Biology Unit 3

  • Created by: YOIMO
  • Created on: 02-06-17 11:02

B3.1 exchange of materials part1

  • osmosis is the diffusion of water across a partially permeable membrane
  • active transport requires the use of energy released in respiration
  • glucose can be reabsorbed in the kidney tubules by active transport
  • sports drinks contain: water to replace water lost when sweating, sugar to replace sugar used for energy release in exercise, mineral ions to replace those lost in sweating
  • isotonic- having the same concentration of solutes as another solution
  • lungs contain a gaseous exchange surface which is increased by the alveoli
  • the alveoli have thin walls, a large surface area and a good blood supply
  • the lungs are ventilated to maintain a steep diffusion gradient
  • oxygen diffuses into the many capillaries surrounding the alveoli and carbon dioxide diffuses back out into the lungs to be breathed out
  • the lungs are situated in the thorax, inside the ribcage and above the diaphragm, which separates the lungs from the abdomen
  • when we breathe in: intercostal muscles, between the ribs and diaphragm contract, volume of thorax increases, pressure in the thorax decreases and air is drawn in
  • when we breathe out: intercostal muscles of the ribcage and diaphragm relax, ribcage moves down and in and the diaphragm becomes domed, volume of thorax decreases, pressure increases and air is forced out
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B3.1 exchange of materials part2

  • reasons for insufficient oxygen in the bloodstream: alveoli are damaged so surface area of gas exchange is reduced, tubes leading to lungs are narrowed so less air can be moved through them, if the person is paralysed then their muscles will not work to pull the ribcage up and out
  • iron lung: used for people with polio who were paralysed, chest sealed in a metal cylinder, the vacuum created a negative pressure
  • breathing aids which force measured amounts of air into the lungs use positive pressure. bags of air linked to masks can force air down the trachea
  • positive pressure aids are often smaller, easier to manage in the home and can be linked to computers for control
  • food is digested in the gut into small, soluble molecules. in the small intestine these solutes are absorbed into the blood. the villi line the inner surface of the small intestine and are the exchange surface for food molecules
  • soluble food materials (solutes) are absorbed by the intestine
  • the villi has: thin walls, capillaries close to wall, rich blood supply with steep concentration gradient, large surface area
  • the villi absorbs soluble products by either diffusion or active transport
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B3.1 exchange of materials part3

  • stomata is controlled by guard cells
  • plants lose water vapour through the stomata due to evaporation in the leaves
  • leaves are flat and very thin so the gases do not need to diffuse very far. there are also internal air spaces
  • water and mineral ions are taken up by the rootsif plants lose water faster than the it is replaced by the roots, the stomatta can close to prevent wilting
  • waxy cuticle- waterproof layer which stops water loss
  • cells not tightly packed in a leaf- have a large surface area available for gas exchange
  • inside of leaf order: upper epidermis, palisade layer, spong layer, lower epidermis
  • movement of water through a plant is called the transpiration stream
  • evaporation is faster in hot, dry, windy conditions
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B3.2 Transporting materials part1

  • the right pump forces deoxygenated blood to the lungs where it picks up oxygen and loses carbon dioxide
  • after returning to the heart, the oxygenated blood is then pumped to the rest of the body by the left pump
  • the heart as 4 chambers. the upper ones called atria where it receives blood from the vena cava on the right and pulmonary vein on the left. the atria contract to move blood into the pulmonary artery from the right side and into the aorta on the left side. valves in the heart prevent blood flowing the wrong direction. the heart muscle is supplied with oxygenated blood via the coronary arteries
  • the action of the two sides of the heart results in a double circulation
  • arteries: carry blood away from the heart, have thick walls containing muscle and elastic tissue, small lumen
  • veins: thinner walls than arteries, often have valves to prevent backflow of blood, large lumen
  • capillaries: narrow thin-walled vessels, carry blood through organs and allow the exchange of substances with all the living cells in the body, narrow lumen
  • stents are inserted to keep blood vessels open. particularly helpful when coronary arteries become narrowed due to fatty deposits which cut off blood supply to the heart muscle
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B3.2 Transporting materials part2

  • fluid plasma contains: red blood cells, white blood cells and platelets
  • blood plasma transports many substances including: carbon dioxide from the organs to the lungs, soluble products of digestion from the small intestine to other organs, urea from the liver to the kidneys where urine is made
  • red blood cells: biconcave discs with no nucleus, contain red pigment haemoglobin, the haemoglobin combines with oxygen to form oxyhaemoglobin in the lungs, the oxyhaemoglobin carries oxygen to all the organs
  • white blood cells: have a nucleus, part of the bodys defence system against microorganisms
  • platelets: small fragments of cells, do not have a nucleus, helps blood to clot at wounds
  • plasma can be given to patients in a transfusion to increase blood volume
  • artificial blood such as perfluorocarbons (PFCs) may be used which does not need to be refrigerated. it does not contain cells so blood matching is not necessary. but it's expensive, does not carry as much oxygen, some types are insoluble in water so do not mix well with blood and some can cause unpleasant side-effects
  • artificial hearts: advantages- no need for immunosuppressant drugs, do not need to match the person's tissue. disadvantages- blood clotting, long stays in hospital and expense
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B3.3 Keeping internal conditions constant part1

