Biology B3 Revision Notes
Everything you need to know for AQA Biology B3
Gills - http://www.fishdoc.co.uk/images/Gill_gross_view.jpg
Kidneys - http://www.unckidneycenter.org/images/glomerulus.jpg
Tranplant - http://kidney.niddk.nih.gov/kudiseases/pubs/transplant/images/transplant.jpg
- Created by: RATM33
- Created on: 10-01-10 16:04
Diffusion and Osmosis
Diffusion
- The net movement of substances from an area of high concentration to an area of low concentration
- Is passive - no energy is required
- The greater the temperature, the greater the rate of diffusion
- The steeper the concentration gradient, the greater the rate of diffusion
Osmosis
- The movement of water particles across a partially permeable membrane from an area of high concentration to an area of low concentration
Active Transport
Active Transport
- Goes against the concentration gradient - (from an area of low concentration to and area of high concentration)
- Uses energy from respiration - (is active)
- uses ATP
- Aided by protein carrier molecules
- enables cells to absorb ions from dilute solutions
Uses of Active Transport
In Root Hair Cell
- There is a greater concentration of minerals in the cell rather than in the soil surrounding
- If diffusion were to take place, minerals would move out of the plant
- To absorb all nutrients, active transport is required
In the Gut
- During digestion, there is sometimes a higher concentration of glucose and ammino acids in the blood, rather than in the gut
- If diffusion were to take place, the glucose and amino acids would move out of the blood
- To absorb all glucose and amino acids, active transport is required.
The Lungs
The lungs are...
- In the throax (upper part of the body)
- protected by the ribcage
- separated from the abdomen (lower part of the body) by the diaphragm
The Breathing system:
- Takes air into and out of the body
- So that Oxygen can diffuse into the bloodstream
- Carbon Dioxide can diffuse out of the bloodstream, into the air
Breathing
Air travels from the -
Trachea --> Bronchus --> Bronchiole --> Alveoli
Breathing In -
- Intercorsal muscles and diaphragm contract
- Thorax volume increases
- Decreases pressure, drawing air in
Breathing Out -
- Intercorsal muscles and diaphragm relax
- Thorax volume decreases
- Air is forced out
Gas Exchange
- Occurs in the alveoli
- Oxygen diffuses into the blood
- Carbon Dioxide diffuses out of the blood, and breathed out
The Alveoli are specialised to maximise diffusion, they have -
- A large surface area
- Moist lining (so gases can diffuse easily)
- Thin walls (short diffusion distance)
- Rich blood supply
Villi
- Found on the lining of the small intestine
- Aid in digestion
- Digested food moves in through diffusion and active transport
The Villi are adapted for digestion -
- Large surface area
- Thin walls (short diffusion distance)
- Rich blood supply (assists quick absorption)
Gas Exhange in Fish (1)
Are large and move alot, so therefore have breathing systems
Gills (a diagram would be useful to understand this, the link to it is in the overview bar)
- groups of blood vessels in a thin membrane bag
- absorb oxygen dissolved in water
- protected by operculum (gill cover)
- arranged in 4 layers on each side
- supported by gill arches
- in the form of filaments, which provides a large surface area
Gas Exhange in Fish (2)
Lamellae - respiratory surface for fish
- Thin Walls
- Branched (surface area)
- Good blood supply
- Counter current against blood supply
Gas Exchange in Insects
Are small and do not move alot, and therefore have small breathing systems or a blood supply
- Have holes on their body surface called spiracles, where air enters
- These lead to thracheae (small tubes)
- which branch off to tracheoles
- gases diffuse out of here and into cells
Air --> Spiracles --> thracheae --> tracheoles --> cells
Gas Exchange in Plants
Leaves are the surface for gas exchange in plants
They are adapted to this because -
- Thin (decreases distance for diffusion)
- Flattened shape - increase surface area
- Internal air spaces (increases the opportunity for gas exchange)
They have stomata to obtain carbon dioxide from the atmosphere
These are pores which allow CO2 in and O2out
The size of the stomata is controlled by the guard cells
Water Maintainence in Plants
Plants lose water vapour from the surface of their leaves
Transpiration - the loss of water vapour from the surface of a leaf through evapouration
Most transpiration is through the stomata
The transpiration stream is a constant movement of water molecules
Wilting is a protection mechanism against further water loss - the leaves collapse and hung down, which means that the surface area for water loss is reduced
Factors that affect Transpiration
LIGHT - as light intensity increases, stomata open wide (to allow more CO2 for gas exchange), which increases the rate of transpiration
HUMIDITY - Diffusion - greater concentration on outside, rate of transpiration slows
TEMPERATURE - More water molecules evapourate, rate of transpiration increases
WIND - water evapourates quicker, molecules dissolved are carried away
WATER SUPPLY - Plants close stomata when water levels in the soil are low, rate of transpiration decreases
Circulatory System in Humans
The heart pumps blood around the body
Blood flows from the heart to the organs through arteries and returns through veins
Substances needed by the cells in the body tissues pass out of the blood
Substances produced by the cells into the blood through the walls of the capillaries
There are two separate circulation systems (double circulatory system); one to the lungs (deoxygenated blood) and one to all the other organs of the body (deoxygenated)
The Blood
Blood Plasma transports:
- Carbon Dioxide - organs --> lungs
- Soluble products of digestion - from small intestine -> organs
- Urea - from the liver --> kidneys
Red Blood Cells:
- Transport oxygen - from lungs --> organs
- Have no nucleus - more space for oxygen
- Contain haemoglobin - contains iron
- in the presence of haemoglobin forms oxyhaemoglobin
- in other organs it splits up into oxygen and haemoglobin (deoxyhaemoglobin)
- Biconcave Disc shape - surface area + easy to fit in capillaries
Effect of exercise on the body
The energy that is released during respiration is used to enable muscles to contract
During exercise -
- Heart rate increases - increase blood flow, so amount of oxygen and glucose that is transported to the lungs increases and amount of carbon dioxide removed increases
- Rate and depth of breathing increases - to increase amount of oxygen taken in and carbon dioxide released
- Arteries supplying muscles dilate (vasodilation) - to increase blood flow
- Glycogen stores in muscles and liver transformed into glucose for use in respiration
Anareobic Respiration
If muscles are subjected to long periods of vigorous activity, they become fatigued (stop contracting efficiently)
If insufficient oxygen is reaching the muscles, they use anaerobic respiration to obtain energy.
