Biochem Ch 11 (Online HW)

Which statement is FALSE about ATP?

**The concentration of ATP in cells is generally much lower than that of AMP.** The intracellular concentration of ATP varies among cell types. Its concentration in a particular cell usually fluctuates very little. Its concentration is maintained in part by adenylate kinase.

Which statement is NOT true about catabolic pathways?

**They have a net consumption of ATP.** They include the citric acid cycle. They have a net release of energy. They liberate smaller molecules from larger ones.

Under physiological conditions the complete oxidation of glucose to carbon dioxide and water in the presence of oxygen has a ΔG of -2900 kJ/mol glucose. This process can be coupled to the synthesis of ~32 mol ATP. The ΔG of the coupled reactions to make ATP is -1300 kJ/mol glucose. Calculate the ΔG for the synthesis of ATP from ADP.

+50 kJ mol-1

Consider a dehydrogenase enzyme whose substrate is the molecule shown below. Predict the product following oxidation of the substrate by the dehydrogenase enzyme with help of NAD+NAD+.

-OH becomes =O

Which of the following statements about metabolism are true? 1. Catabolism is the process in which complex substances are broken down, yielding a net output of energy. 2. Metabolism is an integrated system in which many of the same reactions participate in degradative (catabolic) and biosynthetic (anabolic) pathways. 3. The overall process of metabolism involves the breakdown of polymeric biomolecules and complex lipids to monomers and less complex fats, followed by further degradation to inorganic compounds. 4. All organisms derive raw materials and energy from organic molecules, such as glucose.

1. Catabolism is the process in which complex substances are broken down, yielding a net output of energy. 2. Metabolism is an integrated system in which many of the same reactions participate in degradative (catabolic) and biosynthetic (anabolic) pathways. 3. The overall process of metabolism involves the breakdown of polymeric biomolecules and complex lipids to monomers and less complex fats, followed by further degradation to inorganic compounds.

The combustion of glucose ultimately involves the transfer of electrons to oxygen (O2). In biological systems, this takes place without a large increase in temperature. Which of the following statements about this process in biological systems is true? 1. Coupled oxidation-reduction reactions occur with electrons being passed to intermediate electron carriers. 2. The process involves the transfer of 12 pairs of electrons to oxygen. 3. The transfer of electrons from intermediate electron carriers to molecular oxygen is catalyzed by the electron transport chain. 4. Although the process is a controlled oxidation, some energy is lost as heat.

1. Coupled oxidation-reduction reactions occur with electrons being passed to intermediate electron carriers. 2. The process involves the transfer of 12 pairs of electrons to oxygen. 3. The transfer of electrons from intermediate electron carriers to molecular oxygen is catalyzed by the electron transport chain. 4. Although the process is a controlled oxidation, some energy is lost as heat.

Under certain circumstances, glycolysis takes place anaerobically, 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

1. lactate 2. ethanol 3. carbon dioxide

Which of the following generalized reaction products involve nucleophilic attack on a carbonyl group? 1. β-hydroxy products 2. α, β-unsaturated carbonyl products 3. β-keto products 4. carbinolamine products

1. β-hydroxy products 3. β-keto products 4. carbinolamine products

Assign the definition to the term. 1) autotroph 2) heterotroph 3) aerobic 4) anaerobic A) organism deriving metabolic energy in the absence of oxygen B) synthesizes glucose and all their other organic compounds from inorganic carbon, supplied by carbon dioxide C) coupling of energy generation to the oxidation of nutrients by oxygen D) synthesizes their organic metabolites only from other organic compounds, which must be consumed

1B 2D 3C 4A

Which of the following statements about ATP are true? 1. ATP has reactive phosphoester bonds. 2. ATP has a large free energy of activation for hydrolysis with water. 3. ATP is kinetically stable but thermodynamically unstable. 4. ATP spontaneously phosphorylates other molecules because it has a high group transfer potential.

2. ATP has a large free energy of activation for hydrolysis with water. 3. ATP is kinetically stable but thermodynamically unstable.

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 pyruvate. 3. Glycolysis involves the conversion of pyruvate into glucose to glyceraldehyde-3-phosphate. 4. Glycolysis involves the conversion of pyruvate into acetyl CoA.

2. Glycolysis involves the breakdown of glucose into pyruvate.

Which of the following are nucleophiles? 1. protonated imine 2. carbonyl group 3. carboxylate 4. imidazole

3. carboxylate 4. imidazole

In the conversion of ethanol to acetaldehyde with concomitant conversion of NAD+ to NADH, which of the following statements is true? 1. Ethanol is the oxidant. 2. NAD+ is the reductant. 3. Acetaldehyde accepts electrons. 4. Ethanol gives up electrons.

4. Ethanol gives up electrons.

Substrate-level phosphorylation is a term given to product formation resulting in ________.

ADP Phosphorylation

The main energy-coupling compound in biochemical reactions that allows thermodynamically unfavorable processes to become favorable is ________.

ATP

Which is NOT generally a molecule used to conserve energy?

