OCR F212 Molecules, Biodiversity, Food and Health

Complete notes to F212 OCR Biology.

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OCR AS Biology Unit 2 Module 1-Biological Molecules
Chemical Group Role
Carbohydrates Energy storage and supply, structure (in some
organisms).
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 larger molecules and take
part in some metabolic reactions, some act as
co-enzymes or enzyme activators.
Nucleic acids Information molecules, carry instructions for
life.
Water Takes part in many reactions, support in plants,
solvent/medium for most metabolic reactions,
transport.
Water is a solvent Substances dissolve in it
Polar molecule Negative charge on one side and
positive on the other.
Water polarity also makes it a good solvent. The positive end of a water molecule will be attracted
to a negative ion, and the negative end will be attracted to the positive ion.
The ions will be totally surrounded by water molecules meaning they will be dissolved.
Hydrogen Bonding
The two hydrogens on this side may flip or change position due to the repulsion between the same
charges.
Hydrolysis- Type of reaction that occurs when water is added to break a bond in a molecule.
Hydrophilic- The phosphate group of a phospholipid that readily attracts water molecules.
Proteins
Proteins- Made of long chains of amino acids.
1. A dipeptide is formed when two amino acids come together.
2. A polypeptide is formed when more than two amino acids join together.

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3. Proteins are made of one or more polypeptides. Different amino acids have different variable
groups.
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 to break the peptide bond (Hydrolysis reaction)
4 Structural levels Proteins have
Primary structure- Sequence of amino acids in the polypeptide chain.
Secondary structure- Hydrogen bonds form between the amino acids in the chain.…read more

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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
2. Movement. Collagen is flexible and can change shape.
Carbohydrates
Carbohydrates are made from monosaccharides.
Glucose is a monosaccharide with 6 carbon atoms in each molecule.…read more

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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 are straight.
Cellulose chains linked together by hydrogen bonds to form strong fibres called microfibrils.
Strong fibres means it provides structural support for cells (e.g. in plant cell walls).…read more

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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
orange-red.
Non-reducing sugars- Benedict's test. If reducing
sugars test is negative, boil with HCl, cool and neutralise with Sodium Hydrogencarbonate. Repeat
Benedict's test.
Iodine test for starch- Turns from yellow to blue-black if starch is present.
Emulsion test for lipids- Mix the ethanol and pour into water. If an emulsion forms a lipid is present.…read more

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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
directions.
How does DNA replicate semi conservatively, with reference to DNA polymerase.
1. Double helix is untwisted. Hydrogen bonds between the bases are broken apart and the
DNA unzips to expose the bases.
2.…read more

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Enzymes
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 of reaction increases as there are more collisions.
But very high temperatures denature enzymes. Optimum temperature is 37°C, as this is body
temperature.
2.…read more

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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 decreases because a substrate
molecule is more likely than an inhibitor molecule to collide with the active site. Most competitive
inhibitors do not bind permanently to the active site.…read more

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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 of exercise can lead to obesity
Obesity is defined as being 20% (or more) over the recommended body weight.…read more

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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 over several generations to produce a crop that is disease or pest resistant.
Selective breeding can be used to increase the productivity of animal:
1. Select animals with good characteristics that will increase meat yield.…read more

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