AQA Biology GCSE - B3


AQA Biology GCSE - B3
1. Exchange of Materials
• Exchange of gas in
• Exchange in GUT
• Exchange in
• Exchange in PLANTS
- B3
Transportation in Body
The Exchange of Materials
• ACTIVE TRANSPORT= the movement of a
substance against a concentration gradient.
Uses up energy from respiration, and is found in
the intestines and the kidney (for absorption and
• IT REQUIRES ENERGY from respiration
• Allows cells to absorb ions from very dilute
Breathing system takes air in + out of body
Lungs are protected by ribcage and contain lots of
ALVEOLI= tiny air sacs in the lungs well adapted to
gaseous exchange because:
They create a large surface area
They are moist
They have very thin walls- less distance for
gases to travel
The constant movement of the blood and the
breathing of the lungs keeps a high
concentration gradient perfect for diffusion
The blood capillaries are right next to the
alveoli, meaning easy access for the oxygen to
diffuse into the blood, and the CO2 into the
Breath out= ribcage down, diaphragm up
Breath in= ribcage up, diaphragm down
The Intestine
• VILLI= tiny protrusions in the intestine which
help to absorb the products of digestion
• Use active transport + diffusion to gain as much
of the valuable materials, especially sugar, as
• Villi help increase absorption because they:
– Have a large surface area (squashed up)
– Are moist
– Are very close to a large network of capillaries
(absorbed straight into blood stream)
Exchange in Organisms
• All organisms need large, moist SA, large
conc. grad. and short diffusion distance
• Fish
Gills – rich blood supply, constantly moist (in water) and thin. Constant supply
of water means large conc grad so diffusion is constant. When taken out of
water, gills stick together – smaller SA – and suffocate.
• Tadpoles/Frogs
Tadpoles work same as fish, when turn into frogs they develop simple lungs +
can breathe in air AND water
• Insects
Have no blood supply due to impermeable cover or insects. Instead O2 and
CO2 are pumped directly to cells, so no need for blood. Also have spiracles
(insects version of stomata).
Exchange in Plants
• Need osmosis in roots (for water) and
diffusion near stomata (for CO2)
• Leaves thin + flat to increase SA for light
and a waxy cuticle to prevent evaporation
• Root hair cells increase SA because of
long, thin hairs
• Most minerals + ions needed taken
through roots
• Transpiration = loss of water from surface
of plants + leaves
• Water is often lost through stomata
• Waxy cuticle minimises it
• Water is pulled up through XYLEM to
replace lost water vapour
• Occurs more in hot, dry, sunny, windy
Exchange of Materials in
• STOMATA= holes in the underside of leaves that allow
carbon dioxide in, and oxygen and water vapour out for
gaseous exchange. Guard cells can close off the
stomata in order to stop transpiration.
• TRANSPIRATION= the loss of water vapour through the
stomata, resulting in the movement of water through
osmosis through the plant due the change in
concentration gradient at the top of the plant. This brings
needed ions etc up the plant.
• Transpiration happens more quickly in hot, windy and
dry conditions
• Plants may wilt when they lose water faster than they
gain it from the roots- cells become less rigid due to they
fact they aren’t full of water.
The Circulatory System
Oxygenated blood is pumped to
the heart from the lungs, and to the
body from the heart
De-oxygenated blood is pumped
from the heart to the lungs, and
from the body back to the heart
Circulation system contains
and BLOOD.
VEINS= carry blood to the heart
ARTERIES= carry blood away from
the heart
CAPILLARIES= tiny blood vessels
found near organs and tissues of
the body that exchange substances
with the cells eg glucose, CO2
VERY THIN (1 cell thick)
•Double circulation =
two transport systems
in body, one to carry
blood TO heart, other
to carry AWAY from
•Humans have this.
