Question

Enzyme activity profiles as a function of time in the absence or presence of different types of feedback mechanisms are shown in the figure below. Match the following feedback mechanisms with the corresponding profiles in the figure. 
(p) No feedback mechanism 
(q) Negative feedback mechanism with short delay 
(r) Negative feedback mechanism with long delay 
(s) Positive feedback mechanism 

• A. (p) – (i); (q) – (ii); (r) – (iii); (s) – (iv)
• B. (p) – (iv); (q) – (iii); (r) – (ii); (s) – (i)
• C. (p) – (iv); (q) – (ii); (r) – (iii); (s) – (i)
• D. (p) – (i); (q) – (iii); (r) – (ii); (s) – (iv)

Hint:

Short-delay negative feedback shows quick stabilization with minor oscillations, long-delay negative feedback produces sustained oscillations, while positive feedback amplifies the response. No feedback shows a simple steady rise and plateau.

Answer 1

The Correct Option is B

Step 1: No feedback mechanism (p) 
In absence of feedback, the enzyme activity simply rises after the signal and maintains a constant plateau. This corresponds to profile (iv). 
Step 2: Negative feedback with short delay (q) 
When there is a short delay in feedback, the enzyme activity initially overshoots and then stabilises quickly. This produces a small oscillation before settling, which matches profile (iii). 
Step 3: Negative feedback with long delay (r) 
A long delay in feedback produces sustained oscillations in enzyme activity (repetitive rise and fall cycles). This matches profile (ii). 
Step 4: Positive feedback mechanism (s) 
Positive feedback reinforces the response, leading to a sharp, amplified, and sustained increase in activity once the signal is applied. This corresponds to profile (i). Therefore, the correct matching is: (p) – (iv), (q) – (iii), (r) – (ii), (s) – (i).