Cell Bio Final
Which of the following is important in protein folding after the formation of a polypeptide? A. hydrogen bonding B. ionic bonding C. van der Waals interactions D. hydrogen bonding, ionic bonding, and van de Waals interactions.
D. hydrogen bonding, ionic bonding, and van de Waals interactions.
Intermediate filaments _________________ A. strengthen cells against mechanical stress. B. are larger than microtubules and smaller than actin filaments. C. have intrinsic polarity, with plus and minus ends that assemble with different kinetics. D. require ATP hydrolysis to assemble in cells.
A. strengthen cells against mechanical stress.
Consider the three phases of glycolysis: (1) preparation and cleavage (Gly-1 to Gly-5) (2) oxidation (Gly-6 to Gly-7) (3) pyruvate formation (Gly-8 to Gly-10) Which of these phases produces ATP? A. 2and3 B. 1 C. 3 D. 1and2
A. 2and3
ABC transporters are important for bacterial drug resistance and have 6 transmembrane domains. How many stop-transfer sequences do they have? A. 3 B. 1 C. 5 D. 6
A. 3
Aerobic respiration generates up to ________ ATP molecules per glucose molecule. A. 38 B. 24 C. 16 D. 2
A. 38
The gross output of ATP from glycolysis is ________, whereas the net output of ATP is ________. A. 4;2 B. 4;1 C. 6;4 D. 2;4
A. 4;2
Myosin II motors are most likely to be found in which of the following structures? A. stress fibers. B. the nuclear envelope. C. mitotic spindle. D. microvilli.
A. stress fibers.
The Calvin cycle occurs in the chloroplast __________. A. stroma B. grana C. thylakoid lumen D. thylakoid membrane
A. stroma
Plastocyanin (PC) __________. A. All of the above are true of PC. B. is a mobile electron carrier. C. is functionally similar to plastoquinol. D. carries electrons to PSI.
A. All of the above are true of PC.
Which of the following statements about the cytoskeleton is true? A. All three types of cytoskeletal polymers form from subunits that reversibly associate through non-covalent interactions. B. Microtubules are the largest polymer and transmit forces between cells. C. Intermediate filaments were the first type of cytoskeletal polymer found because they are very stable. D. Microtubules and actin interact with each other but not with intermediate filaments.
A. All three types of cytoskeletal polymers form from subunits that reversibly associate through non-covalent interactions.
Which of the following stabilizes homophilic interactions between the extracellular domains of cadherins on neighboring cells? A. Ca2+ B. integrins C. proteoglycans D. hyaluronate
A. Ca2+
Activation of which of the following is associated with the formation of filopodia? A. Cdc42 B. γ-tubulin C. Rho D. plectin
A. Cdc42
Each of the following is an essential feature of electron transfer from water to NADP+ except: A. Coenzyme Q. B. PSII. C. PSI. D. Cytochrome b6/f complex.
A. Coenzyme Q.
Which of the following carrier molecules has a heme prosthetic group? A. Cytochromes B. Coenzyme Q C. Copper-containing cytochromes D. Iron-sulfur proteins
A. Cytochromes
The mitochondrial ATP synthase consists of several different protein subunits. Which subunit catalyzes the synthesis of ATP as a result of a conformational change? A. F1 ATPase head B. transmembrane H+ carrier C. peripheral stalk D. central stalk
A. F1 ATPase head
Hydrogen bonding is most important in stabilizing the ________ structure of many proteins. A. primary B. secondary C. tertiary D. quaternary
B. secondary
The limit of resolution can best be defined as ___________________ A. the distance that an object must be moved to be distinguished from its background. B. the distance that two objects must be apart to be distinguished as separate objects. C. the amount of solvent that must be available to remix a solution. D. the magnification power of a microscope.
B. the distance that two objects must be apart to be distinguished as separate objects.
The scientific work that established DNA, rather than protein, as the molecule of heredity was performed prior to ________________ A. Mendel's work on heredity. B. the elucidation of the double helix structure of DNA. C. Antonie van Leeuwenhoek's observation of internal cell structures. D. the formation of the chromosome theory of heredity.
B. the elucidation of the double helix structure of DNA.
Saturation can be defined as ________________. A. denaturation of an enzyme. B. the inability to increase reaction velocity beyond a finite upper limit. C. inhibition of enzyme function by blocking the active site. D. the substrate concentration at which velocity reaches one-half maximum velocity.
B. the inability to increase reaction velocity beyond a finite upper limit.
Which of the following is found exclusively in RNA? A. guanine B. uracil C. thymine D. adenine
B. uracil
1 mm = ________ nm A. 1/1000 B. 10 C. 1000 D. 1,000,000
C. 1000
Which of the following is mismatched? A. Mus musculus - immunology B. Escherichia coli - genetics C. Drosophila melanogaster - photosynthesis D. Arabidopsis thaliana - plant gene function
C. Drosophila melanogaster - photosynthesis
In animal cells, the Na+-K+-pump uses the energy from ATP hydrolysis to move _________ the cell. A. 2K+ionsoutofand3Na+ionsinto B. 3K+ionsoutofand2Na+ionsinto C. 2Na+ionsoutofand3K+ionsinto D. 3Na+ ionsoutofand2K+ ionsinto
D. 3Na+ ionsoutofand2K+ ionsinto
Step 3 in glycolysis requires the activity of phosphofructokinase to convert fructose 6- phosphate into fructose 1,6-bisphosphate. Which of the following molecules is an allosteric inhibitor of this enzyme? A. ADP B. AMP C. Pi D. ATP
D. ATP
Which of the following statements is false? A. All organisms consist of one or more cells. B. The cell is the basic unit of structure for all organisms. C. Cells come in a wide variety of sizes and shapes. D. All cells have a membrane-bound nucleus.
D. All cells have a membrane-bound nucleus.
The transfer of energy directly from a photoexcited electron in a pigment molecule to another electron in an adjacent pigment molecule occurs by ______. A. resonance energy transfer. B. photophosphorylation. C. photochemical reduction D. photoexcitation.
A. resonance energy transfer.
Continuous carbon assimilation in the Calvin cycle is made possible by the regeneration of __________. A. ribulose-1,5-bisphosphate. B. 3-phosphoglycerate. C. glycerate-1,3-bisphosphate. D. glyceraldehyde-3-phosphate.
A. ribulose-1,5-bisphosphate.
In relaxed muscle, Ca2+ is found in highest concentration in the ________________ A. sarcoplasmic reticulum. B. sarcoplasm. C. T tubules. D. neuromuscular junction.
