Gas Exchange

Question 1

How does gas exchange take place in small organisms?

Answer 1

Oxygen diffuses directly into the cell from the environment due to small diffusion distances and having a large surface to area ratio
Metabolic demands are low

Question 2

What factors affect the rate of diffusion?

Answer 2

Surface area
Concentration gradient
Diffusion distance

Question 3

What are the features of an effective gas exchange system?

Answer 3

Large surface area
Thin layers to minimise diffusion distance
Rich blood supply to respiratory surfaces
Moist surfaces
Permeable

Question 4

What is the epiglottis?

Answer 4

A flap of tissue that closes over the when food is swallowed to prevent it from going into the lungs

Question 5

What is the trachea?

Answer 5

The major airway into the bronchi

Lined with mucas-secreting cells and cilia

Question 6

Why are the incomplete rings of cartilage in the trachea and bronchi important?

Answer 6

They enable food to be swalloed but still prevent it from collapsing

Question 7

What are bronchioles?

Answer 7

Small tubes that spread through the lungs and end with the alveoli, transporting air

Question 8

What are the alvioli?

Answer 8

The main site of gas exchange in the lungs

Question 9

How thick is the cell wall of the alveoli?

Answer 9

1 cell thick

Question 10

How does has exchange occur at the alveoli?

Answer 10

Blood has a low oxygen concentration while the alveoli is high. Oxygen diffuses across the membrane and into the blood stream
As blood is constantly moving, the gradient is maintained

Question 11

How does breathing take place?

Answer 11

The diaphram lowers which reduces the pressure in the chest cavity. As it’s lower than the atmosphere, air rushes into the lungs and they expand.
When we exhale, muscles surrounding the diaphram relax and the diaphram moves up which forces air out.

Question 12

How are the lungs protected against infection?

Answer 12

The trachea and broncolies are lined with mucas-sectreting cells which catch pathogens and are moved up into the throat by cilia

Question 13

What are the parts of gas exchange in insects?

Answer 13

Spiracles
Tracheae
Tracheoles

Question 14

What are spiracles?

Answer 14

Found along the thorax and abdoman of most insects. Small holes where gases can enter and exit
Kept closed as much as possible to reduce water loss

Question 15

What are tracheae?

Answer 15

Tubes from the spiracles to the tissues in insects that carry gas
They are supported by spirals of chitin for support and branch off to form tracheoles

Question 16

How does gas exchange in insects work?

Answer 16

Air enters the system through spiracles and moves along the tracheae and tracheoles by diffusion into the tissues

Question 17

How is the rate of gas exchange controlled in insects?

Answer 17

Opening and closing of the spiracles

Question 18

What adaptations do very active insects have to meet their higher need for oxygen?

Answer 18

Air is actively pumped into the tracheae

Collapsable tracheae increase the volume of air moved through the system

Question 19

How does gas exchange occur in fish?

Answer 19

Air travels through the mouth and over the gills and out through the operculum. The oxygen is absorbed by the gill filaments through diffusion and goes into the blood stream.
Blood and water flow in opposite directions to maximise gas exchange

Question 20

Why can’t fish breathe out of water?

Answer 20

The gill filaments stick together and surface area is too small

Question 21

What adaptations help fish to breathe?

Answer 21

Countercurrent exchange system to keep steep concentration gradient
Overlapping gill filaments to increase waer resistance and slow the flow enough for diffusion to take place

Question 22

How does air enter the plant during gas exchange?

Answer 22

Air enters through the stomata

Question 23

What is the purpose of gas exchange in plants?

Answer 23

Get carbon dioxide for photosynthesis and release the oxygen produced in respiration

Question 24

How is the rate of gas exchange in plants controlled?

Answer 24

The stomata open and close

Question 25

How do the stomata close?

Answer 25

Turgor in the gard cells decrease and the pores close as the cell wall becomes thicker

Question 26

How do the stomata open?

Answer 26

Potassium ions are moved into the gard cells by active transport and turgor increases