Choose the correct statement(s) -

Options

A. Km (Michaelis - Menten) constant is the substrate concentration at which the enzymatic reaction attains half of its maximum velocity (1/2 Vmax)
B. At lower km, higher the substrate affinity for enzyme
C. Vmax is reached when all the active sites of an enzyme are saturated with substrate
D. All

Answer

To determine the correct statements regarding enzyme kinetics and the Michaelis-Menten equation, let's analyze each option step by step:

### Step 1: Understanding KM
- **KM (Michaelis constant)** is defined as the substrate concentration at which the reaction rate is half of the maximum velocity (Vmax) of the enzyme-catalyzed reaction.
- **Correct Statement**: Option 1 is correct.

### Step 2: Affinity of Enzyme for Substrate
- A lower KM value indicates a higher affinity of the enzyme for the substrate. This means that the enzyme can achieve half of its maximum velocity at a lower concentration of substrate.
- **Correct Statement**: Options 2, 7, and 8 are correct.

### Step 3: Vmax and Saturation
- Vmax is the maximum rate of the enzymatic reaction when all active sites of the enzyme are occupied by the substrate.
- **Correct Statement**: Options 3 and 4 are correct.

### Step 4: Incorrect Statements
- Options 5 and 6 are incorrect because KM is not raised when all active sites are saturated; rather, KM is a constant that describes the affinity of the enzyme for the substrate and does not change based on saturation.

### Summary of Correct Statements
- The correct statements are:
- Option 1: KM is the substrate concentration at which the reaction attains half of its maximum velocity.
- Option 2: At lower KM, there is higher substrate affinity for the enzyme.
- Option 3: Vmax is raised when all the active sites of an enzyme are saturated with substrate.
- Option 4: All KM constants are given by Michaelis-Menten constant.
- Options 7 and 8: At lower KM, there is higher substrate affinity for the enzyme.

### Final Answer
The correct statements are: **Option 1, Option 2, Option 3, Option 4, Option 7, and Option 8.**

---