1. AQA Triple Biology
September 2011

2. To explain how gas and solute exchange surfaces in humans and other organisms are adapted to maximise effectiveness.
Dissolved substances move by diffusion.
HT 􀂙 Substances are sometimes absorbed against a concentration gradient. This requires the use of energy from respiration. The process is called active transport. It enables cells to absorb ions from very dilute solutions. Other substances, such as sugar and ions, can also pass through cell membranes.

5. The Lungs
• Many organ systems are specialised for exchanging materials.
• In humans:
− the surface area of the lungs is increased by the alveoli
− and that of the small intestine by villi.
• The lungs are in the upper part of the body (thorax) protected by the ribcage and separated from the lower part of the body (abdomen) by the diaphragm.
• The breathing system takes air into and out of the body so that oxygen from the air can diffuse into the bloodstream and carbon dioxide can diffuse out of the bloodstream into the air.
• The alveoli provide a very large, moist surface, richly supplied with blood capillaries so that gases can readily diffuse into and out of the blood.
• The villi provide a large surface area with an extensive network of capillaries to absorb the products of digestion by diffusion and active transport.

9. Variable (rarely saturated) Saturated
Composition of inhaled and exhaled air
Inspired Air
Expired air
Oxygen
About 21%
About 16.4%
Carbon Dioxide
About 0.03%
About 4.0%
Nitrogen
About 78.0%
Water Vapour
Variable (rarely saturated)
Saturated
Temperature
Variable
About body temperature
Dust Particles
Variable but usually present
Little if any

14. Examiners comments

17. Plants • In plants: – carbon dioxide enters leaf cells by diffusion
– most of the water and mineral ions are absorbed by root hair cells.
The surface area of the roots is increased by root hairs and the surface area of leaves by the flattened shape and internal air spaces.
• Plants have stomata to obtain carbon dioxide from the atmosphere.
• Plants lose water vapour from the surface of their leaves. This loss of water vapour is called transpiration. Transpiration is more rapid in hot, dry and windy conditions. Most of the transpiration is through stomata. The size of stomata is controlled by guard cells which surround them. If plants lose water faster than it is replaced by the roots, the stomata can close to prevent wilting.

18. The root hair cell helps to absorb water and minerals from the soil
The root hair cell helps to absorb water and minerals from the soil. It does this by increasing the surface area of the root. It has a really thin cell wall to help the water to enter.
Plant root hair cells

21. An osmometer measures the uptake of water through the stem and out of the leaves – the environmental conditions surrounding the leaves can be changed to investigate the change in water uptake

22. Diagram cross section of a leaf

23. Plant – underside of leaf
Stoma – allows an exchange of
gases in a plant

24. Diagram of a stoma – underside of a leaf

28. Circulation system
The heart pumps blood around the body. Blood flows from the heart to the organs through arteries and returns through veins. In the organs, blood flows through capillaries. Substances needed by cells in the body tissues pass out of the blood, and substances produced by the cells pass into the blood through the walls of the capillaries.
• There are two separate circulation systems, one to the lungs and one to all the other organs of the body.
• Blood plasma transports:
− 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.
• Red blood cells transport oxygen from the lungs to the organs. Red blood cells have no nucleus. They are packed with a red pigment called haemoglobin. In the lungs haemoglobin combines with oxygen to form oxyhaemoglobin. In other organs oxyhaemoglobin splits up into haemoglobin and oxygen.

30. Red blood cells function by carrying oxygen to every part of the body, and carbon dioxide is carried back to the lungs in the plasma. Red blood cells are very well designed to perform this important job. First, they are packed full of haemoglobin, which is an iron-bearing protein that transports oxygen to other cells. Interestingly, red blood cells have no nuclei, a feature which makes even more room for haemoglobin. Red blood cells are the only cells in the body that do not have a nucleus.