A. sarcoplasmic reticulum.
Enzyme regulation may occur by several methods. Which of the following is not a means of enzyme regulation? A. saturation B. substrate-level phosphorylation C. feedback inhibition D. allosteric regulation
A. saturation
In multicellular plants, the __________________ is located inside of the __________________. A. secondary cell wall; primary cell wall B. primary cell wall; secondary cell wall C. middle lamella; primary cell wall D. middle lamella; secondary cell wall
A. secondary cell wall; primary cell wall
A protein that is N-glycosylated is expected to be _____________. A. secreted from the cell. B. retained in the endoplasmic reticulum. C. localized in the Golgi body. D. imported into a cell by endocytosis.
A. secreted from the cell.
Which of the following accurately describes the structure of fibrous proteins? A. Fibrous proteins are usually composed of either α helices or β sheets throughout the molecule, giving them a highly ordered, repetitive structure. B. Fibrous proteins usually contain a number of different domains with different structural motifs. C. Fibrous proteins have an extensive tertiary and quaternary structure that affects the strength and elasticity of each fiber. D. Fibrous proteins have a simple primary structure and very little secondary structure, resulting in long, thin fibers.
A. Fibrous proteins are usually composed of either α helices or β sheets throughout the molecule, giving them a highly ordered, repetitive structure.
Secretory vesicles are used to transport proteins from the __________ to the ___________. A. Golgi complex, outside of the cell B. Golgi complex; lysosomes C. nucleus; Golgi complex D. smooth ER; rough ER
A. Golgi complex, outside of the cell
Cytological examination of resting and contracted muscle provides important support for the sliding filaments model for how skeletal muscle contracts. This evidence includes the observation that during contraction the ______________ A. H zone becomes narrower. B. I bands get longer. C. Z lines move farther apart. D. The lengths of the thick filaments shorten significantly.
A. H zone becomes narrower.
Which of the following statements about membrane-bound organelles is true? A. In a typical cell, the area of the ER membrane far exceeds the area of the plasma membrane. B. Organelles diffuse rapidly within the cell because ~90% of the cell volume is cytosol. C. The nucleus is the only organelle that contains DNA. D. All membrane-bound organelles are part of the endomembrane system.
A. In a typical cell, the area of the ER membrane far exceeds the area of the plasma membrane.
Matter and energy flow through the biosphere. The flow of matter, however, differs from the flow of energy. Which of the following statements accurately describes these differences? A. Matter flows in cycles, whereas energy flows in one direction. B. Energy flows as organic molecules are reduced to inorganic molecules, but matter does not. C. Matter does not accompany energy as it enters the biosphere, but it does flow with energy from the biosphere. D. Energy flows from chemotrophs to phototrophs, whereas matter flows from phototrophs to chemotrophs.
A. Matter flows in cycles, whereas energy flows in one direction.
Your house plant is growing slowly and lacks its normal bright green color, so you call a botanist for advice. She suggests that the plant may be deficient in magnesium (Mg2+). Why are these symptoms associated with Mg2+ deficiency? A. Mg2+ is an important component in chlorophyll. B. Mg2+ is important in the structure of many amino acids. C. Mg2+ is a cofactor for NADPH function. D. Lack of Mg2+ in the soil allows pathogenic bacteria to grow.
A. Mg2+ is an important component in chlorophyll.
Retinal is the cofactor in bacteriorhodopsin that absorbs sunlight. What does this allow bacteriorhodopsin to do? A. Move protons (H+) outside the cell B. Transmit a signal inside the cell C. Move Na+ and Cl- outside the cell D. Unblock its β-barrel to let protons move across the membrane
A. Move protons (H+) outside the cell
In studying osteoporosis in humans, you wish to test a newly designed treatment for efficacy. Your best choice for a model organism would be _________________ A. Mus musculus. B. Escherichia coli. C. Caenorhabditis elegans. D. Arabidopsis thaliana.
A. Mus musculus.
Which of the following statements best describes the role of NAD+/NADH in glycolysis? A. NAD+ accepts electrons. B. NADH accepts electrons during fermentation. C. NADH is used to directly create the phosphoanhydride bonds in ATP. D. All of the above are correct.
A. NAD+ accepts electrons.
Which of the following molecules is most likely to cross the cell membrane directly by passive diffusion? A. Na+ B. a steroid hormone (a hydrocarbon) C. fructose (a sugar) D. insulin (a polypeptide)
A. Na+
Which of the following statements correctly describes cyclic electron flow pathways? A. No exogenous electron source is required. B. Water molecules are split. C. Proton gradients are never formed. D. Both PSI and PSII are required.
A. No exogenous electron source is required.
Which of the following statements about nuclear lamins is FALSE? A. Nuclear lamins are only found in skin, muscle, and nerve cells. B. Nuclear lamins disassemble during cell division. C. Mutations in nuclear lamins can result in premature aging. D. Nuclear lamins anchor chromatin to the nuclear envelope.
A. Nuclear lamins are only found in skin, muscle, and nerve cells.
During chemiosmotic coupling, many components transfer energy to and from each other. Which of the following pairs do NOT have an accurate free energy relationship? A. O2>H2O B. NADH > NAD+ C. cytochrome c (red) > cytochrome c (ox) D. ubiquinone(red) > ubiquinone (ox)
A. O2>H2O
Each of the following statements about the citric acid cycle is true except: A. Oxidation by transfer of electrons to coenzymes occurs at two steps. B. Decarboxylation to release CO2 occurs at two steps. C. Substrate-level phosphorylation generates ATP/GTP at one step. D. Acetate enters the citric acid cycle and joins a four-carbon acceptor molecule to form citrate.
A. Oxidation by transfer of electrons to coenzymes occurs at two steps.
The chemiosmotic model of ATP synthesis is based on each of the following lines of experimental evidence except: A. Oxidative phosphorylation does not require a membrane-enclosed compartment. B. Uncoupling agents abolish both the proton gradient and ATP synthesis. C. Electron transport causes protons to be pumped out of the mitochondrial matrix. D. The proton gradient established by electron transport has enough energy to drive ATP synthesis.
