) Which of the following weak interactions is not an electrostatic interaction? A) hydrogen bonds B) charge -charge interactions C) hydrophobic interactions D) van der Waals forces Answer: C Page Ref: Section 5 23) Which of these noncovalent forces in biological systems is usually the strongest? A) hydrogen bonds B) London dispersion forces C) hydrophobic interactions D) van der Waals forces Answer: A Page Ref: Section 5 24) Hydrogen bonds can occur when hydrogen is covalently bonded to atoms like nitrogen and oxygen. What property of nitrogen and oxygen is important for this? A) atomic mass B) ionizability C) hydrophobicity D) electronegativity Answer: D Page Ref: Section 5 25) Attractions of oppositely charged functional groups of proteins are sometimes called . A) salt bridges or ion pairing B) disulfide bridges C) London bridges D) hydrophilic bridges Answer: A Page Ref: Section 5