Topic 4 - Gas Exchange

Question 1

What is the insect exoskeleton made up of and why would this make gas exchange difficult?

Answer 1

Chitin and because chitin is impermeable to oxygen so the insect needs to have trachea in order for gas exchange

Question 2

What is the tracheal system made up of?

Answer 2

A main trachea forming the main pathway along the length of the insect body then smaller branches called tracheoles which lead to the direct tissues. The tracheae is connected to outside valves called spiracles

Question 3

What is the tracheae supported by in an insect and what does this help?

Answer 3

Rings of chitin, which helps support the tracheae as, it means it can cope with lots of pressure and also allows flexibility

Question 4

What type of organism has efficient gas exchange?

Answer 4

Unicellular, they have a high surface area to volume ratio

Question 5

What is a major factor in the efficiency of gas exchange?

Answer 5

Surface area to volume ratio

Question 6

Does a large circular organism have fast or slow gas exchange and why?

Answer 6

Slow because they have a low surface area to volume ratio

Question 7

How may spiracles been seen on an insect?

Answer 7

As 8 small holes on either side of the abdomen and two more pairs on the thorax

Question 8

Why do spiracles have small hairs?

Answer 8

To prevent the entry of small molecules which may block the tracheoles

Question 9

What is the order of the thorax?

Answer 9

Trachea branches into two bronchi which goes to each lung and then divides into bronchioles and then tertiary bronchioles and then respiratory bronchioles then alveoli

Question 10

What supports the human trachea, bronchioles and bronchi?

Answer 10

Cartilage rings

Question 11

What do the pleural membranes do and where are they found?

Answer 11

They secrete plural fluid which protects the lungs from friction during breathing
They are found in the inner layers of the thorax

Question 12

What is pleural fluid made of?

Answer 12

Blood plasma

Question 13

Why do bronchi and large bronchioles have a thin ring or tiny plates of cartilage around them?

Answer 13

To prevent collapse from sudden reductions in pressure

Question 14

When is air taken into the alveoli?

Answer 14

When air pressure in the lungs is lower than atmospheric pressure

Question 15

When is air forced out a human?

Answer 15

When the pressure in the lungs is higher than atmospheric pressure

Question 16

Why would water logging be bad for a plant?

Answer 16

Because most a oxygen for root tissue respiration diffuses straight from soil to a plant through its permeable cell wall and membrane meaning if the soil becomes waterlogged the oxygen in the soil is restricted so the plants growth is stopped

Question 17

What prevents water loss in a plant?

Answer 17

The leaves and stem being covered in a cuticle or a bark - also prevents diffusion of gases

Question 18

Why does a plant need lenticels?

Answer 18

Because the waxy cuticle or bark prevents water loss and diffusion of gases it’s hard for diffusion to take place here therefore, the plant needs air spaces for direct diffusion to happen

Question 19

What a lenticels?

Answer 19

Loosely packed cells (loosely packed so leave air spaces)

Question 20

Where are lenticels found?

Answer 20

On the stem of a plant

Question 21

Where on a plant is the place where most diffusion takes place and why?

Answer 21

The leaves as, co2 is used for photosynthesis

Question 22

How do plant leaves diffuse easily even though they’re covered in a waxy waterproof cuticle?

Answer 22

On the epidermis there’s many thousand small pores called stomata (singular is stoma)

Question 23

What is the epidermis?

Answer 23

The underside of leaves

Question 24

What controls the opening and closing of the stomata?

Answer 24

Guard cells

Question 25

Why does less gas exchange happen at night in plants?

Answer 25

Because plants are not photosynthesising at night so need less oxygen for energy

Question 26

How do guard cells open and close?

Answer 26

When the cell is turgid they become curved and open

When the cell is flaccid they become straight and close the stomata

Question 27

When are the guard cells closed and why?

Answer 27

at night to prevent water loss because there’s less gas exchange

Question 28

How does carbon dioxide enter a plant and where does it enter?

Answer 28

It enters in a leaf
Diffuses through the stomata and then goes into air gaps in the spongey mesophyll where it then dissolves in the water films and can then diffuse easily through cell membranes to the photosynthesis tissues

Question 29

How does oxygen leave a plant?

Answer 29

Dissolves in water films then travels through air gaps in spongey mesophyll and then diffuses out of the stomata

Question 30

What are red blood cells called in a mammal?

Answer 30

Erythrocytes

Question 31

Why might erythrocytes not be considered living?

Answer 31

Because they haven’t got a nucleus

Question 32

Why is blood red if blood plasma is yellow?

Answer 32

Because the thousands of erythrocytes in the blood plasma which contain haemoglobin so are red. About 45% erythrocytes

Question 33

What is partial pressure?

Answer 33

The pressure of individual gases in a mixture

E.g. Oxygen is 20kPa out of the 100kPa atmospheric pressure

Question 34

What is pressure measured in?

Answer 34

kPa

Question 35

What is the total pressure?

Answer 35

The sum of all partial pressures

Question 36

What does the law of partial pressures say?

Answer 36

That the partial pressure of a particular gas in a mixture is its pressure even if the total volume of the mixture was that 1 gas