Biochemistry : Carbohydrate Anabolism

Study concepts, example questions & explanations for Biochemistry

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Example Questions

Example Question #131 : Anabolic Pathways And Synthesis

What two molecules are the links between the urea cycle and gluconeogenesis?

Possible Answers:

Oxaloacetate and citrate

Oxaloacetate and fumarate

Fumarate and citrate

Fumarate and aspartate

Citrate and aspartate

Correct answer:

Fumarate and aspartate

Explanation:

Aspartate can form arginosuccinate, which can then release a fumarate molecule. The fumarate can enter into the Krebs cycle and eventually the pathway can lead to gluconeogenesis. The arginine from the arginosuccinate can continue through the urea cycle.

Example Question #131 : Anabolic Pathways And Synthesis

In order to be added to a growing glycogen chain, glucose must first be activated by which of the following molecules?

Possible Answers:

ADP

ATP

UDP

UTP

GDP

Correct answer:

UDP

Explanation:

UDP-glucose is the activated form of glucose that works to build chains of glycogen. The other listed molecules do not serve this function.

Example Question #132 : Anabolic Pathways And Synthesis

How does ingestion of high amounts of ethanol affect gluconeogenesis?

I. High amounts of ethanol get oxidized producing NADPH.

II. High levels of NADPH inhibit gluconeogenesis. 

III. High levels of NADPH stimulate gluconeogenesis.

IV. High amounts of ethanol get oxidized producing NADP.

Possible Answers:

III only

I and III

II and IV

I and II 

I and IV

Correct answer:

I and II 

Explanation:

Ingestion of high amounts of ethanol leads to increased NADPH. High levels of NADPH inhibit gluconeogenesis followed by low glucose levels in the absence of dietary intake. In acute ingestion of alcohol, hypoglycemia (low levels of glucose in the blood) can follow due to inhibition of gluconeogenesis.

Example Question #131 : Anabolic Pathways And Synthesis

What is the net yield from the pentose phosphate pathway?

I. 

II. 

III. 

IV. 

Possible Answers:

 III only

 II only

 I and II

I only

 IV only

Correct answer:

I only

Explanation:

The pentose phosphate pathway produces NADPH and five-carbon sugars. The net reaction is:

The pathway is also important in purine precursor synthesis.

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