BIOLOGY unit 3

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  • Created by: Koren
  • Created on: 02-05-13 09:17


  • Osmosis is the movement of water.
  • Just like diffusion, the movement of water molecules is random and requires no energy from the cell.
  • Osmosis is the diffusion of water across a partially permeable membrane.
  • The water moves from a region of high water concentration (a dilute solution)  to a region of low water concentration (a more concentrated solution)
  • The cell membrane is partially permeable
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Active transport

  • Cells may need to absorb substances which are in short supply, i.e. against the concetration gradient.
  • Cells use active transport to absorb substances across partially permeable  membranes against the concentration gradient.
  • Active transport requires the use of energy released in respiration
  • Cells are able to absorb ions from dilute solutions. For example, root cells absorb mineral ions from the dilute solutions in the soil by active transport.
  • Glucose can be reabsorbed in the kidney tubules by active transport
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Sports drinks

  • When you exercise , your muscles respire to release energy. Glucose, a sugar, is used in respiration.
  • After a while, your body gets hot and you sweat more to cool down. Sweat countains water and mineral ions.
  • If you sweat alot your body cells may become dehydrated.If you exercise for a long time it may be necessary to replace the sugar, mineral ions and water which have been used or lost.


  • Sports drinks are the solutions of sugar and mineral ions.
  • The water in the drinks is used to rehydrate body cells.The drinks are designed to help balance the concentration of body fliuds and the concentrations inside the cells. If the drink concentration matched the body fluids the solution is called isotonic.
  • The evidence for the benefits of sports drinks varies. Some sport scientists believe the drink will help athletes replace the mineral ions and sugar as well as water during exercise.
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The lungs

  • Large, complex, organisms have special exchange surfaces to obtain all the food and oxygen they need. Soluble food materials (solutes) are absorbed by the intestine. Oxygen is absorbed by the lungs and carbon dioxide is removed from them.
  • Effiecient exchange surfaces have a large surface area, thin walls or a short diffusion path, and an efficient transport system- the bloody supply in animals.
  • The lungs contain the gaseous exchange surface. The surface ares of the lungs is increased by the alveoli(air sacs).
  • 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 diffues into the many capillaries surrounding the alveoli and carbon dioxide diffuses back out into the lungs to be breathed out.
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Ventilating the lungs

  • The lungs contain the exchange surface of the breathing system.
  • The lungs are situated in the thorax, inside the ribcage and above the diaphragm, which separates thelungs from the abdomen.

When we breathe in:

  • The intercostal muscles between the ribs and the diaphragm contract.
  • The ribcage moves up and out and the diaphragm flattens
  • The volume of the thorax increase however the pressure decreases as air is drawn in.

When we breathe out:

  • The intercostal muscles of the ribcage and diaphragm relax .
  • The ribcages moves down and in and the diaphragm becomes domed.
  • The volume os the thorax decreases and the pressure increase as air is forced out.

The movement of air in and out of the lungs is called ventilation.

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Artificial breathing aids

There are many reasons why someone cannot get enough oxygen into their bloodstream:

  • If the alveoli are damaged, the surface area for gas exchange is reduced.
  •  If the tubes leading to the lungs are narrowed, less aire can be moved through them.
  • If the person is paralysed, their mysckes will not work to pull the ribcage up and out.

Several types of breathing aids have been developed:

  • The 'iron lung' was used for people with polio who were paralysed. The person lay their with their chest sealed in a large metal cylinder. When air was drawn out of the cylinder, the person chest moved out and they breathed in. The vacuum which was formed inside the cylinder created a negative pressure. When air was pumped back into the cylinder it created pressure on the chest and forced air out of the persons lungs.
  • Brathing aids which forced 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.
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Exchange in the gut.

  • The food we eat 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.
  • The villi are finger-like projections which greatly increase the surface area for absorption to take place.
  • The walls of the villi are very thin and there are many capillaries close to the wall.
  • The soluble products of digestion can be absorbed into the vill by either diffusion or active transport.
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Exchange in plants

Gases diffuse in and out of leaves through tiny holes called 'stomata'. the size of the stomata is controlled by guard cells. which surround them.

