B3.1 Gas Exchange

Question 1

Properties of gas-exchange surfaces

Answer 1

1. Thin – Short diffusion distance
2. Moist – Dissolve respiratory gases
3. Large Surface area – Maximize diffusion
4. Permeable to respiratory gases – allow oxygen and carbon dioxide to pass through
   E.g. Lung, Gills

Question 2

Ventilation

Answer 2

he inhalation and exhalation_ of air using the ventilation system

Question 3

Gas exchange

Answer 3

The diffusion of gases across the alveoli

Question 4

Cell respiration

Answer 4

A controlled release of energy from organic substance inside the cell.

Question 5

Alveoli – Adaptations

Answer 5

It is the site for gas exchange
Large surface area:
–> There are many spherical shape alveoli

Maintain concentration gradient:
–> Surrounded by rich blood capillaries

Short diffusion distance:
–>Single-cell thick wall of type 1 pneumocytes

Question 6

type 1 pneumocytes

Answer 6

Extremely thin alveolar cells that are adapted to carry out gas exchange

Question 7

Type 2 pneumocytes

Answer 7

Secrete a fluid to keep the inner surface moist and allow gases to dissolve

Solution contain surfactant (natural detergent) to prevent the sides of the alveolus adhering to each other by reducing surface tension.

Question 8

Inspiration (Inhalation)

Answer 8

1) Diaphragm contract and flatten
2) External intercostal muscle contract
3) Internal intercostal muscles relax
4) Ribcage moves up and out
5) This increase thorax volume and _decrease_thorax pressure
6) Pressure inside the lungs is lower than the pressure outside
7) Therefore, air is forced in

Question 9

Expiration (Exhalation)

Answer 9

1) Diaphragm relax and become dome shaped
2) External intercostal muscle relax
3) Internal intercostal muscles contract
4) Ribcage moves down and in
5) This decrease thorax volume and _increase_thorax pressure
6) Pressure inside the lungs is higher than the pressure outside
7) Therefore, air is forced out

Question 10

Spirometer

Answer 10

is used to measure lung to measure lung volume

Question 11

Tidal volume

Answer 11

the volume of air that is breathed in or out when a person is at rest.

Question 12

Inspiratory reserve volume

Answer 12

the _maximum volume_of air that a person can breathe in.

Question 13

Expiratory reserve volume

Answer 13

the _maximum volume_of air that a person can breathe out.

Question 14

Vital capacity

Answer 14

the sum of the inspiratory reserve volume, the tidal volume and the expiratory reserve volume.

Question 15

Waxy Cuticle

Answer 15

Prevent water loss from evaporation

Question 16

Upper epidermis

Answer 16

Clear layer, allow light to pass through

Question 17

Lower epidermis

Answer 17

Horizontal rectangle layer

Question 18

Palisade mesophyll

Answer 18

Regular cells, contain a lot of chloroplasts

Question 19

Spongy mesophyll

Answer 19

Irregular cells with a lot of air space, increases surface area for gas exchange

Question 20

Guard cells

Answer 20

regulate the opening and closing of stomata (vertical rectangular)

Question 21

stomata

Answer 21

allow gas exchange to happen

Question 22

xylem

Answer 22

transport of water and mineral ions (pentagons or hexagon)

Question 23

Phloem

Answer 23

transport of sucrose and amino acid (circular)

Question 24

Factors that affects transpiration rate

Answer 24

Light intensity
Temperature
Air movement
Humidity

Question 25

Light intensity

Answer 25

1. Increase light intensity, increase transpiration
2. Photosynthesis occur under light, when there is light, more stomata open for gas exchange, increase evaporation.

Question 26

Temperature

Answer 26

1. Increase temperature, increase transpiration
2. Increase kinetic energy in water molecules, so water evaporate
   faster.

Question 27

Air movement

Answer 27

1. Increase air movement, increase transpiration
2. Removal of the humid air, increase water potential gradient
   between inside and outside of the leaf. Thus water vapor diffuse
   faster

Question 28

Humidity

Answer 28

1. Increase humidity, decrease transpiration
2. Less water potential gradient differences. Less water vapor
   diffuse out

Question 29

Stomatal density

Answer 29

Density of stomata varies between species of plants.

Using microscope, the stomatal density can be calculated and expressed as mm-2 or 𝜇m-2

Question 30

Haemoglobin and oxygen transport

Answer 30

Oxygen is bound to haemoglobin and carried in red blood cells.

Haemoglobin molecule consists of four polypeptide chains, with a haem prosthetic group at the centre of each chain.

Each haem group contains one iron atom, and one oxygen molecule binds to each iron atom.

So one haemoglobin molecule can bind up to four oxygen molecules.

Question 31

Cooperative binding

Answer 31

• Carrying oxygen
• Binds to haem group
• Increases affinity for more oxygen (induced-fit)
• Slightly alters shape of other 3 proteins

Question 32

Allosteric binding

Answer 32

• Carrying carbon dioxide
• Binds to allosteric site
• _Decreases_the affinity for oxygen (non-competitive inhibition)