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Topic 3
Unit F334

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DNA is a double-stranded helix.

The strands are made up of sugar groups (deoxyribose),
phosphate groups and four different bases ­ adenine,
thymine, cytosine and guanine.

These groups join together in a condensation reaction to
form a long chain of alternating sugar-phosphate groups.
One of the four bases is joined…

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DNA forms by condensation polymerisation

The backbone of DNA is based on a repeated pattern of a sugar group and a phosphate group.
The full name of DNA, deoxyribonucleic acid, gives you the name of the sugar present - deoxyribose.
Deoxyribose is a modified form of another sugar called ribose.…

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It is also a condensation reaction that connects base molecules to sugars in the sugar-phosphate
All of the bases have an NH group in their structure.
It's the N atom of the NH group that bonds to deoxyribose ­ eliminating an OH group from the sugar
and H from…

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RNA is a type of nucleic acid called ribonucleic acid.
The RNA nucleotides are joined to form a single strand.
The nucleotides are joined by a bond between the sugar of one nucleotide and the phosphate of the next.
There are two types of RNA: mRNA and tRNA

RNA differs…

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DNA fingerprinting is used to determine the probability that genetic material came from a particular

It is used for: Solving crimes, clarifying immigration disputes and to establish paternity or maternity

How does it work?
· A DNA sample is obtained and it cut into fragments using a restriction enzyme…

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Amino acids are bifunctional compounds.
They contain at least one amino group and one carboxyl group.
Amino acids can act both as weak acids and as weak bases.

Amino Carboxyl
group group

The ­COOH group donates H+ ions
The ­NH2 groups accepts H+ ions
The proton-donating ­COOH group and the…

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An amino acid contains both an amino group ­NH2 and a carboxyl group -COOH, in the same molecule.
The carbon chain is numbered so that the carbon in the carboxyl group is counted as number 1.
Start by naming the position of the amino group.

2-aminopropanoic acid

Hydrolysis of…

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Four types of interaction are important
in chain folding:

Instantaneous dipole ­ Induced dipole
This occurs between non-polar side chains on amino

Hydrogen bonds
These bonds form between the peptide groups that
link the chain together in secondary structures.
They also form between non-polar side chains.
If amino acids…

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Enzymes are metabolic catalysts that are proteins.
They have high specificity for a given substrate.
All enzymes have an active site, where the tertiary structure of the enzyme exactly matches the
structure of its substrate.

The substrate can weakly bind to the surface.
This is so that binding can be…


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