Module 3: Exchange and Transport

Question 1

Describe the surface area to volume ratio for a small organism

Answer 1

They have very large surface areas to volume ratio.

This means that it has a big surface area and a shorter distance from the outside of the organism to the middle of it.

Therefore simple diffusion is needed.

Question 2

Describe the surface area to volume ratio for a large organism.

Answer 2

They have small surface area to volume ratio as the distance from the centre of the organism to the outside is large.

Large organisms will have a higher metabolic rate.

Question 3

How do single-cellular organisms exchange substances?

Answer 3

They can diffuse directly into or out of the cell across the cell-surface membrane.

The diffusion rate is quick due to the short distances that the substances have to travel.

They also have a high surface area to volume ratio.

Question 4

How do multi-cellular organisms exchange substances?

Answer 4

They need specialised exchange surfaces due to diffusion being too slow. this is due to the following:

Multi-celled organisms have a large diffusion pathway.

They have a small surface area to volume ratio.

They have a large metabolic rate meaning they use up glucose and oxygen faster.

Question 5

What are three features of Exchange surfaces?

Answer 5

They have a large surface area to increase efficiency.

They are thin to decrease the distance that the substances being exchanged have to travel over, and so to improve efficiency.

They have a good supply/good ventilation.

Question 6

Describe the gas exchange surface in mammals.

Answer 6

In mammals the gas exchange surface is the lungs.

They help to get oxygen into the blood , for respiration, and to get rid of carbon dioxide, made by respiring cells, from the body.

When you breathe in, air enters the lungs via the trachea, windpipe. Then the Trachea spilts into 2 Bronchi, 1 Bronchus leading to each lung.

Each Bronchus then branches off into smaller tubes called Bronchioles which end in small air sacs called Alveoli.

This is where the gases are exchanged, and there are a lot of Alveoli in the lungs to provide a large surface area for diffusion.

Question 7

Name the key features of the gaseous exchange system.

Answer 7

Goblet cells

Cilla

Elastic fibres

Smooth muscle

Cartilage

Question 8

What is the structure and function of Cilla?

Answer 8

They are hair-like structures on the surface of epithelial cells that line the airways.

They beat the mucus secreted by the goblet cells and move it upwards away from the alveoli towards the throat where it is swallowed.

Question 9

What is the structure and function of Goblet cells?

Answer 9

They are found in the ciliated epithelium where they secrete mucus.

The mucus traps microorganisms + dust particles in the inhaled air and stops them from reaching the Alveoli.

Question 10

What is the structure and function of Elastic fibres?

Answer 10

Found in the walls of the trachea, bronchi and bronchioles and alveoli and helps with the process of breathing in and out.

When the lungs inflate, the elastic fibres are stretched, which then causes the elastic fibres to recoil to help push the air out of the lungs when exhaling.

Question 11

What is the structure and function of smooth muscle?

Answer 11

They are found in the walls of the trachea, bronchi and bronchioles and allows the diameter to be controlled.

During exercise, smooth muscle relaxes, allowing the tubes to become wider, which means there is less resistance to airflow and air can move in and out of the lungs more easily.

Question 12

What is the structure and function of Cartilage?

Answer 12

Found in rings on the walls of the trachea and bronchi.

Provides supports as it is strong and flexible.

It prevents the trachea and bronchi from collapsing when you breathe in and the pressure drops.

Question 13

What are the main components of the Gas exchange system?

Answer 13

Trachea

Bronchi

Bronchioles

Alveoli

Lungs

Bronchus

Question 14

What is found in the trachea?

Answer 14

Elastic fibres

Smooth muscle

Cartilage

Ciliated epithelium containing goblet cells.

Question 15

What is found in the Bronchus?

Answer 15

Smooth muscle

Small cartilage pieces

Elastic fibres

Ciliated epithelium containing goblet cells

Question 16

What is found in the Bronchiole?

Answer 16

Smooth muscle

Elastic fibres

Ciliated epithelium with goblet cells

Question 17

What is found in the Alveolus?

