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BC 351
Exam 3 lecture 27-41
| Question | Answer |
|---|---|
| An integral membrane protein can be extracted with: | a solution containing detergent. |
| Amphipathic alpha helices associate so that | the hydrophobic sides of the helices interact with the fatty acid tails of the lipid bilayer while the polar sides of the alpha helices point inwards forming a pore. |
| Energy containing nutrients (fats, carbohydrates, and proteins) are broken down via | catabolism |
| Hydropathy plots are a _______________ analysis. | quantitative |
| The sodium/glucose transporter is an example of | secondary active transport. |
| Small hydrophobic molecules pass across a membrane via | free diffusion. |
| The Warburg effect describes the observation that | cancer cells produce energy by a high rate of glycolysis and lactic acid fermentation. |
| How many ATP are produced from one molecule of glucose? | 38 |
| Membrane lipids | are classified first by backbone and second by head group. |
| Which of these statements is generally true of integral membrane proteins? | The secondary structure in the transmembrane region consists solely of α-helices or β-sheets. |
| Amphipathic α-helical structures | can form a hydrophilic pore within a lipid bilayer. |
| A hydropathy plot indicates | a stretch of amino acids forming a single-pass transmembrane domain. |
| yen uses secondary active transport. | uses ~30% of the ATP hydrolyzed in mammalian cells. |
| Which of these statements about facilitated diffusion across a membrane is true? | A specific membrane protein lowers the activation energy for movement of the solute through the membrane. |
| Integral membrane proteins | Associate so that the fatty acid tails are sequestered away from water |
| An amphipathic alpha helix is characterized by | alternating hydrophobic and hydrophillic amino acids every 3-4 residues |
| Catabolism | degrades nutrients (oxidation) and produces ATP |
| The Warburg effect is observed in | cancer cells and the first 3 divisions of embryogenesis |
| Membrane fluidity depends on | temperature and composition |
| The axes on a hydropathy plot are | hydrophillic amino acids (x) and hydrophillicity (y) |
| Which of the following is FALSE about sodium (Na+) transport across a membrane? | Sodium transport always requires ATP hydrolysis. |
| How many ATP are produced during glycolysis? | 4 |
| Aerobic glycolysis or the Warburg Effect | can be visualized through PET scans. |
| Adenosine 5'-triphosphate (ATP) | can be used as a cosubstrate to drive unfavorable reactions. |
| Which of the following is true about ATP-coupled reactions? | Waste is oxidized and nutrients are reduced. |
| Metabolic reactions | are often compartmentalized |
| Energy requiring metabolic pathways that yield complex molecules from simpler precursors are: | anabolic |
| The function of acetyl-CoA is | to transfer acetyl groups for fatty acid biosynthesis |
| The standard free-energy changes for the reactions below are given. | +12.5 kJ/mol |
| The coenzyme NAD+ | carries only one hydride anion (1 H+ and 2 e-s). |
| The conversion of 1 mol of fructose 1,6-bisphosphate to 2 mol of pyruvate by the glycolytic pathway results in a net formation of | 2 mol of NADH and 4 mol of ATP. |
| Biological oxidation-reduction reactions always involve: | transfer of electron(s). |
| Metabolism | consists of metabolic pathways that are linear, cyclic and spiral. |
| Catabolism refers to | a set of metabolic pathways that breakdown molecules into smaller units. |
| Every molecule has a Gibbs Free Energy (G). G is not dependent on | Time |
| The standard reduction potentials (E'°) for the following half reactions are given. | pyruvate would become reduced, NADH would become oxidized. |
| NADH reduces O2 in the first stage of oxidative phosphorylation to produce NAD+ and H2O. From table 13-7 (p. 515) and following the method of | 4 |
| Regarding ATP, | the cycling between ATP and ADP + Pi provides an energy coupling between catabolic and anabolic pathways. |