31. Lungs provide oxygen and remove carbon dioxide
Get a question right
Throw the dice and
Move your counter
A red blood cell or
Plasma
As you pass the
muscle cell, either
deliver oxygen or
collect carbon
dioxide
You get a point
for every one
oxygen AND one
carbon dioxide
delivered to the
right place.
Carbon dioxide to
the lungs, oxygen
to the cells
Two per team
One is the red blood
Cell one in the
plasma 11 1 10 2
Heart double pump
Arteries 4 9 8 3 5
Muscle cells 7
Veins 66 6
Produce CO2 from respiration

37. Respiration

38. to interpret data relating to the effects of exercise on the human body
The energy that is released during respiration is used to enable muscles to contract.
• During exercise a number of changes take place:
− the heart rate increases
− rate and depth of breathing increases
− the arteries supplying the muscles dilate.

39. These changes increase the blood flow to the muscles and so increase the supply of sugar and oxygen and increase the rate of removal of carbon dioxide.
• Glycogen stores in the muscle are used during exercise.
• If muscles are subjected to long periods of vigorous activity they become fatigued, ie they stop contracting efficiently. If insufficient oxygen is reaching the muscles they use anaerobic
respiration to obtain energy.

40. Quick Questions on respiration
1. where does it occur
2+3 what are the 2 reactants
4+5 what are the 2 products
6 give one example that we have covered that it is used for
7 what is the ‘test’ for Carbon Dioxide
8 what is the ‘test’ for oxygen

41. HT 􀂙 Anaerobic respiration is the incomplete breakdown of glucose and produces lactic acid. As the breakdown of glucose is incomplete, much less energy is released than during aerobic respiration. Anaerobic respiration results in an oxygen debt that has to be repaid in order to oxidise lactic acid to carbon dioxide and water

42. Balance the respiration equation

43. Answer

46. Oxygen Debt.  This term describes how the body pays back its debt incurred above after the exercise is over.  You will notice that even after you are done racing you will continue to breath hard.  At this point your body is still trying to repay the oxygen debt that was created when you were working hard.  Technically, it is excessive post-exercise oxygen consumptio

47. Question
The table shows the units of lactic acid produced in the leg muscles of an athlete
Time
LA units
Draw a line graph of the data
When did the lactic acid reach a maximum
When would this be in a race
What happened to the Lactic acid after this
Why

48. The Kidney
to evaluate the advantages and disadvantages of treating kidney failure by dialysis or kidney transplant.
A healthy kidney produces urine by:
− first 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 as urine.

49. HT 􀂙 Sugar and dissolved ions may be actively absorbed against a concentration gradient.
• People who suffer from kidney failure may be treated either by using a kidney dialysis machine or by having a healthy kidney transplanted.
• In a dialysis machine a person’s blood flows between partially permeable membranes. The dialysis fluid contains the same concentration of useful substances as the blood. This ensures that glucose and useful mineral ions are not lost. Urea passes out from the blood into dialysis fluid. Treatment by dialysis restores the concentrations of dissolved substances in the blood to normal levels and has to be carried out at regular intervals. A kidney transplant enables a diseased kidney to be replaced with a healthy one from a donor. However, the donor kidney may be rejected by the immune system unless precautions are taken.
• To prevent rejection of the transplanted kidney:
− a donor kidney with a ‘tissue-type’ similar to that of the recipient is used
− the recipient is treated with drugs that suppress the immune system.

53. Step 1. Blood flows into the glomerulus from the renal artery
Step 2. High blood pressure in the glomerulus forces water, glucose, urea and salts through the capillary wall and into the tubule. Protein molecules and blood cells are too big so they remain in the blood.
Step 3. Blood leaves the glomerulus and flows to the capillaries that surround the renal tubule.
Step 4. The fluid called the glomerular filtrate passes along the tubule.
Step 5. All of the glucose and most of the water and salts are absorbed back into the blood in the nearby capillaries – to ensure there’s the right concentration in the blood.
Step 6. Urea and other unwanted substances stay dissolved in the glomerular filtrate. They pass down the tubule and eventually reach the bladder.
Step 7. Blood flows out of the kidney to the renal vein

