gas exchange

Question 1

Inhalation:

Answer 1

external intercostal muscles contract- internals relax
ribs move up and out
diaphragm contracts and flattens
increases thoracic volume
pressure inside lungs less than outside lungs
air moves in

Question 2

pulmonary ventilation definition

and equation

Answer 2

pulmonary ventilation is total volume of air moving into the lungs in one minute

Pulmonary ventilation dm3 min-1= tidal volume dm3 x ventilation rate min-1

Question 3

Alveoli to capillaries:

Answer 3

gas exchange between epithelium of alveoli and endothelium of capillaries
diffusion of O2 into capillaries, CO2 into alveoli
one cell thick epithelium and endothelium- decrease diffusion distance
many alveoli- large surface area
network of capillaries maintains diffusion gradient

Question 4

Insects:
holes in the body name and purpose
large tubes;
smaller branches;

what are 3 types of gas exchange:

Answer 4

spiracles: opened and closed by valves for gas or water exchange
trachea- large tubes extend throughout body tissues- supported by rings to help collapse
tracheoles: smaller tubes dividing off from the trachea

by diffusion
mass transport
in flight

Question 5

diffusion
mass transport
in flight
explain

Answer 5

cells respire- use o2 and release co2- creates conc gradient from tracheoles to atmosphere

mass transport: contracts and relaxes abdominal muscles to remove gasses

in flight: anaerobic respiration produces lactate, lowers water potential of cells, water moves into cells out of tracheoles by osmosis
decreases volume from tracheoles, more air is drawn in.

Question 6

adaptations of insects gas exchange:

Answer 6

Tracheoles have thin walls so short diffusion distance to cells;

2. Highly branched / large number of tracheoles so short diffusion distance to cells;
3. Highly branched / large number of tracheoles so large surface area (for gas exchange);
4. Tracheae provide tubes full of air so fast diffusion (into insect tissues);
5. Fluid in the end of the tracheoles that moves out (into tissues) during exercise so faster diffusion through the air to the gas exchange surface;

Question 7

why cant fish or insects use theor bodies as gas exchange surfaces?

Answer 7

insects- waterproof exoskeleton-chitin

fish- waterproof impermeable outer membrane and small sa: volume ratio

Question 8

fish transport: 2 features and adaptations:

Explain how the gills of a fish are adapted for efficient gas exchange. (6)

Answer 8

Gills- supported by arches,
have multiple projections of gill filaments
gill filaments stacked up in piles- large surface area

lamellae- right angle to gill filaments- increase surface area and blood and water flow across them in opposite directions
thin lamellae-short diffusion pathway

1. Large surface area provided by lamellae / filaments increases diffusion / makes diffusion efficient;;

Q Candidates are required to refer to lamellae or filaments. Do not penalise for confusion between two

2. Thin epithelium / distance between water and blood;
3. Water and blood flow in opposite directions / countercurrent;
4. (Point 4) maintains concentration gradient (along gill) / equilibrium not reached / as water always next to blood with lower concentration of oxygen;
5. Circulation replaces blood saturated with oxygen;
6. Ventilation replaces water (as oxygen removed);

Question 9

Fish ventilation:

operculum acts as a:

Answer 9

open mouth, lower buccal cavity- water flows in

closes mouth, raises buccal cavity- increases pressure- water flows over gill filaments

oxygen diffuses into bloodstream, CO2 diffuses into water and out of gills

operculum forced open as water leaves and closes when buccal cavity is lowered

valve and pump- pumps water in and lets it out

Question 10

counter current exchange:

Answer 10

maintains a concentration gradient for oxygen to diffuse into blood as water is flowing in opposite direction of blood- across entire length of lamellae

Question 11

adaptations for plants gas exchange:

Answer 11

guard cells control exchange through opening and closing stomata: prevents water loss by evaporation and allows CO2 to diffuse in

thin and flat leaves- short diffusion pathway- small surface are: volume ratio

curled leaves to trap moisture
thicker cuticle to reduce evaporation

many pores on the underside of the leaf allow gasses to easily enter

air spaces in mesophyll allow gases to move around the leaf

hairy leaves trap water vapour- reduce water potential gradient