Which of the following statements is/are true about vitamin B₁₂?
- a. It is also known as cobalamin.
- b. It is composed of cobalt atoms.
- c. It consists of corrin rings.
Choose the correct option:
- AOnly a is true
- BOnly b and c are true
- Ca, b and c are true
- DOnly a and c are true
Show answer and explanation
Correct answers: (c) a, b and c are true or (d) Only a and c are true
Explanation
- a. Correct: vitamin B₁₂ is also called cobalamin.
- b. Loosely worded: vitamin B₁₂ contains cobalt, a single cobalt atom at the centre of the molecule. It is a large organic molecule, so it is not "composed of cobalt atoms".
- c. Correct: the cobalt sits in a corrin ring, a large ring similar to the porphyrin ring of haemoglobin.
Vitamin B₁₂ is needed to form red blood cells and to keep nerves healthy. Its lack causes pernicious anaemia.
The book's key is (c), reading statement b as "contains cobalt". Vitamin B₁₂ has a single cobalt atom in a large organic molecule, so if b is read strictly it is false, and (d) is also accepted.