A. Oxidative phosphorylation does not require a membrane-enclosed compartment.
Consider the following list of phosphorylated compounds with their free energies of phosphate hydrolysis: PEP: -14.8 kcal/mole ATP: -7.3 kcal/mol Glucose-1-phosphate: -5.0 kcal/mol Which of these molecules could phosphorylate an unknown compound whose free energy of phosphate hydrolysis is -10.3kcal/mol? A. PEP only B. ATP only C. ATP and PEP D. Glucose-1-phosphate and ATP
A. PEP only
Before activation of v-SNAREs and t-SNAREs lead to membrane fusion, vesicles "know" they arrive at the correct location because of an interaction between _________________________. A. Rab GTPases and tethering proteins B. cargo receptors and Rab GTPases C. Rab GTPases and t-SNAREs D. v-SNAREs and tethering proteins
A. Rab GTPases and tethering proteins
Which of the following best describes cytoskeletal organization in cilia and flagella? A. Stable arrays of long microtubules that use motors to produce bending forces. B. A pair of long, dynamic microtubules that protrudes from the cell by continuous assembly at the plus ends. C. Stable bundles of long actin filaments oriented with their plus ends protruding from the cell. D. Stable arrays of short microtubules that self- replicate and tether minus ends together.
A. Stable arrays of long microtubules that use motors to produce bending forces.
In which membrane compartment would you find a transporter immediately before it reaches its final destination in the plasma membrane? A. The Golgi apparatus B. The endoplasmic reticulum C. The endosome D. The lysosome
A. The Golgi apparatus
During cell crawling, what provides the force that pushes the front of the cell forward? A. The growth of short actin filaments. B. The pushing of myosin motors on long actin filaments. C. Actin filament capping at plus ends. D. The contraction of the cell cortex.
A. The growth of short actin filaments.
Which of the following statements is true? A. The mitotic spindle helps segregate the chromosomes to the two daughter cells. B. The contractile ring divides the nucleus in two. C. The contractile ring is made largely of microtubules and actin filaments. D. The mitotic spindle is largely made of intermediate filaments.
A. The mitotic spindle helps segregate the chromosomes to the two daughter cells.
________ links the thick filaments to the Z line. A. Titin B. Myomesin C. Nebulin D. Troponin
A. Titin
Muscle cells rapidly contract when Ca2+ released from the ER binds to proteins in the sarcomere. How does Ca2+-binding result in contraction? A. Tropomyosin moves on actin when Ca2+ binds exposing sites for myosin. B. The actin filaments shorten when Ca2+ binds. C. Ca2+ binding removes tropomyosin from the sarcomere allowing myosin to bind. D. Ca2+ binds to myosin motors allowing them to bind to tropomyosin.
A. Tropomyosin moves on actin when Ca2+ binds exposing sites for myosin.
Which of the following statements about the polymerization of macromolecules is false? A. Water is added to join the monomers of the macromolecules. B. Often the energy needed for polymerization is supplied by ATP. C. The polymer chain usually has two different ends. D. Macromolecules are synthesized by the stepwise addition of monomers.
A. Water is added to join the monomers of the macromolecules.
In a chloroplast, the stroma is __________. A. a gel-like matrix between the inner chloroplast membrane and the thylakoid membrane. B. a stack of thylakoids. C. the region between in the inner and outer membranes. D. a connection between the grana.
A. a gel-like matrix between the inner chloroplast membrane and the thylakoid membrane.
Dynamic assembly and disassembly of a cytoplasmic microtubule in a cell occurs primarily at its plus end, because its minus end is usually anchored to ____________ A. a microtubule organizing center. B. the plasma membrane. C. a basal body. D. a centromere.
A. a microtubule organizing center.
Which of the following is closest to a micrometer in size? A. a typical prokaryotic cell B. the width of a strand of DNA C. the length of a plant cell D. the size of a ribosome
A. a typical prokaryotic cell
Both treadmilling and dynamic instability _________________________ A. account for subunit turnover within long-lived cytoskeletal structures. B. occur when subunits incorporate at one end of a filament and leave through the other. C. require GTP hydrolysis to occur. D. explain how new cytoskeletal filaments are made.
A. account for subunit turnover within long-lived cytoskeletal structures.
Using genetic engineering techniques, which of the following would you do to a protein that normally is constitutively secreted to make it accumulate in the ER? A. add a KDEL sequence near its C-terminus B. add an amino acid that would get a mannose-6- phosphate group added to its carbohydrate C. fuse it to GFP D. mutate one of the asparagines that is normally glycosylated to an alanine, which is not glycosylated
A. add a KDEL sequence near its C-terminus
Secretory cells are able to concentrate large amounts of proteins into secretory vesicles. This occurs by ______________________. A. aggregation in response to the acidic and Ca2+- rich environment of the Golgi apparatus B. modification of sugars on the protein surface in the Golgi apparatus C. external activation of a cell signaling pathway D. binding receptors on the trans-Golgi network
A. aggregation in response to the acidic and Ca2+- rich environment of the Golgi apparatus
Plasmodesmata and gap junctions are similar because they both _______________________. A. allow small molecules to pass between cells B. form extracellular fibers that adhere cells together C. are composed of six subunits that span the plasma membrane D. assemble during cell division
A. allow small molecules to pass between cells
Having various types of chlorophylls and accessory pigments for the photosynthetic process _______. A. allows many wavelengths of light to be captured to provide energy for photosynthesis. B. shifts the equilibrium of photosynthesis toward the formation of products. C. allows for a variation in color among plants. D. allows light to be harvested specifically in a stepwise manner.
A. allows many wavelengths of light to be captured to provide energy for photosynthesis.
When a photon is absorbed by a pigment (light- absorbing molecule), such as chlorophyll, the energy of the photon is transferred to ______. A. an electron to move it from a low to a high energy orbital. B. ATP synthase to make ATP. C. plastocyanin to be passed on to PSI. D. NADP+ to make NADPH.
A. an electron to move it from a low to a high energy orbital.
Actin filaments may form each of the following except _________________. A. axonemes containing doublet microfilaments. B. contractile bundles. C. branched networks. D. bundles of parallel filaments.
A. axonemes containing doublet microfilaments.
Proteoglycans are a major component of the __________________. A. bacterial cell walls B. cytoplasm C. cytoskeleton D. extracellular matrix
A. bacterial cell walls
Uptake of low-density lipoproteins (LDLs) occurs by ___________ A. receptor-mediated endocytosis. B. phagocytosis. C. pinocytosis. D. facilitated transport.
