Exchange of materials
Transporting substances around the Body
Diffusion is the movement of a fluid across a concentration gradient
from an area of high concentration to an area of low concentration.
Osmosis is the movement of water across a partially permeable membrane
from an area of high concentration to an area of low concentration.
In active transport, energy is needed.
energy comes from cellular respiration
Happens in the cytoplasm and mitochondria
More respiration happening, more active transport can
This is because the fluid can move from low
to high concentrations.
This is called moving against the gradient.
The uptake of mineral ions through the soil.
The ions are found in very dilute solutions.
The solution inside the plant is a lot stronger.
Ions taken in against the gradient.
Glucose is moved out of kidney into your blood.
It goes against the gradient.
Marine birds consume large amounts of salt when
they drink water.
The kidneys cannot get rid of it all.
They have salt glands which use active transport.
When we breathe in,
our ribcage moves up
Our diaphragm flattens
Air is pulled into the
When we breathe out,
our ribcage moves down
Our diaphragm inflates
Air is forced out of the
Lungs are made up of clusters of alveoli
tiny air sacs with large surface areas
Have a rich blood supply
maintains a concentration gradient in
Oxygen constantly being removed
from the blood and carbon dioxide
constantly entering the lungs
gas exchange happens at the highest
o make it rapid and effective.
The food we eat is broken down in the gut.
It forms simple sugars:
These products are of no use in the gut.
Via active transport and diffusion, the
molecules from food enter the bloodstream.
food is broken down during the digestion
After being broken down, the food molecules are
small enough to pass through the walls of the
small intestine into the blood vessels.
They can move this way because there is a very
high concentration of food molecules in the gut,
and a very low concentration in the blood, so the
process here is diffusion.
They move along a very steep concentration
The lining of the small intestine is folded into
thousands of tiny villi.
They increase the uptake of digested food by
villi increase the surface area dramatically.
Diffusion is very rapid and efficient in the gut,
because it has a rich blood supply
food molecules are carried away the second
a steep concentration gradient is constantly maintained.
Fish have protective scales all over their bodies
They have gills
of very thin layers of tissue
with a rich blood supply.
them from directly taking in oxygen from the
Less surface area for the gas to diffuse across.
Fish do not need to worry about keeping the gills
moist living in water.
Gills do not work in air
“suffocate” out of water
if not kept moist constantly the gills stick together
and there isn’t enough surface area for the fish to get
enough oxygen to survive.
All plants require carbon dioxide and water for
The carbon dioxide is obtained via diffusion
through the leaves.
The flattened shape of the leaves:
the surface area for diffusion to happen.
Ensures the photosynthesising cells are close to an
A problem is that water is always being lost by
carbon dioxide in will also lose water
The plant does not need carbon dioxide all the time
At night there is no sunlight
They are adapted for effective exchange
have stomata (opening holes)
both gas-proof and waterproof.
Roots have been adapted for uptake of water and mineral ions.
can open and close at specific times to allow carbon dioxide in and out.
Have a waxy cuticle covering them
photosynthesis cannot take place.
Water is vital for shaping cells and for photosynthesis.
The roots themselves are thin and have a large surface area.
The root hair cells have also adapted
to increase surface area
increase efficiency of water uptake.
The cell membranes of root hair cells have microvilli
further increase surface area for diffusion and osmosis.
The distance between here and the xylem (transport tissue for the
water) is small.
The loss of water vapour through the surface of
the leaves is called transpiration.
As water is lost through the opening in stomata,
more water is pulled up through the xylem to take
This constant movement of water around the
plant is known as the transpiration stream.
Anything affecting evaporation on a plant will also
Factors which increase evaporation will also
Sunny and warm conditions increase rate of
carbon dioxide is needed
Means stomata are opened
means water is lost
these conditions also increase transpiration rate:
Adaptation to help with the problem of water loss
plant can wilt
happens when more water is lost than gained
prevent much water loss by minimising the surface area
The blood circulation system we have is made up
of three main components:
One transports blood from
the heart to the lungs and
the other takes blood around the rest of the
With this system, we are constantly receiving
oxygenated blood from the lungs.
There are three main blood vessels in the
system, which have all adapted to carry out
arteries carry blood away from the heart to the
organs in the body.
This is usually oxygenated blood, explaining the red
Is our pulse
veins carry blood towards the heart
usually low in oxygen
deep purple-red in colour.
No pulse in veins
do contain valves which prevent the backflow of blood.
capillaries are found in junctions between the
arteries and veins.
These are found in huge networks.
The walls are a single cell thick so diffusion is easy.
Our hearts are made of two pumps, for the
These together beat around seventy times a
The walls of the heart are made pretty much
entirely from muscle which gets oxygen from the
coronary blood vessels.
Split into four chambers
and Atrium for each circulatory system
The liquid part of our blood is called plasma.
It transports red blood cells, white blood cells and
Blood plasma is a yellow liquid which transports all
blood cells and other substances around the body.
