The malate-asparate shuttle is absent in

Options

A. Kidney cells
B. Prokaryotes
C. Brain cells
D. Both (2) & (3)

Answer

To solve the question regarding the absence of the malate-aspartate shuttle, we can follow these steps:

### Step 1: Understand the Malate-Aspartate Shuttle
The malate-aspartate shuttle is a biochemical system that transports electrons produced during glycolysis into the mitochondria, where oxidative phosphorylation occurs. This process is essential for energy production in cells.

**Hint:** Remember that the malate-aspartate shuttle is related to energy production and occurs in specific types of cells.

### Step 2: Identify Where the Shuttle Operates
The malate-aspartate shuttle operates in the mitochondria of eukaryotic cells. It is particularly found in:
- Skeletal muscle cells
- Heart muscle cells
- Brain cells
- Liver cells
- Kidney cells

**Hint:** Focus on the types of cells where this shuttle is known to function.

### Step 3: Analyze the Options Given
The question provides four options:
1. Kidney cells
2. Prokaryotes
3. Brain cells
4. Both 2 and 3 (i.e., both prokaryotes and brain cells)

From our understanding, we know that the malate-aspartate shuttle is present in kidney and brain cells, which are both eukaryotic.

**Hint:** Compare the options with the list of cells where the shuttle is known to be present.

### Step 4: Determine the Absence of the Shuttle
Since the malate-aspartate shuttle is a feature of eukaryotic cells, it cannot be present in prokaryotic cells (which lack mitochondria). Therefore, the malate-aspartate shuttle is absent in prokaryotes.

**Hint:** Recall that prokaryotes are fundamentally different from eukaryotes in terms of cellular structure.

### Conclusion
After analyzing all the information, we conclude that the malate-aspartate shuttle is absent in prokaryotes.

**Final Answer:** The malate-aspartate shuttle is absent in prokaryotes.