Biology 3a; Life Processes
All of the notes needed for the AQA exam board Topic 3a for Biology.
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- Created by: Jess Christian
- Created on: 23-03-13 17:12
Osmosis.
- Define; movement of water molecules through a partially permeable membrane from high concentration to low concentration.
- Partially permeable; membrane with holes that only tiny molecules can pass through, such as water.
- Molecules can pass both ways during osmosis.
- Steady net flow of molecules into the low concentration area.
- Is a type of diffusion.
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Osmosis Within the Body.
- Tissue fluid surrounds body's cells.
- Oxygen and glucose dissolved in water.
- It is taken from blood capillaries to supply cells with everything they need.
- Tissue fluid has a different concentration to fluid inside of cells.
- Water will move into cell from tissue, or out of cell into tissue, by osmosis.
- If cell is short of water, solution will become concentrated.
- Tissue fliud is more dilute, so water will move into the cell.
- If the cell has lot of water, tissue fluid will be more concentrated, so water goes into tissue.
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Gas and Solute Exchange.
- Life processes need gases or other dissolved substances before they can happen.
- Waste substances need to move out of cells.
- These happen by osmosis, diffusion or active transport.
- Substances must move through an 'exchange surface'.
- These are adapted for effectiveness;
- Thin; short distance to diffuse.
- Large surface area; lots can diffuse at once.
- Lots of blood vessels; get in and out of the body quickly.
- Ventilated; air moves in and out .
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Structure of Leaves.
- Carbone dioxide diffuses into air spaces within the leaf.
- Then diffuses into the cells where photosynthesis happens.
- Underneath of the leaf is an exchange surface.
- Covered in stomata which the CO2 diffuses into.
- Oxygen and water vapour diffuse out via the stomata.
- The size of the stomata is controlled by guard cells.
- Close if the plant is losing water faster than it is being replaced by the roots.
- Flattened shape of the leaf increases the area of exchnage surface.
- Walls of the cells inside the leaf form another exchange surface.
- Air spaces within the leaf increase surface area.
- Water vapour evaporates from the cells -> escapes by diffusion.
- Evaporation is quickest in hot, dry, windy conditions.
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The Breathing System.
- Thorax; top part of your body.
- Abdomen; bottom part of your body
- Seperated by your diaphragm.
- Air that is breathed in goes through the trachea.
- This splits into two tubes- bronchi.
- One goes to each lung.
- Bronchi split into smaller tubes- bronchioles.
- Bronchioles go to small bags- alveoli- where gas exchange takes place.
- Breathing in;
- Intercostal muscles and diaphragm contract.
- Thorax volume increases.
- Pressure decreases- air drawn in.
- Breathing out;
- Intercostal muscles and diaphragm relax.
- Thorax volume decreases.
- Increase in pressure- air forced out.
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Artificial Ventilators.
- Ventilators; machines that move air into and out of the lungs.
- Used for people who;
- Are under general anaesthetic.
- Have lung injuries.
- Have a lung disease.
- Old methods were 'iron lung', a giant case that covered the patients whole body.
- Air was pumped out of the case, pressure dropped, lungs expanded, air was drawn into the lungs.
- Air pumped into the case, forcing air out of the lungs.
- This could interfere with blood flow to the lower body.
- Modern ventilators expands and relaxes the ribcage.
- This doesn't interfere with blood flow.
- Occasionally cause damage to lungs, if they can't cope with the artificial air flow.
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Diffusion Through Cell Membranes.
- Lungs.
- Job of the lungs; transfer oxygen to the blood and remove CO2.
- Air sacs called alveoli is where gas exchange takes place.
- Specialised to maximise diffusion;
- Large surface area; 75m in humans.
- Moist lining; dissolving gases.
- Very thin walls.
- Good blood supply.
- Small intestine.
- Inside of the small intestine is covered in millions of projections called villi.
- They increase the surface area.
- Digested food is absorbed quickly into the blood.
- They have;
- Single layer of surface cells.
- Good blood supply to assist quick absorption.
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Active Transport in Root Hairs.
- Cells on the surface of plant roots grow into long 'hairs' that stick into the soil.
- Gives a large surface area for absorbing water and mineral ions from the soil.
- Most water and mineral ions that get into a plant are via root hair cells.
- Gives a large surface area for absorbing water and mineral ions from the soil.
- Concentration of minerals is higher in the root hair cell than in the soil around it.
- Normal diffusion doesn't explain how minerals are taken up into the root hair cell.
