Biology Uint 3 GCSE

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  • Created on: 10-04-13 17:11
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  • Biology Unit 3
    • Exchange of Materials
      • Osmosis
        • Osmosis is a special case of diffusion.
          • The dissolved substance is the solute and the thing it is dissolved into is the solvent.
        • Osmosis ia the diffusion/ movement of water from a dilute to a more concentrated solution through a partially permeable membrane that allows water to pass through it.
        • Differences in the concentration of solutions inside and outside a cell can cause it to move into or out of the cell by osmosis.
        • The cytoplasm of the cell is water with dissolved chemicals.
        • The cell could burst or dry out if osmosis happens too drastically.
        • Gives plants rigidity or makes them wilt.
      • Active Transport
        • Substances are sometimes absorbed against a concentration gradient by active transport.
        • Active transport uses energy from respiration.
          • A useful molecule is moved by a transport protein which is able to rotate using energy from active transport.
        • Cells can absorb ions from very dilute solutions, and actively absorb substances such as sugar and salt against a concentration gradient using active transport.
          • Sugars are  transported out of the blood and kidney.
        • Cells involved need a lot of mitochondria.
      • The Sports Drink Dilemma
        • Most soft drinks contain water, sugar and mineral ions.
        • Sports drinks contain sugars to replace the sugar used in energy release during activity. They also contain water and ions to replace the water and mineral ions lost during sweating.
          • Claim to aid hydration of the tissues, help replace lost energy and replace lost electrolytes (the mineral ions you lose when you sweat).
        • Evidence suggests that for normal levels of exercise water is at least as effective as a sports drink.
      • Exchanging Materials - The Lungs
        • Certain features such as a large surface area, short diffusion paths and steep concentration gradients increase the effectiveness of an exchange surface.
        • The alveoli are the air sacs in the lungs.
        • The lungs are adapted to make gaseous exchange as efficient as possible. They have many alveoli, which provide a large surface area with a good blood supply and short diffusion distances. The lungs are ventilated to maintain  steep diffusion gradients.
        • As  organisms get bigger, their SA to V ratio gets smaller and this causes diffusion to become more difficult.
      • Ventilating the Lungs
        • The lungs are in your thorax protected by your ribcage and separated from your abdomen by the diaphragm.
          • The job of the breathing system is to move air in and out of the lungs.
        • The intercostal muscles contract to move your ribs up and out and flatten the diaphragm, increasing the volume of your thorax. The pressure decreases and air moves in.
        • The intercostal muscles relax and the ribs move down and in, and the diaphragm domes up, decreasing the volume of your thorax. The pressure increases and air is forced out.
        • Lungs maintain a steep concentration gradient.
      • Artificial Breathing Aids
        • Different types of artificial breathing aids have been developed over the years to help people when their lungs or breathing systems don't function properly.
        • The different methods have advantages and disadvantages.
          • The iron lung is based on a negative pressure system where the patient lies in a vacuum which lets air into and out of it therefore forces the person to inhale and exhale.
          • The positive pressure breathing system pushes air into the lungs.
      • Exchange in the Gut
        • The villi in the small intestine provide a large surface area with an extensive network of blood capillaries.
        • This makes the villi well adapted to absorb the products of digestion by diffusion and active transport.
        • Need the products of digestion to provide fuel for respiration and growth and repair.
      • Transpiration
        • The loss of water vapour from the surface of plant leaves is known as transpiration.
        • Water is lost through the stomata, which are opened and closed to let in carbon dioxide for photosynthesis.
        • Transpiration is more rapid in hot, dry, windy or bright conditions.
    • Transporting Materials
      • The circulatory system and the heart.
        • The circulation system consists of the blood vessels, the heart and the blood.
          • Arteries carry blood away from your heart and blood returns to your heart in the veins.
          • In the heart, the blood eneters the atria from the vena cava (right), to the lungs, is oxygenated and reenters through the pulmonary vein into the left atrium and exits in the aorta (large artery).
        • Human beings have a double circulation.
          • One carries blood from your heart to your lungs and back which allows oxygen and carbon dioxide to be exchanged with the air in the lungs.
          • The other carries blood around the rest of your body and back again to the heart.
          • Makes system very efficient.
        • The heart is an organ that pumps blood around the body.
          • 2 pumps beat at around 70 bpm
            • The pumping happens at the same time to increase the strength.
          • The walls of the heart are almost entirely muscle. This muscle is supplied with oxygen via the coronary arteries.
        • The valves make sure blood flows in the right direction through the heart.
      • Keeping the blood flowing
        • The main types of blood vessels are arteries, veins and capillaries.
        • Substances diffuse in and out of the blood in the capillaries.
        • Stents can be used to keep narrowed or blocked arteries open.
        • Damaged heart valves can be replaced.
          • Biological valves
            • Patient does not need any medication although only lasts 15 years. Taken from pigs or cows.
          • Mechanical valves
            • Made with titanium or polymers. Last for a long time although medication is needed to be taken to stop blood from clotting.
        • Veins do not have a pulse.
      • Transport in the blood
        • Your blood plasma transports dissolved food molecules, carbon dioxide and urea and has the blood cells suspended in it.
          • Urea is a waste product formed in your liver from the breakdown of proteins.
        • Your red blood cells carry oxygen from your lungs to the organs of the body.
        • Red blood cells are adapted to carry oxygen by being biconcave, giving them a bigger surface area and having no nucleus so more haemoglobin can fit on.
