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B2 Exam Revision
Plant cells vs. Animal cells
Both types of cell have these:
1) Nucleus
This controls
the cell
2) Cytoplasm
This is the jelly like
substance where chemical
reaction take place
3) Cell
membrane
Controls what goes
in and out of the
cell
4) Mitochondria
Energy is released here by respiration
Only plant cells
have these:
5) Cell wall
Gives support to
the cell
6) Large
vacuole
Large space
filled with cell
sap
7) Chloroplasts
Where photosynthesis takes
place
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
Complete this definition of
Diffusion using the key words:
Partially permeable
Diffusion
Concentration
Gradient
Random movement
Particles
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 ________.
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
Photosynthesis - The equation
1. What factors are needed to make glucose?
2. What products are made by photosynthesis?
Limiting factors
• If you alter the levels of light, carbon
dioxide or change the temperature
the rate of photosynthesis will
change!
What happens to the glucose?
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.
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
+
↔
enzyme
+
products
Factors affecting enzymes
If the temperature and pH changes sufficiently beyond an enzyme’s optimum, the
shape of the enzyme irreversibly changes.
This affects the shape of the active site and means that the enzyme will no
longer work.
When this happens the enzyme is denatured.
heat
pH
normal
denatured
Aerobic Respiration
Oxygen + Glucose
Carbon Dioxide + Water
Energy
+
+
Amylase
Protease
Lipase
Bile
Hydrochloric acid
Where are the
enzymes found?
Enzymes of digestion
Chromosomes, Genes and Alleles
3. ……………..
2. ……….......
b
B
5. …………….
(b)
1. …………..
4. ………………
Nucleus, Gene, Chromosome, Allele, Cell
Gregor Mendel
(The Pea Plant Man)
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.
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
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.
Effect of Exercise
• Energy from respiration used to make muscles
contract
• 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
PHEW!
•Good Luck