IGCSE BIOLOGY REVISION SHEETS 3 : RESPIRATION AND BREATHING (CHAPTER 3 )

Transcription

1 f) Respiration 2.33 recall that the process of respiration releases energy in living organisms the energy is stored in the form of a chemical called ATP energy from respiration is needed for all life processes describe the differences between aerobic and anaerobic respiration NB. All types use glucose and release some energy. Aerobic is the most efficient. 1. aerobic: uses and needs oxygen; 2. anaerobic: when oxygen is not available produces lactic acid 3. anaerobic respiration in bacteria / yeast is called fermentation and produces ethanol and carbon dioxide (how beer is produced) NB Why we breathe hard after strenuous exercise (the oxygen debt) 1. we can t get enough oxygen to the muscles for them to get all the energy for hard exercise just from aerobic respiration, so they use anaerobic respiration 2. anaerobic respiration produces lactic acid 3. this lactic acid can cause cramps and we need to break it down 4. lactic acid is broken down by oxygen, so we need to breathe harder until all the lactic acid is broken down (the amount of oxygen needed = the oxygen debt) 2.35 recall the word equation and the balanced chemical symbol equation for aerobic respiration in living organisms Word equation: glucose plus oxygen => carbon dioxide plus water. Symbol equation: C6H12O6 + 6O2 => 6H20 + 6CO recall the word equation for anaerobic respiration in plants and in animals anaerobic respiration in animals: fermentation in bacteria, plants, yeast: glucose => lactic acid glucose => ethanol + carbon dioxide 2.37 describe simple controlled experiments to demonstrate the evolution of carbon dioxide and heat from respiring seeds or other suitable living organisms Heat from respiration: use peas, for example, in a vacuum flask closed with cotton wool so that gases can enter and leave. The temperature will rise as the peas respire. Control: compare with peas that have been boiled and so are dead and cannot respire; Standardize: sterilise the peas so bacteria cannot grow on their surface; same amount of peas, same size vacuum flask

2 Carbon dioxide from respiration: put small organisms into a tube on a wire mesh above some hydrogencarbonate indicator, and seal the tube (put a bung in). The indicator will change from red to yellow. g) Gas exchange Control: same experiment without organisms, or using dead organisms; Standardize: same size tube / amount of indicator / temperature 2.38 understand the role of diffusion in gas exchange. in the tissues, carbon dioxide diffuses from the cells, where it is at a high concentration because it has been produced by cell respiration, into the capillaries, where it has a lower concentration. in the lungs, carbon dioxide diffuses from the blood, where it is at a high concentration, into the alveoli, where it has a lower concentration and oxygen diffuses from the alveoli, where it is at a high concentration, into the capillaries where it has a lower concentration (Remember factors in diffusion: concentration gradient, surface area and short distance e.g. capillaries are narrow so have a large surface area, and have a thin wall, so a short distance for diffusion 2.44 Breathing in humans: describe the structure of the thorax (to fill in yourself) Structure: Your notes ribs intercostal muscles diaphragm trachea bronchi bronchioles alveoli pleural membranes

3 2.45 understand the role of intercostal muscles and diaphragm, in ventilation (external) intercostal muscles inhalation contract exhalation relax diaphragm contracts and flattens relaxes and becomes tent-shaped rib cage pulled upwards and outwards moves down and inwards volume in the thorax pressure in the thorax increases decreases decreases increases air is forced into the lungs out of the lungs

4 2.46 explain how alveoli are adapted for gas exchange by diffusion between air in the lungs and blood in capillaries 1. alveoli have thin walls (short distance for diffusion) and 2. a large surface area (they are small and there are many of them) 3. capillaries are close to alveoli (short distance for diffusion) and 4. the rich blood supply maintains the concentration gradient by bringing CO2 to the lungs and removing oxygen 2.47 understand the biological consequences of smoking in relation to the lungs and the circulatory system tar in cigarette smoke sticks to and irritates bronchioles which fill up with mucus causing lung infections (bronchitis) and emphysema (enlarged air spaces and less surface area) tar also contains mutagens (see point 3.34) which cause lung cancer carbon monoxide in cigarette smoke binds to haemoglobin and prevents it from carrying oxygen; the heart needs to work harder, leading to heart disease 2.48 describe a simple experiment to investigate the effect of exercise on breathing in humans. Use a treadmill or steps; stopwatch; Measure: count the breaths at rest and immediately after exercise. Standardize: same age, sex, conditions (temperature of surroundings, time of day, size of step, length of exercise...) h) Transport 2.49 understand why simple, unicellular organisms can rely on diffusion for movement of substances in and out of the cell small organisms have a large surface area to volume ratio so diffusion is fast enough to support the organism's needs for nutrition and gas exchange for respiration 2.5 understand the need for a transport system in multicellular organisms large organisms have a lower surface area to volume ratio so diffusion is too slow to support life processes (nutrition and respiration) to support respiration the lungs provide a large surface area for gas exchange, and the circulatory system transports oxygen to the tissues and removes waste carbon dioxide

5 SPECIFICATION FOR THIS TOPIC: TICK OFF WHAT YOU HAVE DONE: f) Respiration: Students will be assessed on their ability to: 2.33 recall that the process of respiration releases energy in living organisms q 2.34 describe the differences between aerobic and anaerobic respiration q 2.35 recall the word equation and the balanced chemical symbol equation for aerobic respiration in living organisms q 2.36 recall the word equation for anaerobic respiration in plants and in animals q 2.37 describe simple controlled experiments to demonstrate the evolution of carbon dioxide and heat from respiring seeds or other suitable living organisms q g) Gas exchange: Students will be assessed on their ability to: 2.38 understand the role of diffusion in gas exchange q Humans 2.44 describe the structure of the thorax, including the ribs, intercostal muscles, diaphragm, trachea, bronchi, bronchioles, alveoli and pleural membranes q 2.45 understand the role of the intercostal muscles and the diaphragm, in ventilation q 2.46 explain how alveoli are adapted for gas exchange by diffusion between air in the lungs and blood in capillaries q 2.47 understand the biological consequences of smoking in relation to the lungs and the circulatory system q 2.48 describe a simple experiment to investigate the effect of exercise on breathing in humans q 2.49 understand why simple, unicellular organisms can rely on diffusion for movement of substances in and out of the cell q