A. receptor-mediated
Protein sorting is typically accomplished by signal sequences of 15-60 amino acid residues that ______________________. A. can be added to cytosolic proteins and redirect them to the same compartment B. are added by post-translational modification C. are always removed from the final protein D. cluster together only after protein folding
A. can be added to cytosolic proteins and redirect them to the same compartment
What inorganic precursors are needed to synthesize proteins? A. carbon, water, oxygen, nitrogen, and sulfur B. carbon, water, oxygen, nitrogen, and phosphate C. carbon, water, oxygen, and phosphate D. carbon, water, and oxygen
A. carbon, water, oxygen, nitrogen, and sulfur
The primary function of focal adhesions is _______. A. cell-ECM adhesion B. cellular signaling pathway regulation C. cell-cell adhesion D. cell-cell communication
A. cell-ECM adhesion
Which of the following is a structural polysaccharide? A. cellulose B. glycogen C. fructose D. starch
A. cellulose
The unfolded protein response is activated when ________________________. A. chaperone proteins are unable to bind all the unfolded proteins in the ER B. unfolded proteins are present in the cytoplasm C. misfolded proteins are detected in the Golgi apparatus D. misfolded proteins bind to chaperones in the ER
A. chaperone proteins are unable to bind all the unfolded proteins in the ER
The negatively charged phosphates of ATP influence one another by ___________________. A. charge repulsion. B. positron emission. C. resonance destabilization. D. All of the above are correct.
A. charge repulsion.
The term amphipathic refers to those molecules that are _____________________ A. charged at one end and nonpolar at the other. B. charged at both ends but with opposite charges. C. hydrophilic. D. hydrophobic.
A. charged at one end and nonpolar at the other.
Which of the following molecules forms the coat during receptor-mediated endocytosis-coated pit formation? A. clathrin B. mannose-6-phosphate C. T-SNARE D. tethering protein
A. clathrin
Ehlers-Danlos syndrome and scurvy both are characterized by defects in _______________ A. collagen. B. desmosomes. C. dystrophin. D. fibronectin.
A. collagen.
The type of inhibitor that binds to the enzyme active site is a(n) ________ inhibitor. A. competitive B. noncompetitive C. uncompetitive D. coenzyme
A. competitive
In electron transport, each of the following respiratory complexes is involved in the flow of electrons from NADH2 to O2 except: A. complex II. B. complex I. C. complex III. D. complex IV.
A. complex II.
The continuous release of mucus by the epithelial cells lining the respiratory tract is an example of _________. A. constitutive secretion. B. regulated secretion. C. the mucus response. D. phagocytosis.
A. constitutive secretion.
Which of the following steps or processes in aerobic respiration include the production of carbon dioxide? A. conversion of pyruvate to acetyl CoA B. breakdown of glycogen C. glycolysis D. oxidative phosphorylation
A. conversion of pyruvate to acetyl CoA
Biosynthesis of sucrose occurs in the __________. A. cytosol. B. chloroplast intermembrane space. C. stroma. D. thylakoid lumen.
A. cytosol.
When the size of a cell increases, the surface area/volume ratio ____________________ A. decreases. B. decreases initially and then begins to increase. C. increases. D. remains the same.
A. decreases.
Which of the following junctions is most abundant in tissues such as skin that are required to resist significant mechanical stress? A. desmosomes B. tight junctions C. gap junctions D. focal adhesions
A. desmosomes
Your friend has recently purified the motor located on vesicles that form the Golgi apparatus in animal cells after cell division. Which type of motor would you expect it to be? A. dyneins B. myosin I C. myosin II D. kinesins
A. dyneins
The advantage to the cell of the gradual oxidation of glucose during cellular respiration compared with its combustion to CO2 and H2O in a single step is that ________________. A. energy can be extracted in usable amounts B. no energy is lost as heat C. more CO2 is produced for a given amount of glucose oxidized D. more free energy is released for a given amount of glucose oxidized
A. energy can be extracted in usable amounts
Which of the following is defined as "disorder"? A. entropy B. enthalpy C. energy output D. free energy
A. entropy
The Emerson enhancement effect __________. A. explains the synergistic effect of two wavelengths of light on photosynthesis. B. explains the lack of O2 release during anoxygenic photosynthesis. C. makes it possible for plants to avoid the Calvin cycle. D. results from the activity of three photosystems.
A. explains the synergistic effect of two wavelengths of light on photosynthesis.
All of the following are actin-dependent non-muscle motilities except ________________________. A. extension of the ER. B. cyclosis or cytoplasmic streaming. C. amoeboid movement. D. cleavage furrow constriction in cytokinesis.
A. extension of the ER.
Photoheterotrophs are best described as organisms that obtain energy to make ATP ______________. A. from sunlight but cannot make organic compounds from CO2. B. and organic compounds from sunlight. C. from organic compounds but use sunlight to produce carbon sources. D. from organic compounds.
A. from sunlight but cannot make organic
Which of the following characteristics is not associated with cardiac muscle? A. fusion of cardiomyocytes into large multinucleated myofibers B. striations C. intercalated discs D. electrical coupling by gap junctions
A. fusion of cardiomyocytes into large
One way in which ions are specifically transported into the cell is via ______________________. A. gated channels B. simple diffusion C. carrier (permease) proteins D. uniport transporters
A. gated channels
Which molecule in the Calvin cycle is used to synthesize starch and sucrose? A. glyceraldehyde-3-phosphate B. ribulose-5-phosphate C. ribulose-1,5-bisphosphate D. 1,3-bisphosphoglycerate
A. glyceraldehyde-3-phosphate
In most individual cells, the cytoskeleton _______________ A. has multiple types of subunits, each forming multiple types of structures at the same time. B. has multiple types of subunits, each forming multiple types of structures at different times. C. is composed of only one of the three types of subunits. D. has multiple types of subunits, each forming a single type of structure.
A. has multiple types of subunits, each forming multiple types of structures at the same time.
In cartilage, proteoglycans form large complexes by attaching to ____________________ A. hyaluronate. B. glycosaminoglycans. C. elastin. D. collagen.
A. hyaluronate.
The equation AB + H2O → A + B would be catalyzed by which of the following classes of enzymes? A. hydrolases B. isomerases C. ligases D. oxidoreductases
A. hydrolases
In eukaryotes, pyruvate is converted to acetyl CoA ________________ A. in the mitochondrial matrix. B. in the cell cytosol. C. during passage through the mitochondrial outer membrane. D. during passage through the inner mitochondrial membrane.
A. in the mitochondrial matrix.
Mutations of keratins in the ________ that resist tensile forces in the skin cause the blistering disease known as epidermolysis bullosa simplex. A. intermediate filaments B. microfilaments C. microtubules D. actin filaments
A. intermediate filaments
The active site for many enzymes ______________. A. involves amino acids that are brought into close proximity by extensive protein folding. B. contains amino acids that are contiguous to one another along the primary sequence of the protein. C. usually involves nonpolar amino acids. D. usually depends on only one amino acid.
