Module 3.1 - Exchange and Transport

Question 1

Give 2 examples of substances cells need to exchange in and out?

Answer 1

In - Oxygen and glucose for aerobic respiration and other metabolic reactions.
Out - Need to excrete waste products from these reactions like carbon dioxide and urea.

Question 2

Would a mouse or a hippo have a bigger surface area?

Answer 2

A mouse has a bigger surface area relative to its volume compared to the hippo.

Question 3

How does exchange in single-celled organisms differ from multicellular organisms?

Answer 3

The substances they need can diffuse directly into or out of the cell across the cell surface membrane. The diffusion rate is quick because of the small distances the substances can travel.

Question 4

Why is diffusion so slow across the outer membrane of multicellular organisms?

Answer 4

> Some cells are deep within the body - there’s a big distance between them and the outside environment.
Larger animals have a low surface area to volume ratio, it’s difficult to exchange enough substances to supply a large volume of animal through a relatively small outer surface.
Multicellular organisms have a higher metabolic rate than single-celled organisms, so they use up oxygen and glucose faster.

Question 5

What are important features of an efficient exchange surface?

Answer 5

> Large surface area
Thin
Good blood supply
Ventilation

Question 6

Give an example of an exchange surface with a large surface area?

Answer 6

Root hair cells -
>The cells on plant roots grow into long ‘hairs’ which stick out into the soil. Each branch of a root will be covered in millions of these microscopic hairs.
>This gives the roots a large surface area, which helps to increase the rate of absorption of water (osmosis) and mineral ions (by active transport) from the soil.

Question 7

Give of an example of an exchange surface that is thin?

Answer 7

The Alveoli -
>Each alveolus is made from a single layer of thin flat cells called the alveolar epithelium.
>O2 diffuses out of the alveolar space into the blood and CO2 diffuses in the opposite direction.
>The thin alveolar epithelium helps to decrease the distance over which O2 and CO2 diffusion takes place, which increases the rate of diffusion.

Question 8

Describe how alveoli in the lungs have a good blood supply and ventilation?

Answer 8

> The alveoli is surrounded by a large capillary network, giving each alveolus it’s own bloody supply. The blood constantly takes O2 away from the alveoli and brings more CO2.
The lungs are also ventilated so the air in each alveolus is constantly replaced.
This helps to maintain a steep concentration gradient.

Question 9

Describe how fish gills have a good blood supply and ventilation?

Answer 9

> The gills are the gas exchange surface in fish. In the gills O2 and CO2 are exchanged between the fish’s blood and the surrounding water.
Fish gills contain a large network of capillaries - this keeps them well supplied with blood. They’re also well-ventilated - fresh water constantly passes over them.
Help to maintain a steep concentration gradient of O2, increasing the rate at which O2 diffuses into the blood.

Question 10

Describe the different features of the lungs?

Answer 10

1) As you breathe in, air enters the trachea (windpipe).
2) The trachea splits into two bronchi - one bronchus leading to each lung.
3) Each bronchus then branches off into smaller tubes called bronchioles.
4) The bronchioles end in small ‘air sacs’ called alveoli where gases are exchanged.
5) The ribcage, intercostal muscles and diaphragm all work together to move air in and out.

Question 11

What is the goblet cells function in the gaseous exchange system?

Answer 11

Goblet cells lie the airways and secrete mucus. The mucus traps microorganisms and dust particles in the inhaled air, stopping them from reaching the alveoli.

Question 12

Where are the goblet cells found in the gaseous exchange system?

Answer 12

Trachea, bronchi, larger bronchiole.

Question 13

What is the cilia’s function in the gaseous exchange system?

Answer 13

Cilia (on the surface of cells lining the airways) beat the mucus. This moves the mucus (with the trapped microorganisms and dust) upward away from the alveoli towards the throat where it’s swallowed. This helps prevent lung infections.

Question 14

What is the elastic fibres function in the gaseous exchange system and where are they found?