Anaerobic respiration is the incomplete breakdown of glucose, and therefore releases less energy compared to Aerobic respiration
C6H12O6 --> 2C3H6O3 + 2 ATP
Glucose --> Lactic Acid + Energy
Anaerobic respiration results in an oxygen debt that has to be repaid in order to oxidise lactic acid into carbon dioxide and water.
Lactic Acid --> Carbon Dioxide + Water
The Kidneys
We have2 kidneys in our body
The Kidneys:
- Prevent the build up of toxins in the blood
- Control the levels of water in the blood (Osmo regulation)
- Control the concentration of ions in the blood (Ion-regulation)
- Produce urine - (a mixture of water, ions and urea)
A build up of excess protein can cause a build up of ammonia in the body, which is poisonous.
The protien is sent to the liver, where it is broken down into - glucose and UREA. The urea is sent to the kidneys.
Ultrafilteration, Reabsorption and Excretion
A healthy kidney produces urine by (see diagram) -
- Filtering blood (ultrafiltration) - high pressure builds up in the bundle of blood capillaries, the membranes between the capillaries and the Bowman's capsule act like a filter and filter out glucose, ions and water. The red blood cells and protein are too large to fit in the filter so they remain in the blood.
- Reabsorbing ALL glucose - through active transport
- Reabsorbing sufficient ions
- Reabsorbing suffcient water
- Releasing urea, ions and water as urine
Kidney Failure
If the kidneys do not work properly, waste substances can build up in the blood, which can result in death.
There are two ways in which Kidney failure can be treated:
- Kidney Dialysis
- Kidney Transplant
Kidney Dialysis
During Dialysis -
- Blood from an artery
- flows through a dialyser (machine)
- the dialysis fluid contains the same concentration of glucose as the blood
- contains ions and water at optimum conditions
- there is NO urea in the dialysis fluid and a greater concentration in the blood, so there is a steep concentration gradient
- the blood flows through a partially permeable membrane
- flows at a counter current
- "Clean" blood flows back into the body through a vein
Kidney Transplant
A kidney transplant enables a diseased kidney to be replaced with a healthy one from a donor.
The healthy kidney is attached to the bladder with a transplanted ureter (diagram)
As with all transplants, there is a high risk of the kidney getting rejected by the body.
This can be prevented by -
- getting a donor kidney with a tissue type similar to that of the patient
- treating the patient with immunosuppressant drugs
Advantages and Disadvantages of Transplants over D
ADVANTAGES -
- No build up of toxins/ keeps blood concentration levels consant
- Prevents high blood pressure
- No restricted diet
- No Time wasted on dialysis
- Risk of infections from dialysis
- Risk of blood clots from dialysis
- Transplants are cheaper than dialysis
DISADVANTAGES -
- Rejection
- Use of Immunosupressant drugs
- Dangers during operation
Biogenesis
The theory of biogenesis states that -
"ALL LIVING ORGANISMS PRODUCE OTHER LIVING ORGANISMS"
The theory of spontaneous generation or abiogenesis states -
"ORGANISMS COME INTO EXISTANCE FROM NON LIVING MATERIALS"
Theodor Schwaan
- His method was to expose boiled broth only to heated air in a glass tube
- The result being that no micro-organisms were detectable
- He was convinced that the idea of spontaneous generation was false
Lazzaro Spallanzani
- Believed in biogenesis
- Knew that boiling killed microbes
His experiment -
- Boiled 2 sets of broth to kill microbes
- Sealed one flask, and left the other one open in air
- Only one went off
- This showed microbes got into food from air
BUT
Some said that it only proved that spontaneous generation occurs in air
http://aportes.educ.ar/biologia/Experimentos+Spallanzani.jpg
Louis Pasteur
- Heated broth in 2 flasks, both open in air
- one has a swan neck so the microbes settle in the bend
- The broth in the swan neck stayed fresh
- The broth is the open neck didn't
This concluded that there was no "life force" in the air, and disproved spontaneous generation
Food Production - Cheese
Cheese is made using BACTERIA
- Bacteria added to milk
- Produce solid curds
- Curds separated from whey
- Enzymes can be added to speed up separation
- Add more bacteria
- Leave to ripen
- Mould/ Bacteria added to give flavour
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