A. involves amino acids that are brought into close proximity by extensive protein folding.
Which type of motor protein is associated with the movement of cargo toward the plus end of microtubules? A. kinesin B. dynein C. myosin I D. myosin II
A. kinesin
Selectins mediate interactions between which of the following? A. leukocytes and blood vessel endothelial cells B. intestinal epithelial cells with neighboring cells C. muscle cells and ECM D. nerve cells and other nerve cells
A. leukocytes and blood vessel endothelial cells
Oxidation reactions in biological systems generally involve ________________________. A. loss of electrons and hydrogen ions. B. addition of electrons and loss of hydrogen ions. C. loss of electrons and addition of hydrogen ions. D. addition of electrons and hydrogen ions.
A. loss of electrons and hydrogen ions.
In the non-cyclic electron-transport chain in chloroplasts, ________-energy electrons are taken from __________. A. low; H2O. B. low; NADPH. C. high; NADPH. D. high; H2O.
A. low; H2O.
Which one of the following amino acids would most likely be important for forming ionic bonds with negatively charged DNA? A. lysine B. glutamic acid C. proline D. tyrosine
A. lysine
Comparing cells synthesizing secretory proteins and cells secreting steroid hormones, the cells synthesizing the steroid hormones have _________. A. more smooth ER. B. more rough ER. C. equal amounts of smooth and rough ER, but more lysosomes. D. equal amounts of smooth and rough ER, but fewer lysosomes.
A. more smooth ER.
In smooth muscle cells, Ca2+-calmodulin stimulates phosphorylation of myosin by ______________________. A. myosin light chain kinase. B. focal adhesion kinase. C. Ca2+-ATPase. D. ryanodine receptor.
A. myosin light chain kinase.
In addition to enabling them to bind DNA, the positively charged tails of histones assist in nuclear import by directly binding to __________________. A. nuclear import receptors B. Ran GTPases C. protein translocators in the nuclear envelope D. cytoplasmic fibrils of nuclear pore complexes
A. nuclear import receptors
Which of the following pairs correctly matches the monomer with its polymer? A. nucleotides; nucleic acids B. terpenes; nucleic acids C. amino acids; polysaccharides D. glucose; proteins
A. nucleotides; nucleic acids
Oxygen is toxic to _________________. A. obligate anaerobes. B. facultative organisms. C. obligate aerobes. D. All of the above.
A. obligate anaerobes.
Which of the following forms a gel that traps water within plant cell walls. A. pectins B. hyaluronates C. lignins D. proteoglycans
A. pectins
The ATP synthase complex associated with the thylakoid membrane __________. A. performs photophosphorylation in oxygenic phototrophs. B. accepts electrons from PSI. C. is identical to the FoF1 complex of mitochondria. D. is a soluble enzyme complex peripherally associated with PSI.
A. performs photophosphorylation in oxygenic phototrophs.
In which of the following organelles does the breakdown of fatty acids occur? A. peroxisomes B. smooth ER C. lysosomes D. mitochondria
A. peroxisomes
The process by which photosynthetic organisms use light energy for ATP production is known as _____. A. photophosphorylation. B. photorespiration. C. photosynthesis. D. photoreduction.
A. photophosphorylation.
In prokaryotes that carry out aerobic respiration, the ________ serves the same purpose as the inner mitochondrial membrane and the ________ serves the same purpose as the mitochondrial matrix. A. plasma membrane; cytoplasm B. cytoplasm; cell wall C. cytoplasm; plasma membrane D. ribosomes; plasma membrane
A. plasma membrane; cytoplasm
Capping proteins ________________ A. prevents assembly and disassembly at microfilament ends. B. forms microfilament branches. C. connects microfilaments to microtubules. D. depolymerizes microfilaments at their plus ends.
A. prevents assembly and disassembly at microfilament ends.
The "9 + 0" pattern of microtubules is associated with ___________________ A. primary (sensory) cilia. B. respiratory tract cilia. C. sperm tail flagella. D. cyanobacterial locomotion.
A. primary (sensory) cilia.
Melvin Calvin and his colleagues used which of the following to deduce the steps in the Calvin cycle? A. radioisotopes B. ultracentrifugation C. Drosophila melanogaster D. electron microscopy
A. radioisotopes
To investigate the role of cadherin in early development, you continuously treat frog zygotes with antibodies that bind EP-cadherin. You most likely would find that ________________ A. the cells associate only loosely and fail to form a properly organized blastula. B. blastula formation and subsequent development proceed normally. C. cell division stops but the existing cells organize to form a small, properly organized blastula. D. the cells associate only loosely but skip the blastula stage to develop into a normal frog.
A. the cells associate only loosely and fail to form a properly organized blastula.
Which phase of microtubule polymerization in vitro would be affected most by adding short microtubules to unpolymerized GTP-tubulin? A. the lag phase B. the treadmilling phase C. addition of tubulin dimers to microtubule (+) ends at the plateau phase D. the elongation phase
A. the lag phase
Three of the ten glycolysis enzyme reactions are not simply reversed in gluconeogenesis and require different enzymes because _________________. A. these three glycolytic steps are the most highly exergonic and thermodynamically difficult to reverse. B. these three glycolytic enzymes are not present in the cells performing gluconeogenesis. C. these three glycolytic enzymes cannot catalyze the reaction in the reverse direction under any circumstances. D. NAD+ needs to be generated from NADH at each of these three steps.
A. these three glycolytic steps are the most highly exergonic and thermodynamically difficult to reverse.
Photosynthesis is a process that takes place in chloroplasts and uses light energy to generate high- energy electrons, which are passed along an electron-transport chain. Where are the proteins of the electron-transport chain located in chloroplasts? A. thylakoid membrane B. thylakoid space C. stroma D. inner membrane
A. thylakoid membrane
Which of the following functions like a fence to block membrane protein movement between the apical and basolateral regions of an intestinal epithelial cell plasma membrane? A. tight junctions B. adherens junctions C. gap junctions D. desmosomes
A. tight junctions
Many types of cells have stores of lipids in their cytoplasm, usually seen as fat droplets. What is the lipid most commonly found in these droplets? A. triacylglycerol B. palmitic acid C. cholesterol D. isoprene
A. triacylglycerol
The citric acid cycle is a series of oxidation reactions that removes carbon atoms from substrates in the form of CO2. Where do the oxygen atoms in the carbon dioxide molecules come from? A. water B. phosphates C. molecular oxygen D. acetyl CoA
A. water
Which of the following is a chemoheterotroph? A. yeast B. grass C. algae D. a photosynthetic bacterium
A. yeast
A catabolic reaction usually ________________. A. yields energy B. is degradative, regardless of energy change C. involves no change in energy D. requires energy
A. yields energy
The sequential process of fatty acid catabolism to acetyl CoA is called the ____________________. A. β-oxidation pathway. B. citric acid cycle. C. glyoxylate cycle. D. oxidative phosphorylation pathway.