These gases are:

  • Oxygen: Needed for respiration and is a waste product of photosynthesis.
  • Carbon dioxide: needed for photosynthesis and is a waste product of respiration. The movement of these gases depends upon which process is takein place the most quickly. 
  • Plants are 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 interal air spaces.
  • Water and mineral ions are taken up by the roots. Root hair cells increase the surface area of the roots for the absorption of water and mineral ions.
  • If the plants lose water faster than it is replaced by the roots, the stomata can close to prevent wilting 
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When the stomata in a leaf are open, plants lose water vapour through them as well. The loss of water vapour is called evaporation. 

As water evaporates from the surface, more water is pulled up through the xylem to take its place. This constant movement of water through the xylem is called the transpiration stream. 

It is driven by the evaporation of water from the leaves, so anything that affects the rate of evaportaion will affect transpiration.

Transpiration it the loss of water vapour from the surface of the leaf. It is more rapid in hot, dry, windy, or bright conditions. 

Most leaves have a waxy, waterproof layer (the cuticle) to prevent uncontrolled water loss which can become very thick when the temperature gets hotter.

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The circulatory system & heart

  • A transport system is vital supply the needs of your body cells and remove waste material they produce.
  • The blood circulatory system has 3 parts, the pipes (blood vessels), the pump (the heart) and the blood.
  • We have a double circulation, one carries blood from your heart to your lungs and back, the other carries blood around the body and back to the heart. 
  • Fully oxygenated blood returns to the heart from the lungs, this blood can be sent of to different parts of the body at high pressure.
  • Valves in the heart prevent a backflow of blood to keep it going in the right direction through the heart.
  • Blood enters the top chambers of your heart (the atria). The blood coming into the right atrium from the vena cava is deoxygenated blood from your body.
  • The blood coming into the left atrium in the pulmonary vein is oxygenated blood from your lungs. 
  • The atria contract, which forces blood down into the ventricles.
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Keeping the blood flow

Blood is carried around your body in 3 mains types of blood vessels, each adapted for a different function by Arteries, Veins & Capillaries.

  • Your ateries  carry blood AWAY from the heart, and is usually bright red oxygenated blood. They have thick walls and a thick layer of muscle and elastic fibres as blood is forced through them and a high pressure. 
  • Your veins carry blood TOWARDS the heart, and is usually low in oxygen and so is a blue, deep purple colour. They have valves to prevent backflow as it moves back to the heart.
  • Your capillaries form a huge network linking the arteries and veins. They have one cell thick walls so diffusion can happen quicker, and are also narrow. 

Stents can be used to keep narrows or blocked arteries open.

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Transport in the blood

Your blood is a tissue that consists of a fluid called plasma. Plasma carries red and white blood cells & platelets. 

  • Your blood plasma transports dissolved food molecules, carbon dioxide and urea suspended in it. 
  • Your red blood cells carry oxygen from your lungs to the organs of your body
  • RBC are adapted to carry oxygen by being biconcave, giving a larger surface area, by containing haemoglobin and by having no nucleus so more haemoglobin can fit in.
  • White blood cells are a part of the defense system, they form antibodies against microorganisms and others digest the bacteria/viruses. 
  • Platelets are used in open wounds as they help clot the blood by forming protein threads across the wound and then forming a scab. 
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Artificial blood

Artificial blood is used when there is a shortage of blood donors if someone is in need for a blood transfusion to replace the blood lost. 

  • A form of artificial blood could be Perfluorocarbons. These are very non-reactive chemicals that carry dissolved gases around the body

Advantages of artificial blood; 

  • its always available 
  • doesn't need to be kept in the fridge
  • no blood group matching is needed

Disadvantages of artificial blood;

  • doesn't carry as much oxygen as whole blood
  • can be broken down easily in the body
  • some artificial bloods can cause unpleasant side-effects.
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Artificial hearts

Advantages of artifical hearts;

  • no need to wait for a donor as more people die before having the transplant
  • no need for a tissue match
  • no need for immunosuppressant drugs

Disadvantages of artificial hearts;

  • they are fairly large in size
  • they have problems with blood clotting which can kill the patient
  • the patient would have to stay in hospital until they have their transplant
  • the expense for the surgery and the temporary model is great
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Transport systems in plant

Phloemtransports sugars made by photosynthesis from the leaves to the rest of the plant. In the growing areas of the stems and roots the sugars here are needed to make new plant cells. Phloem is a living tissue

Xylem; transports water and mineral ions from the soil around the plant, mature xylem cells are dead

The transport of food and water is very important in a plant during photosynthesis, all the cells need sugars for respiration as well as to provide materials for growth. The mineral ions are needed for the production of proteins and other molecules within cells.

