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NEETMDS- biochemistry mcq
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The immunoglobulin secreted in Bile is

1. IgG

2. 1gM

3. IgA

4. IgE

Biochemistry Answer: 3

The immunoglobulin secreted in Bile is IgA

A component of the coenzyme required in a transamination process is
1. Thiamine
2 Folic acid
3 Pyridoxine
4 Riboflavin
Biochemistry Answer: 3

A component of the coenzyme required in a transamination process is Pyridoxine


Iodine is a characteristic component of

1. Cysteine

2. Tyrosine

3. Thyroxine

4.  Thiamin


Biochemistry Answer: 3


odine is a characteristic component of Thyroxine

A vitamin B12 deficiency may affect heme synthesis by reducing the concentration of which of the following? Choose the one best answer.



1) Acetyl-CoA

2) Succinyl-CoA

3) Glycine

4) Alanine


Biochemistry Answer: 2

Vitamin B12 participates in two reactions in the body-conversion of homocysteine to methionine and conversion ofmethylmalonyl-CoA to succinyl-CoA.

Methylmalonyl-CoA is produced via various amino acid degradation pathways, and from oddcarbon chain fatty acid oxidation. In the absence of B12, succinyl-CoA would only be produced as an intermediate of the TCA cycle, and if it were removed from the cycle for heme synthesis, energy production may suffer.

Glycine is usually obtained from the diet, although in a B12 deficiency a functional folate deficiency may also develop, leading to an inhibition of serine hydroxymethyltransferase, the enzyme that converts serine to glycine, and requires free tetrahydrofolate.

Succinyl-CoA and glycine are the precursors for heme synthesis. A B12 deficiency would not inhibit the production of acetyl-CoA, succinate, or alanine. 

Glycolysis occurs in:

1. Cytoplasm

2. Mitochondrion

3. Both In cytoplasm and mitochondria

4. Only in presence of O2

Biochemistry Answer: 1


Glycolysis is a metabolic process that occurs in the cytoplasm of the cell.
The process is central to the conversion of glucose into energy in the form of
adenosine triphosphate (ATP) and is a fundamental part of cellular respiration.


1. Cytoplasm: Glycolysis takes place in the cytoplasm of the cell. The cytoplasm
is the fluid-filled space between the cell membrane and the nucleus (and other
organelles in eukaryotes) where various metabolic reactions occur. This process
involves a series of enzymatic reactions that break down one molecule of glucose
into two molecules of pyruvate, yielding two net molecules of ATP and two
molecules of NADH (a reduced form of nicotinamide adenine dinucleotide) along
with some other byproducts.

2. Mitochondrion: Although glycolysis does not occur in the mitochondrion, the
mitochondrion plays a crucial role in the subsequent stages of glucose
metabolism. After glycolysis, the pyruvate molecules produced in the cytoplasm
can be transported into the mitochondria, where they are further processed in
the citric acid cycle (also known as the Krebs cycle or TCA cycle) and the
electron transport chain to produce more ATP.


The lipids associated with very low density lipoprotein
1.      are usually linked covalently to apoproteins.
2.      belong primarily to the phosphatidylcholine class.
3.      incorporate fatty acids that are synthesized in the liver.
4.      reflect, in general, the types of lipids found in the diet.

Biochemistry Answer: 3

VLDL is a lipoprotein particle synthesized in the liver and secreted into the bloodstream to transport endogenously synthesized triglycerides and cholesterol to peripheral tissues. The triglycerides in VLDL are derived from fatty acids synthesized in the liver, and the cholesterol is derived from both dietary sources and de novo synthesis in the liver. They are not usually linked covalently to apoproteins (Answer 1), nor do they primarily consist of phosphatidylcholine (Answer 2). While the types of lipids found in the diet (Answer 4) can influence the liver's synthesis of VLDL, the statement does not accurately describe the direct composition of VLDL.

Prothrombin production in the liver is dependent upon an adequate dietary supply of

1 Vitamin A

2 Vitamin E

3 Vitamin K

4 None of the above

Biochemistry Answer: 3

Prothrombin production in the liver is dependent upon Vitamin K intake

Rate limiting step in cholesterol synthesis is

1. HMG CoA synthetase

2. HMG CoA lyase

3. HMG CoA reductase

4. Mevalonate synthetase

Biochemistry Answer: 3

The rate limiting step in cholesterol synthesis is HMG CoA reductase. Here's
a detailed explanation:

Cholesterol synthesis is a complex process that involves multiple enzymatic
steps. This process begins with the condensation of acetyl-CoA molecules to form
acetoacetyl-CoA, which is then converted into HMG CoA
(3-hydroxy-3-methylglutaryl-CoA) by the enzyme HMG CoA synthetase. HMG CoA is
further converted to mevalonate by the action of HMG CoA reductase. This
reaction is the rate limiting step of the cholesterol synthesis pathway. The
rate limiting step is the slowest step in a metabolic pathway and is responsible
for controlling the overall rate of the process.

HMG CoA reductase is a critical regulatory enzyme that is tightly controlled
because it is the first committed step in the synthesis of cholesterol from
acetate. This enzyme is responsible for reducing HMG CoA to mevalonate, which is
the precursor of all isoprenoids, including cholesterol, steroids, and other
important biological molecules. The rate limiting nature of this step is due to
the fact that HMG CoA reductase is subject to both allosteric regulation and
feedback inhibition.

Allosteric regulation involves the binding of regulatory molecules, such as ATP,
citrate, and NADH, which can either activate or inhibit the enzyme. For example,
when cellular ATP levels are high, the enzyme is inhibited, which reduces
cholesterol synthesis. Conversely, when ATP levels are low, the enzyme is
activated, leading to increased cholesterol production. Citrate, a molecule
derived from the citric acid cycle, inhibits HMG CoA reductase when it builds up
in the cytosol, indicating that the cell has enough energy and does not need to
synthesize additional cholesterol.

Feedback inhibition occurs when the end product of the pathway, cholesterol,
binds to the enzyme and reduces its activity. This is a form of negative
feedback regulation that helps to maintain homeostasis of cholesterol levels
within the cell. When cellular cholesterol levels are high, the enzyme is
inhibited, which slows down the synthesis of new cholesterol molecules.
Conversely, when cholesterol levels are low, the enzyme is less inhibited, and
the synthesis rate increases.

The other enzymes listed, HMG CoA synthetase and mevalonate synthetase, are
involved in the synthesis of HMG CoA and the subsequent transformation of
mevalonate, but they are not the rate limiting steps. HMG CoA lyase, on the
other hand, is part of an alternative pathway that breaks down HMG CoA into
acetyl-CoA and acetoacetate. This enzyme is not directly involved in the rate
limiting step of cholesterol synthesis.

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