Module 3.1.1

Question 1

Why does the body need to exchange substances?

Answer 1

All cells need a supply of oxygen and nutrients to survive.
They also need waste products removed so they don’t cause a toxic build up.

Question 2

What are the 3 main factors that affect the need for an exchange system?

Answer 2

Size
Surface area to volume ratio
Level of activity

Question 3

How does size affect the need for an exchange system?

Answer 3

In very small organisms (single celled) all cytoplasm is very close to the environment. Simple diffusion is enough.
Multicellular organisms have many layers of cells and so the diffusion pathway is too long and diffusion is too slow to enable a supply to inner cells.

Question 4

Why does surface area to volume ratio affect the need for an exchange system?

Answer 4

Small organisms have a small surface area but they also have a small volume. Their SA is large compared to volume. They have a large SA:V ratio.
Large organisms have a large SA but a larger volume. As size increases, SA:V ratio decreases.

Question 5

How does level of activity affect the need for an exchange system?

Answer 5

Large organisms have a high metabolic rate so need to exchange lots of material quickly, metabolic activity uses energy from food and requires oxygen to release energy in aerobic respiration.
The cells of an active organism need good supplies of nutrients and oxygen to supply energy.

Question 6

What are the features of an efficient exchange surface?

Answer 6

Increased SA.
Thin layers.
Blood supply.
Ventilation.

Question 7

Why is increased SA a good feature of an exchange system?

Answer 7

Provides a larger area over which the exchange of materials occurs.
Overcomes limitations of SA:V ratio of larger organisms.

Question 8

Why are thin layers a good feature of an exchange system?

Answer 8

Creates a short diffusion pathway.
Increases speed and efficiency of exchange.

Question 9

Why is blood supply a good feature of an exchange system?

Answer 9

Maintains a steep conc gradient for diffusion and ensures the exchanged substances are constantly moving to the area needed/removed from an area.

Question 10

Why is good ventilation a good feature of an exchange system?

Answer 10

Maintains the diffusion gradient for gases, makes the processes faster and more efficient.

Question 11

What do larger organisms require specialised gas exchange and transport systems?

Answer 11

To transport substances such as oxygen and nutrients to their cells efficiently.

Question 12

Where does gas exchange occur in insects, fish and mammals?

Answer 12

Gills, spiracles and lungs.

Question 13

What is the pleural cavity?

Answer 13

It is a double membrane that encloses both lungs. The space between these membranes is called the pleural cavity and is filled with a small amount of pleural fluid.

Question 14

What does the pleural cavity do?

Answer 14

The fluid inside lubricates the lungs. It also adheres to the outer walls of the lungs to the thoracic (chest) cavity by water cohesion, so that the lungs expand with the chest while breathing.

Question 15

What are the features of the nasal cavity and how do they help gas exchange?

Answer 15

Large SA and good blood supply - warms the air as it passes into the body.
Hairy lining - hairs trap dust and bacteria in mucus and prevent them from reaching the lungs, which could cause infection.
Moist surfaces - increases the humidity of the incoming air, this reduces the evaporation of water in the lungs.
This means that after the air has passed through the nasal cavity, the air entering the lungs is a similar temperature and humidity to the air already there.

Question 16

What are the features of the trachea?

Answer 16

Supported by a layer of cartilage that holds the trachea open and prevents it from collapsing.
The rings are incomplete to allow it to bend when food is swallowed down the oesophagus behind.
Gaps between the cartilage is filled with smooth muscle and elastic fibres.
The cartilage, muscle and elastic fibres hold the trachea open but allow flexibility during inspiration and expiration.
The trachea is lined with ciliated columnar epthelial cells and goblet cells that prevent dust and bacteria from entering the lungs.
Blood vessels warm the air.

Question 17

What are the bronchus and what are their structure?

Answer 17

They are extensions of the trachea that split into two for the left and right lung.
Has a v. similair structure to trachea but smaller.
Cartilage rings hold the pipes open.

Question 18

What are the bronchioles and what are their structure?

Answer 18

The bronchus splits into much smaller bronchioles.
They are about 1nm or less in diameter.
No cartilage and are held open by smooth muscle.
When this muscle contracts the bronchioles contract, this affects the air flow to the lungs.
Lined with a thin layer of columnar/cuboidal epithelial tissues making some gas exchange possible

Question 19

How does asthma affect the brochioles?

Answer 19

Cells lining the bronchioles release histamines (making epithelial cells inflamed and swollen). These histamines stimulate goblet cells to release excess mucus and smooth muscles in bronchioles walls to contract.
Airways narrow and fill with mucus.

Question 20

What are the two types of drugs available for asthma treatment?

Answer 20

Relievers - give instant relief to symptoms. Chemicals similar to adrenaline, they attach to the active sites on the surface membranes of smooth
muscle cells in the bronchioles, making them relax and
dilating the airways.
Preventers - often steroids, which are taken every day
reduce the sensitivity of the lining of the airways.

Question 21

What are the alveoli and what are they made up of?

Answer 21

Little air sacs, this is
where most of the gas exchange
occurs.
They are made up of a thin layer of flattened (squamous) epithelial cells, as well as some collagen and elastic fibres.
Contain elastic fibres.

Question 22

What are the purposse of elastic fibres in alveoli?

Answer 22

They cause recoil which helps move air out of the alveoli.
Elastic recoil is the ability to return to original shape and size after stretching.

Question 23

What are the features of alveoli that make it good for gas exchange?