Water is needed to hold the plant upright aswell as for photosynthesis. 

When a cell has plenty of water inside it the vacuole presses the cytoplasm against the cell walls. This pressure of the cytoplasm gives support for the young plants and for the structure.

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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. 

  • Two main poisonous waste products - carbon dioxide and urea
  • Carbon dioxide is produced during respiration. Dissolved CO2 can affect the enzymes in your cells. CO2 is removed from the cells via the bloodstream to the lungs where it is breathed out.
  • If you eat more protein than you need, the extra protein has to be broken down. Amino acids cannot be used as fuel for your body. Your liver removes the amino group and converts it into urea, this is removed by your kidneys and passed out of your body in your urine.
  • Water & ion content are carefully controlled, preventing damage to your cells. Water is lost through breathing, sweating and in urine. Ions are lost in sweat and in urine also. 
  • Water balance is vital, if the concentrations of the body fluids change, water will move in and out by osmosis which could damage/destroy your cells. 
  • Homeostasis play a very important part in the body.
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The human kidney

  • Kidneys are involved with the excretion of waste products
  • You produce urea in your liver when you break down excess amino acids, urea is poisonous but your kidneys filter it out of your blood and you get rid of it in your urine, which is produced constantly by your kidneys and stored temporarily in your bladder. 
  • If you are short of water your kidney conserves it, so you produce very little urine and most of the water is saved for the use in your body.
  • If you drink too much water then your kidneys produces alot of urine to get rid of the excess in your body.
  • The ion concentration of your body is very important. You take the mineral ions with your food. If you eat food which is high in salt, the ions are lost through sweat, also through urine. As your kidneys maintains your mineral ion balance.

The kidneys filter the blood. They then reabsorbs everything back that your body needs. They have a rich blood supply. Glucose, amino acids, mineral ions, urea and water all move out of the blood into the kidney tubules. They move by a concentration gradient. Protein molecules are too big to pass through the membrane of the tubule. Glucose is reabsorbed back into the blood by active transport. The amount reabsorbed depends on what the body needs, this is selective reabsorption

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Kidneys can be damaged or destroyed by infections, or a genetic problem. When untreated, toxins, such as urea build up in the body.

  • Two methods for treating kidney failure: kidney transplant & dialysis

Dialysis via a dialysis machine is used to clean the blood. The blood leaves the body and flows through a partially permeable membranes, on the otherside of this membrane is the dialysis fluid which contains the same concentration of the useful substances as the blood.

  • Dialysis takes 8 hours to complete, and has to be repeated at regular intervals, they also have to manage their diets.
  • Arterial blood leaves the arm, goes through a blood thinner, goes into the dialysis machine where the dialysis fluid goes in and then comes out carrying waste products such as urea, it then goes through a bubble trap which returns the clean blood back to the vein in the arm.
  • There is NO active transport
  • No urea in the dialysis fluid so there is a steep concentration gradient
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Kidney Transplants

  • Diseased kidneys can be replaced by kidney transplants.
  • A new kidney can be rejected by your body because the antigens of the donors kidney would be diffferent to the recipient. The antibodies of the immune system might attack those antigens of the donor organ, this results in rejection and destruction of the donor kidney.
  • To reduce the risk of rejection, using similar tissue types can have similar antigens of the donor and the recipient
  • Immunosuppressant drugs are used to prevent the rejection of their new organ, However immunosuppressant drugs can reduce the effieciency of fighting off infections.
  • The average transplanted kidney lasts 9 years, so once this fails the patient returns back to dialysis until another suitable kidney is found.  
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ADV & DISADV of Dialysis & Kidney T


  • A-of receiving a new kidney is that you are free from restrictions
  • You can also eat what you want
  • No regular dialysis sessions
  • D-include the risk of rejection
  • Also have to take drugs for the rest of your life-immunosuppressants
  • Also may never get the chance of a kidney transplant at all


  • A-of dialysis is that it is much more readily available than donor organs
  • Also you can but dialysis machines for home instead of visiting the hospital
  • D-include following a special diet
  • You have to spend 8 hours a week on the machine which it several hours a day
  • Long term dialysis is much more expensive than a donor kidney
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Controlling body temperature

  • Your body must stay at 37 degrees celcius for enzymes to work at their best

Things that affect your internal body temperature include: energy produced in muscles during exercise, fevers caused by disease and the external temperature rising or falling.

