Group I Group II P. Cyanide i. Blocks electron transfer from cyt b to cyt c$_1$ Q. Antimycin A ii. Inhibits F$_1$ R. Aurovertin iii. Uncoupling of phosphorylation from electron transfer S. 2,4-Dinitrophenol iv. Inhibits cytochrome oxidase v. Inhibits K$^+$ ionophore
Understanding Oxidative Phosphorylation Inhibitors
This question requires matching specific chemical agents (Group I) with their mechanisms of action that interfere with oxidative phosphorylation (Group II). Oxidative phosphorylation is the metabolic pathway that converts biochemical energy from nutrients into adenosine triphosphate (ATP), and these agents disrupt this process at different steps.
Analyzing Agent Mechanisms
P. Cyanide
Cyanide is a potent inhibitor of the electron transport chain. Specifically, it binds to and inhibits cytochrome oxidase (Complex IV), the final enzyme complex. By blocking this enzyme, cyanide prevents the transfer of electrons to oxygen, halting electron flow and thus ATP production.
Match: P - iv. Inhibits cytochrome oxidase
Q. Antimycin A
Antimycin A is known to inhibit electron transfer at Complex III (cytochrome bc$_1$ complex). It specifically blocks the transfer of electrons from cytochrome b to cytochrome c$_1$, disrupting the flow of electrons through the chain.
Match: Q - i. Blocks electron transfer from cyt b to cyt c$_1$
R. Aurovertin
Aurovertin interferes with the function of ATP synthase (Complex V). It binds to the F$_1$ subunit of ATP synthase, inhibiting its ability to produce ATP. The $F_1$ component is crucial for the catalytic activity of the enzyme.
Match: R - ii. Inhibits F$_1$
S. 2,4-Dinitrophenol
2,4-Dinitrophenol (2,4-DNP) acts as an uncoupler. Instead of directly blocking electron transport or ATP synthase, it creates a proton leak across the inner mitochondrial membrane. This dissipates the proton gradient that is essential for ATP synthesis, meaning electron transport can continue, but phosphorylation (ATP production) is uncoupled from it.
Match: S - iii. Uncoupling of phosphorylation from electron transfer
Correct Combinations Summary
Based on the analysis of each agent's mechanism:
- Cyanide inhibits cytochrome oxidase (P-iv).
- Antimycin A blocks electron transfer from cyt b to cyt c$_1$ (Q-i).
- Aurovertin inhibits F$_1$ (R-ii).
- 2,4-Dinitrophenol uncouples phosphorylation from electron transfer (S-iii).
The correct combination is P-iv, Q-i, R-ii, S-iii.
Important Questions from Plant Biochemistry Enzymes Reactions
- Match the following digestive enzymes in Column I with their respective functions in Column II.
Column I Column II P. Erepsin (i) converts proteins to peptides Q. Steapsin (ii) activates trypsinogen to trypsin R. Pepsin (iii) converts fat into fatty acid and glycerol S. Enterokinase (iv) converts polypeptides to amino acids - Match the proteins in Column I with the organs in which they are maximally expressed in Column II.
Column I Column II P. Keratin (i) Liver Q. Surfactants (ii) Pancreas R. Pro-carboxypeptidase (iii) Lung S. Albumin (iv) Skin Identify the free radicals (marked as '?') in sequence from the inter-conversion of reactive oxygen species as shown below.
$O_2\rightarrow? \rightarrow H_2O_2 \rightarrow? \rightarrow H_2O$
P. $\mathrm{O}_2^{\bullet -}$
Q. $OH^-$
R. $HO_2^{-}$
S. $\ {}^{1}\mathrm{O}_2$
- Choose the CORRECT set of matches between group I and group II in relation to nitrogen fixation and assimilation
GROUP I GROUP II P. Nitrobacter 1. $NO_3^-$ $\rightarrow$ $NO_2^-$ Q. Nitrite reductase 2. $N_2$ $\rightarrow$ $2NH_3$ R. Nitrogenase 3. $NO_2^-$ $\rightarrow$ $NH_4^+$ S. Nitrate reductase 4. $NO_2^-$ $\rightarrow$ $NO_3^-$ - Select the CORRECT combination by matching Group-I with Group-II.
Group-I Group-II P. Photorespiration 1. Glutamate $\rightarrow$ 2-Oxglutarate Q. Respiration 2. Acetyl-CoA $\rightarrow$ Malonyl-CoA R. Amino acid degradation 3. 2-Oxglutarate $\rightarrow$ Succinyl-CoA S. Fatty acid synthesis 4. Glycine $\rightarrow$ Serine
