B3.1 Gas Exchange Flashcards
1
Q
Why is gas exchange vital for living organisms?
A
- High surface area to volume results in short distance between center and exterior of organism hence, diffusion distance is short which results in rapid gas exchange.
- Decreases in larger organisms hence, require specialised gas exchange surfaces.
2
Q
Properties of gas exchange surfaces to optimize the diffusion of gases.
A
- Permeable: gases can diffuse across freely.
- Large surface area to volume ratio of the organism.
- Moist: gases are able to dissolve.
- Thin short diffusion distance.
3
Q
Smaller vs larger organisms in maintaining concentration gradients.
A
- Smaller orgs: cell respiration continuously uses oxygen and produces carbon dioxide, creating a concentration gradient.
- Larger orgs: aerobic causes the continuous movement of blood throughout the dense network of blood vessels –> low conc of oxygen and high conc of carbon dioxide.
4
Q
Ventilation in mammals
A
- Inhalation: When O2 conc is lower than in air, O2 diffuses out from alveoli into adjacent blood capillaries.
- Exhalation:
CO2 conc in capillaries are higher than in air, CO2 diffuses out from blood in the capillaries into the alveoli.
5
Q
Ventilation in fish
A
- Fresh water pumped into gills & out of gill slits.
- Blood flows in the opposite direction.
- Ensures that O2 conc in the water adjacent to the gills remain high & CO2 conc remains low.
5
Q
Adaptations of mammalian lungs
A
- Small and many alveoli provides a large SA to V ratio for gas exchange.
- Alveoli surrounded by dense capillary networks hence, CO2 is continuously being removed and supplied with O2.
- Thin alveolar walls that are one cell thick hence, short diffusion distance for gases.
- Branched network of bronchioles = even distribution of alveoli
- Moist alveolar walls due to pulmonary surfactant that forma monolayer of phospholipids. Therefore, reduces surface tension and prevents water from adhering to the sides of the alveoli when air is exhaled from the lungs.
5
Q
Explain Inspiration
A
- Diaphragm contracts and moves downwards.
- Abdomen wall muscles relax allowing pressure from diaphragm to push it outwards.
- External intercostal muscles contract, pulling the ribcage upwards and outwards.
- Internal intercostal muscles relax.
- Volume inside thorax increases, pressure decreases, sucking air in.
5
Q
Explain Exhalation
A
- Diaphragm relaxes and moves upwards.
- Abdomen wall muscles contract, pushing the diaphragm upwards.
- External intercostal muscles relax.
- Internal intercostal muscles contract, pulling the ribcage inward and downward.
- Volume inside thorax decreases, pressure increases, forcing air out.
6
Q
Adaptations of gas exchange in plants.
A
- Waxy cuticle: a waterproof layer covering the epidermis to reduce water loss via evaporation.
- Guard cells on epidermis: controls the open/closing of the stomata, facilitating the going in/out of gases.
- Spongy mesophyll: large surface area and moist which allows CO2 to dissolve and diffuse through the mesophyll cell.
- Leaf veins: supply water to the leaf.
6
Q
Draw the leaf structure.
A
Refer to textbook.
7
Q
What are the factors of transpiration?
A
- Higher light intensity and temperature = higher rate of transpiration
- Higher humidity = lower rate of transpiration BCS. of higher moisture in the air.
8
Q
Explain the process of transpiration
A
- Photosynthesis raises the conc of O2 in chloroplasts, O2 diffuses out of the surfaces of spongy mesophyll cells and then into air spaces and out of the leaf.
- When conc of water vapour in the air spaces is higher than in the air outside, water vapor will diffuse out of the air spaces and into the air outside. The humidity of the air spaces will drop below the saturation point, hence more water evaporates from spongy mesophyll cell walls.
9
Q
Stomatal density formula
A
(mean number of stomata) / area of field view
