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16 Jul 2019

Citric acid cycle: A cell has a high demand for ATP and the energy charge in the cell is low. The rate of oxidation of acetyl-CoA, and hence the production of ATP by oxidative phosphorylation, is affected by the overall concentration of the intermediates present in the citric acid cycle.

Under these conditions:

a. What effect would a HIGH concentration of intermediates have on the rate of entry of acetylCoA into the cycle? (1 mark)

b. What effect would a LOW concentration of intermediates have on the rate of entry of acetylCoA into the cycle? (1 mark)

c. How can the concentration of the citric acid cycle intermediates be increased? Give one instance (3 marks)

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Keith LeannonLv2

18 Jul 2019

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Related questions

1. Choose the TWO correct statements describing the citrate cycle.

	ATP is an indirect product of the citric acid cycle
	Acetyl CoA can increase the pool of citric acid cycle intermediates
	Fatty acids can increase the pool of citric acid cycle intermediates
	ADP inhibits Î±-ketoglutarate dehydrogenase
	The pool of mitochondrial oxaloacetate can be increased by pyruvate
	All enzymes of the citric acid cycle are found soluble and free in the mitochondrial matrix

2.Which molecule in the net reaction of the citrate cycle contributes to the inhibition of pyruvate dehydrogenase?

	NADH
	H⁺
	H₂O
	FAD

3. How would a high NADH to NAD⁺ ratio be expected to affect the pyruvate dehydrogenase reaction?

	The E1 subunit is phosphorylated by pyruvate dehydrogenase kinase, and the catalytic activity of pyruvate dehydrogenase decreases.
	The last step of the pyruvate dehydrogenase reaction is blocked, resulting in a decrease in activity.
	The pyruvate dehydrogenase phosphatase-1 enzyme would increase, resulting in pyruvate dehydrogenase activation at an accelerated rate.
	The pyruvate dehydrogenase kinase enzyme activity would increase, resulting in an increase in pyruvate dehydrogenase activity.

force times distance

Question 48

Soccer (assuming field player) is a sport which is 90% aerobic.

True

False

Question 50

Glucose is necessary for fatty acid oxidation because...

		its derivative, pyruvate, is condensated with carbonic acid to form oxaloacetate, which in turn is a necessary carbon compound in the citric acid cycle
		it is needed to convert fatty acids to fatty acyl-CoA which in turn is oxidized to acetyl CoA
		glucose is decarboxylated into cytochrome oxidase which is a necessary intermediate in the citric acid cycle
		its derivative, acetyl CoA, is condensated with carbonic acid to form lactase, which in turn is a necessary carbon compound in the citric acid cycle

Question 51

In aerobic ATP production, the role of oxygen is to...

		to keep the electron transport chain operational
		to accept electrons from the 3rd cytochrome and thereby oxidizing it so it can accept new electrons
		act as a oxidizing agent by accepting electrons from the electron transport chain and combining with hydrogen ions (protons)
		all of the above

Question 52

The primary purpose of the citric acid cycle is...

aerobic glycolysis

gluconeogenesis using lactate

the decarboxylation of carbon compounds to produce NADH.

the shuttling of hydrogen ions through the inner mitochondrial membrane

Question 55

Which of the following is the best predictor of marathon running performance?

	A.	Maximal rate of pyruvate oxidation
	B.	Maximal rate of lactate formation
	C.	Amount of adipose tissue triglycerides
	D.	Pre-race blood glucose concentration

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1. Integrated metabolism

A. A molecule of glucose that you eat can eventually be transformed into part of a fatty acid that you store. Circle the pathways/cycles below that are part of this overall flow of carbon atoms. Cross out any that are not.

Gluconeogenesis, beta-oxidation, citric acid cycle, glycolysis, urea cycle, fatty acid synthesis

B. Trace the metabolic path of this glucose molecule through the enzymes it encounters along the way to being made into fat. Write all the enzymes in the list below into the proper places in the figure below. If the enzyme is not used, write its name in a ânot used" column. If it is used, write the enzyme in the order that the carbon atoms from glucose encounter the enzymes.

Pyruvate dehydrogenase, fumarase, aldolase, lactate dehydrogenase, pyruvate kinase, acetyl CoA carboxylase, fatty acid synthase, hexokinase, carnitine acyltransferase, ATP synthase

B. What is the minimum number of glucose molecules that would be necessary to be the carbon source for synthesis of a 16-carbon fatty acid through this pathway?

C. How many net glucose can be made from one molecule of a 16-carbon fatty acid?

2. Describe each cycle/transport system (compounds, compartments, tissues) and explain its purpose:

A. citrate transport system

B. Cori cycle

C. glucose/alanine cycle

Explain the logic of these pathway regulations:

A. Phosphofructokinase, not hexokinase, is the main regulation site of glycolysis.

B. SuccinylCoA inhibits the entry of acetyl CoA into the citric acid cycle.

C. NADH inhibits pyruvate dehydrogenase.

D. Citrate inhibits the citric acid cycle and activates acetyl-CoA carboxylase.

E. Insulin leads to activation of glycogen synthase.