NEET-PG 2013 - Biochemistry Practice Questions

Q: Mechanism of cyanide poisoning is by inhibiting:

Cytochrome oxidase. ***Cytochrome oxidase*** - Cyanide poisoning works by **irreversibly binding** to the ferric ion (Fe3+) in **cytochrome c oxidase** (Complex IV) of the electron transport chain. - This binding prevents the enzyme from carrying electrons to oxygen, thereby **halting cellular respiration** and ATP production. *Mitochondrial DNA synthesis* - While mitochondria are affected, cyanide does not primarily disrupt **DNA synthesis** in these organelles. - Its main target is the process of energy generation, not genetic replication. *ATP production* - Although cyanide poisoning ultimately leads to a **cessation of ATP production**, this is the *consequence* of its action, not the primary mechanism. - The direct mechanism involves inhibiting a key enzyme in the electron transport chain. *Electron transport chain* - Cyanide does indeed inhibit the **electron transport chain**, but this option is too broad. - The most specific mechanism targets a particular complex within the chain, which is **cytochrome oxidase**.

Question 1

Which one of the following has the maximum ionization potential?

Accepted Answer

Helium ion

Answer

Hydrogen ion

Answer

Neutron

Answer

Helium atom

Question 2

True statement about vitamin K is?

Accepted Answer

Vitamin K affects bone health by activating proteins that bind calcium

Answer

Vitamin K is needed for action of clotting factor 8

Answer

Vitamin K deficiency leads to DVT

Answer

Vitamin K is water soluble

Question 3

Mechanism of cyanide poisoning is by inhibiting:

Accepted Answer

Cytochrome oxidase

Answer

Mitochondrial DNA synthesis

Answer

ATP production

Answer

Electron transport chain

NEET-PG 2013 — Biochemistry