Carbon dioxide produced in the organs is carried in
plasma back to the lungs.
It is the red blood cells which give blood its red
Urea, a waste product formed in the liver is carried
in the plasma to the kidneys.
In the kidneys, urea is removed from the blood and
changed into urine.
All substances are transported in plasma.
The function of red blood cells is to pick up oxygen from the
lungs and deliver it to cells and tissues where it is needed.
Their adaptations to improve efficiency at their job include:
being shaped like biconcave discs increases surface area:volume ratio
over which diffusion takes place
packed full of haemoglobin - pigments which can carry oxygen
Have no nucleus, more room for haemoglobin and diffusion! WOO.
A haemoglobin is a large protein molecule folded around four
iron atoms ( THAT LOOKS PRETTY MINT!)
Oxygen + Haemoglobin ---> Oxyhaemoglobin
In an area of high oxygen concentration, haemoglobin can react
with oxygen to form oxyhaemoglobin, which is bright red in
colour, ergo blood being the colour it is.
Lone haemoglobin after is purple/deep red,
which explains the colour of veins.
Haemoglobin are made from iron
diet lacking iron can results in anaemia
makes you pale and have no energy.
This is because your body cannot make enough red
you cannot carry enough oxygen around the body for
Muscles in our bodies need a lot of energy.
They contain many mitochondria to supply
Muscles also contain glycogen stores
glycogen is a carbohydrate which can turn into glucose.
Our body respires more during exercise so our muscles
glucose + oxygen → carbon dioxide + water (+ energy)
when exercising your muscles contract harder and
more glucose and oxygen to supply their energy
More carbon dioxide is obviously produced –
has to be removed to keep muscles working efficiently.
So during exercise…
heart rate increases and arteries dilate –
This increase the blood flow to exercising muscles
breathing rate increases, and you breathe deeper –
You breathe more often
You draw more air into the lungs with each breath,
increases oxygen and glucose supply
increases the rate of carbon dioxide removal
Increases the amount of oxygen being brought into the body
Increases the amount of oxygen picked up by red blood cells
This oxygen is carried to the exercising muscles
Exercise is very beneficial to us when done regularly.
increases the size of the heart
Increases the size of the lungs
they develop a bigger blood supply
They develop a more efficient blood supply
When you are doing extremely vigorous exercise over
a long period of time, the muscles need so much
oxygen that even an increase in breathing rate and
heart rate does not supply enough.
Respiration which does not involve oxygen must be
done – anaerobic respiration.
Muscles only switch to anaerobic respiration when
they have been exercising for a long time and
Anaerobic respiration is not as efficient as aerobic
the glucose molecules are not completely broken down
less energy is released.
After finishing a lot of exercise, you are out of
breath for quite some time.
Your body does this to get rid of the waste lactic
acid which can cause problems
The lactic acid has to be broken down into
carbon dioxide and water which requires oxygen
The amount of oxygen required to break down all
of the lactic acid is called the oxygen debt.
Oxygen debt repayment:
Your kidneys are vital in maintaining
They filter out urea and remove it in urine
because urea is poisonous.
Water balance in the body must be maintained
because too much water or too little water in
cells can destroy them
kidneys can remove excess water and release it
from the body in urine.
The kidneys can remove excess salt from the
body in the same way.
The kidneys filter the blood and then reabsorb
everything your body needs.
sugar (glucose), amino acids, mineral salts and urea all move out
of the blood and into the kidneys along a concentration gradient.
The blood cells are too big to pass through the tubules and so are
ALL of the sugar is reabsorbed back into the blood by active
The amount of water and the dissolved mineral ions which are
It depends on how much of each is needed by the body – this is
Urine contains waste urea along with excess mineral ions and
water not needed by the body.
The quantities vary depending on how much you have taken in
and given out.
The human kidneys are not immune from damage.
when they are damaged and stop functioning, toxins like
urea stop being removed from the body, leading to death.
The dialysis machine relies on a process called dialysis to
clean the blood.
A person’s blood leaves their body and flows into the
machine, through partially permeable membranes.
A dialysis fluid, which contains a certain concentration of
substances ensures diffusion of unwanted substances from
the blood into the fluid.
However, glucose remains in the blood.
The dialysis machine prevents unwanted
substances from building up and restores them to
However they build up again after a few days,
which means regular dialysis must be done.
Some dialysis machines can be fitted in homes
It is essential the patient does not lose vital
substances from the blood like glucose and
important mineral ions.
The fluid contains the normal content of mineral
ions, so that any excess mineral ions are lost by
diffusion, but no more.
There is no urea in the dialysis fluid.
Advantages of these machines:
Constant medical attention
Much more readily available
Disadvantages of these machines:
repeated use at 8 hours per day
must follow a strict, healthy diet
after some years, the levels can be
hard to maintain
The other solution to the problem of kidney
failure is a kidney transplant.
A replacement kidney must be healthy and
donated by a donor.
