Cambridge (CIE) AS Your notes
Biology
Structure of Nucleic Acids &
Replication of DNA
Contents
Nucleotides
The Structure of DNA
Semi-Conservative DNA Replication
The Structure of RNA
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, Nucleotides
Your notes
Nucleotide Structure
Nucleic acids such as DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are
macromolecules
Like proteins (polypeptides) and carbohydrates (polysaccharides), these nucleic acids
are polymers
This means they are made up of many similar, smaller molecules (known as subunits or
monomers) joined into a long chain
The subunits that make up DNA and RNA are known as nucleotides
Therefore DNA and RNA can also be known as polynucleotides
Nucleotides
Nucleotides are made up of three components:
A nitrogen-containing base (also known as a nitrogenous base)
A pentose sugar (containing 5 carbon atoms)
A phosphate group
Nucleotide Structure Diagram
The basic structure of a nucleotide
Nucleotide Structure Table
Properties DNA RNA
Pentose sugar Deoxyribose Ribose
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, Bases Adenine (A) Thymine (T) Cytosine Adenine (A) Uracil (U) Cytosine
(C) Guanine (G) (C) Guanine (G)
Your notes
Number of Double-stranded (double helix) Single-stranded
strands
Nucleotides in DNA & RNA Diagram
There is much overlap of the nucleotides found in DNA and RNA, the only difference is that
RNA contains uracil (U) instead of thymine (T)
ATP
Adenosine triphosphate (ATP) is the energy-carrying molecule that provides the energy
to drive many processes inside living cells
ATP is another type of nucleotide and hence it is structurally very similar to the
nucleotides that make up DNA and RNA
It is a phosphorylated nucleotide
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Biology
Structure of Nucleic Acids &
Replication of DNA
Contents
Nucleotides
The Structure of DNA
Semi-Conservative DNA Replication
The Structure of RNA
© 2025 Save My Exams, Ltd. Get more and ace your exams at savemyexams.com 1
, Nucleotides
Your notes
Nucleotide Structure
Nucleic acids such as DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are
macromolecules
Like proteins (polypeptides) and carbohydrates (polysaccharides), these nucleic acids
are polymers
This means they are made up of many similar, smaller molecules (known as subunits or
monomers) joined into a long chain
The subunits that make up DNA and RNA are known as nucleotides
Therefore DNA and RNA can also be known as polynucleotides
Nucleotides
Nucleotides are made up of three components:
A nitrogen-containing base (also known as a nitrogenous base)
A pentose sugar (containing 5 carbon atoms)
A phosphate group
Nucleotide Structure Diagram
The basic structure of a nucleotide
Nucleotide Structure Table
Properties DNA RNA
Pentose sugar Deoxyribose Ribose
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, Bases Adenine (A) Thymine (T) Cytosine Adenine (A) Uracil (U) Cytosine
(C) Guanine (G) (C) Guanine (G)
Your notes
Number of Double-stranded (double helix) Single-stranded
strands
Nucleotides in DNA & RNA Diagram
There is much overlap of the nucleotides found in DNA and RNA, the only difference is that
RNA contains uracil (U) instead of thymine (T)
ATP
Adenosine triphosphate (ATP) is the energy-carrying molecule that provides the energy
to drive many processes inside living cells
ATP is another type of nucleotide and hence it is structurally very similar to the
nucleotides that make up DNA and RNA
It is a phosphorylated nucleotide
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