Select the incorrect statement with respect to adult human hemoglobin.

Options

A. It is quaternary structure.
B. It contain four non identical polypeptides.
C. It contains two alpha and two bata chains .
D. Both alpha chains are identical .

Answer

To solve the question regarding the incorrect statement about adult human hemoglobin, we can follow these steps:

### Step 1: Understand the Structure of Hemoglobin
Adult human hemoglobin is a protein that has a quaternary structure, meaning it is composed of multiple polypeptide chains. Specifically, it consists of four subunits.

**Hint:** Remember that quaternary structure refers to the arrangement of multiple polypeptide chains in a protein.

### Step 2: Identify the Composition of Hemoglobin
Hemoglobin is made up of two types of polypeptide chains: alpha (α) and beta (β) chains. In adult human hemoglobin, there are two alpha chains and two beta chains.

**Hint:** Focus on the types and number of chains present in hemoglobin.

### Step 3: Analyze the Statements
Now, let's evaluate the statements provided in the question:
1. Hemoglobin has a quaternary structure. (Correct)
2. It contains four non-identical polypeptides. (Incorrect)
3. It contains two alpha and two beta chains. (Correct)
4. Both alpha chains are identical. (Correct)

**Hint:** Compare each statement with the known structure of hemoglobin to determine its accuracy.

### Step 4: Identify the Incorrect Statement
From the analysis:
- The first statement is true because hemoglobin does have a quaternary structure.
- The second statement is incorrect because hemoglobin has two identical alpha chains and two identical beta chains, making it a total of four polypeptides, but they are not all non-identical.
- The third statement is true as it correctly states the composition of hemoglobin.
- The fourth statement is true because both alpha chains are indeed identical.

**Hint:** Look for the statement that contradicts the known facts about hemoglobin's structure.

### Conclusion
The incorrect statement with respect to adult human hemoglobin is the second statement: "It contains four non-identical polypeptides."

**Final Answer:** Option 2 is the incorrect statement.