Select the incorrect statement

Options

A. Amino acids are substituted methanes
B. Glycerol is trihydroxy propane
C. Lysine is neutral amino acid
D. Lecithine is phospholipid.

Answer

To solve the question "Select the incorrect statement," we need to analyze each of the provided statements regarding amino acids, glycerol, lysine, and lecithin.

### Step-by-Step Solution:

1. **Evaluate the first statement: "Amino acids are substituted methanes."**
- Amino acids consist of an amino group (-NH2), a carboxyl group (-COOH), and a side chain (R group) attached to the alpha carbon.
- The statement is somewhat misleading because while the carbon skeleton of amino acids can be seen as a derivative of methane (CH4), they are not simply substituted methanes.
- **Conclusion:** This statement is generally accepted as true in a broad sense but can be misleading.

2. **Evaluate the second statement: "Glycerol is trihydroxypropane."**
- Glycerol (C3H8O3) has three hydroxyl (-OH) groups, one on each of its three carbon atoms.
- The term "trihydroxypropane" accurately describes glycerol, as it is a three-carbon alcohol with three hydroxyl groups.
- **Conclusion:** This statement is true.

3. **Evaluate the third statement: "Lysine is a neutral amino acid."**
- Lysine is an amino acid that has an additional amino group in its side chain, making it positively charged (basic) at physiological pH.
- Neutral amino acids do not have a net charge at neutral pH, while lysine does.
- **Conclusion:** This statement is false, making it the incorrect statement.

4. **Evaluate the fourth statement: "Lecithin is a phospholipid."**
- Lecithin is indeed a type of phospholipid, which is a major component of cell membranes.
- **Conclusion:** This statement is true.

### Final Answer:
The incorrect statement is: **"Lysine is a neutral amino acid."**

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