UMass Biochem 420 Exam 3

The standard free energy change of the glycolytic pathway to pyruvate is -79.9 kJ/mol, while the standard free energy change associated with gluconeogenesis from pyruvate is -42.7 kJ/mol. What would the standard free energy change be for a direct reversal of the glycolytic pathway?

+79.9 kJ/mol

Taking one mole of glucose through glycolysis and the citric acid cycle generates: 6C02, 10 NADH/H+, 2FADH2 and 2 ATP. 6C02, 10 NADH/H+, 2FADH2 and 4 ATP. 6C02, 8 NADH/H+, 1FADH2 and 2 ATP. 6C02, 8 NADH/H+, 2FADH2 and 4 ATP. 6C02, 8 NADH/H+, 1FADH2 and 1 ATP.

6C02, 10 NADH/H+, 2FADH2 and 4 ATP.

(A)The following two half reactions are paired together to create an overall spontaneous reaction. Which molecule is the reducing agent? NADP+ + 2H+ + 2e- --> NADPH + H+  Eº´ = -0.320 V fumarate + 2H+ + 2e- --> succinate Eº´ = 0.031 V NADP+ fumarate succinate NADPH (B)What is the ΔEº´? -0.289 V 0.289 V -0.351 V 0.351 V

A NAPH B 0.315 V

Which of the following statements correctly compare(s) ΔG and ΔGº′? A- ΔG is a measure of the actual free energy change of a reaction in a cell and ΔGº′ is a measure of the free energy change under biochemical standard conditions, which mimic physiological conditions. B- Both ΔG and ΔGº′ are equal to zero at equilibrium. C- Even if the concentrations of products and reactants in a chemical reaction change, both ΔG and ΔGº′ remain the same. D- All of the above statements are correct.

A- ΔG is a measure of the actual free energy change of a reaction in a cell and ΔGº′ is a measure of the free energy change under biochemical standard conditions, which mimic physiological conditions

In cells, what is usually the immediate source of energy for an endergonic reaction? as spontaneous reactions, endergonic reactions do not need an addition of energy glucose ATP ADP sugar

ATP

Classify these amino acids as acidic, basic, neutral polar, or neutral nonpolar. Glutamine Arginine Asparagine Cysteine Alanine Tyrosine Tryptophan Threonine Valine Glutamic Acid

Acidic Glutamic acid -CH2CH2COO- Basic Arginine -[NHC(NH2)2]+ Neutral polar Asparagine -CH2CONH2 Cysteine -CH2SH Glutamine -CH2CH2CONH2 Threonine -CH(OH)CH3 Neutral non-polar Alanine -CH3 Tyrosine -aromatic ring OH Tryptophan -two rings C/H Valine -CH2(CH3)2

Which of the following are part of the chemiosmotic coupling model? 1) Protons are pumped out of the mitochondrial matrix into the intermembrane space. 2) The active transport of protons is driven by the free energy derived from electron transport. 3) Increasing the concentration of protons on the other side of the inner membrane creates a charge and a pH imbalance that releases energy upon proton flow back into the matrix. 4) The energy released by the return of protons to the matrix is what drives ATP synthesis. Only statements 2, 3, and 4 are correct. Only statements 1, 2, and 3 are correct. Only statements 1, 2, and 4 are correct. All of the listed choices are correct.

All of the listed choices are correct.

Why must a cell have different pathways to synthesize a product and degrade the same product? A. If the pathways were identical, only one pathway would be thermodynamically favored. B. The cycle would be futile. As soon as the product is made it would be immediately broken down. C. All biochemical pathways occur in the cytoplasm of a cell so opposite pathways must be different. Both A and B are correct answers. A, B and C are all correct answers.

Both A and B are correct answers.

Which of the following statements about inhibitors of enzyme-catalyzed reactions is TRUE? A- An uncompetitive inhibitor will always bind at the active site. B- An uncompetitive inhibitor typically affects KM but not kcat. C- A competitive inhibitor does not affect Vmax. D- Reversible inhibitors bind to either free enzyme or the enzyme-substrate complex but not both. E- A competitive inhibitor binds irreversibly to the enzyme at the active site.

C- A competitive inhibitor does not affect Vmax.

