Gas exchange

Question 1

Features of an efficient gas exchange system

Answer 1

1) Large SA:V
2) Short diffusion distance
3) Steep concentration gradient

Question 2

How does SA:V relate to an organisms size?

Answer 2

The smaller the organism the larger the SA:V.

Question 3

How does SA:V relate to organisms metabolic rate?

Answer 3

The smaller the SA:V the higher the metabolic rate.

Question 4

Why do multicellular organisms need gas exchange systems?

Answer 4

Smaller SA:V means more distance needs to be crossed for substances to reach cells.

Question 5

What are insect adaptations to limit water loss?

Answer 5

a) Small SA:V of place where water can evaporate
b) Have chitin waterproof lipid coated exoskeleton so water doesn’t evaporate across body
c) Spiracles can open and close

Question 6

Describe parts of the insect gas exchange system

Answer 6

SPIRACLE: Small valve opening across abdomen which lets O2 in and CO2 out.
TRACHEA: Internal tubing with disks to hold shape.
TRACHEOLS: Extended tubing to respiring tissue/cells

Question 7

How are insects adapted for large SA:V?

Answer 7

Lots of tracheoles.

Question 8

How are insects adapted for short diffusion distances?

Answer 8

Walls of tracheoles are thin + small in size so short distance between spiracles and tracheoles.

Question 9

How are insects adapted for steep diffusion distances?

Answer 9

Constant intake of O2 and production of CO2.

Question 10

Explain the process of gas exchange in insects

Answer 10

1) Simple diffusion: Cells make CO2 and use up O2 which makes a concentration gradient from atmosphere-inside.
2) Mass transport: Contraction and relaxing of abdominal muscles pumps gases across.
3) Pressure gradient: during flight when there is anaerobic respiration = lactate = lower water potential = water osmosis from tracheoles-cells = less volume in tracheoles = less pressure = air enters.

Question 11

Describe the parts of a fish’s gas exchange system

Answer 11

GILLS: 4 layers on each side of head.
GILL FILAMENTS: V shape stack together to make a gill
GILL LAMELLAE: Cover the gill filaments at right angles.

Question 12

How are fish adapted to large SA:V?

Answer 12

Many gill filaments covered by many gill lamellae at right angles.

Question 13

How are fish adapted to short diffusion distances?

Answer 13

Very thin lamellae + capillary bed in every lamellae.

Question 14

How are fishes adapted to steep concentration gradient?

Answer 14

Using the counter current flow mechanism.

Question 15

Explain the counter current flow mechanism

Answer 15

Water flows over gills in the opposite direction to the blood flow in capillaries so water is always slightly more concentrated than the blood. This ensures equilibrium is never reached and diffusion gradient is maintained across entire lamellae.

Question 16

Explain concurrent flow mechanism

Answer 16

Water flows in the same direction as blood ( water= 100% - blood= 0%)
So starts with rapid diffusion but reached 50% so not across entire lamellae.

Question 17

Explain the process of gas exchange in fish

Answer 17

Water in though mouth, water over lamellae, O2 diffuses into blood stream, waste CO2 diffuses into water and out through gills.

Question 18

What are plant adaptions to limit water loss?

Answer 18

a) Stomata: Can open and close- but mostly close
b) Waterproof cuticles: So no water loss across leaf

Question 19

What are some structural features of xerophytes?

Answer 19

a) Thick cuticles: Less evaporation.
b) Curled leaf: Trap water= increase humidity= lowers inside water potential= less water exits.
c) Hairy/ spiky leaf: Traps water.
d) Stomata in pits: Traps water.
e) Longer root network: Reach water in further places.

Question 20

Describe the parts of a plants gas exchange system

Answer 20

STOMATA: Many small pores on underside of leaf which open close to allow gas in and out.
AIR SPACES: In the spongy mesophyll allows gas to move around leaf.

Question 21

How are plants adapted to large SA:V?

Answer 21

Thin and flat leaf.

Question 22

How are plant adapted to short diffusion distances?

Answer 22

Thin and flat leaf.

Question 23

How are plants adapted to steep concentration gradients?

Answer 23

With the stomata open, production and consumption of O2 and CO2 in the leaf is sufficient to maintain a concentration gradient for gas exchange with the atmosphere and inside.

Question 24

Describe the parts of the human gas exchange system

Answer 24

LUNGS
NASAL CAVITY: Warms/moistens air entering lungs + goblet cells secrete mucus to trap dust/bacteria
TRACHEA: Tube supported by C-shaped cartilage to keep passage open during pressure change + lined with ciliated cells
BRONCHI: 2 narrow tubes supported by C-shaped rings + lined with ciliated cells
BRONCHIOLES: Made of muscle/elastic fiber to contract/relax
ALVEOLI: Mini air sacks which are site of gas exchange

Question 25

How are alveoli adapted to large SA:V?

Answer 25

300 million per each lung

Question 26

How are alveoli adapted to short diffusion distance?

Answer 26

Epithelium cells + wall of the capillary are 1 cell thin

Question 27

How are alveoli adapted to steep concentration distance?

Answer 27

Each alveoli is surrounded by a network of capillaries that remove exchanged gas

Question 28

Explain the process of inspiration

Answer 28

- External ICM contract = pulls ribs up and out - Internal ICM relax - Diaphragm contracts = flattens from dome position - Lung volume increases = pressure initially drops = Air moves in from atm pressure to lower pressure = pressure rises

Question 29

Explain the process of expiration

Answer 29

- External ICM relax - Internal ICM contract = pulls ribs down and in - Diaphragm relaxes = returns to dome position - Lung volume decreases = pressure initially > than atm pressure = air moves out of lungs from high pressure to atm pressure = pressure drops

Question 30

Explain gas exchange in the alveoli

Answer 30

- Blood vessel has a high concentration of CO2 = diffuses out to alveoli - Alveoli have a high concentration of O2 = diffuses out to blood vessel

Question 31

What apparatus is used to measure lung capacity?

Answer 31

Spirometer

Question 32

Tidal volume

Answer 32

The volume of air that enters + leaves the lungs at normal resting breath

Question 33

Vital capacity

Answer 33

Max volume of air we can inhale + exhale

Question 34

Residual volume

Answer 34

Volume of air left in lungs after strongest exhalation

Question 35

Total lung capacity

Answer 35

Vital capacity + residual volume

Question 36

Ventilation rate

Answer 36

Breaths per minute

Question 37

Pulmonary ventilation

Answer 37

The total volume of air that is moved into lungs during 1 minute

Question 38

How to calculate pulmonary ventilation

Answer 38

Tidal volume(dm3) * Ventilation rate(min-1)

Question 39

Describe how can lung diseases affect ventilation/gas exchange

Answer 39

- Narrowed bronchioles = less concentration of gas exchanged + less O2 delivered to respiring cells - Broken down/thicker alveoli walls = fewer and larger sacks = less SA:V so less concentration of gas exchange and can't expand as much

Question 40

Evaluate a lung disease graph for cigarettes + lung cancer

Answer 40

- Positive correlation trend - But data overlaps on certain points - Correlation doesn't = causation as other factors e.g. genetics, exposure, pollution, or other lung diseases can cause deaths and are not mentioned - There is no correlation statistic to show correlation is significant