Which of the following connects glycolysis to Krebs cycle ?

Options

A. Substrate level phosphorylation
B. Photophosphorylation
C. `FADH_2` formation
D. Both occur in matrix of mitochondria

Answer

To determine which process connects glycolysis to the Krebs cycle, we need to analyze the options provided:

1. **Substrate Level Phosphorylation**: This is a process that occurs in both glycolysis and the Krebs cycle. In glycolysis, it refers to the direct phosphorylation of ADP to form ATP using a phosphate group from a substrate. Similarly, in the Krebs cycle, substrate level phosphorylation also occurs when GTP or ATP is produced directly from a substrate. Therefore, this option is a strong candidate for connecting glycolysis to the Krebs cycle.

2. **Photophosphorylation**: This process is related to photosynthesis and involves the formation of ATP from ADP and inorganic phosphate using light energy. It does not occur in glycolysis or the Krebs cycle, making this option incorrect.

3. **AFA-DH2 Formation**: This option seems to be a typographical error and likely refers to NADH formation. While NADH is produced in glycolysis and the Krebs cycle, it does not directly connect the two processes. Rather, it is a product of both pathways. Therefore, this option is also not correct.

4. **Both occur in the matrix of mitochondria**: Glycolysis occurs in the cytoplasm, while the Krebs cycle occurs in the mitochondrial matrix. Since these processes occur in different locations, this option is incorrect.

Based on the analysis above, the correct answer is **Substrate Level Phosphorylation**, as it is the only process that occurs in both glycolysis and the Krebs cycle, thereby connecting the two pathways.

### Steps Summary:
1. Analyze the options provided.
2. Identify the role of substrate level phosphorylation in both glycolysis and Krebs cycle.
3. Eliminate incorrect options based on their definitions and locations of occurrence.
4. Conclude that substrate level phosphorylation is the correct answer.