4 - Respiration and Gas Exchange Flashcards
What is respiration?
The process of releasing energy from glucose which happens constantly in every living cell
Energy is released as chemical energy and heat
What is aerobic respiration?
Respiration when there is oxygen available
Glucose + oxygen —> carbon dioxide + water (+ energy)
C6H12O6 + 6O2 —> 6CO2 + 6H2O
What is anaerobic respiration?
Respiration without oxygen
Not the best way to respire as not as much energy is made
Happens during vigorous exercise
Glucose —> lactic acid (+ energy)
The lactic acid can lead to muscle cramps in the body
What is anaerobic respiration in plants?
When plants respire without oxygen
Glucose —> ethanol + carbon dioxide (+ energy)
Describe an experiment to detect the carbon dioxide produced in respiration
- Soak dried beans in water for a day so they begin to germinate (they will respire)
- Boil a similar sized second batch of dried beans
- This kills the beans so they cannot respire (the control)
- Put hydrogen-carbonate indicator into two test tubes
- Place a gauze platform into each test tube to put the beans on
- Seal with a rubber bung
- Leave for an hour
- The CO2 produced will then the indicator from orange to yellow
Describe an experiment to show the heat produced by respiration
- Prepare two sets of beans (one dried and one boiled)
- Add each set to a vacuum flask with a little air at the too (so they respire anaerobically)
- Put a thermometer into each flask and deal with cotton wool
- Record the temperatures daily for a week
- The beans are well-insulated in the flasks so when the germinating seeds respire the flask’s temperature will Rose
How do plants exchange gas?
By diffusion from the environment into the leaf
What does the net exchange of has depend on?
Light intensity
- Plants photosynthesise in light so diffuse CO2 and O2 in and out constantly
- At night there is no photosynthesis so the plant does not release oxygen (it is only taken in) and release only carbon dioxide
How are leaves adapted for gas exchange?
- Broad so large surface area for diffusion
- Thin so less distance to travel
- Air spaces to let CO2 and O2 move easily between cells as well as increasing the surface area for has exchange
- Stomata allow CO2 and O2 diffuse in and out and let’s water escape
- Stomata close at dark so no water is lost
- Stomata will close when there is little water left in the roots (stops the plant from photosynthesising but keeps it alive)
- The opening and closing of stomata are controlled by the guard cells
What does hydrogen-carbonate show?
- Carbon dioxide concentration
- Orange = normal concentration
- Yellow = increased concentration
- Purple = decreased concentration
Describe an experiment to show the difference in net gas exchange in plants
- Add the same volume of hydrogen-carbonate indicator to four boiling tubes
- Put similar leaves into three tubes and seal with a rubber bung (to stop it falling into the solution)
- Wrap one tube in aluminium foil and a second in gauze
- Put all the tubes in bright light
- Leave for an hour
- Tin foil = yellow as respiration took place but no photosynthesis
- Gauze = orange little photosynthesis and little respiration
- Uncovered = purple as lots of photosynthesis using carbon dioxide up
What is the thorax?
The top part of the body separated from the lower part by the diaphragm
Lungs
- Pink like sponges
- Protected by the ribcage
- Surrounded by the pleural membranes
Bronchi
- Air breathed in goes through the trachea to the two tubes of bronchi
- Bronchi split into bronchioles
- Bronchioles end at alveoli where gas exchange takes place
Where does gas exchange take place in humans?
The alveoli
Describe breathing in
- Intercostal muscles and diaphragm contract
- Thorax volume increases
- This decreases pressure an draws air in
Describe breathing out
- Intercostal muscles and diaphragm relax
- Thorax volume decreases
- Air is forced out
Describe an experiment to investigate the effect of exercise on breathing rate
- Sit still for five mins then count number of breaths in 1 min
- Do four mins of exercise and count breaths for 1 min
- Repeat with two other people
- Temperature may have an effect on the experiment
- Muscles respire dying exercise and need more oxygen so more breathing
How is gas exchange carried out in the body?
- The lungs contain millions of air sacs called alveoli
- Blood passing next to alveoli has lots of carbon dioxide and little oxygen
- Oxygen diffuses out of alveoli into blood
- Carbon dioxide diffuses into alveoli to be breathed out
- ## Oxygen is released from the red blood cells into the body cells
How are alveoli specialised for gas exchange?
- Millions of them so large surface area
- Moist lining for gases to dissolve in
- Thin walls (one cell thick) so not far to diffuse
- Good blood supply to maintain a high concentration gradient
- Permeable walls
Why is a good blood supply good in diffusion?
Maintains a high concentration gradient
What are the effects of smoking tobacco?
- Damages walls inside the alveoli, reducing surface area and can less to emphysema
- Tar damages cilia (hairs) in the lungs and trachea making chest infections likely
- Tar irritates the bronchi and bronchioles by encouraging mucus to be produced causing smokers cough and chronic bronchitis
- Carbon monoxide reduces the amount of oxygen the blood can carry increasing heart rate and blood pressure which damages artery walls and leads to blood clots and heart attacks
- ## Tobacco contains carcinogens which lead to cancer
What does cilia do?
Catch dust and bacteria before they reach the lungs and keep the trachea clear by sweeping mucus towards the mouth