          • Need a big SA for the diffusion of oxygen.
          • Oxygen + Haemoglobin ->-< Oxyhaemoglobin.
        • White blood cells are part of the defence system of the body.
          • Some form antibodies. Others digest invading bacteria and viruses.
        • Platelets are cell fragments involved in the clotting of the blood.
          • They help produce a network of protein threads. They capture lots of red blood cells.
      • Artificial or real?
        • Artificial blood is a solution which can be used to replace real blood that is lost.
        • The advantages of artificial blood: it is always available; it doesn't always need to be kept in a fridge; it doesn't contain cells so it can get into any tissue and no blood group matching is needed.
          • The disadvantages:it is expensive; it doesn't carry as much oxygen as whole blood; some artificial blood does not dissovle in water so doesn't mix easily with the blood; most artificial bloods are broken down very quickly in the body; some artificial bloods can cause unpleasant side-effects.
        • The disadvantages:it is expensive; it doesn't carry as much oxygen as whole blood; some artificial blood does not dissovle in water so doesn't mix easily with the blood; most artificial bloods are broken down very quickly in the body; some artificial bloods can cause unpleasant side-effects.
        • Advantages of artificial hearts: no wait for a donor; no need to match tissue; no need for immunosuppressant drugs.
          • Disadvantage: size; problems with blood clotting; until recently always involved staying in hospital; expensive.
        • Disadvantage: size; problems with blood clotting; until recently always involved staying in hospital; expensive.
        • Saline is sometimes out into the body if blood is lost, even though it doesn't transport oxygen or food however keeps the blood at a relatively normal blood pressure.
          • Per-fluorocarbons - more sophisticated form of artificial blood. Haemoglobin based artificial blood only lasts for 20-30 hours.
        • Transport systems in plants
          • Flowering plants have separate transport systems.
          • Xylem tissue transports water and mineral ions from the roots to the stems and leaves.
          • Phloem tissue transports dissolved sugars from the leaves to the rest of the plant, including the growing regions and storage organs.
            • Greenfly and other aphids are plant pests. They stick their sharp mouthparts into the phloem and feed on the sugary fluids.
              • Kill it by taking all of the food.
          • Transport is so important because the cells need sugars for respiration and mineral ions are needed for the production of proteins and other molecules within the cells. The water is needed for photosynthesis and to hold the plant upright.
      • Keeping internal conditions constant
        • Controlling internal conditions
          • The internal conditions of your body have to be controlled to maintain a constant internal environment. These include your body temperature, your water and ion balance and your blood sugar levels.
            • Called homeostasis.
          • Carbon dioxide is produced during respiration and leaves the body via the lungs when you breathe out.
            • Carbon dioxide needs to be removed otherwise it dissolves and produces an acidic solution which stops the enzymes working properly.
          • Urea is produced by your liver as excess amino acids are broken down, and is removed by your kidneys in the urine.
        • The Human Kidney.
          • The kidneys are important for excretion and homeostatis.
          • A healthy kidney produces urine by filtering the blood. It then reabsorbs all of the sugar, plus any mineral ions and water needed by your body.
            • It filters urea out of the blood.
          • Excess mineral ions and water along with urea, are removed in the urine.
            • If you drink a lot of water of eat a lot  of mineral ions (like salt) there is more that needs to be removed from the body.
          • The kidneys filter the blood  by having a rich blood supply and reabsorb the things the body needs by reabsorption. The glucose, amino acids, mineral ions, urea and water are filtered out into the kidney tubules. The larger molecules such as proteins and blood cells do not filter out.
            • All the sugar is reabsorbed through active transport however the amount of water and mineral ions reabsorbed varies depending in a very sensitive feedback mechanism. Known as selective reabsorption.
            • Some urea moves back into the blood by diffusion along the concentration gradient.
        • Dialysis - an artificial kidney.
          • People suffering from kidney failure may be treated by regular sessions on a kidney dialysis machine or by having a kidney transplant.
          • In a dialysis machine, the concentration of dissolved substances in the blood is restored to normal levels.
            • There  are blood thinners in the machine which prevent the blood from clotting. It also has two partially permeable membranes.
          • The levels of useful substances in the blood are maintained, while urea and excess mineral ions pass out from the blood into the dialysis fluid.
            • In a dialysis machine, the concentration of dissolved substances in the blood is restored to normal levels.
              • There  are blood thinners in the machine which prevent the blood from clotting. It also has two partially permeable membranes.
            • The dialysis fluid is in the same composition as the blood however does not contain any urea so the urea leaves the blood by diffusion as does salt.
        • Kidney Transplants.
          • In a kidney transplant, diseased or damages kidneys are replaced with a healthy kidney from a donor.
            • Joined at the groin. Lasts for about 9 years,
          • To try and prevent rejection of the donor kidney, the tissue types of the donor and the recipient are matched as closely as possible. Immunosuppressant drugs are also used.
            • The antigens (proteins on the cell surface) are different. The antibodies will attack the antigens.
            • Immunosuppressant drugs are meaning that getting a really close tissue match is getting less important however they prevent patients from dealing effectively with infectious disease.
        • Controlling body temperature
          • Your body temperature is monitored and controlled by the thermoregulatiry centre in your brain.
          • Your body temperature must be kept at the level at which enzymes work best.
          • Your body responds to cool you down or warm you up if your core body temperature changes.
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