| When a mixture of glucose 6-phosphate and fructose 6-phosphate is incubated with the enzyme phosphohexose isomerase, the final mixture contains twice as much glucose 6-phosphate as fructose 6-phosphate. | ΔG'° is +1.7 kJ/mol. |
| What is the general purpose of nicotinamide cofactors in metabolism? | To transport electrons from one reaction to another. |
| Life is thermodynamically possible because living cells | release heat to the environment. |
| biological oxidation-reduction reactions never involve | formation of free electrons |
| if you mixed succinate, fumarate, FAD, and FADH2 together, all at 1 M concentrations and in the presence of succinate dehydrogenase, which of the following would happen initially? | fumarate would become reduced, FADH2 would become oxidized |
| Living organisms require a continual supply of energy to exist because | they are creating order out of disorder inside their cells. |
| It is true that | life is a thermodynamically spontaneous process. |
| The advantage to a cell of the gradual oxidation of glucose during cellular respiration compared with its combustion to CO2 and H2O in a single step is | energy can be extracted in usable amounts. |
| When a mixture of 3-phosphoglycerate and 2-phosphoglycerate is incubated at 25 °C with phosphoglycerate mutase until equilibrium is reached, the final mixture contains six times as much 2- phosphoglycerate as 3-phosphoglycerate. | ΔG'° is –4.44 kJ/mol |
| In glycolysis, fructose 1,6-bisphosphate is converted to two products with a standard free-energy change (ΔG'°) of +23.8 kJ/mol. Under what conditions encountered in a normal cell will the free-energy change (ΔG) be negative | The reaction will proceed spontaneously to the right if there is a high concentration of fructose 1,6-bisphosphate relative to the concentration of products. |
| For ATP hydrolysis, ATP ADP + Pi, what is the effect of changing the reaction conditions from standard chemical conditions to biochemical standard conditions on ΔG of the reaction? | The ΔG of the reaction will be more negative at a given ADP/ATP ratio. |
| When the concentrations of NAD+, NADH, oxaloacetate, and malate are all 10–5 M, the “spontaneous” reaction is: | Oxaloacetate + NADH + H+ --->malate + NAD+. |
| The structure of NAD+ does not include: | a flavin nucleotide |
| Glycolysis occurs in essentially all cells because | it evolved in an ancestor common to nearly all cells present on earth today. |
| In the breakdown of what you had for breakfast, the stage that generated the most ATP is | oxidative phosphorylation. |
| The purpose of phosphorylation ofglucose to glucose 6-phosphate by the enzymehexokinase as the first step in glycolysis is | to help keep glucose in the cytoplasm |
| The conversion of 1 mol of fructose 1,6-bisphosphate to 2 mol of pyruvate by the glycolytic pathway results in a net formation of: | 2 mol of NADH and 4 mol of ATP |
| Which of the following statements is not true concerning glycolysis in anaerobic muscle? | it is an endergonic process |
| When a lipid bilayer is torn it does not seal by forming a hemi-micelle cap because | membrane lipids are cylindrical |
| If analogous to why lipid bilayers form, the reason for this is | nobody else in the class wants to sit next to them |
| Three enzymes purified from a snake venom were tested for their ability to lyse red blood cells. The phospholipase produced phosphorylcholine and diacylglycerol. The results are explained by | producing a large number essentially non polar membrane lipids |
| Although present in relatively small amounts in mammalian cell plasma membranes, the phospholipid crucial in intracellular signaling is | phosphatidylinositol |
| Phosphatidylserine, normally found primarily only in the cytoplasmic side of the plasma membrane, is found at high levels on outer side in apoptotic cells. This redistribution occurs through | the phospholipid translocators are inactivated. |
| The organism likely to have the highest percentage of unsaturated fatty acid chains in its membranes is | an Antarctic fish. |
| Cholesterol is essential for lipid raft formation because | sphingolipids have large head groups |