Answer 14

Elastic fibres in the walls of the trachea, bronchi and bronchioles (all) and alveoli help the process of breathing out. On breathing in, the lungs inflate and the elastic fibres are stretched. Then, the fibres recoil to help push the air out when exhaling.

Question 15

What is the smooth muscle’s function in the gaseous exchange system and where is it found?

Answer 15

Smooth muscle in the walls of the trachea, bronchi and bronchioles (not in the smallest type) allows their diameter to be controlled. During exercise the smooth muscle relaxes, making the tubes wider. This means there’s less resistance to airflow and air can move in and out of the lungs more easily.

Question 16

What is the cartilage’s function in the gaseous exchange system and where is it found?

Answer 16

Rings of cartilage in the walls of the trachea and bronchi provide support. It’s strong but flexible - it stops the trachea and bronchi collapsing when you breathe in and the pressure drops.

Question 17

Where is epithelium found in the gaseous exchange system?

Answer 17

Ciliated epithelium in the trachea, bronchi and in larger and smaller bronchioles but there is no cilia in the smallest bronchioles and alveoli.

Question 18

What is ventilation in mammals?

Answer 18

Consists of breathing in (inspiration/inhalation) and breathing out (expiration/exhalation).

Question 19

Describe what happens in inspiration in terms of diaphragm, external and internal intercostal muscles and ribcage?

Answer 19

1) The external intercostal muscles and the diaphragm contract.
2) This causes the ribcage to move upwards and outwards and the diaphragm to flatten, increasing the volume of the thorax.
3) The lung pressure decreases (below atmospheric pressure).
4) This causes air to flow into the lungs.

Question 20

What does it mean that inspiration is an ‘active process’?

Answer 20

It requires energy.

Question 21

Describe what happens in expiration?

Answer 21

1) The external intercostal and diaphragm muscles relax.
2) The ribcage moves downwards and inwards and the diaphragm becomes curved again.
3) The thorax volume decreases.
4) The lung/air pressure increases (to above atmospheric pressure).
5) Air is forced out of the lungs.

Question 22

What happens when in expiration the air is pushed out more forcefully?

Answer 22

During forced expiration, the internal intercostal muscles contract, to pull the ribcage down and in.

Question 23

What type of process is exhalation?

Answer 23

It’s a passive process - meaning it doesn’t require energy.

Question 24

What is tidal volume?

Answer 24

The volume of air in each breath.

Question 25

What is a typical tidal volume?

Answer 25

At rest it’s usually between 0.4-0.5 dm^3.

Question 26

What is vital capacity?

Answer 26

The maximum volume of air that can be breathed in or out.

Question 27

What are a few factors vital capacity depends on?

Answer 27

> The size of a person (height).
Age
Gender
Their level of regular exercise.

Question 28

What is breathing rate?

Answer 28

How many breaths are taken - usually in a minute.

Question 29

What is oxygen consumption/uptake?

Answer 29

The rate at which organisms uses up oxygen/ the volume of oxygen absorbed by the lungs in one minute.

Question 30

What is a spirometer?

Answer 30

A machine that can give readings of tidal volume, vital capacity, breathing rate and oxygen uptake.

Question 31

Describe the steps of how you would use a spirometer?

Answer 31

1) A spirometer has an oxygen-filled chamber with a movable lid.
2) The person breathes through a tube connected to the oxygen chamber.
3) As the person breathes in and out, the lid of the chamber moves up and down.
4) These movements are recorded.
5) The soda lime in the tube the subject breathes into absorbs carbon dioxide.

Question 32

Describe the different ways a spirometer trace can be recorded?

Answer 32

> These movements can be recorded by a pen attached to the lid of the chamber, this writes on a rotating drum, creating a spirometer trace.
Or the spirometer can be hooked up to a motion sensor - this will use the movements to produce electronic signals, which are picked up by a data logger.

Question 33

Why does the total volume of gas in the chamber decrease over time?

