Fluid mosaic - called this as
componants can move
around within the membrane
Glycerol and fatty acids combine
by condensation to produce
triglycerides.
The R-group of a fatty acid may be
saturated or unsaturated. In phospholipids,
one of the fatty acids of a triglyceride is
substituted by a phosphate group
Carbohydrates - Carbon
based molecules combined
with water. Contain elements
C,H and O.
The 'standered sugar' - Glucose (C6H12O6)
Disaccharides can be formed from
a condensation reaction with two
monosaccharides
Polysaccharides can be
broken down by hydrolysis
reactions. A disaccharide
would become its two
constituent monosaccharides
Testing for reducing sugars
Heat sugar/food with
Benedict's reagent. If a
reducing sugar is
present, there will be a
colour change from blue
to brick red.
If Benedict's test fails... Heat a
second sample in dilute HCl,
neutralise with NaHCO3, then
repeat benedicts test.
Bonds in biochemistry
Carbohydrates - Glycosidic bond
Lipids - Ester link
Proteins - Peptide bond
Unsaturated - contains
double bonds between
carbons
Sucrose is a disaccharide formed by condensation of
glucose and fructose. Lactose is a disaccharide
formed by condensation of glucose and galactose
Monosaccharides are the basic molecular unitsof which carbohydrates are composed
Inhibition of enzymes
Inhibitors - chemical that slows down rate of reaction in an enzyme
Competitve - competes for active site,
non-competitive doesnt compete for active
site and binds elsewhere.
Non competitive inhibitors bind to the enzyme
changing the shape of it, meaning the substrate
can no longer fit, stopping it completeing the
reaction.
Used in industry to slow
down reactions and also
used in chemistry
Testing for lipids and
proteins
Buiret test for proteins... Add a small sample of substance to a
test tube and crush solid foods. Add distilled water to test tube
and a few drops of buiret reagent. If a proteins is present, there
will be a colour change from blue to purple.
Emulsion test for lipids... Dissolve your sample in
approximately 5ml of distilled water and shake. Add
roughly the same amount of ethanol and shake
again. If a white emulsion Appears, then lipids are
present.
Proteins and enzymes
Enzymes are specific and
only work on 1
molecule/chemical so for
each different job a different
enzyme is needed.
Non competitive inhibitor - not competing for
the active site attracts to the enzyme and
attaches to stop it doing its job.
Catalysis - the acceleration of a chemical
reaction by a catalyst.
Xray crystallography is a method
of figuring out the arrangement of
atoms within a crystal
Virtually all enzymes are proteins.
Induced fit model- When the enzyme and
substrate form a complex, structural changes
occur so that the active site fits precisely
around the substrate. The reaction will take
place and the product, being a different shape
to the substrate, moves away from the active
site. The active site then returns to its original
shape.
Antibodies
A globular protein syntheesised by
B-cells that reacts with an antigen
Secreted by lymphocytes and contain 2 heavy chains and 2
light chains
They have a hinge region to allow
flexibikity and and variable region and
constant region
Chains are held together by disulhide
bridges and it is Y -shaped with 2 active
sites
Agglutination - the clumping together
of antigens by antibkdies. This stops
and immobilises viruses and cells.
One type of antibody, the T cells, mature after having first
migrated from the bone marrow to the thymus gland. The
other type, B cells, migrate to and then mature in either the
bone marrow or in the foetal liver or spleen. Once mature,
they patrol around the blood and body, hunting for foreign
antigens. T cells are involved in the cell-mediated
response, whilst B cells are involved in the humoral
response.
Four types of T
cells...Killer T cells
Helper T cells
Suppressor T cells
Memory cells
Immune system
Phagocytes - non specific white blood cell,
engulfs pathogens and/or antigens, once
engulfed it destorys them and presents
antigens on its surface to activate the rest of the
immune system
Pathogen - a disease causing organism.
On the surface of all cells are
antigens.Your body recognises
the antigens on your cells as your
own so anything with different
antigens stimulates an immune
response
In an immune response, the body will
recognise tan antigen as foreign and will attack
it. The immune system is made up of cells that
work with the body's physical and chemical
barriers. It helps stop any pathogen entering
your body, and your body becoming infected.
