3.3.2 Gas Exchange

Question 1

Describe and explain the mechanism that causes forced expiration

Answer 1

Contraction of internal intercostal muscles
Relaxation of external intercostal muscles
Causes decrease in volume of chest
Air pushed down pressure gradient

Question 2

Explain how the downward movement of the diaphragm leads to air entering the lungs

Answer 2

Increase volume in lungs lowers pressure so air is pushed in by higher outside pressure

Question 3

Abdomimal pumping increases the efficiency of gas exchange between the tracheoles and the muscle tissue of the incsect. Explain why

Answer 3

More oxygen enters which maintains the concentration gradient

Question 4

Why are logarithmic scales used

Answer 4

To fit a wide range of values on a scale

Question 5

Explain how very small/young fish are able to get enough oxygen without having gills

Answer 5

Large surface area to volume ratio

Short diffusion pathway

Question 6

Explain how an asthma attack causes a drop in the FEV

Answer 6

The muscle wall of the bronchi contract and secrete more muscus which reduces the diamater of the aiways and restricts the volume of air able to pass through.

Question 7

Explain the movement of oxygen into the gas exchange system of an insect when it’s at rest

Answer 7

Oxygen used in aerobic respiration
So oxygen concentration gradient established
So oxygen diffuses in

Question 8

Adaptions for gas exchange surfaces on the leaf of dicotyledonous plants (mesophyll and stomata)

Answer 8

Lots of stomata open and close for gas exchange (guard cells) - balances this with water loss
Lots of interconnecting air-spaces throughout mesophyll so gases come in contact with mesophyll cells have large surface area for rapid diffusion

Question 9

Pulmonary ventilation rate =

Answer 9

Tidal volume x breathing rate