Introductory Biology

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BIOLOGY PRESENTATIONS FOR A-LEVEL, IN
MULTIMEDIA JAMES BOWLES, 2001
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A Level Biology

• Nucleic Acids

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Nucleotides
A nucleotide contains
Phosphate Group
Pentose Sugar
Base
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Nucleotides
The phosphate group gives the nucleotide an
acidic nature
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Nucleotides
The pentose sugar may be either Ribose (RNA) or
Deoxyribose (DNA)
Ribose
Deoxyribose
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Nucleotides
There are five bases
Adenine Guanine
Purines
Cytosine Thymine Uracil
Pyramidines
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Polynucleotides
Bonds can form between carbon 3 of the pentose
sugar and the phosphate group on carbon 5 of an
adjacent nucleotide
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Polynucleotides
Long chains can be built up in this way -
Polynucleotides
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Polynucleotides
5
The ends of these chains are named on the basis
of which carbon is not involved in bonding
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DNA
Deoxyribonucleic Acid
Sugar is Deoxyribose
Bases are
Adenine Guanine
Cytosine Thymine
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DNA
Two chains of polynucleotide run anti-parallel to
one another
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DNA
The chains are arranged as a DOUBLE HELIX with 10
bases to each complete turn
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DNA
Base pairing is complimentary
Adenine
Thymine
Guanine
Cytosine
The bonds are hydrogen bonds
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RNA
Ribonucleic Acid
Sugar is Ribose
Bases are
Adenine Guanine
Cytosine Uracil
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Messenger RNA
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Messenger RNA
mRNA
U A A G C G U A U U G G C A U G
Single-stranded, uncoiled polynucleotide
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Messenger RNA
mRNA
U A A G C G U A U U G G C A U G
mRNA is a copy of the DNA code which is exported
from the nucleus
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Transfer RNA
tRNA
Single-stranded RNA arranged in a clover leaf
shape
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Transfer RNA
tRNA
Amino Acid binding site
tRNA attaches to amino acids in the cytoplasm
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Transfer RNA
tRNA
Anticodon
The anticodon lines up alongside the appropriate
codon on mRNA during protein synthesis
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Ribosomal RNA
rRNA
This is a long length of RNA produced in the
nucleolus
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Ribosomal RNA
rRNA
It has areas of single and double helices
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Ribosomal RNA
rRNA
In the cytoplasm it combines with proteins to
form ribosomes
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DNA vs. RNA
DNA
RNA
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DNA vs. RNA






DNA
RNA
May have single or double helix
Always a double helix
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DNA vs. RNA






Sugar is ribose
Sugar is deoxyribose
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DNA vs. RNA






Bases are A, T, G C
Bases are A, U, G C
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DNA vs. RNA






May be temporary
Permanent
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DNA vs. RNA






Chemically very stable
Chemically less stable
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