Gas exchange

Question 1

How do Microorganisms Obtain Nutrients & Remove Waste?

Answer 1

By exchange via their surface

Nutrients (e.g. glucose, oxygen) move in by diffusion via their surface

Waste (e.g. carbon dioxide) moves out by diffusion via their surface

Question 2

Why are Microorganisms able to perform exchange via their surface?

Answer 2

Have a large surface area to volume ratio

Have a short diffusion distance

Have low demand

Question 3

Why can’t Animals/Plants perform exchange via their surface?

Answer 3

Have a small surface area to volume ratio
Multicellular (large diffusion distance and high demand)
Impermeable surface (prevent pathogens entering and reduce water loss)

Therefore, require specialised Exchange & Transport systems

Question 4

Exchange system

Answer 4

Increases the rate of diffusion of nutrients in and wastes out

Question 5

Transport system

Answer 5

Deliver nutrients and remove waste from all cells

Question 6

Why do Fish have Specialised Gas Exchange Systems?

Answer 6

Multicellular organism so has a small surface area to volume ratio, large diffusion distance, high demand & body surface impermeable

Therefore, cannot perform gas exchange (O2 in/CO2 out) via their surface, they require a specialised gas exchange system called Gills

Question 7

Structure of Gills in Fish

Answer 7

Many gill filaments and gill lamellae = large surface area

Gill lamellae have a thin wall (short diffusion distance) and are permeable

Ventilation brings in pure water (high oxygen, low carbon dioxide) and circulation brings in deoxygenated blood (low oxygen, high carbon dioxide), the water and blood pass over in opposite directions (countercurrent flow), which maintains a concentration gradient all the way along the gill lamellae

Question 8

Why do Insects have Specialised Gas Exchange Systems?

Answer 8

Multicellular organism so has a small surface area to volume ratio, large diffusion distance, high demand & body surface made of exoskeleton (impermeable barrier to reduce water loss)

Therefore, cannot perform gas exchange (O2 in/CO2 out) via their surface, they require a specialised gas exchange system called Tracheal System

Question 9

Structure of Tracheal System in Insects

Answer 9

Starts with openings on body surface called Spiracles

Spiracles contain valves, open = gas exchange, closed = prevent water loss

Spiracles connect to Trachea

Trachea connects to Tracheoles

Tracheoles connect directly to Respiring Cells (delivering oxygen, removing carbon dioxide)

Question 10

How does Gas Exchange occur in Tracheal System of Insects?

Answer 10

at rest = down a concentration gradient, oxygen moves in & carbon dioxide moves out by simple diffusion

when active = by ventilation, air inhaled for mass flow of O2 in & air exhaled for mass flow of CO2 out

Question 11

Function of Lungs

Answer 11

Site of gas exchange in mammals (oxygen into blood – used in cells for respiration,
carbon dioxide out of the blood – the toxic waste product of respiration)

Question 12

What are Lungs made up of?

Answer 12

Trachea, Bronchi, Bronchioles, Alveoli (+ capillaries)

Question 13

The function of trachea, bronchi, bronchioles

Answer 13

Transport of air and filter air, (bronchioles also controls the amount of air reaching alveoli)

Question 14

Structure of trachea/bronchi

Answer 14

Wall made of c-shaped cartilage

Cartilage is strong so trachea/bronchi do not collapse

cartilage is c-shaped to give flexibility

lining made of goblet cells and ciliated epithelial cells

goblet cells make mucus, which traps pathogens/particles

ciliated epithelial cells have cilia, which push mucus up and out of the lungs

Question 15

Structure of bronchioles

Answer 15

Wall made of smooth muscle

smooth muscle contracts, lumen narrows, bronchiole constricts

(occurs when surrounded by noxious gases – reduces amount reaching alveoli)

lining made of goblet cells and ciliated epithelial cells

Question 16

Adaptation of alveoli

Answer 16

Millions of tiny alveoli that are folded (large surface area)

Thin wall/one cell thick/squamous epithelial cells (short diffusion distance)

Elastic tissue in wall (stretches when breathing in to increase surface area, recoils when breathing out to push the air out)

Ventilation maintains concentration gradient (high oxygen, low carbon dioxide)

Question 17

Adaptation of capillaries

Answer 17

Millions of tiny capillaries (large surface area)

Thin wall/one cell thick/squamous epithelial cells (short diffusion distance)

Narrow lumen (increases diffusion time, decreases diffusion distance)

Circulation maintains concentration gradient (low oxygen, high carbon dioxide)

Question 18

How O2 moves from the alveoli to the capillaries?

Answer 18

By simple diffusion passing thru the alveolar epithelium and capillary epithelium

Question 19

How CO2 moves from capillaries to the alveoli?

Answer 19

By simple diffusion passing thru the capillary epithelium and alveoli epithelium

Question 20

Describe the process of Breathing/Ventilation

Answer 20

Breathing In/Inhalation = external intercostal muscles contract (rib cage moves up and out) & diaphragm contracts (flattens), therefore increase in volume in chest and decrease in pressure, so air moves in

Breathing Out/Exhalation = external intercostal muscle relax (rib cage moves down and in) & diaphragm relaxes (back to dome shape), therefore decrease in volume in chest and increase in pressure, so air pushed out (aided by elastic recoil in the alveoli)

Question 21

The formula for Pulmonary Ventilation

Answer 21

PV = tidal volume x ventilation rate

Tidal volume = volume of air breathed in/out in one breath

Ventilation rate = number of breaths per minute

Pulmonary Ventilation = volume of air breathed in/out per minute