3.3.2 Gas Exchange

How does many alveoli improve efficiency of gas exchange

It increases surface area across which oxygen and carbon dioxide can diffuse

How does a thin epithelium of the alveoli improve efficiency of gas exchange

The shorter diffusion distance allows O2 and CO2 to diffuse quicker

How does lots of capillaries over the alveoli surface improve the efficiency of gas exchange

By providing a transport system for supply and removal of CO2 and O2 from the alveoli

How does the lungs being surrounded by the diaphragm and intercostal muscles improve efficiency of gas exchange

By allowing the lungs to supply O2 and remove CO2

Why do earthworms have gas exchange on their surface

Due to their large SA:Vol ratio, moist habitat and closed circulatory system with blood pigment

Why do flatworms have no transport system

Because they have a very short diffusion distance

Why might small insects need a gas exchange system

As they have a high demand for energy due to their large movement

How do insects respiratory system bring oxygen to cells

Without lungs, directly through a series of tubes

Why do spiracles open and close

To prevent water loss while allowing air to enter

What 3 things does delivery of oxygen rely on to maximise diffusion

Cells using O2 and pumping abdomen to ventilate tracheal system to maintain a concentration gradient, metabolites reducing water potential of cells, allowing water to leave via osmosis, increase SA

How does water leave tracheal via osmosis

By other metabolic reactions increase solute amounts

Why is water leaving tracheole import for respiration

It increases SA of the tracheole available for exchange

Why do earthworms have a gas exchange on their surface despite large SA:Vol ratio

They live in a moist environment and have a closed circulatory system with blood pigment

Why do flatworms not need a transport system

They’re very flat and have a short diffusion distance

Where does a fishes gas exchange occur

In the gills

How do fish increase their surface area for diffusion

With their filaments and lamella

How do fishes maximise exchange

By using countercurrent flow

Describe countercurrent flow

Blood flows in the opposite direction to water, maintaining the concentration gradient - avoiding equilibrium, maximising exchange

Name features of the fish gas exchange systems which maximise exchange

The two rows of filaments, blood capillary network, short distance between lamellae and blood and the many folds of lamellae

Why can fish not exchange gas outside of water

The lamellae collapse outside water

How does the internal structure of a lead maximise gas exchange

Short diffusion space from air space to cells, large SA from air spaces

How is water loss minimalised in leaves

With a waxy cuticle, stomata and hard cells, internal exchange surface

Name the five layers of the internal structure of a leaf

Waxy cuticle, upper epidermis, palisade mesophyll, sponges mesophyll, lower epidermis

Define transpiration

Movement of water evaporation out the cell and in

Name 4 factors affecting transpiration

Temperature, wind, humidity and number of open stomata

Describe and explain one feature of the alveolar epithelium that makes it a good surface for gas exchange (2)

It has flatted cells and is one cell thick, giving a short diffusion distance

Why is the DNA stained instead of starch when examining lung tissue (2)

Starch is in the cell walls so does not need to be seen whereas DNA shows the nuclei

Why does alveolar epithelium cell death reduce gas exchange (3)

Lowers the surface area and increases diffusion distance so there is less rate of gas exchange

Describe and explain the advantage of counter-current gas exchange across fish gills (3)

Water flows opposite to blood, maintaining concentration gradient across the whole lamellae, as blood always passes water with a higher oxygen concentration

Why would leaf growth of desert plants be different from leaf growth of sunflowers (2)

Less growth due to fewer stomata

Explain why plants that grow in soil with little water, grow slowly (2)

Stomata close, so less CO2 uptake, so less photosynthesis producing glucose

Describe the path taken by an oxygen molecule from alveolus to blood (2)

Across the alveolar epithelium into the capillary epithelium

Describe how we breath out (3)

Internal intercostal muscles contract and diagram relaxes, volume of lungs decreases increasing pressure, air is drawn out via pressure gradient

Name 3 adaptations for an insects tracheal system to maximise gas exchange (3)

Thin walls shorten diffusion distance, highly branches increasing surface area, water leaves via osmosis to increase diffusion surface area

How do gills alcove a damselfly to actively hunt (2)

Higher metabolic rate, needs more O2, gills provide more O2 underwater

Explain 2 ways a fish’s gills are adapted for gas exchange (2)

Many lamellar have a larger surface area for more diffusion, shorter diffusion distance from a thin surface