Nucleotides

Options

A. contain a sugar, a nitrogen-containing base, and a phosphate molecule
B. are the monomers for fats and polysaccharides
C. join together by covalent bonding between the bases
D. all of the above

Explanation

### Step-by-Step Solution for the Question on Nucleotides:

1. **Definition of Nucleotide**: A nucleotide is a basic building block of nucleic acids, which include DNA and RNA. Each nucleotide consists of three main components: a sugar molecule, a phosphate group, and a nitrogen-containing base.

2. **Components of Nucleotide**:
- **Sugar**: The sugar in nucleotides can be either ribose (in RNA) or deoxyribose (in DNA).
- **Phosphate Group**: This group is attached to the sugar and is responsible for the acidic properties of nucleic acids.
- **Nitrogen Base**: There are four types of nitrogen bases in nucleotides: adenine (A), thymine (T), cytosine (C), and guanine (G) in DNA; and adenine (A), uracil (U), cytosine (C), and guanine (G) in RNA.

3. **Structure of Nucleotide**: The structure of a nucleotide can be visualized as follows:
- The phosphate group is linked to the 5' carbon of the sugar.
- The nitrogen base is linked to the 1' carbon of the sugar.
- This arrangement creates a backbone of alternating sugar and phosphate groups.

4. **Bonding in Nucleotides**: Nucleotides are connected to each other through phosphodiester bonds. This bond forms between the phosphate group of one nucleotide and the sugar of the next nucleotide, creating a long chain of nucleotides.

5. **Monomers of Nucleic Acids**: Nucleotides serve as the monomers (the smallest units) that make up nucleic acids (DNA and RNA).

6. **Evaluating Statements**:
- The first statement is correct: Nucleotides contain a sugar, a nitrogen-containing base, and a phosphate group.
- The second statement is incorrect: Nucleotides are not the monomers for fats and polysaccharides; they are the monomers for nucleic acids.
- The third statement is also incorrect: Nucleotides are joined together by phosphodiester bonds, not covalent bonds between the bases.

7. **Conclusion**: The only correct statement regarding nucleotides is that they contain a sugar, nitrogen-containing base, and a phosphate group.