ATP **FAD** NADH QH2

The anabolic and catabolic processes of cellular metabolism can be coupled by ________.

ATP hydrolysis

Phosphorylation by protein kinases coordinates regulation of different pathways. Usually this phosphorylation ________ catabolic pathways and ________ anabolic pathways.

Activates Deactivates

Levels of ATP and ADP are partly maintained in cells by ________.

Adenylate kinase

Under what cellular conditions would both directions in the substrate cycle be strongly favored?

Any condition where the [glucose]/[glucose-6-phosphate] ratio is between 262000 and 1/846.

The most biochemically complex organisms are ________.

Autotrophs

Which bond in ATP is primarily responsible for its being a high energy molecule?

B (picture wouldn't show up)

ATP can be used to activate a substrate by ________.

Both phosphorylation and adding a nucleotidyl group

The ultimate product of complete oxidation of carbohydrates is ________.

Carbon dioxide

Metabolic pathways that involve the degradation of large molecules to smaller ones are classified as ________.

Catabolic

The NAD+/NADH is usually found in which metabolic pathways?

Catabolic pathways

Each of the four stages of cellular respiration occurs in a specific location inside or outside the mitochondria. These locations permit precise regulation and partitioning of cellular resources to optimize the utilization of cellular energy.

Cellular respiration begins with glycolysis in the cytosol. Pyruvate, the product of glycolysis, then enters the mitochondrial matrix, crossing both the outer and inner membranes. Both acetyl CoA formation and the citric acid cycle take place in the matrix. The NADH and FADH2 produced during the first three stages release their electrons to the electron transport chain of oxidative phosphorylation at the inner mitochondrial membrane. The inner membrane provides the barrier that creates an H+ gradient during electron transport, which is used for ATP synthesis.

Which is usually the slowest way to regulate a reaction in a metabolic pathway?

Changing the enzyme concentration

Catabolic processes involve degradation of complex molecules into simpler molecules with the net release of ________.

Chemical energy

An organism that uses organic molecules as carbon sources and obtains energy by oxidizing inorganic molecules is a(n) ________.

Chemoheterotroph

ATP has a high phosphoryl group transfer potential because ________.

Cleavage of either of its two phosphoanhydride bonds proceeds with a large negative △Go' of hydrolysis

Which of the following is NOT a factor contributing to the large free energy of hydrolysis of ATP?

Complexes with Mg2+ or Mn2+ ions.

The flow of material through a reaction pathway usually depends on ________.

Control at several steps in the pathway

Which of the following components is considered an intracellular messenger?

Cyclic AMP

Fatty acid synthesis occurs in the ________, while fatty acid breakdown occurs in the ________.

Cytosol Mitochondria

Which of the following cannot be used as a metabolic control mechanism?

DNA repair

Reactions in metabolic pathways that are subject to regulation are those that are displaced far from ________.

Equilibrium

The flow of material through a metabolic pathway is called the ________.

Flux

An enzyme that catalyzes a committed step in a metabolic pathway has a high ________.

Flux control coefficient

The hydrolysis of ATP to ADP has a ΔG°' of -30 kJ/mol. If in an E. coli cell the concentrations of ATP, ADP and inorganic phosphate are 7.90 mM, 1.04 mM and 7.9 mM, respectively, which statement is TRUE about the hydrolysis of ATP in the cell? (Assume a temperature of 298 K. R = 8.315 J/K-mol)

Hydrolysis can proceed spontaneously

In acetyl CoA formation, the carbon-containing compound from glycolysis is oxidized to produce acetyl CoA. From the following compounds involved in cellular respiration, choose those that are the net inputs and net outputs of acetyl CoA formation.

In acetyl CoA formation, pyruvate (a product of glycolysis) is oxidized to acetyl CoA, with the reduction of NAD+ to NADH and the release of one molecule of CO2.

From the following compounds involved in cellular respiration, choose those that are the net inputs and net outputs of glycolysis.

In glycolysis, the six-carbon sugar glucose is converted to two molecules of pyruvate (three carbons each), with the net production of 2 ATP and 2 NADH per glucose molecule. There is no O2 uptake or CO2 release in glycolysis.

In the last stage of cellular respiration, oxidative phosphorylation, all of the reduced electron carriers produced in the previous stages are oxidized by oxygen via the electron transport chain. The energy from this oxidation is stored in a form that is used by most other energy-requiring reactions in cells. From the following compounds involved in cellular respiration, choose those that are the net inputs and net outputs of oxidative phosphorylation.

In oxidative phosphorylation, the NADH and FADH2 produced by the first three stages of cellular respiration are oxidized in the electron transport chain, reducing O2 to water and recycling NAD+ and FAD back to the first three stages of cellular respiration. The electron transport reactions supply the energy to drive most of a cell's ATP production.

In the citric acid cycle (also known as the Krebs cycle), acetyl CoA is completely oxidized. From the following compounds involved in cellular respiration, choose those that are the net inputs and net outputs of the citric acid cycle.

