1.5 dna and rna molecules worksheet - Free Printable

Problem Analysis and Solution

The provided worksheet focuses on the structure of nucleic acids, specifically nucleotides, and their components. Let's solve each part step by step.

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#### Section 1: Fill in the blanks

1. Monomer for nucleic acid is _________.
- Answer: Nucleotide
- Explanation: The basic building block (monomer) of nucleic acids (DNA and RNA) is a nucleotide.

2. It is made of three components: _________ sugar, _________ base, and _________ group.
- Answer: Pentose sugar, nitrogenous base, phosphate group
- Explanation: A nucleotide consists of:
- A pentose sugar (either deoxyribose in DNA or ribose in RNA).
- A nitrogenous base (adenine, guanine, cytosine, thymine, or uracil).
- A phosphate group.

3. In a nucleotide, _________ is attached to the carbon number one of pentose sugar while _________ is joined to the carbon number five of pentose sugar.
- Answer: Phosphate group, nitrogenous base
- Explanation:
- The phosphate group is attached to the 5' carbon of the pentose sugar.
- The nitrogenous base is attached to the 1' carbon of the pentose sugar.

4. Pentose sugar of DNA is known as _________ sugar while for RNA known as _________ sugar.
- Answer: Deoxyribose, Ribose
- Explanation:
- DNA contains deoxyribose sugar.
- RNA contains ribose sugar.

5. There are two types of nitrogenous base which are _________ and _________.
- Answer: Purines, Pyrimidines
- Explanation: Nitrogenous bases are classified into two categories:
- Purines: Adenine and Guanine.
- Pyrimidines: Cytosine, Thymine (in DNA), and Uracil (in RNA).

6. Purine consist of Adenine and _________ base.
- Answer: Guanine
- Explanation: The purine bases are adenine and guanine.

7. Pyrimidine consist of Cytosine, _________ and Uracil.
- Answer: Thymine
- Explanation: The pyrimidine bases are cytosine, thymine (in DNA), and uracil (in RNA).

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#### Exercise 1.5 (a): Identify each component of the nucleotide below.

The diagram shows a nucleotide with labeled parts. Let’s identify each component:

- Leftmost box: Phosphate group
- Middle circular part: Nitrogenous base
- Central pentagon: Pentose sugar (deoxyribose or ribose)
- Rightmost arrow-like structure: Phosphate group (part of the next nucleotide in a chain)

Final Answer for Exercise 1.5 (a):
- Left: Phosphate group
- Middle circle: Nitrogenous base
- Pentagon: Pentose sugar
- Right: Phosphate group

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#### Exercise 1.5 (b): Name and circle the difference between the two different types of pentose sugars shown in figure below.

The two structures shown are:
1. Structure on the left: Deoxyribose (pentose sugar in DNA)
2. Structure on the right: Ribose (pentose sugar in RNA)

Key Difference:
- Deoxyribose: Lacks an oxygen atom at the 2' position (hence "deoxy").
- Ribose: Has an oxygen atom at the 2' position.

Final Answer for Exercise 1.5 (b):
- Left: Deoxyribose
- Right: Ribose

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Final Summary of Answers

1. Monomer for nucleic acid is nucleotide.
2. Components of a nucleotide: pentose sugar, nitrogenous base, phosphate group.
3. In a nucleotide, phosphate group is attached to C1, and nitrogenous base is attached to C5.
4. Pentose sugar in DNA: deoxyribose, in RNA: ribose.
5. Two types of nitrogenous bases: purines and pyrimidines.
6. Purines: Adenine and guanine.
7. Pyrimidines: Cytosine, thymine, and uracil.

Exercise 1.5 (a):
- Left: Phosphate group
- Middle circle: Nitrogenous base
- Pentagon: Pentose sugar
- Right: Phosphate group

Exercise 1.5 (b):
- Left: Deoxyribose
- Right: Ribose

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Final Boxed Answer

\[
\boxed{
\text{
1. Nucleotide \\
2. Pentose sugar, nitrogenous base, phosphate group \\
3. Phosphate group, nitrogenous base \\
4. Deoxyribose, Ribose \\
5. Purines, Pyrimidines \\
6. Guanine \\
7. Thymine \\
Exercise 1.5 (a): Phosphate group, Nitrogenous base, Pentose sugar, Phosphate group \\
Exercise 1.5 (b): Deoxyribose, Ribose
}
}
\]