Diffusion
Factors affecting the rate of diffusion...
High concentration gradient, short
diffusion pathway, moist surface, large
surface area
Facilitated diffusion - any form of diffusion that requires a protein like helper...
Carrier proteins - molecule specific -
only take one molecule across
Channel proteins - allows any
molecule through unless gated.
the movement of particles from an
area of high concentration to an area
of low concentration until the
concentrations are equal.
Proteins
2 types - fibrous (structural e.g. Collagen)
globular ( functional e.g. Enzymes)
Primary - sequence of amino acids in the protein.
Secondary - formation of alpha helices or beta sheets.
Tertiary - overall 3D shape of the protein.
Quaternary - proteins made from more
than 1 chain have this structure.
Magnification=Size of image/Actual size of object
To get from mm
to um x1000
Microscopy
Resolution - clearing 2 objects close together so they
can be seen as seperates
Magnification - an increase in the
size of an objects to make it visi le
to the human eye
Two types of electron
microscopes - scanning
(shows the outside) and
transmission ( see inside
details )
Scanning - must be in a vacuum so
living specimens cant be observed.
Is only shown in black and white.
Has a lower resolving power than
TEM and shows 3D image easily.
Transmission - must be in a vacuum
so living specimens cant be observed.
Image only in black and white.
Specimen must be extremely thin and
2D images only.
The Digestive System
Mouth
Teeth - Cut, grind and pulverise food,
reducing it to smaller particles
(buccal), which increases surface
area for the action of enzymes.
Tongue - Manoeuvres
food for chewing and
rolls food into bolus for
swallowing
Openings of salivary glands - saliva,
pH 6.5, moistens food, mucus sticks
bolus together and lubricates it for
swallowing. Salivary amylase, if
present, starts digestion of starch.
Oesophagus - 25cm Long
muscular tube connecting
buccal cavity and
stomach. Bolus of food
pushed along the
oesophagus by peristaltic
waves of muscle
contraction.
Stomach - stomach lining
secrete hydrochloric acid and
pepsin. Smooth muscle
contracts which mixes austic
juice and food to make chyme.
Mucus is secreted to protect
from digesting yourself.
Pancreas - secretes
pancreatic juices
down the pancreatic
duct. Contains alkali
salts to help
neutralise stomach
acid and are full of
enzymes.
Small intestine -
chemical
digestion,
absorbs nutrients
and has gentle
peristaltic
contractions.
Large intestine - absorbs water,
stores faeces, has gentle
peristaltic contractions and ends
at the rectum.
Cardiac cycle
Wave of electrical activity spreads
out from the SAN across both atria
causing them to contract
The atrioventricular valve
prevent the wave crossing
to the ventricles.
The wave of electrical
activity is allowed to pass
through the AVN which lies
between the atria
The AVN causes a short delay,
then conveys a wave of electrical
activity between the ventricles along
the Bundle of His
The Bundle of His conducts the wave through
the atrioventricular septum to the base of the
ventricles where the bundle braches into
smaller fibres.
The wave of electrical activity is
released from these fibres causing
the ventricles to contract quickly
from the apex of the heart upwards.
Cardiac output=heart rate X stroke volume
Cell Structure
Mitochondria - Aerobic
respiration. Each has a
smooth outer membrane
and folded inner
membrane.
Nucleus - Contains DNA for proteins
Smooth Endoplasmic
Reticulum -
synthesises, stores
and transports lipids
and carbs
Rough Endoplasmic
Reticulum - Transports
proteins through the
cell
Golgi Apparatus -
Packages proteins before
they are sent to destination
Lysosome - Makes protein molecules
Chloroplast - Contains
chlorophyll for
photosynthesis
Cytoplasm - Contains
enzymes that speed up
biochemical reactions.
