Biology 3a; Life Processes

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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.
  • 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.
  • 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.
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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.
  • 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 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.
  • Walls are one cell thick.
    • Increase rate of diffusion.
      • Decrease in distance 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.
  • 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.
  • 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.
  • 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.
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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.
    • 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.
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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.
  • 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.
  • Reabsorption;
    • Liquids flow along the nephron, and useful substances are reabsorbed into the blood.
      • All sugars (active transport).
      • Sufficient ions (active transport).
      • Sufficient water.
  • Release of Wastes;
    • Remaining substance (including urea) continue out of the nephron.
      • Into the ureter and down the bladder as urine.
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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.
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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.
  • Insulin;
    • Blood glucose level too high: insulin is added.
      • Insulin makes liver turn glucose into glycogen.
        • Glucose removed by liver.
  • Glucagon;
    • blood glucose level too low: glucagon is added.
      • glucagon makes liver turn glycogen into glucose.
        • Glucose added by liver.
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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.
  • 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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