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Describe the properties of gas exchange surfaces in living
organisms and explain how the structure of the mammalian lung
is adapted for rapid gaseous exchange.
Surface area to volume ratio: the amount of surface area per unit volume of an
object or collection of objects.
The higher the SA: V…

Page 2

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Each phospholipid molecule has a hydrophilic head and a hydrophobic tail.
Hydrophilic head point outwards and hydrophobic tails point inwards.
Proteins can float or be fixed.
Glycolipids: Lipid with carbohydrate chain attached.
Glycoprotein: protein with carbohydrate chain attached.
Compone Structure/Description Function
Phospholi -hydrophilic phosphate -forms bilayer
pid heads -impermeable…

Page 3

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Describe how membrane structure can be investigated
practically, e.g. by the effect of temperature on membrane

Beetroot experiment: the higher the temperature, the more colour leaked out
from the beetroot and hence the more damage is done to the cell membrane.
The fatty acid tails of the phospholipid bilayer…

Page 4

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Diffusion -hydrophobic or small, uncharged
-through phospholipid bilayer.
Facilitated Diffusion -hydrophilic molecules or ions.
-through channel/carrier proteins.
Osmosis --through phospholipid bilayer.

Small uncharged molecules e.g. oxygen and CO2 can diffuse across the cell

Channel proteins span the membrane and have a specific shape to transport
specific particles.


Page 5

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Describe the basic structure of mononucleotides and the
structures of DNA and RNA and describe how complementary
base pairing and the hydrogen bonding between two
complementary strands are involved in the formation of the DNA
double helix.
A mononucleotide is made up of a 5-carbon sugar (either ribose or

Page 6

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sugar and phosphate molecules forming the backbone and pairs of bases
forming the rungs, is then twisted into a helix.
The 4 bases pair in a
particular way, based on
their shape and chemical

A and T pair forming 2
hydrogen bonds.
C and G pair forming 3

Page 7

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Outline the process of protein synthesis, including the role of
transcription, translation, messenger RNA, transfer RNA and the
template (antisense) DNA strand.
The sequence of bases in the DNA of the chromosome acts as a coded recipe
for making proteins.


i. Occurs in the nucleus, catalysed by RNA polymerase.…

Page 8

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leaves 61 codons to specify only 20 different amino acids. Therefore, most of
the amino acids are represented by more than one codon. The genetic code is
said to be degenerate (there is more than 1 triplet for each amino acid).

Describe a gene as being a sequence of bases…

Page 9

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Describe the structure of an amino acid and the formation of
polypeptides and proteins and explain the significance of a
protein's primary structure in determining its 3D structure and
Structure of amino acid:

The amino acid monomers join together in a condensation reaction to form
peptide bonds.

Peptide bond:…

Page 10

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an alpha helix or a beta-pleated sheet
is formed.
Tertiary Structure The final 3D shape of the molecule,
held together by ionic bonds,
interactions between hydrophilic R
groups and strong disulphide bridges
between r groups containing sulphur.
Quaternary Structure The final structure if more than one
polypeptide chain is present.…




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