IB DP Biology- B1.2 Proteins - IB Style Questions For SL Paper 1A -FA 2025
▶️ Answer/Explanation
Amino acids are joined by a condensation reaction between the amino group of one amino acid and the carboxyl group of another. This reaction releases a water molecule and forms a covalent peptide bond.
✅ Answer: (D)
▶️ Answer/Explanation
Answer: B. I and III only
Explanation:
Proteins are made of smaller units called amino acids, which are connected by peptide bonds to form a polypeptide chain. The sequence of amino acids in each protein is unique and determines how the protein folds and what function it performs. Some proteins are made of only one polypeptide, while others consist of two or more polypeptides working together.
Option Evaluation:
A. Incorrect – Statement I is correct, but Statement II is wrong. Not all proteins have the same amino acid sequence; each protein has a unique sequence.
B. Correct – Statement I is correct (proteins are made from amino acids linked by peptide bonds), and Statement III is also correct (some proteins consist of more than one polypeptide). This is the correct answer.
C. Incorrect – Statement II is false, so this option is wrong even though Statement III is correct.
D. Incorrect – Statement II is incorrect, so all three statements cannot be true.
▶️ Answer/Explanation
Answer: C. Rhodopsin
Explanation:
Rhodopsin is a light-sensitive protein pigment found in the rod cells of the retina. Rod cells are responsible for vision in dim-light or night conditions. Rhodopsin is made of two components: opsin (a protein) and retinal (a derivative of vitamin A). When light strikes rhodopsin, it undergoes a structural change that initiates nerve impulses to the brain, enabling night vision. A deficiency in vitamin A or a defect in rhodopsin synthesis can cause night blindness.
Option Evaluation:
A. Incorrect – Fibrin is a protein involved in blood clotting, not vision.
B. Incorrect – Myosin is a motor protein that functions in muscle contraction, not visual processes.
C. Correct – Rhodopsin is the correct answer. It is essential for night vision, and abnormalities in rhodopsin cause night blindness.
D. Incorrect – Immunoglobulin refers to antibodies, which are part of the immune system, not related to vision.