Which of the following statements about the electron transport chain is FALSE? During electron transport protons are pumped across the inner mitochondrial membrane from the matrix to the intermembrane space. Oxygen is reduced to water at complex IV of the electron transport chain. All of the protein complexes of the electron transport chain are bound in the inner mitochondrial membrane. Cytochrome c and coenzyme Q are both water soluble electron carriers that are loosely attached to the outside of the inner mitochondrial membrane.

Cytochrome c and coenzyme Q are both water soluble electron carriers that are loosely attached to the outside of the inner mitochondrial membrane.

The reaction ADP + P --> ATP is a(n) _____ reaction. hydrolysis spontaneous exergonic endergonic chemical

Endergonic

In biological systems, _____ of _______ molecules, such as glucose, yield the energy necessary for cellular processes to occur. This energy, called _______, is stored in the chemical bonds of organic molecules. If free energy is release when oxidation occurs then this reaction is considered __________. reduction oxidation endergonic exergonic free energy activiation energy inorganic organic decomposition

In biological systems, oxidation of organic molecules, such as glucose, yield the energy necessary for cellular processes to occur. This energy, called free energy, is stored in the chemical bonds of organic molecules. If free energy is release when oxidation occurs then this reaction is considered exergonic.

Under anaerobic conditions (a lack of oxygen), the conversion of pyruvate to acetyl CoA stops. Which of these statements is the correct explanation for this observation? In the absence of oxygen, electron transport stops. NADH is no longer converted to NAD+, which is needed for the first three stages of cellular respiration. Oxygen is an input to acetyl CoA formation. Oxygen is required to convert glucose to pyruvate in glycolysis. Without oxygen, no pyruvate can be made. ATP is needed to convert pyruvate to acetyl CoA. Without oxygen, no ATP can be made in oxidative phosphorylation.

In the absence of oxygen, electron transport stops. NADH is no longer converted to NAD+, which is needed for the first three stages of cellular respiration.

What is the fate of the phosphate group that is removed when ATP is converted to ADP? It is used to convert an ATP into an AQP. It is acquired by a reactant in an exergonic reaction. It is broken down into one phosphorus and four oxygen atoms. It is acquired by a reactant in an endergonic reaction. It is acquired by a reactant in a spontaneous reaction.

It is acquired by a reactant in an endergonic reaction.

The following reaction is part of glycogen degradation and occurs inside a cell. glucose-1-phosphate → glucose-6-phosphate The phosphoryl group transfer potential for glucose-1-phosphate is -20.9 kJ/mol and for glucose-6-phosphate is -13.8 kJ/mol. What is the Keq (K) at 298 K? Is the conversion of glucose-1-phosphate to glucose-6-phosphate favorable or unfavorable under standard conditions? K = 17.5 and the reaction is favorable. K = 0.057 and the reaction is unfavorable. K = 17.5 and the reaction is unfavorable. K = 0.057 and the reaction is favorable.

K = 17.5 and the reaction is favorable.

Metabolism can be bisected into two subcategories: catabolism and anabolism. ________ takes complex organic molecules and breaks them down into simpler molecules; this is often accompanied by the _______ of energy. ________ builds up biomolecules from simpler substances; this is often accompanied by the __________ of energy. Both pathways use simple two-carbon organic molecules (such as __________) as common intermediates. These intermediates can then enter the __________, where they are further___________ to generate carbon dioxide and _________ electron carriers, along with small amounts of ATP. The electrons on these carriers are finally sent through the _________________ to create a proton (H+) gradient. Release of this proton gradient results in the generation of _______. catabolisim anabolism hydrolized glucose release consumption reduced oxidized electron transport chain citric acid cycle ATP Acetyl CoA glycolysis an amino acid

Metabolism can be bisected into two subcategories: catabolism and anabolism. catabolism takes complex organic molecules and breaks them down into simpler molecules; this is often accompanied by the release of energy. anabolism builds up biomolecules from simpler substances; this is often accompanied by the consumption of energy. Both pathways use simple two-carbon organic molecules (such as acetyl-CoA) as common intermediates. These intermediates can then enter the citric acid cycle, where they are further oxidized to generate carbon dioxide and reduced electron carriers, along with small amounts of ATP. The electrons on these carriers are finally sent through the electron transport chain to create a proton (H+) gradient. Release of this proton gradient results in the generation ofATP.

