β-Carotene, precursor of vitamin A, is oxidatively cleaved by 

(A) β-Carotene dioxygenase 

(B) Oxygenase 

(C) Hydroxylase 

(D) Transferase

Preformed Vitamin A is supplied by 

(A) Milk, fat and liver 

(B) All yellow vegetables 

(C) All yellow fruits 

(D) Leafy green vegetables

Retinal is reduced to retinol in intestinal mucosa by a specific retinaldehyde reductase utilising 

(A) NADPH + H⁺ 

(B) FAD 

(C) NAD 

(D) NADH + H⁺

The performed Vitamin A is supplied by foods such as 

(A) Butter

(B) Eggs 

(C) Fish liver oil

(D) All of these

Retinal is reduced to retinol by retinene reductase in presence of the coenzyme 

(A) NAD⁺ 

(B) NADP⁺ 

(C) NADH + H⁺ 

(D) NADPH + H⁺

The non-protein part of rhodopsin is 

(A) Retinal 

(B) Retinol 

(C) Carotene 

(D) Repsin

Retinal exists as an ester with higher fatty acids in the 

(A) Liver

(B) Kidney 

(C) Lung 

(D) All of these

Provitamins A include 

(A) Retinal 

(B) Retionic acid 

(C) Carotenes 

(D) All of these

Vitamin A or retinal is a

(A) Steroid 

(B) Polyisoprenoid compound containing a cyclohexenyl ring 

(C) Benzoquinone derivative 

(D) 6-Hydroxychromane

In biotin-containing enzymes, the biotin is bound to the enzyme by 

(A) An amide linkage to carboxyl group of glutamine 

(B) A covalent bond with CO₂ 

(C) An amide linkage to an amino group of lysine 

(D) An amide linkage to α-carboxyl group of protein