Search for notes by fellow students, in your own course and all over the country.
Browse our notes for titles which look like what you need, you can preview any of the notes via a sample of the contents. After you're happy these are the notes you're after simply pop them into your shopping cart.
Document Preview
Extracts from the notes are below, to see the PDF you'll receive please use the links above
Biology - Unit 3
Movement of Molecules in and out a Cell
Osmosis
- Osmosis is the movement of water molecules across a partially permeable membrane from a
region of high water concentration to a region of low water
concentration
...
A partially permeable membrane is just one with very small
holes in it
...
2
...
3
...
e
...
4
...
- Osmosis occurs in and out of a cell with the movement of
water, if a cell has lots of water, water will move out to the
lower water concentration and if a cell has little water, water will move into a cell to the lower
water concentration fluid
...
Root Hair Cell
1
...
2
...
- The concentration of minerals within the root hair cell is normally higher than in the soil around
it
...
- Active transport allows the plant to absorb minerals from a very dilute solution, against a
-
concentration gradient
...
Active transport also occurs in the gut absorbing glucose in humans
...
- When there is a higher concentration of amino acids and glucose in the gut than in the blood
then these substances diffuse naturally
...
- Mitochondria produce energy and ATP from anaerobic respiration inside the cells for active
transport to take place
...
- They restore the balance inside the body
...
Protein rotates and releases molecules to the inside of
the cell
...
The protein then rotates back ready to pick up another
molecule
...
minerals required
...
Exchange Surfaces : - Thin, so substances only have a short distance to diffuse acros
- Large surface area, so lots of substances
can diffuse across at once
...
Structure of a Leaf and Gas Exchange
1
...
2
...
3
...
4
...
5
...
6
...
The Breathing System
1
...
Its separated from the lower part of te body (the abdomen) by the diaphragm
3
...
The air that you breathe in goes through the trachea
5
...
The bronchi split into progressively smaller tubes called bronchioles
7
...
Intercostal muscles contract pushing the ribs up and out
...
Diaphragm contracts, moves down and flattens
...
This increase the volume inside the thorax
...
This decreases the pressure so air rushes in
...
Intercostal muscles and diaphragm relax
...
The volume in the thorax decreases and the pressure increases
...
Air rushes out to a lower pressure
...
Older machines sometimes called ‘iron lungs’ use external negative pressure
...
An external negative pressure breathing aid, or ‘iron lung’ was a ventilator developed in the 1920’s
...
Air was pumped out of the chamber, lowering the pressure inside to a pressure below the
pressure in the lungs
...
This increased the volume
and decreased the pressure inside the chest
...
The pump then switches off automatically and air moved back into the chamber, increasing the
pressure
...
This forced air out of the lungs
...
Like blowing up a balloon
...
Elastic recoil then allows the lungs to deflate as the ribs move down again, forcing air out of the
lungs
...
The other method forces air straight into the lung (a positive pressure) this machine connects to
the top of the lungs
...
The Iron Lung:
For a patient the iron lung is very effective in the short term for letting the body recover from an
operation or from polio
...
However the patient is completely restricted to the chamber and cannot stay at home or get up
and move around
...
The Iron Lung can have some negative
effects on the body as well - they can get bleeding in the lower abdomen
...
The patient can remain in the comfort of
their own home, and can remain independent
...
The Positive
Pressure Machine enables patients to have a long successful life, they can do nearly everything they
would've done previously to their injury - they are completely mobile
...
Gas Exchange: The Lungs
1
...
2
...
The Alveoli are Specialised to Suit Their Job:
1
...
2
...
3
...
4
...
Gas Exchange: The Gut
5
...
6
...
7
...
8
...
Transport Systems in Plants
- Plants have two types of transport vessels, the xylem and the
phloem
...
- They transport food substances (mainly dissolved sugars)
made in the leaves to growing regions (e
...
new shoots) and
storage organs (e
...
root tubers) of the plants
...
Xylem
- Made of dead cells joined end to end with no end walls
between them and a hole down the middle
...
Transpiration
- Transpiration is loss of water from a plant, it is caused by diffusion and evaporation of water
from inside a leaf
...
- This in turn means more water is drawn up from the roots and so theres a constant
transpiration stream of water through the plant
...
- They have to have stomata in the so that gases can be exchanged easily
...
What Minerals move from the Soil:
1
...
Magnesium
-> Maximises surface area to take up water and mineral ions
-> Respiration happens in the mitochondria and energy realised is used for active transport
-> Can be broken down as an energy source for respiration - this process needs glucose
Hot, dry and windy conditions all effect the rates of evaporation of water out of a plant
...
Dry:
The dry, humid air means that there aren't many water molecules in the air, this therefore means
there is a lower concentration of water in the air than in a normal climate
...
Evaporation will increase as the water is diffusing at a greater rate than before
...
This means that the concentration outside the leaf will be lower as there are less water molecules
in the air - the diffusion gradient is greater thus diffusion will occur quicker speeding up the
process of evaporation
...
