Question

Arrange steps involved in ATP breakdown during post-mortem changes in fish.
(A) AMP-IMP-
(B) ATP-ADP-
(C) Inosine-Hypoxanthine-
(D) Xanthine-Uric Acid-
Choose the correct answer from the options given below :

• A. (D), (B), (C), (A).
• B. (C), (B), (A), (D).
• C. (B), (A), (C), (D).
• D. (C), (B), (D), (A).

Hint:

To remember the pathway, use the initials of the compounds: \[ \text{ATP} \rightarrow \text{ADP} \rightarrow \text{AMP} \rightarrow \text{IMP} \rightarrow \text{Inosine (HxR)} \rightarrow \text{Hypoxanthine (Hx)} \] IMP represents freshness, while Hypoxanthine (Hx) accumulation indicates bacterial spoilage.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Following the death of a fish, cellular respiration stops, and adenosine triphosphate (ATP) is degraded through a predictable pathway of enzymatic autolysis.
This metabolic breakdown pathway is used to monitor post-mortem changes and freshness (via the K-value).
Detailed Explanation:
The sequential post-mortem enzymatic pathway of ATP degradation in fish muscle tissue is:
\[ \text{Adenosine Triphosphate (ATP)} \rightarrow \text{Adenosine Diphosphate (ADP)} \rightarrow \text{Adenosine Monophosphate (AMP)} \] \[ \rightarrow \text{Inosine Monophosphate (IMP)} \rightarrow \text{Inosine (HxR)} \rightarrow \text{Hypoxanthine (Hx)} \rightarrow \text{Xanthine} \rightarrow \text{Uric acid} \] Let us arrange the given steps in order:
-
Step 1: (B) ATP-ADP- (occurs rapidly after death via ATPase).
- (A) AMP-IMP- (mediated by adenylyl deaminase, producing IMP which contributes to the pleasant umami flavor of fresh fish).
-
Step 2: (C) Inosine-Hypoxanthine- (IMP is degraded to Inosine by 5'-nucleotidase, which is then converted to Hypoxanthine by nucleoside phosphorylase, indicating early spoilage).
-
Step 4: (D) Xanthine-Uric Acid- (Hypoxanthine is further oxidized to Xanthine and then to Uric acid by xanthine oxidase).
The correct sequence is (B), (A), (C), (D).

Step 2: Final Answer:
The correct post-mortem ATP breakdown sequence is (B), (A), (C), (D), corresponding to option (3).