| Which of the following statements is not true concerning glycolysis in anaerobic muscle? | It results in net synthesis of ATP. |
| If the glyceraldehyde 3-P dehydrogenase active site cysteine (-SH) were replaced with a serine (-OH), the effect would be | oxidization of the substrate without releasing it. |
| When 1 mole of ATP is hydrolyzed in a test tube without an enzyme, about twice as much heat is given off as when 1 mole of ATP is hydrolyzed in a cell. The observations are best explained by | In the cell, the hydrolysis of ATP is coupled to other endergonic reactions. |
| It is true that | the ΔG° for the oxidation of the aldehyde group on glyceraldehyde 3-phosphate to form a carboxylic acid is more negative than the ΔG° for ATP hydrolysis. |
| Arsenate (AsO43-) can replace phosphate (PO43-) in many metabolic reactions, but the anhydride bond with arsenate is rapidly hydrolyzed. Arsenate is preferred over phosphate by murderers, but not cells | allows 3-P glycerate formation in the absence of ATP synthesis in glycolysis. |
| Radiolabeled fluoro-2-deoxyglucose labels tumor cells brightly in positron emission tomography (PET). This bright labeling is due to | cancer cells using high levels of glucose and producing large amounts of lactate. |
| Which of these cofactors participates directly in most of the oxidation-reduction reactions in the fermentation of glucose to lactate? | NAD+/NADH |
| At what point does glycolysis "break even" for ATP consumption and production? | When 1,3-bisphosphoglycerate is converted to 3-phosphoglycerate by phosphoglycerate kinase. |
| Which of the following reactions in glycolysis produce ATP?/The enzyme(s) that catalyze reactions in glycolysis that produce ATP are | Phosphoglycerate kinase and pyruvate kinase |
| The irreversible steps of glycolysis are catalyzed by | hexokinase, phosphofructokinase, and pyruvate kinase. |
| All of the following enzymes involved in the flow of carbon from glucose to lactate (glycolysis) are also involved in the reversal of this flow (gluconeogenesis) except | phosphofructokinase-1. |
| Which of the following statements about gluconeogenesis in animal cells is true? | The conversion of fructose 1,6-bisphosphate to fructose 6-phosphate is not catalyzed by phosphofructokinase-1, the enzyme involved in glycolysis. |
| Glycolysis | converts 1 molecule of glucose to 2 molecules of pyruvate and 2 molecules of ATP. |
| Allosteric enzymes | change conformation upon binding of an effector. |
| There are a total of ____ ATP molecules and ____ NADH molecules produced during glycolysis. | 4, 2 |
| Phosphofructokinase-2 and fructose 2,6 bisphosphatase | are regulated in their relative activities through phosphorylation by PKA. |
| Phosphoglycerate kinase | catalyzes the reaction of 1,3-bisphosphoglycerate and ADP to ATP and 3-phosphoglycerate. |
| The anaerobic conversion of 1 mol of glucose to 2 mol of lactate by fermentation is accompanied by a net gain of: | 2 mol of ATP. |
| The regulated steps in glycolysis and gluconeogenesis | are paired, but involve different enzymes |
| Gluconeogenesis | generates glucose from non-carbohydrate carbon sources. |
| Which of the following statements about allosteric control of enzymatic activity is false? | Heterotropic allosteric effectors compete with substrate for binding sites. |
| A reaction at equilibrium in a metabolic pathway is | a rapid and reversible step. |
| Glycolysis and gluconeogenesis | inhibit each other to prevent a futile cycle of producing glucose only to break it down. |
| The anaerobic conversion of glucose to pyruvate produces ____ molecules of ATP. | 2 |
| NADH is produced in glycolysis by | glyceraldehyde phosphate dehydrogenase |
| In the first step of glycolysis | hexokinase uses ATP to produce glucose-6-phosphate. |
| Which of the following reactions in glycolysis produce NADH? | Glyceraldehyde phosphate dehydrogenase. |
| The first reaction in glycolysis that results in the formation of an energy-rich compound (has a -ΔG˚’ of hydrolysis great enough to drive ATP synthesis) is catalyzed by: | glyceraldehyde 3-phosphate dehydrogenase. |
