Question

An aminoacyl-tRNA exhibits which one of the following characteristics?

	A.	It is produced by a synthetase that is specific for the amino acid, but not the tRNA
	B.	It is composed of an amino acid esterified to the 5’ end of the tRNA
	C.	It requires GTP for its synthesis from an amino acid and a tRNA
	D.	It contains an anticodon that is complementary to the codon for the amino acid

Concerning generation of ATP from glucose during glycolysis which of the following statements is not correct?

	A.	There is a net yield of 2 ATPs
	B.	There is a net yield of 4 ATPs
	C.	More ATP can be produced from the generated NADH in the presence of oxygen
	D.	Direct generation of ATP in glycolysis is an example of substrate level phosphorylation

Insulin results in phosphorylation of acetyl-coA carboxylase, which stimulate fatty acid synthesis?

True

False

Which of the following statement(s) is or are correct?

	A.	Excess proteins are stored as peptides in humans
	B.	Excess even chain fatty acids can be used to synthesize glucose through gluconeogenesis
	C.	Glycogen is one of the substrate for gluconeogenesis
	D.	Excess dietary proteins can be stored either as glycogen or lipids
	E.	All of the above

Which of the following would be observed in a person who is resting after an overnight fast?

	A.	Liver glycogen are completely depleted
	B.	Liver gluconeogenesis is not an important process
	C.	Muscle glycogen stores are used to maintain glucose
	D.	Fatty acids are released from adipose triacylglycerol stores
	E.	The liver is oxidizing ketone bodies to meet its energy needs

Answer 1

D. An aminoacyl tRNA contains an anticodon that is complementary to the codon for the amino acid.

Explanation ---

There are 20 different aminoacyl transferase each for one amino acid complementary to the codon coding for protein in the process of translation.

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B. There is a net yield of 4 ATP

Explanation ----

Glycolysis is the process of breakdown of glucose into 2 pyruvate molecule which occurs through a series of steps.

In the first two steps glucose molecule is used up to convert it into three carbon containing compoung which fructose - 1,6- Biphosphate where the ATP molecule is used up.

In fifth step, conversion of glyceraldehyde-3-phosphate into 1,3-Biphosphoglycerate where NAD+ is reduced to NADH.

In In the next step, conversion of 1,3- biphosphoglycerate into 3- phosphoglycerate, two molecules of ATP are formed.

In the last step, conversion of phosphoenolpyruvate into pyruvate again results in production of 2 ATP molecules.

This direct generation of energy from ATP molecule is an substrate level phosphorylation.

Thus in the process of glycolysis, 4 ATP and 2NADH were formed out of which 2 ATP were used in the initial steps. Therefore, net yield is 2ATP and 2NADH and 2 pyruvate molecules.

Note - net yield means sum total minus the losses.

Therefore, option B tells total ATP not the net yield..

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False

Explanation --

Acetyl co- A carboxylase is needed in the synthesis of fatty acids which is done by stimulation of acteyl co-a enzyme by dephosphorylation with insulin.

This Acetyl Co-A enzyme activated by removing the phosphate group ie, dephosphorylation which is done by insulin wheras glucagon and epinephrine have opposite effects to that of insulin.