  • homeostasis- the maintenance of internal body conditions: temperature, blood, glucose, water & ion content and waste products
  • waste products: CO2- produced by respiration from the lungs, urea- produced in the liver from the breakdown of amino acids which is removed by the kidneys in the urine and temporarily stored in the bladder
  • urea is made in the liver
  • water and ions enter the body when we eat and drink
  • kidneys excrete substances that the body does not want
  • kidney produces urine by: filtering the blood, reabsorbing all the sugar, reabsorbing the dissolved ions needed by the body, reabsorbing as much water as the body needs, releasing urea, excess ions and water in the urine
  • urine is temporarily stored in the bladder before being removed from the body
  • the dialysis fluid contains the same concentration of useful substances that the patient's blood does eg glucose and mineral ions. this means that these substances do not diffuse out of the blood so they do not need to be reabsorbed. urea diffuses out from the blood into the dialysis fluid
  • dialysis restores the concentration of substances in the blood back to normal, but needs to be carried out at regular intervals
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B3.3 Keeping internal conditions constant part2

  • the new kidney must be a very good tissue match to avoid rejection
  • there are proteins called antigens on the surface of the cells. the recipient's antibodies may attack the antigens on the donor organ because they recognise them as being foreign
  • the recipient must take immunosuppressant drugs to suppress the immune response to prevent rejection
  • disadvantages of transplants are that the body is vulnerable to common infections as it involves suppressing the immune system
  • thermoregulatroy centre in the brain monitors the body tempreture. it has receptors which detect tempreature change in the blood
  • temperature receptors in the skin also send impulses to the brain to give information about skin temperature
  • if the core temp rises: blood vessels dilate allowing more blood flow through the capillaries where energy is transferred by radiation and the skin cools, sweat glands produce more sweat which is evaporated from our skin
  • if the core temp falls: blood vessels constrict allowing less blood flow through the capillaries and less energy is radiated, we shiver where our muscles contract quickly which requires respiration and some of the energy released warms the blood
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B3.3 Keeping internal conditions constant part3

  • doctors considerations for kidney transplants: general health, length of time on dialysis, total cost of treatment, risks eg anaesthetics, availability of donors
  • ethical issues: should everyone be on the transplant register, should people be paid to be donors, should people pay to jump the queue
  • pancreas monitors and controls the level of glucose in the blood
  • if there is too much glucose in our blood then we produce the hormone insulin
  • insulin causes the glucose to move from the blood into the cells
  • in the liver, excess glucose is converted into glycogen for storage
  • if not enough insulin is produced than the blood glucose level may become very high AKA type 1 diabetes
  • glucagon causes glycogen to change to glucose which goes back into the blood when blood glucose levels are too low
  • type 1 diabetes are treated with human insulin produced by genetically engineered bacteria
  • ways to cure type 1: pancreas transplants, transplanting pancreas cells, using embryonic stem cells to produce insulin secreting cells, adult stem cells from diabetic patients, genetically engineering pancreas cells
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B3.4 How humans can affect the environment part1

  • sewage must be treated properly to remove gut parasites and toxic chemicals or these can get onto the land
  • fertilisers and untreated sewage can cause a high level of nitrates in the water
  • acid rain can change the soil pH which damages roots and may release toxic minerals. for example, aluminium ions are released which also damages organisms in the soil and in waterways
  • carbon dioxide is sequestered by plants and water as it dissolves in oceans, rivers, lakes and ponds
  • two types of biofuel: biogas and ethanol-based fuels
  • ethanol-based fuels can be produced by fermentation
  • microorganisms respire anaerobically to produce the ethanol, using sugars from crops as the energy source
  • glucose is produced from maize starch by the action of a carbohydrase
  • the glucose and sugar cane juices can be fermented by yeast to produce ethanol
  • the ethanol is extracted by the process of distillation and can then be used as a fuel in motor vehicles
  • ethanol is described as carbon neutral
  • biogas is produced by fermentation and the bacteria respire anaerobically using waste carbohydrate
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B3.4 How humans can affect the environment part2

  • mycoprotein: protein-rich food suitable for vegetarians, grown from fungus (Fusarium), grown aerobically on cheap sugar syrup made from waste starch and the mycoprotein harvested
  • microorganisms grow on a large scale in industrial fermenters
  • industrial fermenters are large vessels which have: air supply providing oxygen for respiration, stirrers to keep organisms spread out to provide an even temperature, a water-cooled jacket around the outside as the respiring microorganisms release energy which heats the contents, sensors to monitor both pH and temperature
  • Xylem- water and mineral ions from the roots to the stem, leaves and flowers
  • phloem- dissolved sugars from the leaves to the rest of the plant, including growing regions
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