Gas Exchange

Question 1

Surface area: volume ratio

Answer 1

The important relationship between the surface area of a biological unit such as a cell or a whole animal, and its overall volume, which affects many aspects of its biochemistry. As the size of the unit increases, its surface area grows relatively more slowly than its volume.

Question 2

Surfaces across which substances could be transferred. To allow exchange to be efficient, surfaces will often have a large surface area:volume ratio, be very thin and selectively permeable. There will also often be movement of the environmental medium and a transport system to ensure the movement of the internal medium.

Answer 2

Exchange surface

Question 3

The difference between the concentration of a gas or substance inside and outside of the cell. The steeper the concentration gradient, the faster the rate of diffusion.

Answer 3

Concentration gradient

Question 4

Tracheae

Answer 4

A large internal network of tubes in insects with supported rings to prevent them collapsing.

Question 5

These tubes extend from the tracheae and extend throughout all the body tissues of the insect to allow atmospheric air to be brought directly to respiring tissues.

Answer 5

Tracheoles

Question 6

Tiny pores that allow gases to enter and leave the tracheae (and water vapour to leave as well). They are opened and closed by a valve.

Answer 6

Spiracle

Question 7

Gill

Answer 7

Located within the body of the fish, behind the head.

Question 8

Make up the gills of a fish – they are stacked up in a pile.

Answer 8

Gill filaments

Question 9

At right angle to gill filaments, which increase the surface area of the gills.

Answer 9

Gill lamellae

Question 10

Countercurrent flow

Answer 10

Describes how the flow of water over the fill lamellae and the flow of blood within them are in opposite directions. Allows a diffusion gradient to be maintained all the way across the gill lamellae.

Question 11

Minute pores that occur mainly on the leaves, especially on the underside. They allow gaseous exchange (and water vapour to leave as well). They are opened and closed by guard cells.

Answer 11

Stomata

Question 12

Guard cells

Answer 12

Control the opening and closing of stomata.

Question 13

Tissue in the leaf, which has large air spaces so gases can readily come into contact with mesophyll cells and large surface area of mesophyll cells for rapid diffusion.

Answer 13

Spongy mesophyll

Question 14

Xerophyte

Answer 14

Plants which have a restricted supply of water which have evolved a range of adaptations to limit water loss through transpiration.

Question 15

A pair of lobe structures made up of a series of highly branched tubules called bronchioles, which end in tiny air sacs called alveoli.

Answer 15

Lungs

Question 16

Ventilation

Answer 16

The process in which air is constantly moved in and out of the lungs to maintain diffusion of gases across the alveolar epithelium. Also known as breathing.

Question 17

Trachea

Answer 17

A flexible airway that is supported by rings of cartilage which prevent it collapsing as the air pressure inside falls when breathing in. Its walls are made up of muscle, lined with ciliated epithelium and goblet cells.

Question 18

Two divisions of the trachea each leading to one lung. Amount of cartilage reduces as they get smaller. Also produce mucus to trap dirt particles and cilia that move this towards the throat.

Answer 18

Bronchi

Question 19

A series of branching subdivisions of the bronchi whose walls are made up of muscle (which constricts to control the flow of air in and out of the alveoli) lined with epithelial cells.

Answer 19

Bronchioles

Question 20

Minute air-sacs with a diameter of between 100µm and 300µm at the end of the bronchioles. They are lined with epithelium. Between the alveoli there are some collagen and elastic fibres.

Answer 20

Alveoli

Question 21

Inspiration

Answer 21

An active process when external intercostal muscles contract, internal intercostal muscles relax, ribs are pulled upwards and outwards and the diaphragm muscles contract causing it to flatten, increasing the volume of the thorax, which reduces the pressure.

Question 22

Expiration

Answer 22

A largely passive process when external intercostal muscles relax, internal intercostal muscles contract, ribs move downwards and inwards and the diaphragm muscles relax, decreasing the volume of the thorax, which increases the pressure.

Question 23

A sheet of muscle that separates the thorax from the abdomen.

Answer 23

Diaphragm

Question 24

the bony frame formed by the ribs round the chest

Answer 24

Rib cage

Question 25

Lie between the ribs. Two sets – internal whose contraction leads to expiration and external whose contraction leads to inspiration.

Answer 25

Intercostal muscles