In PS I, the reaction centre chlorophyll a has an absorption peak at

Options

A. 650 nm
B. 660 nm
C. 680 nm
D. 700 nm.

Answer

To solve the question regarding the absorption peak of chlorophyll a in Photosystem I (PS I), we can follow these steps:

### Step 1: Understand the context of Photosystems
Photosystems are complexes in plants that play a crucial role in photosynthesis. There are two main types: Photosystem I (PS I) and Photosystem II (PS II). Each has a specific role in the light-dependent reactions of photosynthesis.

**Hint:** Remember that PS I and PS II are named based on the order of their discovery, not their function.

### Step 2: Identify the absorption peaks of chlorophyll a
Chlorophyll a is the primary pigment involved in photosynthesis, and it has specific absorption peaks. For PS I, the absorption peak is significant for capturing light energy.

**Hint:** Look for the specific wavelengths associated with chlorophyll a in both PS I and PS II.

### Step 3: Recall the specific absorption peak for PS I
The absorption peak for chlorophyll a in PS I is at 700 nm. This is also why it is referred to as P700.

**Hint:** Remember that the naming convention (P700) indicates the wavelength at which the pigment absorbs light most effectively.

### Step 4: Compare with PS II
For context, PS II has an absorption peak at 680 nm, known as P680. This comparison helps clarify the distinction between the two photosystems.

**Hint:** Knowing the absorption peaks of both PS I and PS II can help reinforce your understanding of their functions in the light-dependent reactions.

### Step 5: Conclude with the answer
Based on the information gathered, the absorption peak of the reaction center chlorophyll a in PS I is 700 nm.

**Final Answer:** The absorption peak of chlorophyll a in Photosystem I (PS I) is at 700 nm.