Answer 23

Inner surface moist –prevents drying from air.
Surfactant – prevents surfaces sticking.
Macrophages – combat pathogens.
Epithelium cells – flattened
(squamous) for easy diffusion.
Single layer cells in capillaries.
Large SA.
Large diffusion gradient for both gases.

Question 24

How is the structure of alveoli kept during inhalation when pressure decreases?

Answer 24

Lung surfactant - it is a phospholipid that coats the surfaces of the lungs. Without it, the watery lining of the alveoli would create a surface tension, which would cause it to collapse.

Question 25

What is the process of passive expiration?

Answer 25

Diaphragm relaxes and moves up.
External intercostal muscles relax and move down and in.
Thoracic volume decreases.
Thoracic pressure increases.
Air flows out the lungs to equalise pressure.

Question 26

Why is mouth to mouth resuscitation effective?

Answer 26

In one breathing cycle the lungs only lose some of the oxygen content.

Question 27

What are the 3 ways to measure lung capacity?

Answer 27

Peak flow meter.
Vitalograph.
Spirometer.

Question 28

How does a peak flow meter work to measure lung capacity?

Answer 28

It measures the rate at which air is expelled from the lungs. (Asthma users use it)

Question 29

How does a vitalograph measure lung capacity?

Answer 29

It is a more sophisticated peak flow meter. The patient breathes out as quickly as they can and a graph is produced. (forced expiratory volume in one second)

Question 30

How does a spirometer work?

Answer 30

Static lower half of tank is full of water.
Mobile upper half is full of oxygen.
Breathe out into the tank and the upper half will rise, breathe in from the tank and the upper half will fall.
Trace marker is attached to the mobile upper half.

When breathing in the trace will go down and expiring the trace climbs up. The peak of inspiration to the trough of expiration shows the volume of one breath.

Soda lime absorbs CO2, when breathing oxygen is used from the tank and the volume of gas used up is the volume of oxygen used.

Question 31

What are the precautions that have to be made when using a spirometer?

Answer 31

Subject should be healthy (esp. free from asthma)
Use fresh, functioning soda lime
No air leaks in apparatus (invalid/inaccurate results)
Sterilised mouthpiece

Question 32

What is tidal volume?

Answer 32

The volume of air that moves into and out of the lungs per breath.

Question 33

What is vital capacity?

Answer 33

Largest volume of air that can be breathed in.
Strongest inhale followed by strongest exhale.

Question 34

What is the inspiratory reserve volume?

Answer 34

The maximum volume of air you can breathe in over and above normal inhalation.

Question 35

What is the expiratory reserve volume?

Answer 35

Max volume of air you can force out of your lungs over and above the normal tidal volume of air you breathe out.

Question 36

What is the residual volume and what is it’s purpose?

Answer 36

The volume of air that is left in your lungs when you have exhaled as hard as possible.
It allows the alveoli to be kept open and allows continual gas exchange between breaths.

Question 37

What is the total lung capacity?

Answer 37

Sum of the vital capacity and residual volume.

Question 38

What is the breathing rate?

Answer 38

Number of breaths per minute.

Question 39

What is ventilation rate and calculation?

Answer 39

Total volume of air inhaled per minute. Tidal volume x breathing rate (per minute)

Question 40

What are insect’s exoskeletons made up of? How does this affect gas exchange?

Answer 40

Chitin. No gas exchange happens over it.
Gas exchange system has evolved to deliver oxygen directly to cells and remove it the same way.

Question 41

What are spiracles and what are they for?

Answer 41

Small opening along the thorax and abdomen.
They are used in gas exchange and also water loss. They can be opened and closed by sphincters, they close when the insect is inactive and oxygen demands are low.

Question 42

What runs from the spiracles to the tissues?

Answer 42

Tracheae.

Question 43

What do tracheae branch into and where do these go?

Answer 43

They branch into tracheoles which divide until their microscopic ends penetrate into individual body cells.

Question 44

How wide are tracheae in diameter?

Answer 44

1mm.

Question 45

What are tracheae covered in and what functions does this have?

Answer 45

Chitin.
Prevents gas exchange.
Supports the tracheae, preventing it from collapsing and keeping the airway open.

Question 46

How large are tracheoles diameter?

Answer 46

0.6-0.8um diameter.

Question 47

Do tracheoles have chitin lining and what does this mean for gas exchange?

Answer 47

No.
Gas exchange is possible in the large network of tracheoles which form a large surface area.

Question 48

How does air move along the tracheoles?

Answer 48

By diffusion.

Question 49

What are the features of the insect tracheal/tracheole system?

Answer 49

Large SA.
Moisture on walls of tracheoles.
Tracheal fluid at the end of tracheoles.
Oxygen dissolves in the fluid and diffuses directly into surrounding cells.

Question 50

What happens during strenuous activity in insects?

Answer 50

More oxygen is required to meet the demands.
The muscles of the insect start respiring anaerobically and and start producing lactic acid.
Lactic acid builds up in the muscle tissue, lowering the water potential of the tissues.
This causes water to move out of the tracheoles (high water potential) into the respiring cells (low potential) by osmosis.
As fluid moves away from the tracheoles, more SA is exposed for more efficient gas exchange to help meet the demand for oxygen,

Question 51

How do insects remove carbon dioxide?

Answer 51

The CO2 produced diffuses down the concentration gradient out of the respiring cell.
It is carried through the haemolymph.
It passes out via the tracheoles -> trachea -> spiracles.
Respiration generates heat which causes the gas to expand and make them less dense and so they rise up by convection.
Helps remove CO2 from the insect especially if they are in more dense environments like ant hills.