3A - Exchange and Transport Systems

Question 1

How does gas exchange occur in single celled organisms?

Answer 1

Substances diffuse directly into (or out of) the cell across the cell surface membrane.
Diffusion is quick as there is a small diffusion pathway.

Question 2

Features of a gas exchange surface

Answer 2

1. Large surface area
2. Short diffusion pathway
3. Moist lining
4. Steep concentration gradient

Question 3

Describe the structure of gills.

Answer 3

Made of lots of thin plate called gill filaments.

Filaments are covered in small structures called lamellae which have a good blood supply.

Question 4

Explain counter current flow.

Answer 4

Blood and water flow in opposite directions in the lamellae which means than water with a relatively high oxygen concentration always flows next to blood with a lower oxygen concentration which MAINTAINS A STEEP CONCENCRATION GRADIENT.

Question 5

What is the gas exchange surface in plants.

Answer 5

Mesophyll cells

Question 6

How do gases enter plants

Answer 6

Stomata in the lower epidermis.

Question 7

What controls the stomata

Answer 7

Guard cells

Question 8

Explain gas exchange in insects.

Answer 8

Have small air filled pipes called tracheae.
Air moves into the tracheae through pores called spiracles.
The tracheae branch into small pipes called tracheoles which go to individual cells. Oxygen diffuses from the tracheoles into the cells.

Question 9

How do plants control water loss?

Answer 9

1. Sunken stomata to trap water vapour
2. A thin layer of hair on the epidermis to trap water vapour
3. Curled leaves to protect the stomata from the wind
4. Reduced number of stomata.
5. This waxy cuticle
6. When the plant becomes dehydrated the guard cells loose water and become flaccid which closes the stomata.

Question 10

How do insects control water loss?

Answer 10

They use muscles to close spiracles, have hairs over their body and a waxy cuticle layer.

Question 11

Why do humans need oxygen in their blood.

Answer 11

So cells can use it for respiration

Question 12

How does oxygen enter the blood.

Answer 12

Trachea => Bronchi => Bronchioles => Alveoli => Alveolar epithelium => Capillary endothelium => Blood

Question 13

Describe what happens during inspiration.

Answer 13

External intercostal muscles and the diaphragm contract which moves the rib cage up and out. The diaphragm flattens which increases the volume in the thorax. As a result pressure in the thorax decreases and air is forced into the lungs.

Question 14

Describe what happens during expiration.

Answer 14

The diaphragm and external intercostal muscles relax which moves the rib cage in and down. The diaphragm curves upwards and the volume of the thorax decreases. This increases pressure in the thorax and air is forced out of the lungs.

Question 15

What is meant by the intercostal muscles being antagonistic and when does this occur?

Answer 15

They are moving in opposite directions -external relax and internal contract
Happens during forced expiration.

Question 16

Name the 4 measure of lung function.

Answer 16

Tidal Volume - volume of air in each breath
Ventilation Rate - number of breaths per minute
Forced Expiratory Volume - volume of air that can be breathed out in 1 second
Forced Vital Capacity - volume of air that can be forced out after one deep breath

Question 17

Tuberculosis

Answer 17

Caused by bacteria
Hard lumps called tubercles form which damage the exchange surface
Decreases tidal volume
Increased Ventilation rate

Question 18

Fibrosis

Answer 18

Formation of scar tissue in the lungs
From exposure to irritants such as dust and asbestos
The scar tissue that forms is less elastic than normal tissue and so the lungs cant expand as much and so contain less air
Increased ventilation rate
Decreased tidal volume
Decreased FVC

Question 19

Asthma

Answer 19

Airways become inflamed as a result of an allergen
Muscles in the bronchioles contract and excess mucus is produced which reduces the lumen of the bronchioles
FEV is reduced

Question 20

Emphysema

Answer 20

Caused by smoking or long term exposure to air pollution
Inflammation occurs which generates an immune response in the area which results in an enzyme being produced which breaks down the elastin in the walls of the alveoli.
This means the alveoli are unable to return to their original shape and so can rupture and become damaged which reduces surface area
Increased ventilation rate