A. β-oxidation pathway.
Which of the following types of work involves a change in position of the cell or a cell structure? A. synthetic B. mechanical C. concentration D. bioluminescent
B. mechanical
Cell-cell communication in plants takes place via specialized structures called _____________. A. chloroplast outer membrane pores B. plasmodesmata C. gap junctions D. lipid rafts
B. plasmodesmata
Which of the following best describes a metastable state? A. This state changes the position of the equilibrium but not the rate. B. A state of the substrate(s) in which the reaction can proceed but typically requires a catalyst. C. This state is composed of the difference in activation energy of a catalyzed versus an uncatalyzed reaction. D. A state formed by transient complexes with the substrate.
B. A state of the substrate(s) in which the reaction can proceed but typically requires a catalyst.
Which of the following statements about self- assembly is false? A. Self-assembly requires specific chemical conditions. B. Self-assembly only occurs in structures composed of protein. C. Molecular chaperones are sometimes required for the proper folding and assembly of complex proteins. D. The noncovalent interactions that drive supramolecular assembly processes are similar to those that dictate the folding of individual protein molecules.
B. Self-assembly only occurs in structures composed of protein.
You are researching a cytoplasmic protein associated with a nerve disorder. The native form of the enzyme appears to be globular protein; however, when a sample of the purified protein is treated with a chemical that reduces disulfide bonds, the enzymatic activity decreases dramatically and multiple globular proteins can be detected in the sample. What does this tell you about the protein? A. The primary structure of the protein contains multiple cysteine residues that are hydrolyzed by the chemical reductant. B. The protein is most likely composed of multiple polypeptide chains that are held together by disulfide bonds. C. The protein is most likely composed of α helices that are held together by disulfide bonds. D. The protein is most likely composed of β sheets that are held together by disulfide bonds.
B. The protein is most likely composed of multiple polypeptide chains that are held together by disulfide bonds.
Biologically, which of the following is the least important characteristic of water? A. Water molecules are polar. B. Water typically contains isotopes of hydrogen. C. Water molecules form numerous hydrogen bonds. D. Water is a good solvent.
B. Water typically contains isotopes of hydrogen.
Which of the following types of organisms contain sphingomyelin in cell membranes? A. prokaryotes B. animals C. yeast D. plants
B. animals
The composition of lipids in the outer and inner monolayers of cell membrane lipid bilayers is ________________________ A. identical in each monolayer. B. asymmetrical; i.e., different in each monolayer. C. twice as concentrated in the inner monolayer as in the outer monolayer. D. highly random for each monolayer.
B. asymmetrical; i.e., different in each monolayer.
An enzyme _______________________. A. decreases the rate of a reaction. B. binds substrates in a manner that facilitates the formation of product. C. changes the position of the equilibrium of the reaction. D. is always a protein.
B. binds substrates in a manner that facilitates the formation of product.
Cholesterol _____________. A. is found in abundance in prokaryotic cell membranes. B. buffers membrane fluidity by increasing fluidity at low temperature and decreasing fluidity at high temperature. C. increases permeability for Ca2+. D. increases permeability for small polar molecules.
B. buffers membrane fluidity by increasing fluidity at low temperature and decreasing fluidity at high temperature.
The steady state vital to life is possible because all __________________________ A. cells are autotrophic. B. cells continually takes up energy from the environment. C. reactions are at equilibrium. D. reactions are exothermic.
B. cells continually takes up energy from the environment.
Which of the following organelles is not generally found in animal cells? A. contractile vacuole B. central vacuole C. centriole D. endoplasmic reticulum
B. central vacuole
The genome of a cell _________________. A. constantly changes, depending upon the cell's environment. B. consists of all of a cell's DNA. C. is defined as all the genes being used to make protein. D. is altered during embryonic development.
B. consists of all of a cell's DNA.
Which of the following biochemical techniques uses an electrical field to separate macromolecules based on their mobility through a semisolid gel? A. chromatography. B. electrophoresis. C. mass spectrometry. D. ultracentrifugation.
B. electrophoresis
Energy-requiring reactions can occur in biological systems because they can be coupled with reactions that are ____________________. A. endergonic. B. exergonic. C. spontaneous and endergonic. D. not spontaneous.
B. exergonic.
Each of the following molecules move across membranes by simple diffusion except A. oxygen B. glucose C. fatty acids D. water
B. glucose
Which of the following processes would be most likely to occur in the Golgi complex? A. synthesis of DNA B. glycosylation of proteins C. production and packaging of lipids D. detoxification of drugs
B. glycosylation of proteins
Each of the following is a function of membranes except ________. A. defining cell and organelle boundaries. B. information storage. C. sites for specific biochemical functions. D. regulation of transport.
B. information storage.
A peptide bond ______________________ A. is a covalent bond between the functional R groups of adjacent amino acids. B. is a covalent bond between the carboxyl carbon of one amino acid and the amino nitrogen of a second amino acid. C. is a covalent bond between the NH group of one polypeptide and the CO group of an adjacent polypeptide that holds together multimeric proteins. D. is a noncovalent bond that dictates the tertiary structure of a protein.
B. is a covalent bond between the carboxyl carbon of one amino acid and the amino nitrogen of a second amino acid.
Of all 20 standard amino acids, cysteine is special because _____________ A. it has the smallest side chain which allows it to be more flexible than the other amino acids. B. it has a reactive sulfur atom that can form a covalent bond with another cysteine. C. it is less flexible than the other amino acids, so it disrupts protein secondary structure. D. it is used as the first residue of proteins.
B. it has a reactive sulfur atom that can form a covalent bond with another cysteine.
Which of the following macromolecules is insoluble in water? A. nucleic acids B. lipids C. disaccharides D. amino acids
B. lipids
A hungry yeast cell lands in a vat of grape juice and begins to feast on the sugars there, producing carbon dioxide and ethanol in the process: C6H12O6 +2ADP+2Pi +H+ 2CO2 + 2CH3CH2OH + 2ATP + 2H2O Unfortunately, the grape juice is contaminated with proteases that destroy some of the transport proteins in the yeast cell membrane, and the yeast cell dies. Which of the following could account for the yeast cell's demise? A. Toxic buildup of carbon dioxide inside the cell. B. Toxic buildup of ethanol inside the cell. C. Inability to import sugar into the cell. D. Diffusion of ATP out of the cell.
C. Inability to import sugar into the cell.
Why is a selectively permeable membrane so important to living things? A. Proteins will avoid a selectively permeable membrane. B. It allows cells to attach to adjacent tissues. C. It provides a good barrier between the inside and outside of the cell. D. The membrane may absorb several times its weight in cholesterol.