Rigid Cell Wall -
Made of cellulose to
give the cell support
Oral rehydration therapy
cholera produces a toxin which causes Na
and Cl ions to be released into the lumen,
lowering water potential. water diffuses by
osmosis across the epethelial cells into the
lumen to even water potential but does not
get reabsorbed and causes diarrhoea. ORT
is given containing salts and water to
replace the fluid lost.
rehydration therapy contains... water- to rehydrate tissues,
sodium- to replace lost sodium ions, glucose- to stimulate
the uptake of sodium ions and provide energy, potassium -
to replace lost potassium ions and stimulate appetite, and
other electrolytes - such as chloride & citrate ions to help
prevent electrolyte imbalance.
Vaccinations
immunity - the resisting of infection
Passive immunity - giving antibodies to an individual.
This is short lasting as once they are denatured they
are gone e.g. anti venom. These are not stimulated to
make memory cells.
Active immunity - Stimulating an immune response in a
person so that memory cells are produced. These are long
lasting and this is a vaccination.
Vaccination - Injecting someone
with a substance to stimulate
active immunity.
Herd immunity - If a large enough
proportion are vaccinated, then those
that aren't are still protected.
Diseases
Fibrosis- : The transport of
chloride ions and water by the
cells in the airways, lungs and gut
is disrupted. This causes thick
mucus to line the lungs and ducts
in the gut. Because the thick
mucus is not shifted easily, it is
more likely that a sufferer will pick
up a bacterial infection
Asthema - fluid and mucus
collects in the airways,
blocking the smaller ones.
Muscles in the trachea,
bronchi and bronchiole walls
contract, and breathing
becomes difficult
Emphysema-Due to constant infection,
phagocytes are attracted to the lungs
where they release elastase - an enzyme
that breaks down the elastin in the alveoli
walls, to enable them to reach the surface
where the bacteria are. Without adequate
elastin, the alveoli cannot stretch, so they
recoil and many burst. Large air spaces
appear, reducing the surface area for gas
exchange and making sufferers breath
more rapidly. As it progresses, patients
become breathless and wheezy - they may
need a constant supply of oxygen to stay
alive.
Tuberculosis - The cause of
tuberculosis is the bacterium
Mycobacterium tuberculosis. Infected
water droplets ejected by a sneeze or
cough from a person with the active
pulmonary infection, are inhaled by
another person who breathes in and
retains the bacterial cells.
Gas exchange in fish
Gills have numerous folds that give them a
very large surface area. The rows of gills are
called gill lamellae. The folds are kept
supported and moist by the water that is
continually pumped through the mouth and
over the gills.
Fish also have an efficient transport system within
the lamellae which maintains the concentration
gradient across the lamellae. The arrangement of
water flowing past the gills in the opposite direction
to the blood is called countercurrent flow and this
means that they can extract oxygen at 3 times the
rate a human can.
Lifestyles and risk
Smoking
Nicotine-This drug is absorbed readily into the blood and
stimulates the nervous system to reduce the diameter of arterioles
and the adrenal glands to release adrenaline. This increases heart
rate and blood pressure and decreases the blood supply to the
Carbon monoxide- A gas that diffuses across the alveoli
into the blood and onto the red blood cells, combining
with haemoglobin to form carboxyhaemoglobin. This
stops the haemoglobin from becoming fully saturated.
Tar - a mixture of aromatic substances, which
settles on the airway linings and stimulates
changes that may lead to obstructive lung
disease and lung cancer.
Smoking increases the concentration of
blood cholesterol, which increases the risk
or having heart doesease or a stroke
Risk - the probability that an event will
occur and have a hazardous result
Osmosis
Osmosis is a form of diffusion in which water
moves from a solution of higher water
potential to a solution of lower water potential
through a partially permeable membrane
Isotonic- Occurs when an equal solute
concentration exists inside and outside the cell.
Gas exchange in the lungs
Lots of alveoli are supplied with gases via the
trachea, splitting into two bronchi and lots of
bronchioles connected to the outside by the mouth
and nose.
The alveoli provide a large
surface area through which
gases can diffuse. these gases
diffuse a short distance from
the alveolus and the blood as
the lining of the lung and the
capillary are only one cell thick.
There is a large blood supply,
which allows for oxygen to be
carried away to the cells as soon as
it has diffused into the blood.
Ventilation movement also helps
maintain a concentration gradient as air
is regularly moving in and out of the
lungs.