Lesson 18 - Nucleic Acid Structure

What is the monomer of nucleic acids?

Nucelotides

What are nucleotides made of?

Phosphate group, Sugar, Nitrogenous base

What are the two main types of nucleic acids and their primary functions?

DNA and RNA

DNA 

stores hereditary information; genes are discrete units of hereditary info that often code for proteins

RNA

assists in protein production

What are the three main components of a nucleotide?

• Phosphate group

• Pentose sugar (5-carbon sugar)

• Nitrogenous base (A, G, C, T for DNA; U replaces T in RNA)

What distinguishes ribose from deoxyribose?

Deoxyribose lacks a hydroxyl group (-OH) on the 2’ carbon, having -H instead.

Which nitrogenous bases are pyrimidines?

Pyrimidines (single ring): Cytosine (C), Thymine (T, DNA only), Uracil (U, RNA only)

Which nitrogenous bases are purines?

Purines (double ring): Adenine (A), Guanine (G)

Why is carbon numbering in sugars important?

It helps differentiate sugar carbons (1’, 2’, etc.) from carbons in nitrogenous bases (plain numbers), critical for understanding nucleotide bonds and polymer formation.

Which carbon is double-bonded to oxygen (carbonyl) in the sugar?

Carbon #1 (1’C)

How is a nucleoside formed?

Nitrogenous base attaches to the 1’ carbon of the sugar via a dehydration reaction, forming a covalent bond: Sugar + Base = Nucleoside.

How is a nucleotide formed?

A phosphate group covalently bonds to the 5’ carbon of a nucleoside via a dehydration reaction: Phosphate + Nucleoside = Nucleotide

How are nucleotides linked in DNA/RNA polymers?

Through dehydration reactions: the 3’ hydroxyl (-OH) of one nucleotide bonds with the 5’ phosphate of the next, forming a polynucleotide chain.

How are nucleotides linked in DNA/RNA polymers?

Through dehydration reactions: the 3’ hydroxyl (-OH) of one nucleotide bonds with the 5’ phosphate of the next, forming a polynucleotide chain.

what does 1’ carbon do?

attaches nitrogenous base

what does 2’ carbon do?

distinguishes ribose (–OH) from deoxyribose (–H)

what does 3’ carbon do?

attaches to next nucleotide’s phosphate (polymerization)

what does 4’ carbon do?

forms the ring

what does 5’ carbon do?

outside the ring, attaches to phosphate group

Describe the structure of DNA.

• Two strands of polynucleotides

• Complementary base pairing between strands

• Strands form a double helix

• Strands are antiparallel (5’→3’ runs opposite)

What does “DNA is antiparallel” mean?

The two strands run in opposite directions: one 5’→3’, the other 3’→5’.

Describe the structure of RNA.

• Usually single-stranded polynucleotide

• Bases in one part can hydrogen bond with complementary bases in another part of the strand

• Can form complex 3D structures

How are the strands in DNA and RNA?

double-stranded, single-stranded

What is the location of DNA and RNA?

in the nucleus, nucleus and cytoplasm

What bases are used in DNA?

A,T,C,G

What bases are used in RNA?

A,U,G,C

What sugar is used in DNA and RNA?

Deoxyribose, Ribose 

What are the main processes involving DNA and RNA?

1. DNA Replication

2. DNA Transcription

3. RNA Translation

DNA Replication

DNA copies itself for cell division (nucleus)

DNA Transcription

DNA creates messenger RNA (nucleus)

RNA Translation

RNA is translated to produce proteins (cytoplasm)

How do nucleotides link together to form polynucleotides?

The 3’ hydroxyl (-OH) of one nucleotide bonds to the 5’ phosphate of the next via a dehydration reaction, forming a covalent phosphodiester bond.

What roles do complementary base pairing and hydrogen bonding play in nucleic acids?

• Complementary bases ensure accurate pairing for replication and transcription

• Hydrogen bonds stabilize DNA/RNA structures while allowing strands to separate when needed

How does the 2’ carbon difference between DNA and RNA affect structure?

DNA’s 2’ H makes it more stable; RNA’s 2’ –OH allows it to fold into complex 3D shapes for functional roles.