3.1 - Exchange Surfaces and Breathing

Question 1

What four things need to be interchanged between an organism and its environment?

Answer 1

Respiratory gases (O2 and CO2)
Nutrients (glucose, fatty acids, amino acids, vitamins and minerals)
Waste products (urea and CO2)
Heat

Question 2

In what two ways can exchange occur?

Answer 2

Passively (no energy required) - diffusion and osmosis

Actively (energy required) - active transport

Question 3

In what way are small organisms able to exchange efficiently?

Answer 3

Large surface area to volume ratio. Surface area is large enough compared to their volume.

Question 4

How are organisms adapted to exchange if diffusion is the only transport method?

Answer 4

Flat shape so that no cell is ever far from the surface. Specialised exchange surfaces with large surface areas to increase SA:V ratio.

Question 5

What are the features of a specialised exchange surface?

Answer 5

Large surface area
Short diffusion distance
Steep concentration gradient maintained

Question 6

Define simple diffusion.

Answer 6

The net movement of molecules from an area of high concentration to an area of low concentration.

Question 7

What is the equation for Fick’s law?

Answer 7

Rate of diffusion = (surface area x concentration gradient) divided by diffusion distance

Question 8

Describe the changes when you inspire (breathe in).

Answer 8

External intercostal muscles contract, internal intercostal muscles relax.
Ribs move up and out.
Diaphragm contracts (flattens).
Volume of the thorax increases.
Air pressure in the lungs decreases.

Question 9

Describe the changes when you expire (breathe out).

Answer 9

External intercostal muscles relax, internal intercostal muscles contract.
Ribs move down and in.
Diaphragm relaxes (domed).
Volume of the thorax decreases.
Air pressure in the lungs increases.

Question 10

Describe the structure and function of the trachea.

Answer 10

Flexible airway made of rings of cartilage.
Cartilage stops collapsing when air pressure changes.
Walls made up of ciliated epithelia and goblet cells.
Goblet cells produce mucus that traps dirt particles and bacteria from air breathed in.
Cilia move dirty mucus up to throat where it passes down oesophagus into stomach.

Question 11

Describe the structure and function of the bronchi.

Answer 11

Two divisions of the trachea, each leading to one lung.

Similar function to the trachea (mucus moved up).

Question 12

Describe the structure and function of the bronchioles.

Answer 12

Branching subdivisions of the bronchi, muscle walls lined with epithelial cells.
Muscle allows for constriction to control air flow in and out of the alveoli.

Question 13

Describe the structure and function of the alveoli.

Answer 13

Minute air sacs at the end of bronchioles, contain elastic fibres and are lined with epithelial cells.
Elastic fibres allow for stretching and recoil when breathing in and out.

Question 14

Why is diffusion from alveoli to blood rapid?

Answer 14

Walls of alveoli and capillaries are very thin, and red blood cells are squeezed flat against capillary walls - short diffusion pathway.

Question 15

What are the causes, effects and symptoms of asthma?

Answer 15

Smooth muscle walls of bronchi/bronchioles contract and secrete more mucus.
Constriction and inflammation decreases the diameter of the airways.
Air flow in and out reduced, reducing the amount of oxygen to the alveoli.
Lower concentration gradient so lower rate of diffusion.

Question 16

What is the function of the squamous epithelium?

Answer 16

Provides short diffusion distance.

Question 17

What is the function of the ciliated epithelium?

Answer 17

Cilia waft mucus along airway.

Question 18

What is the function of the glandular tissue?

Answer 18

Produces mucus.

Question 19

What is the function of the cartilage?

Answer 19

Supports the airway.

Question 20

What is the function of the smooth muscle?

Answer 20

Constricts the airway.

Question 21

What is the function of the elastic tissue?

Answer 21

Recoils to dilate airways or to help expel air from the alveoli.

Question 22

What is the function of the blood?

Answer 22

Transports gases.

Question 23

What is the function of the nervous tissue?

Answer 23

Carries messages to coordinate action.

Question 24

What is the function of the connective tissue?

Answer 24

Holds other tissues together.

Question 25

What machine is used to measure the air into and out of the lungs?

Answer 25

A spirometer.

Question 26

What does tidal volume mean?

Answer 26

Volume of air inhaled or exhaled in one breath during normal breathing.

Question 27

What does vital capacity mean?

Answer 27

The maximum volume of air that can be moved by the lungs in one breath.

Question 28

What does residual volume mean?

Answer 28

Volume of air that remains in the lungs even after forced expiration.

Question 29

What does total lung capacity mean?

Answer 29

Vital capacity + residual volume.

Question 30

State the equation for calculating minute ventilation.

Answer 30

Minute ventilation = tidal volume x ventilation rate

Question 31

How do you calculate oxygen uptake on a spirometer trace?

Answer 31

Exhaled CO2 is absorbed by the soda lime in the spirometer, so the volume of air decreases.
Measure the gradient of the decrease to calculate rate of oxygen uptake.

Question 32

How do fish ensure a one-way flow of water over their gills?

Answer 32

Mouth opens - opercular valves closed.
Floor of the mouth moves downwards increasing the volume and decreasing the pressure and so water moves into the buccal cavity.
Mouth closes - floor is raised again, decreasing the volume. Opercular valves open to reduce pressure in the opercular cavity, helping water to flow through the gills.

Question 33

Describe the structure of the gills.

Answer 33

Gills are located behind the head.
Gills are made up of gill filaments, these are stacked up in a pile.
Gill lamellae are at right angles to the gill filaments.

Question 34

How are the gills adapted for efficient gas exchange?

Answer 34

Gill filaments and lamellae are very thin - providing a short diffusion distance.
Many gill filaments and lamellae provide a large surface area.
Countercurrent exchange system maintains a concentration gradient.

Question 35

Describe how countercurrent exchange works.

Answer 35

Water and blood flow in opposite directions along the whole length of the gill.
Water is always next to blood with a lower concentration.
In this way the concentration gradient is maintained and hence a fast rate of diffusion.

Question 36

Describe how oxygen reaches the muscle of the wings in an insect.

Answer 36

Air enters through spiracle.
Respiring cells have a low concentration of O2.
Passes along the tracheae/tracheole along a concentration gradient.
Gases diffuse into tracheole fluid and then directly into the muscle cells.
CO2 moves in the opposite direction (from cells to the atmosphere) along its concentration gradient.
This is a passive process.

Question 37

How do tracheoles increase the rate of diffusion?

Answer 37

There is a short diffusion pathway between the tracheoles and the tissues.
Extensive network provides a large surface area.

Question 38

How can insects respond to a high oxygen demand?

Answer 38

Tracheal fluid is withdrawn, increasing the surface area for exchange.
Changing the volume of the thorax and/or the abdomen which forces movements of air in and out of the tracheae along a pressure gradient.