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OCR AS Biology Unit 2-Module 1-Jessica Birbeck…read more

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They all contain carbon, hydrogen, oxygen and nitrogen. Only some contain sulphur.
They make up 50% of the organic matter of a cell
Are large molecules (polymers), formed from many amino acids (monomers)
The amino acids are joined together by peptide bonds which will be covered in later slide.
Functions of proteins:
Structural components (muscle, bone etc.)
Membrane carriers and pores
All enzymes are proteins
Many hormones are proteins
Antibodies are proteins…read more

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Amino Acid Structure
Amine Group
Acid Group
Different amino acids have different R-groups. There are 20 different R-Groups and therefore
20 different amino acids in total. Some R groups can be small (the smallest is a single
hydrogen atom), however most are usually large. You will find some that are hydrophilic and
others that a hydrophobic. Some may be negatively charged whilst others are positive. The
amine group, acid group and the hydrogen atom bonded to the centre carbon will be the same
for all amino acids…read more

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Joining Amino Acids
Condensation Reaction
A condensation reaction involves a molecule of water to be released inn order to form a
covalent bond between two amino acids. This bond is called a peptide bond. These bonds occur
between the carbon in the acid group and the nitrogen in the amine group and overall
producing a dipeptide.
Hydrolysis Reaction
In reversal, a hydrolysis involves a molecule of water being added in order for the peptide bond
to be broken.
Condensation Hydrolysis…read more

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Breaking Down Proteins And Polypeptides
Peptide bonds require an enzyme in order to be formed or broken. Polypeptides are very
stable molecules and the covalent bonds holding it together are strong and not broken easily
in the conditions found in the body.
The name given to these which catalyse the breaking of peptide bonds are called protease
enzymes. Two examples are:
Hormone regulation-the enzymes found in the target cell of an hormone breaks down that
hormone-meaning that other cells are not being affected by this hormone so it is easier to
control and the effects are not permanent.
Ageing-Older people tend to have much less elasticated skin and appears to be wrinkled. This
is because older skin is less able to rebuild collagen, a fibrous protein, and loses its elasticity
and smoothness.…read more

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Making Polypeptides and Proteins
Polypeptides and proteins are synthesised on ribosomes found inside the cells of the body.
Messenger RNA is used to put amino acids in the correct order to make the polypeptide
When an mRNA passes through a ribosome, amino acids join together in a certain order and
for each one a condensation reaction takes place in order for peptide bonds to be formed.
The mRNA determines the sequence of amino acids and the sequence of amino acids
determines the actual protein shape. (see in more detail in later slide)
More and more amino acids are added to the chain, resulting in a large polypeptide chain
with many peptide bonds. This chain of amino acids is called the primary structure of a
protein…read more

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