Right side= pumps low O2 blood to
Left side= pumps high O2 blood to
WHITE BLOOD CELLS- fight infection
PLATELETS- help blood to clot
PLASMA- holds dissolved substances, glucose (taken
from the small intestine to the body organs), CO2,
waste products (urea from the kidneys)
No nucleus- more room for haemoglobin
Special shape with a lowered centre- greater surface area to
absorb gas
HAEMOGLOBIN- substance which gains oxygen from the
lungs to form OXYhaemoglobin. Then releases oxygen into
Reversible 
Oxygen + Haemoglobin ↔OXYhaemoglobin
Effect of Exercise
• Energy from respiration used to make muscles
• When this happens, you need more respiration
to take place (ie more O2 + glucose, quicker
CO2 release)
• Causes increased heart/breathing rate
• Arteries dilate  more blood for muscles
increases oxygen/glucose supply CO2 is
removed quicker
Anaerobic Respiration
• Your everyday muscle movements are made
possible by AEROBIC respiration
• If heart rate is increased, blood cant supply O2
quick enough
• Anaerobic respiration doesn’t involve O2 and is
less efficient
• Glucose  Lactic Acid (+ energy)
• Lactic acid needs to be got rid of (by reacting
with O2 to form CO2 + water) = OXYGEN DEBT
Human Kidney
• Vital for homeostasis
• Works by filtering everything from blood and then
reabsorbing all the sugar, as well as the mineral ions
and water needed.
• Active transport ensures ALL sugar is reabsorbed and
diffusion makes sure mineral ions and water is
reabsorbed in the right amounts
• Hot day with little water intake = little urine
• Cold day with large water intake = lots of urine
• Kidney failure results in toxins such as
urea building up + salt/water balance
being lost – certain death without dialysis
• In a dialysis machine, blood thinners prevent
clotting, dialysis fluid containing right amounts of
minerals allows blood to diffuse to normal levels
(urea etc go into dialysis fluid and are removed)
and then passed through a bubble trap to get rid
of any bubbles
Kidney Transplants
• New kidney is placed inside the person, and
the old kidneys are left in the body
• If everything goes well, it will function as a
normal kidney
• The donor kidney may be rejected by the
recipient’s immune system
• To minimise this, immunosuppressant drugs
are used, as well as finding very close
• Despite this, it is very hard to find donors
Dialysis Vs Transplants
•Much more readily
•Enables you to lead
relatively normal life
•No risk of rejection
•No need for
•Eat what you like
•Lead a normal life
•Free from
restrictions which
come with regular
dialysis sessions
Growing Microbes
• Micro-organisms grow in an agar culture
medium with a carbohydrate energy
source and various other vitamins,
minerals and proteins
• You need to take careful safety measures
and use sterilized equipment to ensure the
growth of uncontaminated cultures
Food Production + Yeast
• Yeast is a single celled organism which can
respire both aerobically and an anaerobically
• Aerobic respiration produces CO2 and water
and is used to make bread rise
• Anaerobic respiration produces CO2 and
ethanol, the process is known as fermentation
• This is used in the production of beer, wine and
other alcoholic drinks
Food Production + Bacteria
• Bacteria are used to make cheese abd yoghurt
• Yoghurt is formed when bacteria act on lactose
(sugar in the milk), producing lactic acid and
changing the texture and taste of the milk
• Different type of bacteria is added for cheese,
making much more lactic acid is made and it is
thicker (curds)
• This is cooled and left in moulds to set and then
more bacteria is added to give different flavours
Large Scale Microbe Production
• Can be grown on a large scale using fermenters
• Fermenters have features such as an oxgen
supply, stirrer to keep microorganisms in
suspension and maintain an even temp, watercooler jacket to remove excess heat and
measuring instruments such as pH and
temperature gauges
• Mycoprotein is produced by allowing the fungus
‘Fusarium’ to grow on sugar syrup in aerobic
Antibiotic Production
• Discovery of penicillin was made by Alexander
Fleming, however he could mass produce it
• Howard Florey + Ernst Chain discovered a way
to mass produce by being able to store the
penicillin for a long time
• Penicillium is now used as it provides more
penicillin, as it is made in a fermenter
• Mould only starts making penicillin after all
nutrients are used up, so there is a lag time
between the production of the mould and
• Biogas – mainly methane – produced by
anaerobic fermentation of a wide range of
plants and waste materials that contain
• Gets rid of waste, solves energy needs and is
renewable, however hard to do it on a large
• Different types of biogas plants (floating-drum
Vs. fixed dome) mainly built underground for
Other Biofuels
• Ethanol based fuels can be produced from
anaerobic fermentation of sugar cane
juices by the enzyme carbohydrase
• +ves = doesnt produce toxic gases, muych
cleaner and can be mixed with petrol,
carbon neutral
• -ves = needs lots of space, poor countries
grow cash crops instead of feeding people
 starvation
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B3 syllabus