Gas Exchange

Question 1

Explain why stomata open due to increase in light intensity

Answer 1

Allowing carbon dioxide to enter for photosynthesis.

Question 2

Describe how carbon dioxide in the air outside a leaf reaches mesothelioma cells inside the leaf

Answer 2

Carbon dioxide enter via stomata .
Stomata open by guard cells.
Diffusion through air spaces.
Down diffusion gradient

Question 3

Describe and explain an advantage and disadvantage to have higher stomata density

Answer 3

Adv: more carbon dioxide uptake.
More photosynthesis so faster growth.
Dis:more transpiration.
Less photosynthesis so slower growth

Question 4

Adaptations to desert plants.

Answer 4

Hairs so trap water vapour and water potential gradient decrease.
Stomata in pits so trap water vapour and water potential gradient decreased.
Thick waxy cuticle layer so increase diffusion distances.
Waxy cuticle so reduces transpiration.
Folded leaves so trap water vapour and water potential gradient decreased.
Spines so reduces surface area to volumes ratio.

Question 5

Countercurrent mechanism

Answer 5

Blood and water flood in opposite directions.
Blood always passing water with a higher oxygen concentration.
Diffusion gradient maintained along whole length of lamella

Question 6

Explain 2 ways in which the structure of fish gills is adapted for efficient gas exchange

Answer 6

Many lamella so large surface area.
Thin surface so short diffusion pathway.

Question 7

Describe and explain how structure of the insect gas exchange system provide cells with sufficient oxygen

Answer 7

Spiracles lead to tracheae that lead to tracheoles.
Oxygen diffusion through tracheae.
Tracheoles are highly branched so large surface area for exchange.
Tracheoles walls thin so short diffusion distances to cells.
Tracheoles walls are permeable to oxygen

Question 8

Describe and explain how the structure of the insect gas exchange system limits water loss,

Answer 8

Chitin in tracheae impermeable so reduces water loss.
Spiracles close during activity presenting water loss.

Question 9

Abdominal pumping

Answer 9

Abdominal pumping in tubes linked to carbon dioxide release .
Abdominal pumping raises presssure in body.
Carbon dioxide pushed out of body. Carbon dioxide moves down pressure gradient to atmosphere

Question 10

Explain 3 ways in which an insects tracheal system is adapted for efficient gas exchange

Answer 10

Tracheoles have thin walls so short diffusion distances to cells.
Large number of tracheoles so short diffusion distances to cells.
Highly branched of tracheoles so large surface area for gas exchange.
Tracheae provide tubes full of air so fast diffusion into insect tissues.
Fluid in the end of the tracheoles that moves out into tissues during exercise so aster diffusion through the air to the gas exchange surface.
Body can be moved by muscles to move air so maintain concentration gradient for oxygen and carbon dioxide

Question 12

Describe and explain one feature of the alevolar epithelium that makes the epithelium well adapted as a surfaces for gas exchange

Answer 12

Single layer of cells, so reduces diffusion pathway.
Permeable, so allow diffusion of oxygen or carbon dioxide.
Moist, so increase rate of diffusion.

Question 13

Describe the pathway taken by an oxygen molecule from an alveolus to the blood

Answer 13

Across alveolar epithelium .
Endothelium of capillary.

Question 14

Describe and explain inhaling

Answer 14

Diaphragm muscle contract and external intercostal muscle contract.
Causes volume increase and pressure decrease.
Air moves down pressure gradient.

Question 15

Describe the pathway taken by an oxygen molecule from an alveolus to the blood

Answer 15

Across alveolar epithelium.
Endothelium of capillary.

Question 16

Explain how one feature of an alveolus allows efficient gas exchange to occur

Answer 16

The alveolar epithelium is one cell thick .
Creating short diffusion pathway.

Question 17

Describe the gross structure of the human gas exchange system

Answer 17

Trachea.
Bronchi.
Bronchioles.
Alevoli..

Question 18

Describe how we breath in and out

Answer 18

Breathing in, the diaphragm contract and external intercostal muscles contract .
Cause volume increase and presssure decrease in thorax to below atmospheric , resulting in air moving in.
Breathing out, internal intercostal muscle contract and diaphragm relax and external intercostal muscle relax, lung tissue elastic recoils..
Causes volume to decrease and pressure increase in thorax, to above atmospheric resulting air moving out.

Question 20

Describe how oxygen in the air reaches capillaries surrounding alveoli in the lungs

Answer 20

Trachea and bronchi and bronchioles.
Down pressure gradient.
The pen down diffusion gradient across alveolar epithelium across capillary endothelium

Question 21

State 2 ways in which the structure of fish gills is adapted for efficient gas exchange

Answer 21

Thin surface so short diffusion pathway.
Many lamellar to increase surface area so faster rate of gas exchangae

Question 22

Volume of water passing over the gills increase if the temperature of water increase suggest why.

Answer 22

Increase enzyme activity, so less oxygen dissolved in water.

Question 23

Explain how oxygen is loaded transported and unloaded in blood.

Answer 23

Oxygen is loaded in lung at high partial pressure of oxygen. Haemoglobin has high affinity for oxygen .
Haemoglobin unload oxygen to respiring tissues of low partial pressure of oxygen.
Unloading of oxygen linked to high carbon dioxide concentration

Question 24

Insect lives in dry conditions. Suggest an advantage of the pattern of spiracle movement

Answer 24

Spiracle not open all the time , therefore less water loss by diffusion through spiracle