If the
water molecules are moving quicker it means that diffusion will occur at a faster rate due to the
faster moving molecules
...
The
stomata open and close to allow carbon dioxide in but at the same time water is lost
...
Circulatory System
The circulatory system carries blood and dissolved substances in the blood to and from different
places in the body
...
They are pumped round the
body in blood vessels
...
Arteries go away from the heart
...
Coronary Arteries is the hearts own blood supply
...
If these stop working the heart would have no blood supply meaning that the heart would shut
down and blood would stop being supplied to the rest of the body
...
Pulmonary artery- From the heart to the lungs deoxygenated blood
Pulmonary vein- From the lungs to the heartoxygenated blood
Vena cava- the rest of the body to the heartdeoxygenated blood
Aorta- from the heart to the rest of the bodyoxygenated
The circulatory system had 2 parts right - deoxygenated blood
left - oxygenated blood
The heart:
3
...
The atria contracts and forces blood into the ventricle
5
...
Valves in the heart ensure the blood flows in the correct direction
7
...
Returns through the veins
9
...
Systemic Circulation - Taking blood to the body cells and back to the heart
...
- Thick walls
...
- They have a narrow hole (lumen) which carry the blood
...
They have permeable walls so substances can diffuse in and out of it
...
They have very thin walls usually only one cell thick, this decreases the diffusion distance
increasing the rate of diffusion
...
The blood is at a lower pressure so the walls dont need to be as thick as arteries
...
They have valves which prevent the blood from flowing in the wrong direction
...
It allows blood flow, blood clots could be very dangerous
...
BUT it could build up and takes a long time to insert it
...
- They have a concave, doughnut like shape, which gives them a large surface area for absorbing a
-
large amount of oxygen quicker
...
They contain a red pigment called haemoglobin
...
In the body cells the opposite happens to release oxygen back into the cells
...
They produce antibodies to recognise antigens on the surface of pathogens
...
They do have nucleus’
...
- They have no nucleus
...
- Lack of platelets can cause excessive bleeding and bruising
...
- It also contains nutrients like amino acids and glucose
...
- It contains urea from the liver to the kidneys
...
- Antibodies and antitoxins are produced by the white blood cells and carried in the blood
...
- Salt solution or ‘saline’ is used to replace the lost volume of blood
Replacing Heart Valves
Mechanical Valves
They consist of 2 semi-circular carbon leaflets that pivot on hinges
...
They are strong and last a lifetime,often used in young patients
...
-
- For patient with heart disease they can either have a heart transplant or an artificial heart
...
- They are at the experimental stage and are still not actually being used at the moment, the results haven’t
been promising
...
Surgery to fit them can lead to bleeding and infection
...
Artificial hearts dont work as well as donor hearts, parts
of the heart could wear out or the electrical motor
could fail
...
Blood doesn't flow through them as smoothly which
could lead to blood clots and then strokes
...
Homeostasis
Homeostasis is the maintenance of a constant internal environment
...
The body temperature cant get too hot or too cold
...
Water content mustn’t get too high or low, or too much water could move into or out of our
cells and damage them
...
If the ion content of the body is wrong, the same thing could happen
...
The blood sugar level needs to stay within certain limits
...
Carbon Dioxide is a product of respiration
...
It leaves the body by the lungs when you breathe out
...
Urea is a waste product made from excess amino acids
...
Sweating
2
...
Stretching Out/Curling Up
4
...
This is so the warm blood loses heat
...
This is so the blood doesn't lose heat and
cool the body
...
- It contains receptors which are sensitive to the temperature of blood flowing through the brain
...
In Cold Condition
Hair pulled erect
No sweat, no
evaporation, no
heat loss
Hair traps a layer
of air as insulated
Less blood flows
through the
surface capillaries
Sweat gland stop
producing sweat
In Hot Condition
Hair lies flat,
trapping less air so
less insulated
More sweat, more
evaporation cools
the skin
More blood flows
to surface
capillaries
Temperature
Rises above set
point (37oC)
Detected by
receptors in
thermoregulatory
centre of the brain
Effectors stimulated
and corrective
mechanisms are
triggered
Norm or Set Point
Temperature
falls below set
point (37oC)
Detected by
receptors in
thermoregulatory
centre of brain
Effectors stimulated
and corrective
mechanisms are
triggered
Homeostasis: The kidney
Kidneys Perform 3 Main Roles:
1
...
Adjustment of ions
3
...
Removal of Urea
- Proteins can’t be stored by the body - so any excess amino acids are converted into fats and
carbohydrates, which can be stored
...
Urea is produced as a waste product from these reactions
...
- The kidneys then filter it out of the blood, it is temporarily stored in the bladder in urine until it
is excreted from the body
...
2
...
- If the ion content of the body is wrong, this could upset the balance between ions and water,
meaning too much or too little is drawn into cells by osmosis
...
For example, a salty meal will contain
too much sodium so some of it is removed from the blood by the kidneys
...
- The balance is always maintained by the kidneys
...
Adjustment of Water Content
Water is taken into the body as food and drink and lost in three ways:
1
...
