Which of the following statements about mitochondria is not correct?

Question

Accepted Answer

Option 3 is the correct answer because it contains an incorrect statement about the synthesis of ATP in mitochondria. In mitochondria, ATP synthesis occurs on the matrix side of the inner mitochondrial membrane, not towards the perimitochondrial space. The enzyme ATP synthase, also known as ATP synthetase, is embedded in the inner mitochondrial membrane and facilitates the production of ATP from ADP and inorganic phosphate. The protons flow back into the mitochondrial matrix through ATP synthase, driving the synthesis of ATP. Therefore, the statement in Option 3 is incorrect.

Now, let's explain why each of the other options is correct:

1. **Option 1: Cytochrome-c is the only peripheral member of ETS.**
   - This statement is correct. Cytochrome-c is a small heme protein associated with the inner membrane of the mitochondrion. It is a peripheral protein, meaning it is loosely attached to the membrane and can easily be removed. It plays a crucial role in the electron transport chain (ETS) by transferring electrons between Complex III and Complex IV.

2. **Option 2: Succinate dehydrogenase is the membrane-bound enzyme of the Krebs cycle.**
   - This statement is correct. Succinate dehydrogenase is an enzyme that participates in both the Krebs cycle and the electron transport chain. It is unique because it is the only enzyme of the Krebs cycle that is embedded in the inner mitochondrial membrane, where it also functions as Complex II of the electron transport chain.

3. **Option 4: Net gain of ATP is two in glycolysis.**
   - This statement is correct. Glycolysis is the process of breaking down glucose into pyruvate, and it occurs in the cytoplasm of the cell. During glycolysis, a total of four ATP molecules are produced, but two ATP molecules are consumed in the initial steps. Therefore, the net gain of ATP in glycolysis is two.

In conclusion, Option 3 is the correct answer because it inaccurately describes the location of ATP synthesis in mitochondria, while the other options accurately describe the respective biological processes.