- They should go the other way if they followed the rule of diffusion.
- Active transportation allows the plant absorb minerals from a very dilute solution.
- Against concentration gradient.
- It needs energy from respiration to make it work.
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Active Transport in the Gut.
- Low concentration of nutrients in the gut, but a high concentration in the blood.
- Sometimes there is a higher concentration of glucose and amino acids in the gut.
- They diffuse naturally into the blood.
- Sometimes there's a lower concentration of nutrients in the gut than in the blood.
- The concentration gradient is the wrong way.
- Active transport allows nutrients to get into the blood supply.
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Water Flow Through Plants.
- Phloem Tubes; transport food.
- Columns of living cells with holes at each end.
- Transport food substances- dissolved sugars.
- Made in leaves, taken to growing regions or storage organs- new shoots, root tubers.
- Transport in both directions.
- Xylem Tubes; take water up.
- A hollow tube made of dead cells joined end to end with no end walls.
- Carry water and minerals from roots to stem and leaves in the transpiration stream.
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Transpiration.
- Transpiration is caused by the evaporation and diffusion of water from inside the leaves.
- This makes slight shortage of water within the leaf.
- Water is drawn from the rest of the plant through the xylem vessels.
- More water is then drawn up from the roots.
- There is constant tanspiration stream of water through the plant.
- Water is drawn from the rest of the plant through the xylem vessels.
- Transpiration is a side-effect of the ways are adapted for photosynthesis.
- They have stomata in them so that gases can be exchanged easily.
- There is more water inside the plant than in the air outside.
- Water escapes from the leaves through the stomata.
- They have stomata in them so that gases can be exchanged easily.
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Circulatory System; The Heart.
- We have a double circulatory system; two circuits joined together.
- The first pumps deoxygenated blood to the lungs to get oxygen.
- Then returns to the heart.
- The second pumps oxygenated blood around all other organs.
- Gives oxygen to body cells and the deoxygenated blood returns to the heart.
- The first pumps deoxygenated blood to the lungs to get oxygen.
- Walls of the heart are made from muscle tissue.
- It has valves to make sure the blood flows the right way.
- Prevents it flowing backwards.
- Has four chambers
- Right atrium.
- Right ventricle.
- Left atrium.
- Left ventricle.
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How the Heart Works.
- Blood flows into the two atria via the vena cava and pulmonary vein.
- Atria contract.
- Blood pushed into ventricles.
- Ventricles contract.
- Blood pushed into pulmonary artery and aorta.
- Out of the heart.
- Blood pushed into pulmonary artery and aorta.
- Blood flows to the organs through arteries.
- Returns to heart heart via veins.
- Atria fill again.
- Cycle restarts.
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Circulatory System; Blood Vessels; Arteries.
- Arteries;
- Carry blood away from the heart. (blue)
- Heart pumps at high pressure.
- Artery walls are strong and elastic.
- Walls are thick compared to size of hole down the middle (lumen).
- Contain thick layers of muscle.
- Makes them strong.
- Have elastic fibres.
- Allow for them to stretch and spring back.
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Circulatory System; Blood Vessels; Capillaries.
- Capillaries;
- Exchange of materials at the tissues.
- Branch off of arteries.
- Very small
- Too small to see.
- Carry blood close to every cell.
- Able to exchange substances with them.
- Permeable walls.
- Substances diffuse in and out.
- Supply food and oxygen.
- Take away waste; CO2.
- Substances diffuse in and out.
- Walls are one cell thick.
- Increase rate of diffusion.
- Decrease in distance of diffusion.
- Increase rate of diffusion.
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Circulatory System; Blood Vessels; Veins.
- Veins;
- Carry blood to the heart. (red)
- Capillaries join up to make veins.
- Blood is at lower pressure in veins.
- Walls don't need to be as thick as artery walls.
- Bigger lumen than arteries.
- Help blood flow despite the lower pressure.
- Have valves.
- Makes blood flow inthe right direction.
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Circulatory System; Blood; Blood Cells.
- Red Blood Cells.
- Carry oxygen from the lungs to all other cells in the body.
- Doughnut shape.
- Give large surface area for absorbing oxygen.
- Don't have a nucleus.
- More room for carrying oxygen.
- Red pigment; haemoglobin.
- In the lungs, it combines with oxygen to become oxyhaemoglobin.
- The reverse happens in body tissue.
- Oxyhaemoglobin splits up to release oxygen into the cells.
- White Blood Cells.
- Change shape to eat unwelcome microorganisms.