  • Control of your core body temperature relies on the thermoregulatory centre in your brain. It contains receptors that are sensitive to temperature changes. They monitor the temperature of blood flowing through the brain.

If your temperature starts to rise, your sweat glands release more sweat, this makes you lose water and mineral ions. Your skin looks redder as more blood flows through it, cooling you down. The blood vessels in your capillaries open wider(dilate) allowing more blood flow.

If you temperature falls, you will look pale as less blood flows through, preventing you from losing energy. The blood vessels that supply your skin capillaries constrict to reduce the flow of blood, you also shiver as your muscles constrict and relax rapidly.  

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Controlling blood glucose

  • Glucose- a sugar found in the blood
  • Glycogen- a storage carbohydrate found in the liver and muscles
  • Glucagon- a hormone.
  • The pancreas is a small pink organ found under your stomach, it constantly monitors and controls your blood glucose concentration using two hormones, i.e insulin.
  • When your blood glucose concentration rises, insulin is released. It alloows glucose to move into your cell where it is used. Soluble glucose is converted glycogen (insoluble). Insulin controls the storage of glycogen in your liver. This glycogen can be converted back to glucose when its needed by glucagon.
  • If your pancreas does not make enough(or any) insulin, your blood sugar concentration is not controlled. Type 1 diabetes
  • Without insulin, glucose cannot get into your cells so you lack energy and feel tired.
  • To treat type 1, you inject insulin at certain times of the day,
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Treating diabetes

Curing type 1 diabetes

  • Pancreas transplants, though they are risky and rather difficult
  • Transplanting the pancreatic cells that make insulin from both dead or living donors.

Curing type 2 diabetes

  • Eating a balanced diet with carefully controlled amounts of carbohydrates
  • losing weight
  • doing regular exercise
  • drugs that help insulin work better
  • drugs that help your pancreas make more insulin
  • drugs that reduce the amoiunt of glucose you absorb from your gut
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  • The human population is growing rapidly and the standard of living is increasing, this is due to the better medical research which has successfully cured and prevented killer diseases. 
  • More waste is being produced, and if it is not handled properly it can pollute the water, the air and the land. 
  • The huge population drains non-renewable energy from the earth as they are being rapidly used up, such as oil & natural gas. 
  • The Increase of manufacturing & industry to produce goods has led to industrial waste.
  • The waste produced can cause serious pollution if not maintained properly.
  • Our water may be polluted by sewage, by fertilisers from farms and toxic chemicals from industrys. The air we breathe may be polluted with smoke and poisonous gases, such as sulphur dioxide.
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Land and water pollution

  • The increased population increases bodily waste and waste water from our homes (sewage) and if not treated properly the soil becomes polluted with unpleasant chemicals and gut parasites.
  • Household waste goes to landfill sites , which take up alot of room and destroy natural habitats. Toxic chemicals also spread from the waste into the soil.
  • Land can also be polluted from a side effect of farming. Weedkillers and pesticides are poisonous chemicals, which get into the soil and can end up into streams. THIS can get into foodchains and can lead to poisonous levels in the top predators.
  • Untreated sweage that is washed into the waterways or pumped out into the sea causes high levels of nitrates in the water.
  • Oxygen levels in the water fall so low that all the aquatic animals die and the pond or stream becomes dead, this is eutrophication
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Air pollution

  • When fossil fuels are burned, CO2 is released into the atmosphere as a waste product. However fossil fuels often contain sulfur impurities which react with oxygen to for sulphur dioxide gas.
  • Nitrogen oxides are released from car engines into the atmosphere
  • Sulfer dioxide & nitrogen oxides can cause serious health problems for people if the concentrations get too high. These dissolve in rainwater and react with oxygen in the air forming dilute sulfuric acid and nitric acid. Producing acid rain
  • Acid rain directly damages the environment. It can destroy whole ecosystems. It is very difficult to control as it is formed by pollution from factories. 
  • Air pollution can cause global dimming as tiny solid particles in the air which reflect away the sunlight. In developing countries, dimming continues to get worse as air pollution grows.
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Deforestation& Peat bogs

