Which one is absent in human RBC ?

Options

A. Biomembrane
B. Enzymes
C. Hyaloplasm
D. Kreb's cycle

Explanation

**Step-by-Step Solution:**

1. **Understanding Human RBCs**: Human red blood cells (RBCs), also known as erythrocytes, are specialized cells responsible for transporting oxygen throughout the body. They are produced in the bone marrow through a process called erythropoiesis.

2. **Structure of RBCs**: In their early developmental stages, RBCs contain various organelles, including a nucleus and mitochondria. However, as they mature, they undergo a process where they lose some of these organelles.

3. **Loss of Organelles**: The key organelles that human RBCs lose during maturation are:
- **Nucleus**: RBCs do not have a nucleus in their mature form, which means they lack genetic material.
- **Mitochondria**: These organelles are responsible for ATP production through the Krebs cycle.

4. **Identifying the Absent Component**: The question asks which component is absent in human RBCs. The options provided are:
- Biomembrane
- Enzymes
- Hyloplasm
- Krebs cycle

5. **Analyzing Each Option**:
- **Biomembrane**: The biomembrane (plasma membrane) is present in RBCs throughout their life.
- **Enzymes**: Various enzymes are present in RBCs, including proteases and protein kinases.
- **Hyloplasm**: This is the fluid portion of the cytoplasm, which is also present in RBCs.
- **Krebs Cycle**: The Krebs cycle is not present in mature RBCs because they lack mitochondria, which are essential for this cycle.

6. **Conclusion**: The component that is absent in human RBCs is the **Krebs cycle**.

**Final Answer**: The Krebs cycle is absent in human RBCs.

---