complete according to the specification.

HideShow resource information

First 257 words of the document:

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 ratio, the more effective the process of diffusion.
In larger organisms, there is a reduced surface area to volume ratio, which is a
problem for the exchange of substances between the organism and the
The respiratory system provides a large surface area to volume ratio to ensure
efficient gas exchange.
Adaptation of lungs for exchange:
1. Large surface area- for molecules to diffuse through. This increases rate
of diffusion (alveoli)
2. Permeable barrier- for oxygen and carbon dioxide to be easily
3. Thin barrier (flattened epithelial cells)- which reduces
diffusion distance (alveoli, capillary wall is one cell thick)
4. Maintain steep concentration gradient- having fresh supply
of molecules to keep concentration high and removal of
required molecules to keep concentration low
Explain how models such as the fluid mosaic model of cell
membranes are interpretations of data used to develop scientific
explanations of the structure and properties of cell membranes.
The fluid mosaic model describes the plasma membrane of animal cells.
The cell membrane is made up of a phospholipid bilayer.
Phospholipids: fatty acid chains with phosphorous attached.

Other pages in this set

Page 2

Preview of page 2

Here's a taster:

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 barrier
-hydrophobic fatty acid
Cholester -type of lipid -stability and strength
ol -small -holds phospholipids
Glycoprot -insoluble protein with -cell signalling and cell
ein carbohydrate chain recognition.
attached.…read more

Page 3

Preview of page 3

Here's a taster:

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 begin to denature at high temps.
and cholesterol loses its structure, meaning the bilayer becomes more fluid
allowing more movement. This affects permeability of cell which allows
foreign molecules to enter.…read more

Page 4

Preview of page 4

Here's a taster:

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.
Carrier proteins bind with the molecule or ion, change shape and transport the
particles across the membrane.
Active transport: a kind of transport wherein ions or molecules move against a
concentration gradient (low to high conc.…read more

Page 5

Preview of page 5

Here's a taster:

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
deoxyribose), a phosphate group and a base (adenine, cytosine, guanine,
thymine or uracil).
DNA is a type of nucleic acid called
deoxyribonucleic acid. It is a long chain
molecule made up of
nucleotides.…read more

Page 6

Preview of page 6

Here's a taster:

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
hydrogen bonds.
Purines: double ring ­ A and
Pyramidines: single ring ­ C
and T
RNA (ribonucleic acid) is made up of a single strand of nucleotides. In RNA the
pentose sugar is called ribose and the base uracil replaces the base thymine.…read more

Page 7

Preview of page 7

Here's a taster:

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.
ii. DNA helix unwinds, h-bonds break/weaken and free-floating RNA
nucleotides pair with the exposed bases on the template (antisense)
strand of DNA.
iii.…read more

Page 8

Preview of page 8

Here's a taster:

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 on a DNA molecule
coding for a sequence of amino acids in a polypeptide chain.
A gene is a sequence of bases on a DNA molecule coding for a sequence of
amino acids in a polypeptide chain.…read more

Page 9

Preview of page 9

Here's a taster:

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: a ­CO-NH- linkage forming between the carboxyl group of one
amino acid and the amino group of another.…read more

Page 10

Preview of page 10

Here's a taster:

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.
Disulphide bond: a strong covalent bond, important in linking polypeptide
chains in proteins, the linkage arising as a result of the oxidation of the
sulphydryl (SH) groups of 2 molecules of cysteine.…read more



hi this is really gud :)


hi this is really gud :)

Samir Bouchenga

shut ub

Chris Brown

sikkkk!!!!!!!!!!! xxxxxxxxxxxxxx

Similar Biology resources:

See all Biology resources »See all resources »