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OCR AS Biology Unit 2 Module 1-Biological Molecules

Chemical Group Role
Carbohydrates Energy storage and supply, structure (in some
Proteins Structure, transport, enzymes, antibodies and
most hormones.
Lipids Membranes, energy supply, thermal insulation,
protective layers/padding, electrical insulation
in neurones, some hormones.
Vitamins and minerals Forms parts of some…

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3. Proteins are made of one or more polypeptides. Different amino acids have different variable

Amino acids are joined by peptide bonds.

Linked together by peptide bonds to form dipeptide and polypeptides molecule of water is
released during the reaction.
Reverse of this reaction-Adds a molecule of water…

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4. Minerals can bind to the triple helix to increase its rigidity (stiff).
Exam Question
Q) Collagen is found in the ligaments which holds bonds together at joints.
State two properties of collagen that make it suitable for this purpose.
1. Strong with microfibril strength to make bonds hard…

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Structures very similar to amylopectin, except it has more side branches coming off it.

A very compact molecule and very good for storage.
Cellulose- Major component of cell walls in plants. Made of long, unbranched chains of beta- glucose.
Bonds between the sugars are straight, so the cellulose chains…

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Biuret test for protein. If protein is present, turns from pale blue to lilac.
Benedict's test for reducing sugars. Add benedict's, heat to 80°C. Colour changes from blue to

Non-reducing sugars- Benedict's test. If reducing
sugars test is negative, boil with HCl, cool and neutralise with Sodium Hydrogencarbonate.…

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Deoxyribonucleic Acid (DNA)

DNA is a polynucleotide, usually double stranded made up of nucleotides containing the bases
Adenine (A), Thymine (T), Cytosine (C) and Guanine (G).

Strands are anti-parallel and the sugars are pointing in opposite

How does DNA replicate semi conservatively, with reference to DNA polymerase.


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Enzymes are globular proteins, with a specific tertiary structure, which catalyse metabolic reactions in
living organisms.

Enzyme action can be intracellular meaning they act inside the cell and extracellular meaning that they
work outside the cell.

Factors which affect enzyme activity

1. Temperature- As this increases the rate…

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Competitive inhibitors- These are similar shapes to
the substrate and they occupy the active site and form enzyme inhibitor-complexes. This means a
product isn't released because the inhibitor and the active site don't have the same shape. As the
number of substrate molecules is increased, the level of inhibition…

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Module 2-Diet and Food Production
Balanced Diet- A diet that contains adequate amounts of all the necessary nutrients required for
healthy growth and activity.
Malnutrition- A diet which lacks the nutrients needed for a body. For example too little iron in your
diet causes anaemia.

Over- nutrition and lack…

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3. Continue this over several generations until a high-yielding plant is produced.

Selective breeding to produce plants that are resistant to disease or pests:

1. Plants showing a high level of resistance are bred together.
2. The offspring that show most resistance are then bred together.
3. This continues…


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