Specialised Gas Exchange Surfaces

Question 1

Why do all orgaisms need to exchange substances with their environment?

Answer 1

• Oxygen + Glucose is needed for aereobic respiration to generate ATP
• Oxygen diffuses into cell through cell membrane
• CO2 diffuses out of the cell through cell membrane

Question 2

Why do microscopic organisms exchanges all the substances they need through cell membrane?

Answer 2

1. They have low rate of respiration - not active organisms
2. SA is large compared to volume of cell

Question 3

How do calculate SA:V ratio?

Answer 3

Ratio = SA ÷ V

Question 4

Describe the trend in SA:V ration in terms of cell size?

Answer 4

The SA:V ratio decreses as cells get larger

Question 5

Single-celled organisms

Answer 5

• Large SA:V ratio
• Transfer all substances diffuse directly across cell membrane
• Quick diffusion rate due to short diffusion distance

Question 6

Multicellular organisms

Answer 6

• Small SA:V ratio
• difficult to exchange substances to supply large volume through small SA
• Slow diffusion rate due to large diffusion distance between cells and outside environment
• Higher metabolic rate so use Oxygen and glucose faster

Question 7

Speciialised exchange surface in plants

Answer 7

• Large Surface Area
• hair cells on plant roots in soil
• increases rate of absorbing water by osmosis
• increase rate of absorbing mineral ions by active transport

Question 8

Speciialised exchange surface in alveoli 1

Answer 8

• Alveoli are made from thin layer of flst cells - alveolar epithilium (AE)
• decreases diffusion distance for O2 in and CO2 out of the blood
• increses diffusion rate

Question 9

Specialised exchange surface in alveoli 2

Answer 9

• large capillary network so good blood supply
• increased exchange of O2 and CO2
• lungs are ventilated so air in alveoli constantly replaced
• maintain concentrtion gardients of O2 and CO2

Question 10

Speciialised exchange surface in Fish

Answer 10

• Gills have large capilary network so good blood supply
• Gills exchanges gas between fish’s blood and water
• Gills are ventilated due tp fresh water
• maintain concentration gradient of O2 so increased diffusion rate

Question 11

Describe the structure of the lungs for gas exchange

Answer 11

1. Air enters trachea
2. Trachea splits into to bronchi - one bronchus for each lung
3. Bronchus branches into bronchioles
4. Gases exchange in alveoli at the end of bronchioles
5. Ribcage, intercostal muscle, diaphragm move air in and out of

Question 12

Structure 1 for efficient gas exchange

Answer 12

• Goblet Cells line the airways (nasal cavity)
• secrete mucus to trap dust and pathogen when air is inhaled
• stops them from reaching alveoli

Question 13

Structure 2 for efficient gas exchange

Answer 13

• Cilia on surface of epithelial cells
• Beat the mucus trapped with pathogens and dust
• Moves mucus upwards away from alveoli towards the throat to be swallowed & digested by stomach enzymes
• Prevents lung infections

Question 14

Structure 3 for efficient gas exchange

Answer 14

• Elastic Fibres in walls of trachea, bronchi, bronchioles and alveoli
• Inhalation: lungs inflate & elastic fibres are stretched
• Exhalation: fibres recoil to push air out
• Help the process of breathing out

Question 15

Structure 4 for efficient gas exchange

Answer 15

• Smooth Muscle in walls of trachea, bronchi and bronchioles
• Allows diameter to be controlled
• During exercise smooth muscle relaxes, makes tubes wider
• Less resistance to airflow, air moves in & out of lungs easily

Question 16

Structure 5 for efficient gas exchange

Answer 16

• Cartilage in walls of trachea and bronchi
• provides support
• Strong and flexible
• stops trachea & bronchi from collapsing when inhaling and pressure drops

Question 17

How is the Trachea adapted for efficient gas exchange?

Answer 17

• cartilage - C-shaped: no cartilage near oesophagus to allow food to pass down easily
• smooth muscle
• Ciliated epithelium
• Goblet cells

Question 18

Which Adaptation do all parts of the lumg have?

Answer 18

• Elastic fibres
• Help the process of breathing out

Question 19

How is the Bronchi adapted for efficient gas exchange?

Answer 19

• Cartilage - small pieces
• smooth muscle
• ciliated epithelium
• Goblet cells

Question 20

One structure all sizes of bronchioles don’t have?

Answer 20

• NO Cartilage
• to allow for flexibility and efficient airflow
• cartilage would restrict ability to expand and contract

Question 21

How is the Large Bronchiole adapted for efficient gas exchange?

Answer 21

• smooth muscle
• ciliated epithelium
• goblet cells

Question 22

How is the Smaller Bronchiole adapted for efficient gas exchange?

Answer 22

• Smooth muscle
• Ciliated epithelium

Question 23

How are the Smallest Bronchioles adapted for efficient gas exchange?

Answer 23

• Elastic fibres
• NO smooth muscle - maximise air flow efficiency in narrow airways, muscle contraction could restrict air passage.
• NO ciliated epithelium - prevent clogging, very small diameter of airways remains open for gas exchange.

Question 24

Why do smaller bronchioles, smallest bronchioles not have goblet cells?

Answer 24

• maximize airflow efficiency
• mucus production could obstruct air flow.

Question 25

How are the Alveoli adapted for efficient gas exchange?

Answer 25

• Elastic fibres
• Large SA - lots of alveoli
• Short diffusion distance - very thin walls, made squamous epithelial cells.
• Maintains a concentration gradient - large capillary network to remove exchanged gases
• NO smooth muscle - flexibility to expand and contract freely for efficient gas exchange
• NO ciliated epithelium - primary function is gas exchange, not removing mucus & pathogens