The majority of the time, it doesn’t just function
The antigens on the kidney will be different from
The problem with this is that the recipient’s
immune system may reject the new kidney
your body will destroy it.
During a transplant, everything is done to prevent
such a thing, but it is always a risk.
There are certain things that can be done to
minimalize the risk of rejection:
a donor similar to the recipient with the same
This means they will share some of the same antigens.
Given to recipients which
suppress their immune system
– for the rest of their lives.
means you are prone to
your body cannot deal well
with any infection once
continue life freely without dialysis.
Can eat what you like without worrying
borrowed kidney will only last about 9 years before
Have to take your medicine everyday for the rest of your
life in case it is ever rejected by the immune system.
lists for kidney recipients can go on for years.
Finding a suitable donor often proves hard.
Yeast is probably the most important microorganisms for
Yeasts are single-celled organisms with a nucleus,
cytoplasm and membrane surrounded by a cell wall.
They reproduce by asexual budding (splitting into two to
form two new yeast cells).
Provided with a lot of oxygen, yeast cells will respire
They break down sugar as an energy source, producing the
waste products carbon dioxide and water.
When there is a lack of oxygen they respire anaerobically,
which produces ethanol and carbon dioxide.
Ethanol is alcohol.
This process of anaerobic respiration
in yeast cells is called fermentation.
Yeast is used to produce bread and alcoholic
In bread production, the yeast grows and
respires – producing carbon dioxide which
causes the bread to rise.
The gas bubbles expand when baked due to
the high temperatures, giving the bread its
All yeast cells are killed by the heat in the
We can make beers and wines using yeast.
Making beer relies on the process of malting,
where barley grains are soaked in water to keep
Germination begins and enzymes break down the
starch in the grains into a sugary solution.
This solution is extracted and used as an energy
source for the yeast.
The yeast and sugar mixture is fermented to
produce alcohol, when hops are often added to
give the drink its flavour.
The beer is then left to settle, clear and develop
fully its flavour.
Making wines uses the natural sugars found in
grapes for the yeast’s energy source.
The grapes would be pressed for their juice,
which is mixed with yeast and water.
The yeast is then left to respire anaerobically
until all of the sugar is used up.
The wine is later filtered to remove the
yeast, and stored in bottles, where it is left
for some time to mature.
Yoghurt is formed by the bacteria action on the lactose
You can make yoghurt by:
adding a culture of the right type of bacteria to warm milk
keeping the mixture warm so the bacteria grow, reproduce and
as the bacteria break down the lactose, lactic acid is produced
this process is lactic fermentation
the lactic acid causes the milk to clot and solidify to form a
further bacterial action gives the yoghurt its creamy
The same bacteria used to make yoghurt will also keep it
Colourings, flavourings and other additives can be added
to the yoghurt to improve its taste, appearance and
We need microbes in large quantities for production of drugs, like antibiotics, and
To grow microbes on an industrial scale, large vessels called fermenters are used.
These have been developed to prevent occurrences which stop bacterial growth.
They react to changes, to try and maintain a stable environment
Industrial fermenters usually have:
An oxygen supply so the microorganisms
A stirrer to keep the microbes in
this maintains a constant temperature
and makes sure that the oxygen and food
are evenly spread out throughout the
A water-cooled jacket which removes
excess heat produced from the respiration
Measuring devices for pH and temperature
so changes can be made if necessary
A flammable mixture of gases forms when bacteria break down waste
material of dead animals or plants in anaerobic conditions.
The main component is methane, although the contents varies.
The methane content tends to be around 50 to 80 per cent of the gas, the
rest is made of carbon dioxide, water, hydrogen and hydrogen sulphide.
Animal waste, dead animal and plant material and garden waste all
contain carbohydrates which make them good energy sources for biogas
They tend to work best at around 30°C so are usually in hot countries.
On average, every 10kg of dry dung can produce 3 cubic metres of biogas
which is about 3 hours.
Another advantage of these generators is that the waste, can be used as
A type of food based on fungi is called mycoprotein.
It is produced using the fungus Fusarium,
It requires aerobic conditions to grow.
Its mass doubles every 5 hours
this biomass is harvested, purified and dried to leave
It is pale yellow in colour and tastes faintly of
grows and reproduces very rapidly based on a cheap
energy supplyin a large fermenter.
a range of colours and flavours can be added to it to
Mycoprotein serves as a high-protein, low-fat meat
This means it is good for dieters and vegetarians.
Spontaneous generation is the belief that all living things
come from a non-living thing.
Biogenesis is the idea that living things created other living
Louis Pasteur's broth
Louis broiled broth for 15 min.
He then let it sit for some time in a swan neck flask.
He noticed that some dust had accumulated in the top
part of the flask.
He took a sample from the broth inside the flask.
He noticed that nothing was growing in it.
So he then preceded to shake the broth in the flask in
such a way, that it would touch the dust at the top.
He then took a sample from that and it was highly