3.1 Exchange Surfaces

Question 1

Why do organisms need specialised exchange surfaces?

Answer 1

• Larger organisms have a decrease in SA:V ratio meaning the diffusion distance would increase - not efficient
• Need lots of oxygen for respiration to produce ATP
• Need to remove CO2 as a metabolic waste product

Question 2

What is BMR

Answer 2

Basal Metabolic Rate:
The metabolic rate of an organism when at rest - at rest the body only requires energy for the functioning of vital organs such as the lungs, heart and brain

Question 3

What factors affect metabolic rate?

Answer 3

• Greater the mass the higher the metabolic rate
• Greater the SA:V the higher the metabolic rate

Question 4

What are key features of an efficient exchange surface?

Answer 4

• Large surface area
• Short diffusion distance
• Good blood supply
• Ventilation mechanism

Question 5

Which cell has an efficient exchange surface with a large surface area?

Answer 5

Root hair cells:
- increased the surface area so the rate of water/ion uptake by osmosis is greater

Question 6

Which cell has an efficient exchange surface with a short diffusion distance?

Answer 6

Alveoli:
- Walls are only one cell thick
- This leads to a very short diffusion distance for gas exchange

Question 7

Which cell has an efficient exchange surface with a good blood supply?

Answer 7

Fish Gills:
- The concentration gradient must remain constant to enable efficient gas exchange between the blood and water
- Have an extensive capillary network in the gills - the counter-current system

Question 8

Explain the structure and function of cartilage in the mammalian gas exchange system

Answer 8

• Strong flexible tissue
• C-shaped rings in the trachea
  –> helps to support the trachea and ensure it stays open while allowing it to move and flex while we breathe

Question 9

Explain the structure and function of ciliated epithelium in the mammalian gas exchange system

Answer 9

• Tissue found along trachea along to the bronchi
• Each cell has small projections of cilia which sweep mucus, dust and bacteria upwards and away from the lungs and the epithelium itself
• Goblet cells are found within the CE tissue
  —> They secrete mucus to trap dust/pathogens

Question 10

Explain the structure and function of smooth muscle in the mammalian gas exchange system

Answer 10

• Smooth muscle is found throughout the walls of the bronchi and bronchioles
  —> helps to regulate the flow of air into the lungs by dilating when more air is needed and constricting when less air is needed

Question 11

Explain the structure and function of elastic fibres in the mammalian gas exchange system

Answer 11

• present in all lung tissues. ——> They are very important as they enable the lung to stretch and recoil. This ability to recoil is what makes expiration a passive process

Question 12

What are the stages of inhalation?

Answer 12

1. External intercostal muscles contract, internal relax
2. Ribcage moves up and out
3. Diaphragm contracts and flattens
4. Volume of Thorax increases
5. Pressure inside thorax decreases
6. Air is drawn in

Question 13

What are the stages of exhalation?

Answer 13

1. External intercostal muscle relax, internal contract
2. Ribcage moves in and down
3. Diaphragm relaxes
4. Volume of thorax decreases
5. Pressure inside thorax increases
6. Air is forced out

Question 14

What is vital capacity?

Answer 14

the maximum volume of air that can be breathed in or out in one breath

Question 15

What is Tidal volume?

Answer 15

the volume of air that is breathed in or out during normal breathing (at rest)

Question 16

What is breathing rate

Answer 16

the number of breaths taken in one minute (one breath = taking air in and breathing it back out again)

Question 17

What is oxygen uptake?

Answer 17

the volume of oxygen used up by someone in a given time

Question 18

What is a spirometer used for?

Answer 18

Measures all the factors and their relationship

Question 19

What is the function of soda lime in the spirometer?

Answer 19

Absorbs CO2 expelled into the spirometer

Question 20

What is a spiracle?

Answer 20

an opening in the exoskeleton of an insect which has valves
It allows air to enter the insect and flow into the system of tracheae

Question 21

What liquid is inside the insects tracheoles?

Answer 21

Tracheal fluid

Question 22

What occurs at rest and when active for the insect?

Answer 22

1. Tracheal fluid seeps into the ends of the tracheoles from surrounding tissues
2. When active, muscles contract and draw the tracheal fluid up the tracheoles
   3, Gas exchange occurs with respiring tissues
3. Pressure in tracheoles lowers so more air from outside is drawn in - SA of tracheoles increases
4. More O2 diffuses through them directly to the tissues
5. Fluid moves back into the tracheole when the muscle relaxes

Question 23

Describe the mechanism of breathing in bony fish

Answer 23

1. Mouth opens, buccal cavity floor drops, operculum flap closes
2. Pressure decreases in mouth
3. Volume increases in mouth
4. Water moves into mouth
5. Mouth closes, buccal cavity floor rises, operculum flap opens
6. Pressure increases in mouth
7. Water moves down a pressure gradient, forced out over the gills through the operculum flap

Question 24

Explain the counter-current system in fish

Answer 24

• When swimming, the fish keeps a continuous flow of water over the gills
• This causes a steep concentration gradient to allow efficient gas exchange