Section 4 - Respiration and Gas Exchange Flashcards

1
Q

How do plants exchange gases by diffusion (3)

A
  • 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)
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2
Q

How does the net exchange of gases depend on light intensity (2)

A
  • 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
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3
Q

During the day, what happens to the net exchange of gases (3)

A
  • 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.
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4
Q

At night, what happens to the net exchange of gases (2)

A
  • 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
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5
Q

How are leaves adapted for efficent gas exchange (6)

A
  • 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
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6
Q

How does hydrogen-carbonate indicator show changes in carbon dioxide concentration (3)

A
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7
Q

Describe an experiment to show how light affects gas exchange (7)

A
  • 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

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8
Q

Describe how a human breathes in (3)

A
  • Intercostal muscles contract
  • diaphragm contract
  • Thorax volume increases
  • Decrease in pressure
  • draws air in
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9
Q

Describe how a human breathes out (3)

A
  • Intercostal muscles and diaphragm relax
  • Thorax volume decreases
  • Air is forced out
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10
Q

Describe an investigation of the effect of exercise on breathing rate (5)

A
  • 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
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11
Q

Why does exercise increase your breathing rate (3)

A
  • Muscles respire more during exercise
  • They need to be supplied with more oxygen
  • And have more carbon dioxide removed
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12
Q

Explain giw alveoli carry out gas exchange in the body (6)

A
  • 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
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13
Q

How are alveoli specialised for gas exchange (5)

A
  • 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.
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14
Q

Explain how smocking tobacco can affect your lungs and circulatory system (5)

A
  • 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
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15
Q
A
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