The document outlines key biological concepts such as the differences between plant and animal cells, the processes of diffusion and osmosis, and the role of photosynthesis in energy transfer within food chains. It discusses the efficiency of food production, the carbon cycle, enzyme functionality, and homeostasis. Additionally, it touches on genetics, including inheritance patterns of diseases like Huntington's and cystic fibrosis.

1. B2 Exam Revision

2. Plant cells vs. Animal cells
Both types of cell have these: Only plant cells
have these:
Nucleus
This controls
the cell
Cytoplasm
This is the jelly like
substance where
chemical reaction
take place
Cell wall
Gives support to
the cell
Large
vacuole
Large space
filled with cell
sapCell
membrane
Controls what goes
in and out of the
cell
1)
2)
3)
6)
5)
7)
Mitochondria
Energy is released here by respiration
4)
Chloroplasts
Where photosynthesis takes
place

3. Complete this definition of
Diffusion using the key words:
Diffusion is the _______ __________ of ______
from where there are lots of particles ( high
__________) to where there are less particles.
We say the particles diffuse down a concentration
_________.
In cells, the cell membrane has small holes that allow
small particles through, but not large molecules. We
call this membrane ________ ________.
The bigger the difference in concentration, the faster
the rate of ________.
Partially permeable
Diffusion
Concentration
Gradient
Random movement
Particles

4. Osmosis is diffusion but with …
WATER

5. OSMOSIS IS THE MOVEMENT OF
WATER PARTICLES
FROM WHERE THERE ARE LOTS OF THEM
(Dilute solutions)
TO WHERE THERE ARE NOT VERY MANY OF THEM
(concentrated solutions)
THROUGH A SEMI-PERMEABLE MEMBRANE
(LIKE A CELL WALL)
OSMOSIS

6. Photosynthesis - The equation
1. What factors are needed to make glucose?
2. What products are made by photosynthesis?

7. Limiting factors
• If you alter the levels of light, carbon
dioxide or change the temperature
the rate of photosynthesis will
change!

8. What happens to the glucose?

9. Mineral needs
Can you fill in this table?
Mineral Needed for Deficiency
disease
Nitrates
Magnesium

10. Mineral needs
Mineral Needed for Deficiency
disease
Nitrates Healthy leaves
Good all round
growth
Purple leaves, poor
growth
Magnesium To make chlorophyll Yellow leaves

11. Food chains
A food chain shows where the energy goes in a food chain
(in other words, “what gets eaten by what”):
Cabbage Rabbit Stoat Fox
The arrows indicate where
the energy is going
Plants convert the
sun’s energy into food

12. Pyramids of biomass
In this food chain we can see that the mass of organisms in
each stage is less than in the previous stage:
Cabbage Rabbit Stoat Fox
We can draw a “Pyramid of Biomass” to show this pattern:
Mass of cabbages
Mass of rabbits
Mass of stoats
Mass of foxes

13. Energy flow in a food chain
Consider the energy flow in this food chain:
Cabbage Rabbit Stoat Fox
100% 10% 1% 0.1%
Clearly, not all of the ___’s energy that becomes stored in the
_______ will end up in the fox. Only around ______ is passed
on to the next stage in each food chain.
Energy is lost at each stage because of a number of reasons:
1) Each organism has to ____, keep warm etc
2) Energy is lost through faeces (______)
Words – 10%, move, sun, waste, cabbage

14. Improving the efficiency of a food chain
Clearly, food chains aren’t very efficient. How could the
efficiency of a food chain be improved?
1) Reduce the number of stages in the chain:
Cabbage Rabbit Stoat
2) Limit an animal’s movement
or keep it warm:
Fox
3) Use plant hormones to
regulate the ripening of fruit

15. Energy in food production
• Biomass and energy is lost at each stage of
a food chain. The efficiency of food
production can be improved by reducing the
number of stages in our food chains. It
would be most efficient if we all ate just
plants
• If you stop animals moving around and
keep them warm they lose a lot less energy
which makes food production more
efficient

16. Decay
• Decay is carried out by micro-
organisms which work faster in warm,
moist conditions with a good supply of
oxygen.
• The decay process releases
substances that plants need to grow.

17. Carbon cycle
• The constant cycling of carbon is known as
the carbon cycle
• Carbon dioxide is removed from the
atmosphere by photosynthesis
• It is returned to the atmosphere by
respiration and combustion
• Microbes that decay waste and dead matter
respire and produce carbon dioxide

18. Map from memory

19. Enzymes
• Enzymes are biological catalysts, they
increase the rate of reactions.
• Enzymes are protein molecules made
up of long chains of amino acids.
• When enzymes are denatured the
active site changes shape.

20. What happens at the active
site?
In the same way that a key fits into a lock, so a substrate is thought to fit into
an enzyme’s active site. The enzyme is the lock, and the reactant is the key.
+ ↔ ↔ +
enzyme
reactant
+
enzyme-reactant
complex↔
products
enzyme
+↔

21. Factors affecting enzymes
If the temperature and pH changes sufficiently beyond an enzyme’s optimum, the
shape of the enzyme irreversibly changes.
normal denatured
heat
pH
This affects the shape of the active site and means that the enzyme will no
longer work.
When this happens the enzyme is denatured.

22. Aerobic Respiration
Oxygen + Glucose Carbon Dioxide + Water
Energy
+ +

23. Amylase
Protease
Lipase
Bile
Hydrochloric acid
Where are the
enzymes found?

24. Enzymes of digestion

25. Homeostasis
• The internal conditions of your body need
to be controlled to maintain a constant
internal environment
• Waste products such as carbon dioxide and
urea need to be constantly removed
• Urea is produced by your liver as you break
down excess amino acids and is removed by
your kidneys as urine

26. Five factors we need to keep constant.
• 1. temperature
• 2. water
• 3. sugar
• 4.waste products (need to remove)
• 5. ions
B2
Homeostasis

27. Use these words to complete the notes.
receptors brain receptors
The thermo-regulatory centre of the ______
monitors and controls the temperature of
blood as it passes through.
This centre has __________which are
sensitive to the temperature of the blood.
The skin also has _________ sensitive to
temperature.
B2
Homeostasis

28. Glucose control
• Your blood glucose concentration is
monitored and controlled by your pancreas
• Insulin and glucagon are the hormones
involved in controlling blood sugar. Insulin
converts glucose to glycogen and glucagon
converts glycogen to glucose
• In diabetes the blood glucose may rise to
fatally high levels because the pancreas
does not produce enough insulin. It can be
controlled by injections and diet

29. Chromosomes, Genes and Alleles
1. …………..
2. ……….......
3. ……………..
4. ………………
B
b
5. …………….
Nucleus, Gene, Chromosome, Allele, Cell
(b)

31. Why was his work not spread quickly?
• He was not a famous scientist –
nobody knew about him at the time.
• His job as abbot stopped him giving
lectures at universities.
• He published his work in an obscure
journal that few people read.
• Biologists at the time did not think
mathematics had anything to do with
Biology.
Gregor Mendel
(The Pea Plant Man)

32. Disease
• Some disorders are inherited
• Huntington’s disease is caused by a
dominant allele of a gene and can be
inherited from only one parent
• Cystic fibrosis is caused by a recessive
allele of a gene and so must be inherited
from both parents

33. Cystic Fibrosis
• The treatment
involves chest
physiotherapy.
• They are very prone
to chest infections
and malnutrition.
• The mucus
encourages the
growth of pathogenic
microbes that cause
infection and cause
long term lung
damage.

34. PHEW!
•Good Luck