In the citric acid cycle, the two carbons from the acetyl group of acetyl CoA are oxidized to two molecules of CO2, while several molecules of NAD+ are reduced to NADH and one molecule of FAD is reduced to FADH2. In addition, one molecule of ATP is produced.

Intermediary metabolism is the term applied to reactions that ________.

Involve low molecular weight metabolites

For a step in a reaction pathway to serve as a control point it should be ________.

Irreversible

A reaction that best serves as a control point for regulation ________.

Is metabolically irreversible

Compartmentation of enzymes ________.

Keeps separate pools of metabolites in cells Helps prevent loss by diffusion Can help control metabolic pathways **All of the above**

Nucleoside triphosphates exist in a cell as complexes with ________.

Mg2+ and sometimes Mn2+

Which statement does NOT explain, why many biochemical processes are carried out via multi-step pathways rather than by single-step reactions (or only a few steps)?

Multi-step pathways allow for more control points to regulate biochemical processes. Sharing of intermediates between pathways is facilitated this way. There is greater control over the amounts of energy that are consumed or released at any one time. **The end products of most pathways can usually be produced only by the pathway reactions that nature has evolved.**

NAD+ kinase catalyzes the ATP-dependent conversion of NAD+ to NADP+. How many reducing equivalents are involved in this reaction?

N=0 reducing equivalent(s)

How many reducing equivalents are involved in the conversion of NADP+ to NADPH?

N=2 reducing equivalent(s)

How many reducing equivalents are involved in reducing one molecule of carbon dioxide to methane by bacteria?

N=8 reducing equivalent(s)

The chemical energy generated by oxidation reactions cannot be captured by ________.

NADH

The degradation of which class of biochemical does NOT significantly contribute to the release of energy to cells?

Nucleic acids

Identify whether the following molecules contain functional groups that act as electrophiles, nucleophiles, or both.

Nucleophilic groups include: alkoxide hydroxide ion carbanion carboxylate thiolate amine imidazole Electrophilic groups include: carbonyl protonated imine phosphate proton

Anabolic and catabolic reactions in eukaryotes can occur simultaneously in cells. This is possible because ________.

Of the compartmentation of metabolites for the reactions of opposing pathways

ATP is classified as an energy-rich compound because ________.

Of the free energy released from cleavage of the phosphoanhydride bond

Name the type of reaction that involves reversible electron transfer between a donor and an acceptor.

Oxidation-reduction

Which of the following produces the largest number of reducing equivalents when oxidized?

Palmitic acid

Which of the following statements is FALSE about most metabolic pathways?

Pathways serve to increase the efficiency of energy transfers. **Most pathways are reversible under physiological conditions.** The enzymes that catalyze reactions in metabolic pathways generally catalyze only a single step. The rates of pathway reactions vary to respond to changing conditions.

Phosphocreatine and phosphoarginine are ________ that are energy rich phosphate storage molecules found in animal ________ cells.

Phosphagens; muscle

The amount of energy recovered as ATP can be estimated by measuring free energy of hydrolysis of ________

Phosphoanhydride bonds in ATP

Which compound has a greater free energy of hydrolysis than ATP?

Phosphoenolpyruvate

How are metabolic pathways controlled?

Regulation of a pathway is distributed among all the enzymes involved in the pathway.

he formation of acetyl CoA is driven to completion by ________.

Removal of the product pyrophosphate by the enzyme pyrophosphatase

In theory at least, the energy released by the oxidation of one molecule of NADH is sufficient to form ________ ATP molecule(s).

Several

In order for a reaction to proceed spontaneously from left to right as written ________.

The overall free-energy change must be negative

The oxidation of glucose requires 6 moles of O2 and generates 6 moles of CO2. The oxidation of palmitic acid requires 23 moles of O2 and yields 16 moles of CO2. Which of the following statements is true?

The oxidation of glucose yields more ATP than that of palmitic acid on a molar basis. The oxidation of glucose has a lower respiratory quotient than palmitic acid. **On a molar basis, the combustion of palmitic acid has greater potential to generate more ATP.** Both processes generate an equal amount of ATP.

What ultimately controls the direction of net conversion of a substrate cycle such as this in the cell?

The relative concentrations of allosteric regulators that exert kinetic control over the enzymes in the opposing pathways.

Identify each type of chemical reaction.

These reaction types are based on the transition of a pair of electrons from an electron-rich atom to an electron-poor one and are represented in a vast number of biochemical pathways. Though they are conducted via different mechanisms, they have a common goal: to provide the human body with energy and a variety of molecules necessary for metabolic needs.

Thioesters are similar to oxygen esters of carboxylic acids EXCEPT that ________.

They are less stable because S is present instead of O in the linkage

What important high energy functional group is shown in molecule shown?

Thioester

Metabolism can be divided into three stages. Which description fits stage 2 best?

the interconversion of monomeric sugars, amino acids, and lipids with still simpler organic compounds

A futile cycle is ________.

two reactions or pathways that share substrates and products, and result in no net gain of ATP.