The genetic disease caused by the absence of an enzyme that breaks down phenylalanine is: MCQ with Answer and Explanation

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The genetic disease caused by the absence of an enzyme that breaks down phenylalanine is:

A. Sickle cell anemia

B. Cystic fibrosis

C. Phenylketonuria

D. Albinism

Answer: Option C

Solution (By JKSSB Mock Tests)

Phenylketonuria (PKU) is an autosomal recessive disorder due to deficiency of phenylalanine hydroxylase, leading to accumulation of phenylalanine, causing mental retardation if untreated. Albinism is tyrosinase deficiency, sickle cell HbS mutation, cystic fibrosis CFTR defect.

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Question #1

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Consider the following statements about immunity:
1. Innate immunity is non-specific.
2. Antibodies are produced by T-cells.
3. Vaccination provides active immunity.
Which of the above is/are correct?

A. 1 and 3 only

B. 1 and 2 only

C. 1, 2, and 3

D. 2 and 3 only

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Correct Answer: Option A

Explanation:
Innate immunity is non-specific; vaccination induces active immunity. Antibodies are made by B-cells, not T-cells. So 2 is incorrect.

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Question #2

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The natural place of an organism where it lives and reproduces is called its:

A. Niche

B. Habitat

C. Biome

D. Ecosystem

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Correct Answer: Option B

Explanation:
Habitat refers to the physical environment where an organism lives (address), whereas niche refers to its functional role in the ecosystem (profession), including interactions and resource use. Ecosystem is the community plus abiotic factors, biome is a large ecological area with similar climate and vegetation. A pond habitat can have various niches.

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Question #3

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Which of the following vitamins is a water-soluble vitamin that acts as a coenzyme in the metabolism of amino acids and fatty acids?

A. Vitamin A

B. Vitamin B6 (Pyridoxine)

C. Vitamin K

D. Vitamin D

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Correct Answer: Option B

Explanation:
Vitamin B6, in its active form pyridoxal phosphate (PLP), is a crucial water-soluble coenzyme involved in over 100 enzymatic reactions, primarily in amino acid metabolism (transamination, decarboxylation) and fatty acid metabolism. It is also essential for neurotransmitter synthesis and hemoglobin formation. Vitamins A, D, and K are fat-soluble vitamins. Exam tip: B-complex and C are water-soluble; A, D, E, K are fat-soluble.

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