3.1.1 Exchange surfaces

Question 1

Why do organisms need a gas exchange system

Answer 1

supply of oxygen to produce ATP through aerobic respiration
removal of carbon dioxide (waste product of aerobic respiration) - also can alter pH if it accumulates in tissues

Question 2

What is an organisms metabolic rate

Answer 2

the amount of energy expended by that organism in a given time

Question 3

What is an organisms basal metabolic rate

Answer 3

the metabolic rate at rest

Question 4

Give three ways which basal metabolic rate can be measured

Answer 4

1) respirometer - oxygen consumption
2) carbon dioxide probe - carbon dioxide consumption
3) calorimeter - heat production

Question 5

What is the equation for the surface area of a sphere

Answer 5

4(pi)r^2

Question 6

What is the equation for volume of a sphere

Answer 6

4/3(pi)r^3

Question 7

Give four features of an efficient gas exchange surface

Answer 7

1) large surface area
2) short diffusion distance
3) good blood supply
4) ventilation mechanism

Question 8

What is the function of smooth muscle tissue

Answer 8

helps to regulate flow of air by dilating / constricting when more / less air is needed in the lungs

Question 9

What is the function of elastic fibres

Answer 9

enables lung tissue to stretch and recoil, which makes expiration a passive process

Question 10

What is the function of ciliated epithelial cells

Answer 10

waft mucus produced in the goblet cells to the mouth where mucus is swallowed to the stomach (destroyed by stomach acid) or sneezed out

Question 11

What is the function of goblet cells

Answer 11

produce mucus which traps pathogens and prevents them from entering the lungs and bloodstream

Question 12

What is the function of squamous epithelial cells

Answer 12

they form the wall of the alveoli
- only one cell thick
- flattened cells which minimises diffusion distance for gases

Question 13

What tissues are present in the trachea

Answer 13

• connective tissue
• smooth muscle and elastic fibres
• ciliated epithelial cells + goblet cells
• c shaped cartilage ( no cartilage present where spine is to prevent friction from rubbing)

Question 14

Describe the structure of the bronchi

Answer 14

• similar structure to trachea but they have thinner walls and a smaller diameter
• cartilage is not c-shaped: may form full rings or irregular blocks

Question 15

Describe the structure of the bronchioles

Answer 15

• not usually supported by cartilage
• lined with ciliated epithelium but usually no goblet cells
• largest bronchioles have both smooth muscle and elastic fibres
• smallest bronchioles have only elastic fibres

Question 16

Describe the structure of alveoli

Answer 16

• one cell thick (squamous epithelium) - short diffusion distance
• good blood supply - concentration gradient is maintained as deoxygenated blood is constantly pumped through
• surfactant - gases dissolve into this to diffuse quicker

Question 17

Describe how the intercostal muscles work

Answer 17

they work antagonistically

Question 18

Describe the process of inhalation

Answer 18

1) external intercostals contract and internal intercostals relax
2) ribs move up and out
3) diaphragm contracts and flattens
4) volume in the thorax increases
5) pressure in the thorax decreases
6) atmospheric pressure is higher than the pressure in the lungs
7) so air moves along a pressure gradient into the lungs

Question 19

Describe the process of exhalation

Answer 19

1) external intercostals relax and internal intercostals contract
2) ribs move down and in
3) diaphragm relaxes
4) volume in the thorax decreases
5) pressure in the thorax increases
6) atmospheric pressure is lower than the pressure in the lungs
7) so air moves along a pressure gradient out of the lungs

Question 20

Describe how forced expiration occurs during exercise

Answer 20

1) internal intercostal muscles contract
2) ribs move down and out FAST
3) abdominal muscles contract
4) increase in upward pressure of diaphragm leading to forced expiration

Question 21

Describe how the spirometer equipment works

Answer 21

subject breathes into pipe and air enters chamber filled with water
- exhalation increases volume of water
this causes the trace to move upwards
carbon dioxide is absorbed by soda lime to prevent subject from reinhaling carbon dioxide
the total volume in the tank decreases over time as O2 is used up and CO2 is absorbed
- so trace falls over time

Question 22

Give some precautions when using a spirometer

Answer 22

ensure soda lime is present
wear a nose clip to prevent breathing through nose
use a clean mouthpiece

Question 23

Define tidal volume

Answer 23

the volume of air moved in and out of the lungs with each breath AT REST

Question 24

Define residual volume

Answer 24

volume of air that always remains in the lungs

Question 25

Define vital capacity

Answer 25

the largest possible volume of air that can be moved in and out of the lungs in one breath

Question 26

Define inspiratory reserve volume

Answer 26

how much more air can be breathed in over and above tidal volume

Question 27

Define expiratory reserve volume

Answer 27

how much more air can be breathed out over and above tidal volume

Question 28

Define total lung capacity

Answer 28

vital capacity + residual volume

Question 29

What is the calculation for ventilation rate (dm3/min)

Answer 29

tidal volume x breathing rate (/min)

Question 30

How do you find oxygen consumption (dm3/min) from a spirometer graph

Answer 30

the decrease in peaks over 1 minute

Question 31

Why are spiracles needed on insects

Answer 31

all insects have a rigid exoskeleton with a waxy coating so they are impermeable to gases

Question 32

Describe the structure of the ventilation mechanism in insects

Answer 32

air passes through the spiracle and enters the tracheae - supported by rings of chitin for structure (not cartilage) air moves into the tracheoles ends of tracheoles are filled with tracheal fluid - gases can dissolve into this to diffuse quicker

Question 33

How might insects adapt their ventilation mechanism when they are at rest

Answer 33

they may close their spiracles to reduce water loss by evaporation

Question 34

Give three ways how insects might adapt their ventilation mechanism when they are active

Answer 34

insects can contract and relax their thorax and abdominal muscles to alter the pressure inside the trachea - this draws air in and out during flight, tracheal fluid is drawn out of tracheoles into the respiring muscles - this reduces the diffusion distance between the air and muscle cells, increasing rate of diffusion larger insects may have air sacs which can be ventilated by using wing movement

Question 35

Describe the structure of a gill

Answer 35

each gill arc is attatched to two stacks of filaments on the surface of each filament are rows of lamellae lots of capillaries are in lamellae, and flow in the opposite direction to the flow of water

Question 36

Why do gills have a counter-current system

Answer 36

(blood flows in the opposite direction to the flow of water) ensures that the concentration gradient is maintained along the whole length of the capillary

Question 37

Describe how a fish's ventilation mechanism works

Answer 37

1) mouth opens and water enters buccal cavity 2) buccal cavity constricts and mouth closes, increasing pressure inside buccal cavity 3) water is forced into gill cavity and increases pressure there 4) increased pressure forced opercular valve to open, opening the operculum and water moves out over the gills 5) pressure outside the fish is greater than in the gill cavity so the opercular valve shuts 6) pressure in the buccal cavity has dropped and the buccal cavity expands as the mouth opens