C. It provides a good barrier between the inside and outside of the cell.
Which of the following is consistent with, but not evidence for, the endosymbiotic origin of mitochondria? A. Mitochondria have a circular genome B. Ribosomes in mitochondria and bacteria are similar in size. C. Mitochondria are found in regions of cells that require high amounts of energy. D. Mitochondria are not part of the endomembrane system.
C. Mitochondria are found in regions of cells that require high amounts of energy.
How does brightfield microscopy allow images to be visualized? A. Electrons strike the specimen being examined. B. Specimens are fixed and have bright fluorescent molecules attached to them. C. Specimens are illuminated with white light. D. Specimens are viewed under phased light to improve magnification.
C. Specimens are illuminated with white light.
Cell theory developed in the 1800s. Which of the following statements is part of cell theory? A. all cells must have a constant supply of energy B. all cells evolved from a single organism C. all living organisms are composed of cells D. cells are microscopic.
C. all living organisms are composed of cells
When a transporter moves two solutes in opposite directions across a membrane, it is considered a(n) ____________ A. passive transporter B. uniporter C. antiporter D. symporter
C. antiporter
An allosteric inhibitor _____________________. A. increases the rate of substrate binding. B. binds to the active site. C. binds at the regulatory site. D. binds and activates the high-affinity state of the enzymes.
C. binds at the regulatory site.
All of the following are common functional groups found in biological molecules except __________ A. phosphate groups. B. carbonyl groups. C. butyl groups. D. amino groups.
C. butyl groups.
Living cells maintain themselves in a steady state, by keeping most of their reactions ____________. A. conserving energy. B. conserving matter. C. far from thermodynamic equilibrium. D. near thermodynamic equilibrium.
C. far from thermodynamic equilibrium.
Reduction involves the ______________________. A. increase in oxidation state. B. loss of electrons. C. gain of electrons. D. loss of neutrons.
C. gain of electrons.
Which one of the following amino acids has a non- polar side chain? A. arginine B. glutamine C. isoleucine D. tyrosine
C. isoleucine
Proline is referred to as the "helix breaker" because _____________________ A. its only found in the L form, which is incompatible with helical protein structure. B. it lacks a charged functional groups for ionic bonding. C. it lacks the hydrogen atom needed for hydrogen bonding. D. it has a polar functional group.
C. it lacks the hydrogen atom needed for hydrogen bonding.
Localized regions of plasma membranes that contain cholesterol and proteins involved in cell signaling are known as _____________. A. arterial plaques B. cadherin junctions C. lipid rafts. D. gap junctions
C. lipid rafts.
Fatty acids are ________; they function in the cell as ________. A. short chains of double-bonded carbon molecules; storage lipids B. short chains of double-bonded carbon molecules; vitamins and cofactors C. long, unbranched hydrocarbon chains with a carboxyl group at one end; building blocks for other lipids D. four-ringed hydrocarbon molecules; key components of membranes
C. long, unbranched hydrocarbon chains with a carboxyl group at one end; building blocks for other lipids
Which of the following is characteristic of eukaryotic cells? A. binary fission B. peptidoglycan cell wall C. membrane-bounded nucleus D. smaller than 5 μm in diameter
C. membrane-bounded nucleus
The hierarchical nature of cellular structure is accurately illustrated in which of the following lists of substances (from smallest to largest)? A. protein, membrane, amino acids, chloroplast, cell B. cellulose, glucose, cell wall, cell C. nucleotides, DNA, chromosome, nucleus, cell D. nucleotides, chromosome, DNA, nucleus, cell
C. nucleotides, DNA, chromosome, nucleus, cell
Which of the following types of protein would be most easily removed from a membrane by changing pH or ionic strength? A. fatty acid-anchored protein B. integral protein C. peripheral protein D. glycosylated integral protein
C. peripheral protein
The cell membrane can be described most accurately as ____________________ A. impermeable to all polar molecules. B. permeable to all small molecules and ions. C. permeable to some molecules and impermeable to others. D. permeable to all molecules except water.
C. permeable to some molecules and impermeable to others.
Which of the following is smallest? A. ribosome B. virus C. protein D. prokaryote
C. protein
The rough endoplasmic reticulum functions in synthesis of __________________________ A. DNA. B. polysaccharides. C. proteins. D. lipids.
C. proteins.
In a chemical reaction, if Keq < 1.0, this means that _________________________________. A. the reaction is at equilibrium under standard conditions B. the standard free energy change (ΔG°) is negative C. reactants predominate over products at equilibrium under standard conditions D. ΔG > 0 at equilibrium.
C. reactants predominate over products at equilibrium under standard conditions
Water moves across the plasma membrane into or out of a cell by osmosis when ________________. A. there is an equal solute concentration on both sides of the membrane B. ATP hydrolysis drives aquaporin transport C. water diffuses through a semipermeable membrane toward a higher solute concentration D. water diffuses through a semipermeable membrane toward a lower solute concentration
C. water diffuses through a semipermeable membrane toward a higher solute
FRAP has revealed that some proteins move in cell membranes much slower than they move in reconstituted liposomes. Which of the following could account for limited mobility of proteins in cell plasma membranes? A. Association with lipid rafts. B. Anchorage to the extracellular matrix. C. Anchorage to the cell cytoskeleton. D. All could limit protein mobility.
D. All could limit protein mobility.
Which of the following is a characteristic of facilitated diffusion (passive transport) of a molecule across a membrane? A. Its rate is higher than that of simple diffusion of the molecule. B. It is highly specific for the molecule being transported. C. The direction of transport is determined by concentration and/or electrochemical gradients. D. All of the above are true.
D. All of the above are true.
The primary structure of a protein ___________ A. is important for determining the secondary and tertiary structure of a protein. B. is simply the order of amino acids from one end of the protein to another. C. is important both genetically and structurally. D. All of these statements are true.
D. All of these statements are true.
Which of the following is not a fundamental property of carbon? A. Carbon-containing molecules may form stereoisomers. B. Carbon-containing molecules are stable. C. Carbon has a valence of 4. D. Carbon atoms are most likely to form ionic bonds with one another.
D. Carbon atoms are most likely to form ionic bonds with one another.
In animal cells, glycolysis and gluconeogenesis are regulated to ensure that both processes are reciprocally active. This regulation involves each of the following compounds except __________. A. acetyl CoA B. AMP C. fructose-2,6-bisphosphate D. NADH
D. NADH
Pyruvate can be a substrate or product involved in each of the following except ________________. A. fermentation. B. aerobic glycolysis. C. amino acid biosynthesis. D. Pyruvate can be involved in all of the above.
