Section 4 - Respiration and Gas Exchange Flashcards
How do plants exchange gases by diffusion (3)
- When a plant is photosynthesising it uses up CO2, so there’s hardly any inside the leaf. Meaning more CO2 diffuses into the leaf (area of high conc to low)
- At the same time, oxygen is being made as a waste product of photosyenthesis
- Some is used up in respiration, and the rest diffuses out through the stomata (area of high conc to low conc)
How does the net exchange of gases depend on light intensity (2)
- Photosynthesis only happens during the day (no light at night) however plants respire all the time, to get energy to survive
- During the day, plants make more oxygen by photosynthesis than they use in respiration
During the day, what happens to the net exchange of gases (3)
- During the day, there is light, meaning plants can photosyenthesise. They also respire day and night, to get the energy they need to survive
- During the day, plants make more oxygen by photosyenthesis than they use in respiration. So, in daylight, they release oxygen.
- They also use up more carbon dioxide than they produce, so they take in carbon dioxide.
At night, what happens to the net exchange of gases (2)
- At night, there is no light, meaning plants can’t photosyenthesise. However they can respire at night.
- At night, plants take oxygen and release carbon dioxide
How are leaves adapted for efficent gas exchange (6)
- Leaves are broad, so there’s a large surface area for diffusion
- Leaves are thin, meaning gases only have to travel a short distance to reach the cells where they’re needed
- Air spaces: Let gases like carbon dioxide and oxygen move easily between cells, also increases surface area for gas exchange
- Stomata : Let gases like carbon dioxide and oxygen diffuse out, also allow water to transpire.
- Stomata close in the dark, so they don’t let carbon dioxide in, and don’t allow water to escape
- Opening and closing of the stomata is controlled by guard cells
How does hydrogen-carbonate indicator show changes in carbon dioxide concentration (3)
Describe an experiment to show how light affects gas exchange (7)
- Add the same volume of hydrogen-carbonate indicator to 4 boiling tubes
- Put three same sized leaves into 3 of the tubes and seal with a rubber bung
- Keep the fourth empty as a control, still seal with a rubber bung
- Completly wrap one tube in aluminium foil, and a second tube in gauze
- Place all the tubes in bright light : this will let plenty of light to the uncovered leaf, a little light to the gauze, and no light to the foil.
- Leave for an hour, and check colour of the indicator :
Control - No Change
Darkened Tube - Yellow (more carbon dioxide) no photosyenthesis
Shaded Tube - No Change; because respiration and photosyenthesis cancel each other out
Well lit - Purple (less carbon dioxide) more photosyenthesis than respiration
Describe how a human breathes in (3)
- Intercostal muscles contract
- diaphragm contract
- Thorax volume increases
- Decrease in pressure
- draws air in
Describe how a human breathes out (3)
- Intercostal muscles and diaphragm relax
- Thorax volume decreases
- Air is forced out
Describe an investigation of the effect of exercise on breathing rate (5)
- Sit still for 5 minutes, then for one minute, count the number of breaths you take
- 4 munutes of running, stop, count breathes for a minute
- Get 3 other people to do the same (compare results)
- Excercise increases breathing rate
- Control : time spent exercising, temperature, same exercise type
Why does exercise increase your breathing rate (3)
- Muscles respire more during exercise
- They need to be supplied with more oxygen
- And have more carbon dioxide removed
Explain giw alveoli carry out gas exchange in the body (6)
- Lungs contain millions of little air sacs called alveoli, where gas exchange happens
- Blood passing next to the alveoli contains lots of carbon dioxide and little oxygen
- Oxygen diffuses out of the alveolus into the blood, carbon dioxide diffuses out of the blood into the alvelous to be breathed out
- When the blood reaches body cells oxygen is released from red blood cells, and diffuses into body cells
- At the same time, carbon dioxide diffuses out of body cells, into blood, then carried back to the lungs
How are alveoli specialised for gas exchange (5)
- Huge number of microscopic alveoli gives the lungs an enormous surface area
- There’s a moist lining for gases to dissolve in
- Thin walls, one cell thick, so gas doesn’t have far to diffuse
- Great blood supply, to maintain a high conc gradient
- Permeable walls, so gases can diffuse across easily.
Explain how smocking tobacco can affect your lungs and circulatory system (5)
- Damages walls of the alveoli, reducing surface area for gas exchange, leading to diseases like emphysema.
- Tar in cigs damages the cilia in your lungs and trachea. Makes chest infections more likely
- Tar irritates the bronchi and bronchioles, mucus produced which cannot be ceared by damaged cilia - this causes smoker’s cough and chronic bronchitis
- Carbon monoxide reduces amount of oxygen the blood can carry. Blood pressure increases, damaging artery walls, blood clots more likely.
- Carcinogens, which are chemicals that lead to cancer