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AQA Triple Biology. September 2011. To explain how gas and solute exchange surfaces in humans and other organisms are adapted to maximise effectiveness. Dissolved substances move by diffusion .
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AQA Triple Biology September 2011
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.
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.
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.
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
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
Plant – underside of leaf Stoma – allows an exchange of gases in a plant
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.
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.
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
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.
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.
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
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
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
Question • The table shows the units of lactic acid produced in the leg muscles of an athlete • Time 0 10 20 30 40 50 60 70 80 • LA units 0 1 7 12 9 6 3 1 1 • 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
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.
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.