Below are two reduction half reactions. In glycolysis, these two half reactions create a coupled reaction that produces NADH and 1,3-bisphosphoglycerate. 1,3-bisphosphoglycerate + 2H+ + 2e- ⇔ glyceraldehyde-3-phosphate + Pi E°' = -0.29 V NAD+ + H+ + 2e- ⇔ NADH E°' = -0.315 V Under standard conditions for this coupled reaction, becomes reduced and the ΔG°' is _______. (NOTE: Refer to your notes/textbook for any equation or constant needed.) 1,3-bisphosphoglycerate; 4.82 kJ/mol 1,3-bisphosphoglycerate; -4.82 kJ/mol NAD+; 4.82 kJ/mol NAD+; -4.82 kJ/mol

NAD+; 4.82 kJ/mol

Which of the following are products of glycolysis? 1) ATP 2) pyruvate 3) NAD+ 4) NADP+ Only 1 and 2 are products of glycolysis. Only 2 and 4 are products of glycolysis. Only 1 and 3 are products of glycolysis. Only 1, 2, and 3 are products of glycolysis.

Only 1 and 2 are products of glycolysis.

Under certain circumstances, fast (anaerobic) respiration occurs in the absence of oxygen. When this happens, which of the following products may be produced? 1) lactate 2) ethanol 3) carbon dioxide 4) acetyl CoA Only 1 and 2 may be produced. Only 1 and 3 may be produced. Only 1, 2, and 3 may be produced. All four products may be produced.

Only 1, 2, and 3 may be produced.

Which of the following four statements is/are accurate with respect to glycolysis? 1) Glycolysis involves the conversion of monosaccharides into glucose. 2) Glycolysis involves the breakdown of glucose into glyceraldehyde-3-phosphate. 3) Glycolysis involves the conversion of pyruvate into glucose to glyceraldehyde-3-phosphate. 4) Glycolysis involves the conversion of pyruvate into acetyl CoA. Only statement 2 is correct. Statements 1 and 2 are correct. Statements 1, 2, and 4 are correct. All four statements are correct.

Only statement 2 is correct.

Reaction #8 in the citric acid cycle is shown below. The ΔGº' for this reaction is +29.7 kJ/mol. This is a significantly endergonic reaction so how is it possible that this reaction occurs in the cell? malate + NAD+ ⇔ oxaloacetate + NADH + H+ The concentration of oxaloacetate in the cell is extremely low. The concentration of malate in the cell is extremely low. Both of these strategies would allow the reaction to occur in the cell. Neither of these strategies would allow the reaction to occur in the cell.

The concentration of oxaloacetate in the cell is extremely low.

When oligomycin is added to an actively respiring muscle cell, ATP synthase is inhibited. Which of the following predicts the effect of oligomycin on the rate of oxygen usage and the rate of electron transport through the ETC? The rate of oxygen usage remains the same, but the rate of electron transport through the ETC decreases. The rate of electron transport through the ETC remains the same, but the rate of oxygen usage decreases. The rates of both oxygen usage and electron transport through the ETC decrease. The rates of both oxygen usage and electron transport through the ETC remain the same.v

The rates of both oxygen usage and electron transport through the ETC decrease.

Consider the following paired redox reaction: NADH + FAD + H+ → NAD+ + FADH2. Which of the following statements is correct? Please refer to Table 3.6 or the standard reduction table in the lecture notes. NADH is the oxidizing agent. FAD is the reducing agent. The ΔE° for this reaction is negative. This reaction is favorable.

This reaction is favorable.

Pentoses and hexoses can form stable ring structures. True False

True

Select ALL the following TRUE statements about glucose metabolism. Pyruvate is used in reactions that produce ethanol and CO2, lactate, or acetyl CoA. Glycolysis followed by fermentation can proceed without the presence of oxygen. Fast (anaerobic) respiration produces ATP more quickly than slow (cellular) respiration. Eukaryotic cells can only produce ATP by slow (cellular) respiration.

True Pyruvate is used in reactions that produce ethanol and CO2, lactate, or acetyl CoA. Glycolysis followed by fermentation can proceed without the presence of oxygen. Fast (anaerobic) respiration produces ATP more quickly than slow (cellular) respiration.