55. Microbes

56. to explain how scientists such as Spallanzani, Schwann and Pasteur were involved in the development of the theory of biogenesis.
Microorganisms are used to make food and drink:
− bacteria are used in yoghurt and cheese manufacture
− yeast is used in making bread and alcoholic drinks.
• Yeast is a single-celled organism. The cells have a nucleus, cytoplasm and a membrane surrounded by a cell wall.
• Yeast can respire without oxygen (anaerobic respiration), producing carbon dioxide and ethanol (alcohol). This is called fermentation. In the presence of oxygen yeast carries out aerobic respiration and produces carbon dioxide and water. Aerobic respiration provides more energy and is necessary for the yeast to grow and reproduce.
• In brewing beer and wine-making, carbohydrates are used as an energy source for yeast to respire. For making beer:
− the starch in barley grains is broken down into a sugary solution by enzymes in the germinating grains, in a process called malting
− the sugary solution is extracted then fermented
− hops are then added to give the beer flavour.
• In wine-making the yeast uses the natural sugars in the grapes as its energy source.
• In the production of yoghurt:
− a starter of bacteria is added to warm milk

57. Lazzaro Spallanzani
After the discovery of microbes by Leeuwenhoeck Needham proposed that the primitive unicellular organism could have arisen from non-living matter. He boiled mutton gravy, filled it in corked vial and showed the appearance of minute living organisms in the gravy after a few days.
In the 18th century, Lazzaro Spallanzani contradicted Needam’s observation by conducting following experiments. He poured hay infusion In 8 bottles and boiled all of them. 4 of them were corked and other 4 were made aright. After a few days he found there was thick growth of microorganism in all the corked bottles but not in the airtight bottles. He argued that air contained micro organisms and was the source of contamination.

58. Schwann
Discovered that animals were made of cells - Yeast were single celled animals

59. Pasteur’s famous experiment

60. microorganisms

61. Yoghurt
The fermentation of milk is started by the addition of several strain of bacteria. When cultured at the right temperature that milk will become yoghurt. The two "classic" starter bacteria in yogurt are Lactobacillus bulgaricus and Streptococcus thermophilus. Almost every yogurt will contain these two although remember if the yogurt has been heat treated after manufacturer they will have been killed.

62. Cheese and microorganisms
Small cheese factories accept either morning milk (which is richer), evening milk, or both. Because it is generally purchased from small dairies which don't pasteurize, this milk contains the bacteria necessary to produce lactic acid, one of the agents that triggers curdling. The cheese makers let the milk sit until enough lactic acid has formed to begin producing the particular type of cheese they're making. Depending on the type of cheese being produced, the cheese makers may then heat the ripening milk. This process differs slightly at large cheese factories, which purchase pasteurized milk and must consequently add a culture of bacteria to produce lactic acid.

63. Bread
Bread
A yeast called Saccharomyces cerevisiae is mixed with sugar, flour and warm water to make bread. The yeast uses the sugar and the sugars present in the flour as its food. It breaks them down to provide the yeast with energy for growth. The yeast grows by budding. As it does this bubbles of the gas carbon dioxide are produced in the dough.
The bubbles make the dough expand and rise. This is because the dough is extremely sticky and it traps the bubbles, preventing them from escaping. When the dough is baked the heat kills the yeast and the dough stops expanding. 

65. Fermentation
Part of the process which microbes use to produce ENERGY when oxygen is unavailable (anaerobic) lactic acid or alcohol is a byproduct
milk products: lactose → lactic acid
sugary solutions: glucose → CO2 + EtOH

66. Beer Production 101
Barley germinated in water produces a sweet syrup, termed ‘malting’. The barley malting process lasts for forty-eight hours.
The sprouted barley grain (‘malt’) is then roasted. A longer, higher roast produces a darker, more flavorful barley, hence a darker, more flavorful beer. Conversely, a lower, shorter roast produces a less flavorful beer.
The roasted barley kernels are ground and mixed with water to form a ‘mash’. Enzymes in the grain convert the starches of the mashed grains into sugar. The sweet liquid is called a wort.
Wort is boiled and Hops are added to create a ‘hopped wort’.
5) The liquid is cooled to the right temp & yeast are added.

