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
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 ________.
Osmosis is diffusion but with …
WATER
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
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?
Mineral needs
Can you fill in this table?
Mineral
Nitrates
Magnesium
Needed for
Deficiency
disease
Mineral needs
Mineral
Needed for
Deficiency
disease
Nitrates
Healthy leaves
Good all round
growth
Purple leaves, poor
growth
Magnesium
To make chlorophyll
Yellow leaves
Food chains
A food chain shows where the energy goes in a food chain
(in other words, “what gets eaten by what”):
Cabbage
Rabbit
Plants convert the
sun’s energy into food
Stoat
Fox
The arrows indicate where
the energy is going
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 foxes
Mass of stoats
Mass of rabbits
Mass of cabbages
Energy flow in a food chain
Consider the energy flow in this food chain:
100%
10%
Cabbage
Rabbit
1%
Stoat
0.1%
Fox
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
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
2) Limit an animal’s movement
or keep it warm:
3) Use plant hormones to
regulate the ripening of fruit
Stoat
Fox
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
Decay
• Decay is carried out by microorganisms which work faster in warm,
moist conditions with a good supply of
oxygen.
• The decay process releases
substances that plants need to grow.
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
Map from memory
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
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
Five factors we need to keep constant.
•
•
•
•
•
1. temperature
2. water
3. sugar
4.waste products (need to remove)
5. ions
B2
Homeostasis
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
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
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.
PHEW!
•Good Luck