  • Deforestation is the destruction or removal of areas of forest or woodland. No trees are planted to replace the ones that've been cut down.
  • Deforestation increases the amount of CO2 released into the atmosphere. This affects the rate at which carbon dioxide is removed from the air by plants.
  • Deforestation causes a loss of biodiversity, especially in tropical rainforests, as many species have not been identified which can be used as a source for future medicines.
  • More rice fields and cattle have led to increased levels of methane in the atmosphere because rice and cattle both produce methane as they grow. Methane gas affects global warming.
  • Peat bog destruction release CO2 into the atmosphere. They are made of plant material that cannot decay completely because the conditions are very acidic and lack oxygen. Peat acts as a massive carbon store.
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Global warming

  • CO2 is removed by plants for photosynthesis and huge amounts are dissolved in the oceans, lakes and rivers . CO2 is sequestered in plants and water.
  • Increasing levels of CO2 and methane in the atmosphere give an increased greenhouse effect, leading to global warming- an increase in temperature of the surface of the earth.

Global warming can increase the overall temperature of the atmosphere. This can affect:

  • Big changes in the Earths climate- will increase in severe and unpredictable weather conditions
  • A rise in sea level- Earth warms up so glaciers melt causing flooding on low-lying shores
  • Reduced biodiversity-many organisms wont survive and will be come extinct
  • Changes in migration patterns-as the climates change, animals will move to find their most likely habitat
  • Changes in distribution-  Some animals may extend their range as climate changes conditions more favourable. 

As sea temperature rises, less CO2 can be held in the water, condensing the CO2 in the atmosphere making it worse.

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Land that has been used for deforestation can be used to grow biofuels, such as sucarcane and maize. 

These sugar-rich products are fermented anaerobically with yeast which produces ethanol and CO2, ethanol can be obtained through distillation and use it for car fuel. 

Advantages of biofuels

  • Efficient and does not produce toxic gases
  • Less polluting, especially if mixed with conventional petrol
  • It is carbon neutral, so is no overall increase in CO2.

Disadvantages of biofuels

  • Takes alot of plant material to produce ethanol
  • limited space to grow the plants
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Biogas is a flammable mixture of gases and is formed when bacteria break down waste material from animals in anaerobic conditions.

Components of biogas - Methane, CO2, Water vapour & hydrogen

In a biogas generator, bacteria decompose waste material in anaerobic conditions and produce methane, this can be used as a fuel for heating, cooking, electricity or fuel for cars.

Bacteria in a biogas production work best at 30 degrees celcius. The process releases energy(exothermic) and also the biogenerator should be well insulated to prevent energy loss.

They can be small enough to supply a single family or large enough to deal with the sewage from an entire city.

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Food Production

  • Biomass and energy are reduced at each stage of the food chain. The effieciency of food production is improved by reducing the number of stages in our food chain.

Energy is used in maintaining their body temperature and moving around. Farmers want to get the maximum possible increase in biomass from animals without feeding extra food. They do this by:

  • Limiting the movement of animals: so they dont use as much energy in moving their muscles.
  • Controlling the temperature of their surroundings: so they dont waste energy warming up or cooling down.
  • Another aspect of food efficiency is the foodmiles, as food can travel thousands of miles. This increases the release of CO2 in the atmosphere, which leads people to buying food more locally
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Sustainable food production

As the population increases, the awareness of sustainable food production increases.

It is important to maintain fish stocks at a level where breeding continues because of the increase of large fishing ships with big nets- overfishing, as certain fish are becoming dangerously low as almost all of the breeding fish have been caught.

The conserve the fish population, controlling the net sizes of the holes in the net so more fish can become free. and only the biggest fish can be caught. Aslo bans on fishing during breeding season and very strict quotas imposed on fishermen.

Mycoprotein, is protein from fungus which grows and reproduces rapidly on a relatively cheap sugar syrup in specialised containers called fermenters.


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These notes are beautiful! SNM

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