Chapter 7 - Gas Exchange

Question 1

Why can a single celled organism rely on diffusion?

Answer 1

There is a short diffusion distance and a large surface area to volume ratio.

Question 2

What branches off the tracheae and leads directly into the muscle fibres?

Answer 2

Tracheoles.

Question 3

What is abdominal pumping?

Answer 3

The process in which insects close their spiracles and muscles pull the skeletal plates of the abdomen together. This pumps air into the air sacs.

Question 4

Why does water fill the narrow ends of the tracheoles when the insect is resting?

Answer 4

So that when the insect starts exercising water is drawn into the muscle cell (by osmosis), neutralising lactic acid

Question 5

Each gill arch has two stacks of thin plates called…

Answer 5

Filaments.

Question 6

What is the name of the cartilage that stops food from travelling down the trachea?

Answer 6

The epiglottis.

Question 7

Describe the counter-current system in the context of fish gills.

Answer 7

The blood system in the lamellae is arranged so that the water flows in the opposite direction to the blood flow in the capillaries. This MAINTAINS the concentration gradients along the ENTIRETY of the gill.

Question 8

In what way is the structure of tracheoles in insects similar to trachea in humans?

Answer 8

They both have rigid rings to keep them from collapsing (in humans it is made from cartilage).

Question 9

What makes the lamellae suitable for gas exchange?

Answer 9

It is moist from all the water flowing over it and there is just once cell between the outside water and the network of capillaries.

Question 10

What is the name of the holes in an insects’ exoskeleton that allow air to enter?

Answer 10

Spiracles.

Question 11

Why do we need to remove CO2 from the body?

Answer 11

Because it decreases the pH (makes it more acidic) which is the opposite of what enzymes need.

Question 12

In what pH do the majority of enzymes work best?

Answer 12

pH 7.4

Question 13

What happens in the lungs when a patient has emphysema?

Answer 13

The alveoli burst and fuse to make large air spaces. SA decreased.

Question 14

How does the diaphragm move when we breathe?

Answer 14

During inspiration the muscle flattens to make room for the air and during expiration it arches back up.

Question 15

How are alveoli adapted to conduct effective gas exchange?

Answer 15

1) The air inside is more moist than the air outside the lungs.
2) There is a very short diffusion distance to get into the network of capillaries.
3) There are a very large number of them in the lungs which increases surface area.

Question 16

What is the epithelium?

Answer 16

The tissue that lines the outside of all our organs.

Question 17

What happens to the alveoli when a patient has pneumonia?

Answer 17

Alveoli fill with thick fluid making gas exchange difficult.

Question 18

Why is the inner surface of the alveoli lined with water?

Answer 18

Because the cell surface membranes are permeable to water meaning that gases diffuse into the water and then diffuse out - into the capillaries.

Question 20

What is the endothelium?

Answer 20

The tissue that lines the inside of all of our organs.

Question 22

What does the epithelium of the trachea have on it to trap dust/bacteria?

Answer 22

Cilia (tiny hairs) and mucus secreting cells.

Question 23

On the top of each filament is a very thin row of…

Answer 23

Lamellae

Question 24

Why might the alveoli shown in the photomicrograph be irregular shapes?

Answer 24

Because the tissue sample is not alive so are not inflated and it’s shape could have been altered when is was cut.

Question 25

What happens to the lungs when a patient has pulmonary tuberculosis?

Answer 25

Tubercles encapsulate bacteria, elasticity of the lungs is reduced.

Question 26

How do you calculate standard deviation?

Answer 26

• work out the mean of all the numbers
• subtract the mean from each separate number and square it BEFORE adding them together
• work out the mean of those squares numbers by adding them and dividing them by the number of samples you have MINUS 1
• square root the answer

Question 27

Why do bronchi and bronchioles have muscles and elastic fibres in their walls?

Answer 27

So that they can expand and contract with ventilation.

*bronchi also have small sections of cartilage to stop them from collapsing, bronchioles don’t need this because they’re smaller.

Question 28

When we breathe what happens to the EXTERNAL intercostal muscles?

Answer 28

During inspiration they contract and during expiration they relax.

Question 29

How does the volume of the thorax change during ventilation?

Answer 29

Increases as air enters the lungs and decreases as air leaves.

Question 30

List the path of air going through the human body.

Answer 30

Nasal cavity -> trachea -> bronchi -> bronchioles -> alveoli

Question 30

What gradient changes with ventilation?

Answer 30

The pressure gradient.

Question 33

Describe the term “Potassium Pump”

Answer 33

• K+ ions have the same concentration in epidermal cells as they do in guard cells (no concentration gradient)
• LIGHT activates K+ PUMPS which ACTIVELY TRANSPORTS (uses energy/ ATP) K+ from the epidermal cells into the guard cells

Question 34

What happens to surface area to volume ratio as the volume increases?

Answer 34

It decreases.

Question 34

How does the pressure in the thorax change during ventilation?

Answer 34

It decreases during inspiration and increases during expiration.

Question 35

What does turgid mean?

Answer 35

There is an abundance or water.

Question 36

When we breathe in what happens to the INTERNAL intercostal muscles?

Answer 36

They relax during inspiration and contract in expiration.

Question 36

What does flaccid mean?

Answer 36

There is a lack of water.

Question 38

Where are the guard cells?

Answer 38

On each stomata.

Question 39

Why would the guard cells shut?

Answer 39

When there is a lack of water, they shut to ensure no water evaporates because they need to conserve it.

Question 40

What happens to the lungs when a patient has pulmonary fibrosis?

Answer 40

Fibrous connective tissue builds up in lunch’s reducing their elasticity.

Question 41

What does increased light intensity do to the stomata?

Answer 41

Causes it to open.

Question 43

Why does the “potassium pump” cause water to move into the stomata?

Answer 43

Because the increased concentration of K+ ions in guard cells causes the water potential to decrease, thus, meaning that water moves into the stomata by osmosis.

Question 44

In what climates to Xerophytes live?

Answer 44

In hot, dry climates.

Question 45

Name the 4 characteristics that all gas exchange systems need:

Answer 45

1) a large Surface Area
2) thin membranes (short diffusion distance)
3) moist
4) permeable

Question 45

Xerophyte plants have adaptations to reduce the rate of transpiration. What does “transpiration” mean?

Answer 45

Transpiration is effectively water loss.

• the movement of water from the roots of the plant to the small pores on the underside of the leave where it changes into vapour and evaporates.

Question 46

Name 5 adaptations of Xerophytes.

Answer 46

1) Thick waxy cuticle
2) Reduced leaf area (some leaves are rolled)
3) Hairy leaves
4) Sunken stomata
5) Humidity

Question 47

Explain how Marram grass is adapted.

Answer 47

• it has sunken stomata
• rolled leaves
• tiny sharp hairs to discourage animals and trap water vapour diffusing out of the stomata

Question 48

What carries the air directly from the spiracles?

Answer 48

The tracheae.

Question 48

What happens to a patients respiratory system when they have asthma?

Answer 48

Airways are inflamed, bronchioles constrict.

Question 48

What happens to a patients ventilation when they have bronchitis?

Answer 48

Their airways become inflamed and coughing brings up pus and mucus.