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 where the malate-aspartate shuttle is absent, we can follow these steps:

### Step 1: Understand the Malate-Aspartate Shuttle
The malate-aspartate shuttle is a biochemical system that helps in transferring electrons from the cytosol into the mitochondria, which is crucial for ATP production. It primarily functions in regulating glycolysis and lactate metabolism.

**Hint:** Remember that the malate-aspartate shuttle is involved in energy production and electron transfer.

### Step 2: Identify Where the Shuttle Functions
The malate-aspartate shuttle is known to be present in certain tissues of the body. It is predominantly found in:
- Liver
- Kidney
- Brain (to a lesser extent)

**Hint:** Think about which organs are involved in energy metabolism and where this shuttle is essential.

### Step 3: Determine Where It Is Absent
The question specifically asks where the malate-aspartate shuttle is absent. It is important to note that this shuttle is not found in prokaryotic cells (such as bacteria), as they lack mitochondria and the specific metabolic pathways that utilize this shuttle.

**Hint:** Consider the difference between prokaryotic and eukaryotic cells regarding cellular structures and metabolic processes.

### Step 4: Conclude the Answer
Based on the information gathered, the malate-aspartate shuttle is absent in prokaryotes. Therefore, the correct answer to the question is that the malate-aspartate shuttle is absent in prokaryotic cells.

**Final Answer:** Prokaryotes

### Summary of Steps:
1. Understand the function of the malate-aspartate shuttle.
2. Identify tissues where the shuttle is present.
3. Determine where the shuttle is absent (prokaryotes).
4. Conclude the answer.