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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 to each sugar residue.
Each sugar phosphate base group is called a nucleotide.
The two strands in DNA are held together by hydrogen
bonds between pairs of bases.…read more

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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.
Ribose is the sugar in the backbone of RNA, ribonucleic acid.
The sugar phosphate backbone is formed by condensation polymerisation.…read more

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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 the NH to form water.…read more

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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 from DNA in the following ways:
Stage 1: Transcription Stage 2: Translation
The first is messenger RNA, or mRNA.…read more

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DNA fingerprinting is used to determine the probability that genetic material came from a particular
individual.…read more

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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 proton accepting ­NH2 group can react with one another to for
Amino acids can exist in three different ionic forms, depending on the pH of the solution.…read more

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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 Peptides/Proteins
When a peptide or protein is refluxed with moderately concentrated acid or alkali for several hours, the
C-N bond in the peptide link is broken.…read more

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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 with polar side chains are situated on
the outside of proteins, then hydrogen bonds can form
to water molecules surrounding the protein.…read more

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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 readily reversed when the products need to leave the active site.
The bonds are usually hydrogen bonds or interactions between ionic groups.…read more


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