67. to interpret economic and environmental data relating to production of fuels by fermentation and their use
• to evaluate the advantages and disadvantages of given designs of biogas generator.
Microorganisms can be grown in large vessels called fermenters to produce useful products such as antibiotics. Industrial fermenters usually have:
− an air supply – to provide oxygen for respiration of the microorganisms
− a stirrer to keep the microorganisms in suspension and maintain an even temperature
− a water-cooled jacket to remove heat produced by the respiring microorganisms
− instruments to monitor factors such as pH and temperature.
• The antibiotic, penicillin, is made by growing the moul Penicillium, in a fermenter. The medium contains sugar and other nutrients eg a source of nitrogen. The Penicillium only starts to make penicillin after using up most of the nutrients for growth.
• The fungus Fusarium is used to make mycoprotein, a protein-rich food suitable for vegetarians. The fungus is grown on starch in aerobic conditions and the biomass is harvested and purified.
• Fuels can be made from natural products by fermentation. Biogas, mainly methane, can be produced by anaerobic fermentation of a wide range of plant products or waste material
containing carbohydrates.
• On a large scale, waste from, for example, sugar factories or sewage works can be used. On a small scale, biogas generators can be used to supply the energy needs of individual families or farms. Many different microorganisms are involved in the breakdown of materials in biogas production.
• Ethanol-based fuels can be produced by the anaerobic fermentation of sugar cane juices and from glucose derived from maize starch by the action of carbohydrase. The ethanol is
distilled from the products of the fermentation and can be used in motor vehicle fuels.
Microorganisms can be grown in a culture medium containing carbohydrates as an energy source, mineral ions, and in some cases supplementary protein and vitamins. These nutrients are often contained in an agar medium which can be poured into a Petri dish.
• In order to prepare useful products, uncontaminated cultures of microorganism are required. For this:
− Petri dishes and culture media must be sterilised before use to kill unwanted microorganisms
− inoculating loops used to transfer microorganisms to the media must be sterilised by passing them through a flame
− the lid of the Petri dish should be taped down to prevent microorganisms from the air contaminating the culture.
• In school and college laboratories, cultures should be incubated at a maximum temperature of 25 °C which greatly reduces the likelihood of pathogens growing that might be harmful to
humans. In industrial conditions higher temperatures can produce

68. Fusarium Venenatum
Fusarium venenatum, the principal ingredient of Mycoprotien is an ascomycota, one of the largest groups within the fungi family, which also includes truffles and morels. It is one of a genus of filamentous fungi, meaning it is comprised of a web of finely spun strands (hyphae).

69. Biogas generator
It works by capturing the methane gas that gets released when waste breaks down. Usually, sewage treatment plants just vent that gas into the air, but if methane gas gets captured, it can be used for things like cooking and generating electricity.

70. Microorganism fermenter
Microbes can be used by industry to mass produce certain important chemicals. Some of these, like insulin are used in medicine to treat patients. Microbes are very efficient and produce less waste than chemical means. Often a product cannot be made any other way.
The vessel itself is made from stainless steel which does not corrode or affect the microbes and fermentation products. It can also be easily cleaned. Microbes and nutrients are put into the fermenter and air is bubbled through so that the microbes can respire aerobically. As carbon dioxide builds up the gas outlet releases it to avoid build up of pressure. A water jacket surrounding the fermenter maintains an optimum temperature so the proteins do not become denatured. Temperature, pH and oxygen probes are linked to a computer which monitors the conditions inside the vessel. Paddle stirrers ensure that the microbes, nutrients and oxygen are well mixed and distributes the heat evenly. The product is run off from the bottom. It is separated from the microbes and purified so that it can be sold or distributed.

71. How biofuels are made

72. Aseptic technique achieves two things: first, it protects you from your cultures; second, it protects your cultures from you and other sources of contamination in the environment.
Inoculate a small area of the plate with a 'smear' of the bacterial suspension using a circular motion - you should brush the surface gently with the loop taking care that it does not dig into the nutrient agar.
Next, sterilise the loop by carefully heating it to red heat. By sterilising the loop you ensure that you don't carry over too many organisms from the original inoculum.