Biology Notes OCR F212

The OCR Unit F212 in complete, following the exam board specification.

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Jack Wilson 12WT
F212 Notes ­ From the Specification.
Biological Molecules:
Biological Molecules
Describe how hydrogen bonding occurs between water molecules, and relate this, and other
properties of water, to the roles of water in living organisms
A hydrogen bond is formed due to the partial charges (+/- ) which reside on the
oxygen (-) and the hydrogen (+) respectively. This occurs between a single
hydrogen atom in one molecule and the oxygen atom in the next. This is the
strongest form of intermolecular bonding.
This provides water with a high specific heat capacity, which is the amount of
energy which is needed to raise one gram of a substance by 1K. A high specific
heat capacity means that water is thermally stable, as a lot of energy is required
to heat it up.
Water also has a high latent heat of evaporation. This is similar to having a high specific heat capacity,
yet it states that a lot of energy is required to break hydrogen bonds, allowing water to evaporate
and turn into a gas (steam). This is useful for organisms as it allows them to cool themselves down
easily, as when water evaporates the steam carries away the heat energy after evaporation.
Water is also very cohesive due to its polarity. Cohesion is the attraction between molecules of the
same type, so in this case water attracted to water. They are attracted to each other by the partial
charges on both oxygen and hydrogen. Being cohesive water is able to flow very well which makes it
adept at transporting substances.
Water is a lower density as a solid than it is at as a liquid. This means that when it freezes and
becomes ice, it floats on the surface of water. This provides a habitat for animals such as polar bears
or penguins and that when water freezes; fish are able to move about.
Finally, water is also a good solvent. This is due to salts for example being ionic compounds, and
water being polar. This means for example the Cl is surrounded by the H atoms in water as they
have a + charge. This is particularly useful as it increases the ease of transport for substances across
an organism's body.

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Describe, with the aid of diagrams, the structure of an amino acid
An amino acid monomer consists of an amine group, a carboxylic acid group
and a carbon group in the middle which links to the R-Group (any alkyl group
to make the specific amino acid). Key amino acids ­ cysteine (contains
sulphur, therefore forms disulphide bridges) and glycine (R-group is a single
H. This amino acid makes 35% of collagen's structure).…read more

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Explain, with the aid of diagrams, the term quaternary structure, with reference to the structure
of haemoglobin
Quaternary structure is only used to describe a protein which has more than one polypeptide chain.
The quaternary structure is the way which the polypeptide chains are assembled together, which
tends to be determined by the tertiary structure of individual chains.
Describe, with the aid of diagrams, the structure of a collagen molecule
Collagen is a structural protein. It is fibrous and made up of three
polypeptide chains.…read more

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The structural difference between -glucose and -glucose is where the OH group on carbon-1
resides. In -glucose it is above the plane, whereas in -glucose it is below the plane. This is only for
carbon-1 ­ all of the other OH groups remain in the same position.…read more

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Explain how the structures of glucose, starch (amylose), glycogen and cellulose molecules
relate to their functions in living organisms
Glucose: Small. Easily broken down and harnessed as energy in the form as ATP.
Starch: Large molecule. Good for storage. Straight chains and branches. Branches can be picked off.
Glycogen: Large. More compact. Lots of branches. Easier to be picked off.
Cellulose: Long, unbranched chains. Cellulose chains linked by Hydrogen bonds, increase strength.…read more

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Comparing solutions with a colorimeter:
Photoelectric cell picks up light that has passed through the sample.
Place the solution in a sample chamber between the light and photoelectric cell in a cuvette.
The more copper sulphate that is used up in a Benedict's test, the less light will be blocked out.
Prepare a calibration curve by taking a range of known concentrations.
Carry out a Benedict's test on each one. Filter out precipitate.
Use a colorimeter to give readings about light transmittance.…read more

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Outline, with the aid of diagrams, how DNA replicates semi-conservatively, with reference to
the role of DNA polymerase
Hydrogen bonds between two DNA strands break. The double helix unzips and forms two single
strands. Each original strand now acts as a template for a new strand. Free floating DNA nucleotides
join exposed bases on each original strand ­ sticking to the rules of complementary base pairing. The
nucleotides on the new strand are joined together by the enzyme DNA polymerase.…read more

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Secondly, if an enzyme is catalysing a breakdown reaction, fitting into an active site puts a strain on
the bonds within the substrate. This strain means that the substrate molecule breaks up easier.
The `lock and key model'
This model states that a substrate fits into an enzyme the same way that a key fits into a lock.
Active site and substrate have a complementary shape.…read more

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To investigate the mentioned effects, you must keep everything else constant.
pH: Kept constant through the use of pH buffers, which maintain pH at a set level by keeping the H
ions in a solution constant. This is done because pH affects reaction rate by changing the shape of the
active site of an enzyme.
Temperature: This can be done by carrying out enzyme-controlled reactions in a water bath.…read more

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Interfere with metabolic reactions which can cause damage, illness or death. Often are enzyme
inhibitors. An enzyme of which being cyanide, a non-competitive inhibitor of cytochrome c oxidase
which is an enzyme which catalyses respiration reaction.
State that some medicinal drugs work by inhibiting the activity of enzymes
Drugs work by inhibiting enzymes. For example penicillin works by inhibiting the enzyme
transpeptidase which catalyses the formation of proteins in the bacterial cell wall.…read more


Georgia Danielle

These are really, really good notes!! Thank you for putting them on here, they are fantastic as a final run through of everything.

Asha Ibrahim


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