3.2 - Gas Exchange

Question 2

How to single-celled organisms exchange substances?

Answer 2

Diffusion across the cell membrane directly into or out of the cell

Question 3

Give two reasons why in multicellular organisms diffusion across out of membranes would be too slow

Answer 3

The diffusion distance is too large due to internal organs as well as a low surface area: volume ratio

Question 4

What two things do you gas exchange surfaces have that increase the rate of diffusion?

Answer 4

Small diffusion distance and a large surface area

Question 5

What is the priciple called that fish use for gas exchange?

Answer 5

Countercurrent principle

Question 6

What is each gill made up of giving it a large surface area?

Answer 6

Gill filaments

Question 7

What are gill filaments covered in increasing its surface area?

Answer 7

Lamellae

Question 8

Explain the countercurrent system in fish

Answer 8

Water and blood flowing opposite directions this maintains a constant diffusion gradient due to water having a high oxygen concentration and blood having a low oxygen concentration

Question 9

What is the pathway of exchange in fish?

Answer 9

Oxygenated water enters through the mouth, water passes over the gills then deoxygenated water leaves

Question 10

What is the specialised gas exchange organ in a fish?

Answer 10

Gills

Question 11

How is a concentration gradient maintained in the fish?

Answer 11

Thhe blood flows towards the front of the fish in the gill lamellae while the water flows towards the back. This means that there is always a higher concentration of O2 in the water than in the blood, so oxygen continues to diffuse into the blood along the whole length of the lamellae.

Question 12

What four adaptations do fish have for efficient gas exchange?

Answer 12

1) Each gill hass four gill arches which have thousands of filament attached.

2) Filaments are covered in feathery lamallae each only a few cells thick.

3) Structure gives large SA and short diffusion distance.

4) Water flows over the filaments and lamellae and oxygen can diffuse down its concentration gradient in a countercurrent system.

Question 13

What is the main gas exchange surface in plants?

Answer 13

Mesophyll

Question 14

Where do gases move in and out in the leaf?

Answer 14

Through the stomata in the lower epidermis

Question 15

What controls the opening and closing of stomata?

Answer 15

Guard cells

Question 16

What are the 4 mechanisms for gas exchange in plants?

Answer 16

1) When the guard cells are turgid (full of water) the stoma remains open allowing air to enter the leaf.

2) The air spaces within the spongy mesophyll layer allows CO2 to rapidly diffuse into cells.

3) The CO2 is used up in photosynthesis by cells containing chloroplasts, maintaining the concentration gradient.

4) No active ventilation is required as the thinness of the plant tissues and the presence of stomata helps to create a short diffusion pathway.

Question 17

Explain how plants control water loss

Answer 17

Water enters guard cells making them turgid which open the stomatal pore and if the plant loses water the guard cells lose water and the pores close

Question 18

What are xerophytes?

Answer 18

Plants that live in extremely dry or windy environments where water loss is an issue

Question 19

Give five examples of adaptations that xerophytes have to control water loss

Answer 19

Sunken stomata, wax layer, curled leaves and layers of hairs to trap water vapour

Question 20

What are the microscopic air filled pipes in insects called?

Answer 20

Tracheae

Question 21

What are the pores on the surface of an insect called?

Answer 21

Spiracles

Question 22

What has a tendency to make an organism lose water?

Answer 22

Exchanging gases

Question 23

What do insects do/have to control water loss?

Answer 23

Spiracles that close, waterproof wax cuticle, and tiny hairs

Question 24

How is concentration gradient maintained in insects?

Answer 24

A concentration gradient is maintained as gases diffuse in and out of the trachea along their concentration gradient. Muscles can contract to squeeze the trachea when the insect moves. This can move air in and out.

Question 25

What are 2 limitations of insect gas exchange?

Answer 25

1) System is effective but relies only on diffusion for gases to reach the tissues. 2) Requires short distance and limits the size of insects.

Question 26

Why do insects have a waterproof exoskeleton?

Answer 26

For protection and to prevent the insect from drying out

Question 27

What are tracheae and tracheoles held open by?

Answer 27

Rings of chitin

Question 28

Why do insects need to respire quickly?

Answer 28

They are relatively small

Question 29

Which three things work together to move air in and out of the lungs?

Answer 29

Diaphragm, intercostal muscles and rib cage

Question 30

What do external intercostal and diaphragm do during inspiration?

Answer 30

Contract

Question 31

What type of process is inspiration?

Answer 31

Active

Question 32

What happens to the external intercostals and diaphragm during expiration?

Answer 32

Relax

Question 33

What type of process is normal expiration?

Answer 33

Passive

Question 34

What happens to the external and internal intercostals during forced expiration?

Answer 34

They contract

Question 35

What are alveoli?

Answer 35

Small air sacs in the lungs where gas exchange takes place

Question 36

What are the alveoli wall made from?

Answer 36

Alveolar epithelium

Question 37

What are the walls of the capillary made from?

Answer 37

Capillary endothelium

Question 38

What protein do the walls of the alveoli contain?

Answer 38

Elastin

Question 39

What is the role of elastin in the walls of alveoli?

Answer 39

Helps alveoli return to normal shape after inhaling and exhaling air

Question 40

What 3 features does alveoli have that increases the rate of diffusion?

Answer 40

Short diffusion distance, large surface area, steep concentration gradient.

Question 41

What is the tidal volume?

Answer 41

The maximum amount of air inhaled in one breath.

Question 42

How do you calculate stroke volume?

Answer 42

Tidal volume X HR

Question 43

What is asthma?

Answer 43

A condition caused by inflammation of the bronchioles

Question 44

What is COPD?

Answer 44

Chronic Obstructive Pulmonary Diseases

Question 45

How are epithelial cells adapted for gas exchange?

Answer 45

Epithelial cells support a rich network of blood capillaries. As oxygenated blood flows away, it is replaced with deoxygenated blood which maintains a steep concentration gradient so that oxygen can continue to diffuse in.

Question 46

How are alveoli adapted for gas exchange?

Answer 46

Alveolar walls are very thin and the cells of the wall are flattened, short diffusion pathway. Alveolar walls are permeable allowing oxygen to pass into cells and lets water out, so the gas exchange surface is always moist.

Question 47

What happens when we breathe in (inspiration)?

Answer 47

1) External intercostal muscles contract, raising the ribcage and increasing the volume inside the thorax. 2) The diaphragm muscles contract, lowering the diaphragm. 3) Air flows into the lungs down a pressure gradient.

Question 48

What happens when we breathe out (expiration)?

Answer 48

1) External intercostal muscles relax, allowing the ribcage to move back to its original position, which decreases the volume inside the thorax. 2) The diaphragm muscles relax, allowing the diaphragm to move back to its original position and decreasing the volume of the thorax. 3) Air flows out of the lungs down a pressure gradient.