Answer 33

Because the air breathed out is a mixture of CO2 and O2 and the CO2 is absorbed by the soda lime - so there’s only oxygen in the chamber which the subject inhales from. As this oxygen gets used by respiration, the total volume decreases.

Question 34

How can you read/analyse data of a graph for oxygen uptake?

Answer 34

It can be read by taking the average slope of the trace.

Question 35

What gives the gills of fish a large surface area for gas exchange?

Answer 35

Each gill is made of lots of thin branches called gill filaments or primary lamellae. The gill filaments are covered in lots of tiny structures called gill plates or secondary lamellae, which increase the S/A even more, Each gill is supported by a gill arch.

Question 36

Describe the counter-current system in fish?

Answer 36

Blood flows through the gill plates in one direction and water flows over in the opposite direction. It maintains a large concentration gradient between the water and the blood.

Question 37

What feature of fish help speed up the diffusion of oxygen?

Answer 37

The gill plates have lots of blood capillaries and a thin surface layer of cells to speed up diffusion.

Question 38

Why is there a steep concentration gradient between the blood of the fish and the water?

Answer 38

The concentration of oxygen in the water is always higher than in the blood, so as much oxygen as possible diffuses from the water into the blood.

Question 39

Describe how fish gills are ventilated?

Answer 39

1) The fish opens its mouth, lowering the floor of the buccal cavity which means the volume of the buccal cavity increases, decreasing the pressure.
2) Water is then sucked into the cavity.
3) When the fish closes it’s mouth, the floor of the buccal cavity is raised again, the volume decreases, the pressure increases.
4) Water is forced out of the cavity across the gill filaments.
5) The increase in pressure forces the operculum on each side of the head to open, allowing water to leave the gills.

Question 40

What is the buccal cavity?

Answer 40

The space inside the mouth.

Question 41

What is the operculum?

Answer 41

Each gill is covered by a bony flap called the operculum, which protects the gill.

Question 42

Describe the method/steps of how to dissect fish gills?

Answer 42

1) Make sure you’re wearing an apron/labcoat and gloves because it can be messy.
2) Place your fish in a dissection tray or on a cutting board.
3) Push back the operculum and use scissors to carefully remove the gills. Cut each gill arch through the bone at the top and bottom.
4) You should be able to see the gill filaments and finish off by drawing and labelling the gill.

Question 43

What are trachae in insects?

Answer 43

Microscopic air-filled pipes called tracheae which they use for gas exchange.

Question 44

Explain the type of circulatory system insects have?

Answer 44

Insects have an open circulatory system in which the body fluid acts as both blood and tissue fluid. Circulation is slow and can be affected by body movements.

Question 45

Describe how oxygen is transported around an insect?

Answer 45

1) Air moves into the tracheae through pores on the insect’s surface called spiracles.
2) The tracheae branch off into smaller tracheoles which have thin, permeable walls, and go to individual cells. The tracheoles also contain tracheal fluid, which oxygen diffuses into.
3) the oxygen then diffuses from this fluid into the body cells and carbon dioxide diffuses in the other direction.

Question 46

Describe 2 ways of how insects ventilate themselves?

Answer 46

> Insects use rhythmic abdominal movements to change the volume of their bodies and move air in and out of the spiracles.
When larger insects are flying, they use their wing movements to pump their thoraxes too.

Question 47

Describe the method of how to dissect the gaseous exchange system in insects?

Answer 47

Big insects like grasshoppers or cockroaches are usually best for dissecting -

1) Fix the insect to the dissecting board and put dissecting pins through it’s legs to hold it in place.
2) To examine the tracheae, you need to carefully cut and remove a piece of exoskeleton from along the length of the insect’s abdomen.
3) Use a syringe to fill the abdomen with saline solution and you should be able to see a network of very thin, silvery-grey tubes - these are the tracheae. They look silver for they’re filled with air.
4) You can examine the tracheae under a light microscope using a wet mount slide and you should eb able to see rings of chitin in the walls of the tracheae, there for support.