Answer 17

Elastic Fibres

Alveolar Epithelium

Capillary

Question 18

What does Ventilation in mammals consist of?

Answer 18

Ventilation consists of Inspiration (breathing in) and Expiration (breathing out) controlled by the movement of the diaphragm, intercostals muscles and ribcage.

Question 19

Describe the process of Inspiration.

Answer 19

The external intercostal muscle and diaphragm contracts.

This causes the ribcage to move up and out and the diaphragm to flatten and move downwards

The volume of the thorax (the space where the lungs are) increases. this means that the pressure in the lungs decreases tom below atmospheric pressure

This causes air to flow into the lungs, it is an active process as it requires energy.

Question 20

Describe the process of Expiration.

Answer 20

The external intercostal muscles and the ribcage relax.

This causes the ribcage to move down and in and the diaphragm become curved again.

The thorax volume decreases causing the pressure to increase above atmospheric pressure

It is a passive process and does not require energy.

Question 21

What is a spirometer and what are its components?

Answer 21

A spirometer is a machine that can be used to investigate breathing

The components include:

Oxygen chamber

inhaled air

Pen that writes the spirometer trace

a rotating drum

soda lime

mouth piece

valve that makes inhaled air and exhaled air go in different directions

Question 22

Define Total volume (TV)

Answer 22

The volume of air in each breath. This is usually about 0.4 dm3

Question 23

Define Total Capacity

Answer 23

This is the maximum volume of air that can be breathed in or out.

Question 24

Define breathing rate.

Answer 24

How many breaths are taken per unit time (usually per minute)

Question 25

Define oxygen uptake.

Answer 25

This is the rate at which a person uses up oxygen.

Question 26

How is a Spirometer used?

Answer 26

The person breathes in and out through the spirometer through the mouth piece while also wearing a nose piece.

Carbon dioxide is absorbed from the exhaled air by soda lime in order to stop the concentration of carbon dioxide in the re-breathed air from getting too high, as this can cause respiratory distress

a trace is drawn on a rotating drum of paper or a graph is formed digitally, which can be viewed on a computer

From this trace, the subject’s vital capacity, tidal volume and breathing rate can all be calculated

Question 27

Describe the structure of Fish Gills.

Answer 27

Each gill is made of lots of thin plates called gill filaments or primary lamellae which give a big surface area for exchange of gases.

The gill filaments are covered in lots of tiny structures called gill plates/secondary lamellae, which increases the surface area even more.

Each gill is supported by a gill arch.

The gill plates have lots of blood capillaries and a thin surface layers of cells to speed up the diffusion between the water and the blood.

Question 28

Explain the counter-current system in Fish.

Answer 28

In the gills of fish, the blood flows through the gill plates in one direction and water flows over in the opposite direction.

This means that the water with a high oxygen concentration always flows next to the blood with a lower concentration of oxygen.

This in turn means that a steep concentration gradient is maintained between the water and the blood, so as much oxygen as possible diffuses from the water into the blood.

Question 29

Describe ventilation in Fish.

Answer 29

When the fish opens its mouth, the floor of the bottom of the mouth (the buccal cavity) lowers, increasing the mouth’s volume.

Pressure decreases inside the mouth, causing water to move through the mouth and into the buccal cavity.

When the fish closes its mouth, the floor of the buccal cavity moves up, reducing its volume.

Pressure increases, forcing water out of the cavity and across the gill filaments.

Each gill is covered by a protective bony flap called the operculum. When water moves over the gill filaments, it increases the pressure and forces the operculum on each side of the head to open. This allows water to leave the gills.

Question 30

Describe ventilation in insects.

Answer 30

Insects have a tracheal system for gas exchange.

Air enters the insect through pores in their outer surface called spiracles.

Air then moves down the trachea, which branches off into a large number of tracheoles.

The walls of the tracheoles are thin and porous, speeding up diffusion of gases to cells.

Rhythmic abdominal movements push air into and out of the spiracles and maintain a steep concentration gradient.