- Produce anitbodies to fight microorganism.
- Also antitoxins to neuteralise any toxins produced by microorganisms.
- They do have a nucleus.
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Circulatory System; Blood; Platelets and Plasma.
-
- Small fragments of cells that have no nucles.
- Help clot the blood at a wound.
- Stops blood pouring out.
-
- Stops microorganisms getting in
- Lack of platelets can cause excessive bleeding and bruising.
- Platelets.
- Plasma.
- Carries everything around.
- Red and white blood cells.
- Platelets.
- Nutrients.
- Glucose and amino acids.
- Carbon dioxide (from organs to lungs).
- Urea (from liver to kidneys).
- Hormones.
- Antibodies and antitoxins.
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Circulation Aids; Artificial Blood.
- When someone loses excessive blood, their heart continues to pump the red blood cells.
- This only happens as long as the volume of blood can be topped up.
- Artificial blood is a substitute.
- A salt solution - saline - is usually used.
- It is safe and can keep peopl alive if they have used 2/3 of their red blood cells.
- This gives them enough time to produce new red blood cells.
- If not they need a blood transfusion.
- A salt solution - saline - is usually used.
- Ideally, artificial blood would replace the function of red blood cells.
- Theses are being developed, but currently have side- effects.
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Circulation Aids; The Heart.
- Artificial hearts are mechanical devices that replace the heart if it cannot work.
- They are temporary until a donor heart can be found.
- Advantage.
- Cannot be rejected by the body's immune system.
- As they are metal/ plastic, the body does not see them as a danger.
- Cannot be rejected by the body's immune system.
- Disadvantages.
- Surgery can lead to bleeding and infection.
- They do not work as well as natural hearts.
- The artificial heart could wear out or the electrical motor could fail.
- Blood doesn't flow through them as smoothly.
- Could casue blood clots and lead to strokes.
- Patients have to take drugs to thin their blood so this doesn't happen.
- This causes problems with bleeding if they are in an accident.
- If just the heart valves don't work, these can be replaced with mechanical ones.
- Replacing a valve is a less drastic procedure.
- Still have problems with blood clots.
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Circulation Aids; Stents.
- Coronary Heart Disease; arteries that supply the heart with blood get blockeed with fat.
- Causes arteries to become narrow.
- Blood flow restricted.
- Result can be a heart attack.
- Causes arteries to become narrow.
- Stents; tubes inserted inside of arteries to keep them open.
- Makes sure blood can pass through to the heart.
- Lower the risk of heart attacks in people with coronary heart disease.
- The artery can narrow again as the artery gets irritated and scar tissue grows.
- The patient has to take drugs to stop blood clotting on the stent.
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Homeostasis; What is Controlled.
- Homeostasis; the maintenance of a constant internal environment.
- Body Temperature;
- Can't get too hot or cold.
- Water content;
-
- If there is too much water, it might move into/ out of the cells and damage them.
- Ion Content;
- The same happens as with water content.
- Blood Sugar Level;
- Needs to stay within certain limit.
- Carbon Dioxide;
- Product of respiration.
- Toxic in high quantities so must be removed.
- Urea;
- Waste product made from excess amino acids.
- Body Temperature;
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Homeostasis; Body Temperature.
- Enzymes work best at a certain temperature- 37'C in humans.
- If too hot or cold, they won't work properly.
- Thermoregulatory centre within your brain acts as a thermostat.
- Contains receptors that are sensitive to the temperature of blood within the brain.
- Receives impulses from the skin, giving skin temperature.
- Hot (to cool you down);
- Hairs lie flat.
- Sweat is produced and evaporates from the skin.
- Blood vessels dilate so more blood flows close to the surface of the skin.
- Heat is transferred from the blood to the environment.
- Cold (to warm you up);
- Hairs stand up to trap an insulation layer of air.
- No sweat is produced.
- Blood vessels constrict to close off the skin's blood supply.
- You shiver (muscles contract).
- This needs respiration, which releases energy to warm up your body.
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Homeostasis; Kidneys; Removal of Urea.
- Removal of Urea;
- Proteins can't be stored.
- Excess amino aicds are turned into fats and carbohydrates.
- These can be stored.
- Excess amino aicds are turned into fats and carbohydrates.
- This happens in the liver.
- Urea is the waste product of it.
- Urea is released in the bloodstream by the liver.
- It is poisonous.
- The kidneys filter it out. .
- It's temporarily stored in the bladder in urine, then excreted.
- Proteins can't be stored.
