chapter three section one: nucleotides

What are the two types of nitrogenous bases found in nucleotides?

Purines and pyrimidines. The common purines are adenine (A) and guanine (G), while the common pyrimidines are cytosine (C), uracil (U), and thymine (T).

What three components make up a nucleotide?

A nucleotide consists of

1) A nitrogenous base (purine or pyrimidine)

2) A pentose sugar (ribose or deoxyribose)

3) One or more phosphate groups

How do DNA and RNA differ in their nucleotide composition?

DNA contains adenine, guanine, cytosine, and thymine deoxyribonucleotides. Whereas RNA contains adenine, guanine, cytosine, and uracil ribonucleotides. The key differences are

1) DNA uses thymine; RNA uses uracil

2) DNA contains deoxyribose sugar; RNA contains ribose sugar

What is the difference between a nucleotide and a nucleoside?

A nucleoside is composed of a nitrogenous base linked to a sugar (ribose or deoxyribose). A nucleotide is a nucleoside with one or more phosphate groups attached to the sugar.

How do purines and pyrimidines form bonds with the pentose sugar?

Purines form bonds to the pentose sugar via their N9 atoms, whereas pyrimidines form bonds through their N1 atoms.

What is the structural difference between ribose and deoxyribose?

In deoxyribose, the carbon at position 2′ lacks a hydroxyl group (OH) that is present in ribose. This is why it's called "deoxy" (meaning "without oxygen").

Where can phosphate groups bond in a nucleotide?

Phosphate groups can bond to either the C3′ or C5′ atom of the pentose sugar, forming a 3′-nucleotide or a 5′-nucleotide, respectively.

What is ATP and what makes it significant?

ATP (adenosine triphosphate) is a nucleotide containing adenine, ribose, and a triphosphate group. It is significant as the primary energy currency of cells, storing and transferring energy for cellular processes.

What counterion is typically associated with free nucleotides in cells?

Free nucleotides, which are anionic (negatively charged), are almost always associated with the magnesium ion (Mg²⁺) as a counterion in cells.

Name the eight common varieties of nucleotides found in biological systems.

The eight common nucleotides are

1) Adenine ribonucleotide (in RNA)

2) Guanine ribonucleotide (in RNA)

3) Cytosine ribonucleotide (in RNA)

4) Uracil ribonucleotide (in RNA)

5) Adenine deoxyribonucleotide (in DNA)

6) Guanine deoxyribonucleotide (in DNA)

7) Cytosine deoxyribonucleotide (in DNA)

8) Thymine deoxyribonucleotide (in DNA)

Why are nucleotides described as planar, aromatic, heterocyclic molecules?

1) Planar: their structure lies in a flat plane

2) Aromatic: they contain ring structures with alternating single and double bonds

3) Heterocyclic: their rings contain atoms of more than one element (carbon and nitrogen)

Which bases appear in both DNA and RNA?

Adenine (A), guanine (G), and cytosine (C) appear in both DNA and RNA.