Biomolecules

To determine the correct statement about the zwitterionic form of amino acids, let's analyze the structure and behavior of amino acids in solution.

1. Understanding Zwitterions:
A zwitterion is a molecule that contains both positive and negative charges but is overall electrically neutral. For amino acids, this occurs when:

• The carboxyl group (-COOH) loses a proton (H⁺) to become -COO⁻ (negatively charged).
• The amino group (-NH₂) gains a proton (H⁺) to become -NH₃⁺ (positively charged).

2. Analyzing the Functional Groups:
In the zwitterionic form:

• The -COO⁻ group is the acidic part (can donate H⁺ if needed).
• The -NH₃⁺ group is the basic part (can accept H⁺ if needed).

This is because: - -COO⁻ can act as an acid by accepting H⁺ to reform -COOH. - -NH₃⁺ can act as a base by donating H⁺ to reform -NH₂.

3. Evaluating the Options:

1. "Basic -COO⁻ group and acidic -NH₃⁺ group" → Incorrect. -COO⁻ is acidic, not basic.
2. "Basic NH₂ group and acidic -COOH group" → Incorrect. This describes the non-zwitterionic form.
3. "The basic -NH₃⁺ group and acidic -COO⁻ group" → Correct. This matches the zwitterion's properties.
4. "Basic -NH₂ and acidic -H⁺ group" → Incorrect. -H⁺ is not a functional group in amino acids.

4. Final Answer:
The correct statement is: The basic -NH₃⁺ group and acidic -COO⁻ group.

Therefore, the correct option is:

RNA, which stands for Ribonucleic Acid, is a nucleic acid similar to DNA but differs in several key aspects. One major difference lies in the nitrogenous bases that are part of its structure. RNA contains the bases Adenine, Cytosine, Guanine, and Uracil.

Unlike DNA, which contains Thymine as one of its four bases, RNA lacks Thymine. Instead of Thymine, RNA contains Uracil, which pairs with Adenine during the process of transcription. This means that, unlike DNA, which has the base pairs Adenine-Thymine and Guanine-Cytosine, RNA will often have Adenine-Uracil and Guanine-Cytosine.

Given the options:

• Cytosine
• Adenine
• Uracil
• Thymine

The correct answer is Thymine, as it is not present in RNA; instead, RNA contains Uracil.

To solve the problem, we need to determine which statement is true for the aqueous solutions of 0.1 M urea, 0.2 M glucose, and 0.3 M sucrose.

1. Understanding Colligative Properties:
Colligative properties depend on the number of solute particles in a solution, not the type of solute particles. These properties include elevation in boiling point, depression in freezing point, vapor pressure lowering, and osmotic pressure. The more particles that are present in the solution, the more significant the colligative effects.

2. Analyzing the Solutions:
- Urea (0.1 M) does not dissociate into ions, so the number of particles in solution is the same as the molarity.
- Glucose (0.2 M) and sucrose (0.3 M) also do not dissociate, and their molarity represents the number of particles in solution.
Since the depression in freezing point, elevation in boiling point, and vapor pressure lowering are all directly proportional to the concentration of solute particles, solutions with higher concentrations will show more significant effects.

3. Focusing on the Correct Answer:
The statement "The boiling point is the lowest for urea" is true because urea has the lowest concentration (0.1 M). This leads to the smallest effect on the boiling point elevation compared to glucose (0.2 M) and sucrose (0.3 M), which have higher concentrations and thus cause a greater increase in boiling point.

4. Conclusion:
The correct statement is that the boiling point is the lowest for urea, as urea has the lowest molarity and therefore the smallest effect on the boiling point elevation.

Final Answer:
The correct answer is: The boiling point is the lowest for urea.