생화학 16,17,18장

33問 • 2年前

問題一覧

Why are steps 4 and 5 essential to the operation of the PDH complex?

They reoxidize the reduced lipoamide cofactor.

The pyruvate dehydrogenase (PDH) complex catalyzes the oxidative decarboxylation of pyruvate to acetyl-CoA and CO... Multiple copies of pyruvate dehydrogenase (E), dihydrolipoyl transacetylase (E2), and dihydrolipoyl dehydrogenase (E3) along with five cofactors form the PDH complex. Biochemists have studied the PDH complex for decades, in part due to its interesting use of substrate channeling during catalysis. What is the benefit of substrate channeling?

Intermediates of a multistep reaction sequence do not dissociate from the enzyme complex.

What is the molecular mechanism of substrate channeling in the PDH complex?

The swinging lipoyllysyl arm of E2 carries electrons and an acetyl group from E1 to E2.

What is the direction of the metabolite flow through the citrate synthase reaction in rat heart cells? Why?

toward citrate, because the free-energy change (델타G) is negative

Identify the reactions of the citric acid cycle that provide reducing power for the electron-transport chain.

conversion of isocitrate to a-ketoglutarate, conversion of a-ketoglutarate to succinyl-CoA

In animal tissues, the ratio of active, unphosphorylated to inactive, phosphorylated pyruvate dehydrogenase (PDH) complex regulates the rate of pyruvate conversion to acetyl-CoA. Treatment of a preparation of rabbit muscle mitochondria containing the PDH complex with pyruvate dehydrogenase kinase, ATP. and NADH causes the rate of this reaction to___________

decrease

Treatment of a preparation of rabbit muscle mitochondria containing the PDH complex with pyruvate dehydrogenase phosphatase and Ca2+ causes the rate of this reaction to __________

increase

Treatment of a preparation of rabbit muscle mitochondria containing the PDH complex with malonate causes the rate of this reaction to__________

decrease

On the basis of these observations, how might succinyl-CoA regulate the activity of citrate synthase?

Succinyl-CoA inhibits citrate synthase.

Why is succinyl-CoA an appropriate signal for regulation of the citric acid cycle?

By regulating citrate synthase, succinyl-CoA controls entry of acetyl-CoA into the citric acid cycle.

How does the regulation of citrate synthase control the rate of cellular respiration in pig heart tissue?

Citrate synthase regulates the supply of reduced electron carriers and, thus, the flow of electrons to O₂.

Choose the statements that are reasonable explanations for the right-ward shift of the velocity curve caused by succinyl-CoA.

Succinyl-CoA competes with acetyl-CoA for binding at the active site., Succinyl-CoA binds at a regulatory site other than the active site.

Citrate synthase is regulated by another metabolite that has the opposite effect (i.e., stimulates citrate synthase). Choose the description of a condition where a positive regulator activates citrate synthase.

Low [ATP/ADP] ratio. ADP is an allosteric activator of citrate synthase.

which molecules inhibit reaction1?

citrate, NADH, succcinyl-CoA

which molecule inhibits reaction 3?

NADH

which molecules or ions activate reaction 3?

Ca2+, ADP

which molecules inhibit reaction4?

succinyl-CoA, NADH

which molecules or ion activates reaction 4?

Ca2+

The acyl-CoA synthetase reaction is readily reversible, with an equilibrium constant near 1. How can this reaction be made to favor formation of fatty acyl-CoA?

Hydrolysis of PP1 by an inorganic pyrophosphatase pulls the reaction in the direction of fatty acyl-CoA formation.

What changes in fatty acid metabolism would result from a mutation in the muscle carnitine acyltransferase I in which the mutant protein has lost its affinity for malonyl-CoA but not its catalytic activity?

Fatty acid synthesis in the cytosol and fatty acid oxidation in the mitochondria could occur simultaneously.

How many turns of the fatty acid oxidation cycle are required for complete oxidation of arachidic acid (20:0) to acetyl-CoA? number of ẞ-oxidation cycles:___________

A fatty acid composed of 18 carbon atoms undergoes ẞ-oxidation. How many acetyl CoA, FADH,, and NADH does Bẞ-oxidation of this fatty acid generate?

9 acetyl CoA, 8 FADH2, 8 NADH

Calculate the net ATP generated by the B-oxidation of the 18-carbon fatty acid. Assume that each FADH, generates 1.5 ATP and each NADH generates 2.5 ATP. number of ATP molecules:

120

A weight-reducing diet heavily promoted some years ago required the daily intake of a "liquid protein" soup made of hydrolyzed gelatin (derived from collagen), water, and an assortment of vitamins. All other food and drink were to be avoided. People on this diet typically lost 10 to 14 lbs in the first week. Note that gelatin naturally possesses an unbalanced distribution of amino acids and completely lacks tryptophan. Opponents argued that the weight loss was almost entirely due to water loss and would be regained very soon after a normal diet was resumed. What is the biochemical basis for this argument?

The gelatin diet generates an abundance of urea, which must be diluted with water prior to excretion as urine.

consuming only gelatin may cause

dehydration and ammonia toxicity

2 Glutamate + CO2 +O2+2 ADP+2Pi→

2 a-ketoglutarate + urea + 3H2O+ 2 ATP

Using the Metabolic Map as a resource, select the statement that best describes the purpose of the urea cycle in the cells of land mammals.

to convert highly toxic free ammonia into less toxic urea

Using the Metabolic Map as a resource, select the urea cycle reactions that occur in the mitochondria. 답 2개

ammonia + bicarbonate →carbamoyl phosphate, ornithine + carbamoyl phosphate → citrulline

Using the Metabolic Map as a resource, select the statement that describes the similar roles of ornithine in the urea cycle and oxaloacetate in the citric acid cycle.