In sweat
3
...
- On a cold day if you dont sweat you'll produce more urine which is pale and dilute (less
concentrated)
- On a hot day if you sweat you'll produce
less urine that is dark and concentrated
(more concentrated)
Nephrons are the Filtration Units in the
Kidney
1
...
- The membrane between the blood vessels
and the Bowman’s capsule acts like a filter,
so big molecules like proteins and blood
cells are not squeezed out, they stay in the
blood
...
Reabsorption
As the liquid flows along the nephron, useful substances are reabsorbed back into the blood:
- All the sugar is reabsorbed
...
- Sufficient ions are reabsorbed
...
Active transport is needed
...
3
...
Kidney Failure
Dialysis
Pros: - Machines usually available
...
Cons: - Has to happen at least twice a week for life
...
- Have to watch your diet
...
1
...
2
...
3
...
4
...
Transplant
Pros: - No special diet
...
- Relatively inexpensive, particularly after surgery
...
- Need tissue match otherwise may suffer rejection
...
- The patient is treated with drugs which suppress the immune system, so that their immune
system won’t fight off and reject the kidney
...
Homeostasis: Controlling Glucose
-
Eating foods that contain carbohydrates puts glucose into the blood from the gut
...
Vigorous exercise removes much more glucose from the blood
...
Diabetes
Type 1 - A persons blood glucose concentration may rise to a high level because the pancreas
doesn't produce enough of the hormone insulin to break down the sugars
...
Humans and Their Environment
If waste is not properly handled, more harmful pollution will be caused
...
Water - Sewage and toxic chemicals from industry can pollute lakes, rivers and oceans, affecting
the plants and animals that rely on them for survival
...
Land - We use toxic chemicals for farming (e
...
pesticides and herbicides)
...
Air - Smoke and gases released into the atmosphere can pollute the air, e
...
sulfur dioxide can
cause acid rain
...
Building
2
...
Dumping Waste
4
...
g
...
Why?
- To provide timber to use as a building material
- To clear more land for farming
- to produce paper from wood
Deforestation leads to 4 Main Problems
1
...
Rice is grown in warm, waterlogged conditions, ideal for decomposers, these organisms
produce a lot of methane so more is released
2
...
More Carbon Dioxide in the Atmosphere
1
...
Microorganisms feeding on bits of dead wood release carbon dioxide as a waste product of
respiration
3
...
Cutting down loads of trees means that the amount of carbon dioxide removed from the
atmosphere during photosynthesis is reduced
4
...
Biodiversity is the variety of different species in a habitat - the more species, the greater the
biodiversity
2
...
This causes a number of lost opportunities e
...
there are probably loads of useful products that
we will never know about because the organisms that produced them have become extinct
...
- The plants rot and this releases CO2, which is built up and stored in the bog
...
Biofuels
An increase in global warming may lead to:
- Big changes in the earths climate
- Rises in sea levels
- Reduce biodiversity
- Changes in immigration patterns in animals
- Fuels can be made by fermentation of natural products; waste products can often be used
- Fermentation is when bacteria or yeast break down sugars by anaerobic respiration
Ethanol
1
...
Sugar cane juices can be used, or glucose can be derived from maize starch by the action of
carbohydrase
3
...
They ferment plant and animal
-
waste, which contains carbohydrates
Its made in a simple fermenter called a digester or generator
Biogas generators need to be kept at a constant temperature to keep the microorganisms
respiring
Batch Generators - Make biogas in small batches, manually loaded up with waste which is left to
digest
...
Food Production
The Efficiency of Food Production can be Improved by:
1
...
- This is because the number of animals in a food chain is reduced
...
Restricting the Energy Lost by Farm Animals
- In some countries animals such as pigs and chickens are often intensively farmed, they're kept
close together indoors
...
- This makes the transfer of animal feed to animal more efficient
...
Developing New Food Sources like Mycroprotein
-
Mycroprotein makes protein from fungi
...
g
...
A fungus called Fusarium is the main source of mycroprotein
...
The fungus respires aerobically, so oxygen is supplied together with nitrogen and other minerals
...
Fish Stocks
1
...
2
...
A lot of modern fishing vessels use sonar because it allows them to pinpoint the exact location
of whole shoals of fish
...
(a) The Bluefin Tuna is on the brink of commercial extinction (b) However this species is yet to
have been given protection because some countries fishing fleets catch large amount of
bluefin tuna, in other countries blue fin tuna is eaten as a delicacy so the consumers didn't
want the number bought to be reduced
...
Ocean food webs must be taken into account because over fishing can lead to an imbalance of
ecosystems
...
This can cause an abundance in their prey
...
The aim of fisheries management organisations is sustainable fishing - this is catching a
consistent amount of fish over an indifferent period of time without otherwise damaging the
environment
...
Controlling fish net size is a conservation method to protect fish stocks, this means that the
mesh size is big enough to allow small fish to escape and to also allow juvenile fish to escape
and live to grow and reproduce
...
Each fishing vessel is given an individual fishing quota for different types of fish species