| During strenuous exercise, the NADH formed in the glyceraldehyde 3-phosphate dehydrogenase reaction in skeletal muscle must be reoxidized to NAD+ if glycolysis is to continue. The most important reaction involved in the reoxidation of NADH is: | pyruvate → lactate |
| The first step of glycolysis | is irreversible |
| catabolic metabolic pathways | function to convert the energy stored in the nutrient chemical bonds to energy carried in ATP |
| aerobic glycolysis in brain cells | consists of commensal metabolic relationship between astrocytes and neuronal cells |
| substrate level phosphorylation | is the only means of ATP synthesis under anaerobic conditions |
| 3-bromopyruvate (BrPA) inhibits hexokinase and glyceraldehyde 3-P dehydrogenase. Question 2. The above data suggests | some cancer cells are highly dependent on glycolysis for ATP production |
| In the mass ratio of lipids to proteins in membranes | the mass ratio of lipids to proteins varies widely in different membranes |
| The forces that hold a membrane protein in the lipid bilayer and those that lead to protein folding into their tertiary structure | both involve the minimization of the interaction of hydrophobic amino acid R groups with the aqueous environment |
| Membrane proteins contain a lysine-rich sequence ending in a cysteine at their C-terminus that is required for membrane association. These proteins require detergents for release from membrane. These proteins are likely associated with membranes | through a covalent bond between the C-terminal cysteine and a lipid anchor |
| A bacterial small protein causes red blood cell lysis. It also make artificial liposomes very permeable. This bacterial toxin is likely | a β-barrel protein |
| The best candidate amino acid sequence for a monomeric single-pass transmembrane α-helix is (non identical; non-polar) | Ile-Thr-Leu-Ile-Tyr-Phe-Gly-Val-Met-Ala-Gly-Val-Ile-Gly-Thr-Ile-Leu-Leu-Ile-Ser. |
| The best candidate amino acid sequence for a β-strand in a β-barrel pore is (non identical; nonpolar) | Ala-Asp-Phe-Lys-Lue-Ser-Val-Glu-Lue-Thr. |
| The correct order of these molecules for the ability to cross lipid bilayers from most to least readily is | CO2>ethanol>H20>glucose >Ca2+>RNA |
| Membrane electrochemical gradients | involve both charge and concentration components with regard to Na+ but not K+ in most mammalian cells. |
| The ΔG for a molecule can be at equilibrium across a lipid bilayer and yet have different concentrations on one side than the other. | True |
| Cells A and B are the same size, shape, and temperature, but cell A is metabolically quiet and cell B is actively consuming oxygen. More oxygen will diffuse into cell _____ because _____. | B ... the concentration gradient into cell B is steeper |
| Membrane transporter proteins have been imagined to function through a revolving door mechanism. From what you know about membrane protein structure is this is likely to be the most plausible mechanism? | No |
| In most animal cells, channel proteins allow | Na+ into a cell. |
| If the plasma membrane becomes permeable to Na+ and K+, the Na+/K+ pump would | continue to pump ions and to hydrolyze ATP, but only generate heat in the process. |
| Consider the transport of protons and sucrose into a plant cell by the sucrose-proton cotransport protein. Plant cells continuously produce a proton gradient by using the energy of ATP hydrolysis to pump protons out of the cell. | The movement of protons through the cotransport protein cannot occur unless sucrose also moves at the same time. |
| A change you could make to the Na+- glucose transporter sufficient to make it pump glucose out of the cell rather than in include | making it a Na+-glucose antiporter |
| An ATP-dependent ion pump for heavy metal ions like Zn2+ functions similarly to Na+K+ pumps including changes in phosphorylation state. Addition of Zn2+ and ATP results in Zn2+ being pumped in. | a small amount of Zn2+ will move inside, no K+ will move outside, and the protein will become dephosphorylated |
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