Both accept material during their respective cycle.

What is the first urea cycle intermediate that will contain the labeled nitrogen?

argininosuccinate

Where is labeled nitrogen incorporated?

Use your knowledge and understanding of the citric acid cycle and -oxidation pathway to arrange the intermediates in the proper metabolic sequence for isoleucine degradation. 순서 적어!

isoleucine -> 2 -> 4 -> 1 -> 5 -> 3

How does amino acid degradation produce urea?

Ammonia is removed from glutamic acid and reacts with carbon dioxide.

생화학 14, 15장

생화학 14, 15장

해생2 퀴즈1

해생2 퀴즈1

해생 퀴즈3

해생 퀴즈3

해생 퀴즈4

해생 퀴즈4

해생퀴즈5

해생퀴즈5

생화학 19,21,22장 퀘뱅

생화학 19,21,22장 퀘뱅

19 20 21 문제

19 20 21 문제

생화학 주관식 문제

생화학 주관식 문제

7주차

7주차

독성학

독성학

한약 생약 암기

한약 생약 암기

한약 응용 암기 1

한약 응용 암기 1

Head and neck

Head and neck

問題一覧

Why are steps 4 and 5 essential to the operation of the PDH complex?

They reoxidize the reduced lipoamide cofactor.

Intermediates of a multistep reaction sequence do not dissociate from the enzyme complex.

What is the molecular mechanism of substrate channeling in the PDH complex?

The swinging lipoyllysyl arm of E2 carries electrons and an acetyl group from E1 to E2.

What is the direction of the metabolite flow through the citrate synthase reaction in rat heart cells? Why?

toward citrate, because the free-energy change (델타G) is negative

Identify the reactions of the citric acid cycle that provide reducing power for the electron-transport chain.

conversion of isocitrate to a-ketoglutarate, conversion of a-ketoglutarate to succinyl-CoA

decrease

Treatment of a preparation of rabbit muscle mitochondria containing the PDH complex with pyruvate dehydrogenase phosphatase and Ca2+ causes the rate of this reaction to __________

increase

Treatment of a preparation of rabbit muscle mitochondria containing the PDH complex with malonate causes the rate of this reaction to__________

decrease

On the basis of these observations, how might succinyl-CoA regulate the activity of citrate synthase?

Succinyl-CoA inhibits citrate synthase.

Why is succinyl-CoA an appropriate signal for regulation of the citric acid cycle?

By regulating citrate synthase, succinyl-CoA controls entry of acetyl-CoA into the citric acid cycle.

How does the regulation of citrate synthase control the rate of cellular respiration in pig heart tissue?

Citrate synthase regulates the supply of reduced electron carriers and, thus, the flow of electrons to O₂.

Choose the statements that are reasonable explanations for the right-ward shift of the velocity curve caused by succinyl-CoA.

Succinyl-CoA competes with acetyl-CoA for binding at the active site., Succinyl-CoA binds at a regulatory site other than the active site.

Low [ATP/ADP] ratio. ADP is an allosteric activator of citrate synthase.

which molecules inhibit reaction1?

citrate, NADH, succcinyl-CoA

which molecule inhibits reaction 3?

NADH

which molecules or ions activate reaction 3?

Ca2+, ADP

which molecules inhibit reaction4?

succinyl-CoA, NADH

which molecules or ion activates reaction 4?

Ca2+

The acyl-CoA synthetase reaction is readily reversible, with an equilibrium constant near 1. How can this reaction be made to favor formation of fatty acyl-CoA?

Hydrolysis of PP1 by an inorganic pyrophosphatase pulls the reaction in the direction of fatty acyl-CoA formation.

Fatty acid synthesis in the cytosol and fatty acid oxidation in the mitochondria could occur simultaneously.

How many turns of the fatty acid oxidation cycle are required for complete oxidation of arachidic acid (20:0) to acetyl-CoA? number of ẞ-oxidation cycles:___________

A fatty acid composed of 18 carbon atoms undergoes ẞ-oxidation. How many acetyl CoA, FADH,, and NADH does Bẞ-oxidation of this fatty acid generate?

9 acetyl CoA, 8 FADH2, 8 NADH

Calculate the net ATP generated by the B-oxidation of the 18-carbon fatty acid. Assume that each FADH, generates 1.5 ATP and each NADH generates 2.5 ATP. number of ATP molecules:

120

The gelatin diet generates an abundance of urea, which must be diluted with water prior to excretion as urine.

consuming only gelatin may cause

dehydration and ammonia toxicity

2 Glutamate + CO2 +O2+2 ADP+2Pi→

2 a-ketoglutarate + urea + 3H2O+ 2 ATP

Using the Metabolic Map as a resource, select the statement that best describes the purpose of the urea cycle in the cells of land mammals.

to convert highly toxic free ammonia into less toxic urea

Using the Metabolic Map as a resource, select the urea cycle reactions that occur in the mitochondria. 답 2개

ammonia + bicarbonate →carbamoyl phosphate, ornithine + carbamoyl phosphate → citrulline

Using the Metabolic Map as a resource, select the statement that describes the similar roles of ornithine in the urea cycle and oxaloacetate in the citric acid cycle.

Both accept material during their respective cycle.

What is the first urea cycle intermediate that will contain the labeled nitrogen?

argininosuccinate

Where is labeled nitrogen incorporated?

Use your knowledge and understanding of the citric acid cycle and -oxidation pathway to arrange the intermediates in the proper metabolic sequence for isoleucine degradation. 순서 적어!

isoleucine -> 2 -> 4 -> 1 -> 5 -> 3

How does amino acid degradation produce urea?

Ammonia is removed from glutamic acid and reacts with carbon dioxide.