Many enzymes operate using an acid catalysis mechanism; during this reaction an amino acid R group functions as an acid by accepting a proton. donating a proton. donating a water molecule. accepting a water molecule.

donating a proton

Which of these reactions requires a net input of energy from its surroundings? catabolic exergonic ATP --> ADP + P endergonic hydrolysis

endergonic

A(n) _____ reaction occurs spontaneously. chemical exergonic anabolic kinetic endergonic

exergonic

In a cell, the energy for a significantly endergonic reaction often comes from a(n) _____ reaction. dehydration anabolic ATP formation exergonic

exergonic

The energy for an endergonic reaction comes from a(n) _____ reaction. ADP + P --> ATP exergonic glucose + glucose --> maltose synthesis anabolic

exergonic

The reaction A --> B + C + heat is released in a(n) _____ reaction. endergonic exergonic dehydration synthesis anabolic exchange

exergonic

Select the INCORRECT association. kinetic energy ... motion exergonic ... spontaneous enzyme ... protein potential energy ... positional energy exergonic ... uphill

exergonic ... uphill

Of the events listed below, select ALL that are common to BOTH glycogen synthesis and glycogen degradation. formation of an α(1→6) glycosidic bond formation of an α(1→4) glycosidic bond cleavage of an α(1→4) glycosidic bond cleavage of an α(1→6) glycosidic bond

formation of an α(1→4) glycosidic bond cleavage of an α(1→4) glycosidic bond

Which of the following processes is common to BOTH fast respiration and slow respiration? glycolysis fermentation acetyl-CoA formation citric acid cycle

glycolysis

Glycolysis and gluconeogenesis share multiple enzymes. This is possible because the reactions catalyzed by the shared enzymes have free energy changes near zero. do not generate ATP or reduced electron carriers. have smaller activation energies. require fewer substrates.

have free energy changes near zero

The enzyme that catalyzes the addition of carbon dioxide to pyruvate during gluconeogenesis is classified as a(n) hydrolase ligase isomerase transferase

ligase

The purpose of the citric acid cycle is to complete the of glucose started in glycolysis. oxidation reduction dephosphorylation phosphorylation

oxidation

Isocitrate is converted to α-ketoglutarate during the citric acid cycle. The enzyme that catalyzes this reaction belongs to which group of enzymes? oxidoreductase lyase ligase transferase

oxidoreductase

The conversion of ADP + Pi to ATP is endergonic by more than 30 kJ/mol. Which of the following hydrolyses could drive this conversion? Please consult Table 3.5. glucose-6-phosphate to glucose PPi to 2 Pi glucose-1-phosphate to glucose phosphoenolpyruvate to pyruvate all of the above

phosphoenolpyruvate to pyruvate

Electrons are transferred through the respiratory chain from reduced NADH or FADH2 to oxygen in small steps with each step in the pathway associated with a slightly more ________ reduction potential.

positive

For a redox reaction to be spontaneous the overall ΔEº' is positive and transfer of electrons occurs from a molecule with lower affinity to one with higher affinity. positive and transfer of electrons occurs from a molecule with higher affinity to one with lower affinity. negative and transfer of electrons occurs from a molecule with lower affinity to one with higher affinity. negative and transfer of electrons occurs from a molecule with lower affinity to one with higher affinity.

positive and transfer of electrons occurs from a molecule with lower affinity to one with higher affinity.

At the end of glycolysis, most of the energy from a molecule of glucose is in the form of ____. At the end of the citric acid cycle, most of the energy from a molecule of glucose is in the form of ______. reduced electron carriers; ATP pyruvate; ATP pyruvate; reduced electron carriers ATP; reduced electron carriers

pyruvate; reduced electron carriers

Oxidative phosphorylation refers to the synthesis of ATP using stored energy created from passing of electrons along the electron transport chain. the transfer of electrons to oxidized electron carriers in the citric acid cycle. the use of ATP to create molecules with a higher phosphoryl group transfer potential. the formation of a proton gradient across the inner membrane of the mitochondrion.

the synthesis of ATP using stored energy created from passing of electrons along the electron transport chain.

What is energy coupling? the use of energy released from an exergonic reaction to drive an endergonic reaction the hydrolysis of ATP to ADP + P a description of the energetic relationship between the reactants and products in an exergonic reaction the use of an enzyme to reduce EA a barrier to the initiation of a reaction

the use of energy released from an exergonic reaction to drive an endergonic reaction

The enzyme that catalyzes the phosphorylation of fructose-6-phosphate during glycolysis is classified as a(n) transferase lyase ligase hydrolase

transferase