D. Pyruvate can be involved in all of the above.
An enzyme synthesized in the laboratory is found to have little activity when compared to the enzyme extracted from cell culture. Both enzymes were examined and have identical amino acid composition. What is the best explanation for the lack of activity of the synthesized enzyme? A. Denaturation of the synthesized enzyme was not complete. B. The van der Waals radius was altered during laboratory synthesis. C. The synthetic enzyme was not made of amino acids. D. The synthesized enzyme was not folded correctly because molecular chaperones were not present.
D. The synthesized enzyme was not folded correctly because molecular chaperones were not present.
Which is true of heterotrophs? A. They capture light energy. B. They cannot be unicellular. C. They store energy in the form of heat. D. They can obtain energy by consuming phototrophs.
D. They can obtain energy by consuming phototrophs.
The moon lacks life and varies dramatically in temperature. If we could keep a layer of water spread on the surface of the moon, what effect would it have? A. Physical conditions would remain the same. B. Because water has a high heat of vaporization, the temperatures would rise to the upper extremes. C. Life would be possible, but it would have to withstand these extremes in temperature. D. Water would absorb and hold heat and moderate the temperature extremes.
D. Water would absorb and hold heat and moderate the temperature extremes.
Which of the following is an example of a prosthetic group? A. hexokinase B. a glycine residue C. ATP D. a heme group
D. a heme group
In the first step of glycolysis, glucose can be phosphorylated to glucose-6-phosphate, because ________________. A. transfer of a phosphate from ATP to glucose is endergonic. B. the reaction does not require an enzyme. C. the reaction is highly reversible. D. a phosphoanhydride bond has higher energy of hydrolysis than is required for formation of a phosphoester bond.
D. a phosphoanhydride bond has higher energy of hydrolysis than is required for formation of a phosphoester bond.
Whereas animal cells drive indirect transport with a Na+ gradient, most other organisms use ________. A. light energy B. osmosis C. a glucose gradient D. a proton gradient
D. a proton gradient
Pumps are transporters that are able to harness energy provided by other components in the cells to drive the movement of solutes across membranes, against their concentration gradient. This type of transport is called _____________. A. osmosis B. free diffusion C. facilitated diffusion D. active transport
D. active transport
The phosphate group that is removed from PEP when it becomes pyruvate is ______________. A. added to NAD+ to make NADP. B. added to fructose-6-phosphate to make fructose-1,6-bisphosphate. C. released as Pi. D. added to ADP to make ATP.
D. added to ADP to make ATP.
Which one of the following biological polymers is mismatched with its monomer? A. DNA - nucleotide B. enzyme - amino acid C. chitin - monosaccharide D. cellulose - amino acid
D. cellulose - amino acid
Aldolase breaks down fructose-1,6-bisphosphate into two trioses that are __________________. A. identical and each singly phosphorylated. B. identical and each doubly phosphorylated. C. different and each doubly phosphorylated. D. different and each singly phosphorylated.
D. different and each singly phosphorylated.
A scientist is examining motile protist. He wishes to determine their direction of movement. Which of the following microscopic techniques is least likely to be used to view these cells? A. phase-contrast microscopy B. differential interference contrast microscopy C. fluorescence microscopy D. electron microscopy
D. electron microscopy
Which of the following polymers of glucose is used as a vehicle to store energy reserves in animal cells? A. cellulite B. starch C. glucagon D. glycogen
D. glycogen
Which of the following is not a major functional class of proteins? A. enzymes B. regulatory proteins C. structural proteins D. hereditary proteins
D. hereditary proteins
Hydrogen bonds are the principal force that _________________. A. connects amino acids into a polypeptide B. allows Na+ and Ca2+ ions to bind proteins C. stabilizes fatty acid chains within a membrane D. holds the two strands of DNA together
D. holds the two strands of DNA together
Prions are ___________________. A. the site of protein synthesis in prokaryotic cells. B. simple viruses composed of protein. C. infectious circular RNA molecules that replicate in host cells. D. infectious misfolded proteins that cause normal protein molecules to misfold.
D. infectious misfolded proteins that cause normal protein molecules to misfold.
Once a hypothesis becomes a scientific theory, it __________________ A. cannot be changed. B. cannot be challenged. C. becomes static. D. is subject to modification.
D. is subject to modification.
In anaerobic conditions, skeletal muscle produces _____________. A. ethanol only B. lactate and CO2 C. ethanol and CO2 D. lactate only
D. lactate only
When glucose is being used up and not replaced from food intake, the blood sugar level can be maintained by synthesizing glucose from smaller molecules such as pyruvate or lactate. This process is called gluconeogenesis. Which organ is principally responsible for supplying glucose to the rest of the body when glucose reserves are low? A. brain B. pancreas C. spleen D. liver
D. liver
Feedback inhibition prevents cells from _________. A. destroying enzymes by proteolytic cleavage when they are needed in biosynthetic pathways. B. accumulating unnecessary proteins. C. the harmful effects of enzyme activation by covalent modification of unneeded enzymes. D. making products that are not needed by inhibiting the activity of enzymes in biosynthetic pathways allosterically.
D. making products that are not needed by inhibiting the activity of enzymes in biosynthetic pathways allosterically.
The most prominent lipids in animal cell membranes are _____________ A. cholesterol. B. glycolipids. C. phytosterol. D. phospholipids.
D. phospholipids.
An enzyme is active in the stomach of an animal but quickly loses its activity when it leaves the stomach. This example illustrates that enzymes are _______________________. A. specific to the organs in which they are produced. B. inactivated by movement. C. digested in the small intestine. D. sensitive to changes in pH.
D. sensitive to changes in pH.
During the conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate and phosphoenolpyruvate, a phosphate group is added to ADP to generate ATP. The mechanism for ATP production in this reaction is _______________ phosphorylation. A. aerobic phosphorylation. B. oxidative phosphorylation. C. product-level phosphorylation. D. substrate-level phosphorylation.
D. substrate-level phosphorylation.
An enzyme reduces the free energy of which of the following? A. cofactor B. product C. substrate D. transition state
D. transition state
You are working on a project that involves the direct observation of DNA molecules. The microscope that would give you the best information at this time would be the ___________ A. digital video microscope. B. fluorescent microscope. C. phase-contrast microscope. D. transmission electron microscope.
D. transmission electron microscope.
In a biochemical reaction, reactants may be converted into products. The extent to which this occurs spontaneously is expressed as which of the following? A. Keq<1 B. ΔS<0 C. TΔS>0 D. ΔG<0
D. ΔG<0