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Homeostasis; Kidneys; Adjustment of Ion Content.
- Ions - such as sodium - are taken into the body by food.
- These are then absorbed into the blood.
- If the ion content is wrong, it would upset the balance between water and ions.
- Too much/ little water would bee drawn into the cells by osmosis.
- Would damage the cells.
- Too much/ little water would bee drawn into the cells by osmosis.
- Excess ions are removed by the kidneys.
- Some ions are also lost in sweat.
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Homeostasis; Kidneys; Adjustment of Water Content.
- Water is taken into the body as food and drink.
- It is then lost as;
- Urine.
- Sweat.
- Air we breathe out.
- The body has to constantly balance the water going out and coming in.
- Water balance is between;
- Liquids consumed.
- Amount sweated out.
- Amount excreted by the kidneys as urine.
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Kidney Function.
- Ultrafiltration;
- High pressure builds up, which squeezes water, urea, ions and sugar out of blood.
- Goes into Bowman's capsule.
- Membranes bewteen blood vessles and Bowman's capsule act as filters.
- Big molecules - proteins and blood cells - are kept in the blood.
- High pressure builds up, which squeezes water, urea, ions and sugar out of blood.
- Reabsorption;
- Liquids flow along the nephron, and useful substances are reabsorbed into the blood.
- All sugars (active transport).
- Sufficient ions (active transport).
- Sufficient water.
- Liquids flow along the nephron, and useful substances are reabsorbed into the blood.
- Release of Wastes;
- Remaining substance (including urea) continue out of the nephron.
- Into the ureter and down the bladder as urine.
- Remaining substance (including urea) continue out of the nephron.
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Kidney Failure; Dialysis.
- If they don't work properly, waste builds up in the blood and the ability to control ion and water levels is gone.
- This can be helped with dialysis treatment;
- Has to be done regulary.
- In a dialysis machine, blood flows along a selectively permeable barrier.
- this is surrounded in dialysis fluid.
- It is permeable to ions and waste substances, but not big molecules- proteins.
- Dialysis fluid has same concentration of ions and glucose as blood.
- Only waste substances- urea - and excess ions and water diffuse across the barrier.
- Patients have dialysis three times a week.
- Each session is three to four hours.
- May cause blood clots or infections.
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Kidney Failure; Transplants.
- Kidney transplant is currently the only cure for kidney failure.
- Kidneys can be transplanted from both dead and living people.
- Donor kidneys can be rejected by the patient's immune system.
- Foreign anitgens on the kidney are attacked by the patient's antibodies.
- Precautions are taken to stop this;
- Donor and patients are matched if they have similar tissue types.
- Tissue type is based on antigens- proteins on the surface of cells.
- Patient is given drugs to suppress the immune system.
- Immune system won't attack the kidney.
- Donor and patients are matched if they have similar tissue types.
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Controlling Blood Glucose.
- Glucose - a type of sugar - comes from eating carbohydrates.
- Goes from the gut into the blood.
- Normal metabolism of cells removes glucose from the blood.
- Exercise removes much more glucose from the blood.
- Glucose levels in the blood must be kept steady.
- Monitored and controlled by the pancreas.
- Uses hormones - insulin and glucagon.
- Monitored and controlled by the pancreas.
- Insulin;
- Blood glucose level too high: insulin is added.
- Insulin makes liver turn glucose into glycogen.
- Glucose removed by liver.
- Insulin makes liver turn glucose into glycogen.
- Blood glucose level too high: insulin is added.
- Glucagon;
- blood glucose level too low: glucagon is added.
- glucagon makes liver turn glycogen into glucose.
- Glucose added by liver.
- glucagon makes liver turn glycogen into glucose.
- blood glucose level too low: glucagon is added.
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Type 1 Diabetes.
- Type 1 Diabetes; caused by pancreas producing little or no insulin.
- Person's blood glucose can rise to a level that could kill them.
- Can be controlled by;
- Avoiding foods rich in carbohydrates.
- Exercise after eating to use up extra glucose.
- Injecting insulin into the blood at mealtimes.
- Liver will remove glucose as soon as it enters the blood.
- Amount injected depends on person's diet and how active they are.
- Made by genetic engineering.
- Can't control as accurately as the pancreas- still long-term health problems.
- Avoiding foods rich in carbohydrates.
- Can have pancreas transplant.
- Could be rejected by the body.
- Have to take costly immunosuppressive drugs.
- May have serious side- effects.
- There is research being done into artificial pancreases and stem cell research.
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