Exchange

Question 1

What is the relationship between the size and structure of an organism and its SA:vol ratio?

Answer 1

As the size or structure of an organism increases the SA:vol ratio decreases because vol increases at much faster rate than SA

Question 2

What things need to be transferred between an organism and its environment?

Answer 2

Oxygen,co2,urea,heat,waste and nutrients

Question 3

How do you calculate SA:vol ratio?

Answer 3

Assume a uniform shape calculate SA and volume then divide the surface are by the volume

Question 4

What is Ficks law

Answer 4

Rate of diffusion = surface area x concentration difference / distance

Question 5

What are the 6 features of a specialist gas exchange surface?

Answer 5

1. Large SA to vol ratio increases rate of exchange
2. Very thin so short diffusion distance
3. Selectively permeable only allows certain materials to cross
4. Movement of environmental medium to maintain steep diffusion gradient eg in air as fastest
5. Moist surface
6. Located internally to be protected

Question 6

What is the relationship between surface area to volume ratio and metabolic rate?

Answer 6

The higher the metabolic rate the greater the SA:vol ratio so it looses more heat so needs a higher metabolic rate for greater delivery of o2 to the tissues and cells. Generally smaller organisms

Question 7

How do single celled organisms exchange substances?

Answer 7

Have a large SA:vol ratio so oxygen is absorbed by diffusion across cell membrane the gas exchange surface making it easier to perform gas exchange

Question 8

How do larger organisms have to perform gas exchange?

Answer 8

Have a transport system

Question 9

How are insects adapted for efficient gas exchange?

Answer 9

Evolved an internal network of tubes called trachea supported by strengthened rings to prevent collapse. The trachea divides into smaller dead end tubes called tracheoles which extend into the body tissue of the insects. This creates a short diffusion pathway from oxygen in the air to the respiring tissues via the tracheoles

Question 10

How do insects reduce water loss? When they need large sa:vol ratio for gas exchange?

Answer 10

Waterproof covering on body made up if chitin with a waterproof cuticle. Spiracles can open and close when they close it reduces water loss and also the tracheal system is internal.

Question 11

What three ways do respiratory gases move in and out of the tracheal system?

Answer 11

1. Along a diffusion gradient
2. Mass transport
3. The ends of tracheoles are filled with water

Question 12

How does an insect move gas out along a diffusion gradient?

Answer 12

1. Along a diffusion gradient when cells respire oxygen is used up so concentration at ends of tracheoles is low so O2 diffuses down trachea and tracheoles where there is a high concentration. When co2 is produced by respiration it creates a diffusion gradient in opposite direction high to low in air out of trachea. Diffusion occurs in air so much more rapid

Question 13

How do insects move gas by mass transport?

Answer 13

2. Mass transport- contraction of muscles of insects squeeze trachea allowing mass movement of air in and out sped up by abdominal pumping

Question 14

How does air move into the insect due to water at end of tracheoles?

Answer 14

3. The ends of tracheoles are filled with water when cells respire anaerobically produces lactate lowering water potential so water moves into cells from tracheoles by osmosis decreasing volume of water in tracheoles so they can draw air further into them the final diffusion pathway is a gas as rapid but greater water evaporation

Question 15

What have fish evolved for efficient gas exchange?

Answer 15

Gills located behind the head which are a specialist gas exchange surface.

Question 16

What are gills made up of and how does this help?

Answer 16

Made up of gill filaments stacked up in piles at right angles are gill lamellae which increase the surface area

Question 17

What happens to water when it gets to the gills?

Answer 17

Forced over the gills

Question 18

What are gills made up of?

Answer 18

Gill filaments in piles with gill lamellae at right angles which increases surface area

Question 19

Why are gills needed?

Answer 19

In water there is 25x less oxygen than air

Question 20

How do fish maintain steep concentration gradients?

Answer 20

Ventilation and good supply

Question 21

What is countercurrent flow?

Answer 21

Blood moves through the capillaries in the lamella in the opposite direction to the flow of water over the gill lamella.

Question 22

Why is countercurrent flow more efficient for diffusion?

Answer 22

Diffusion gradient existe over the whole length of the lamella so oxygen is constantly diffusing from the air down a diffusion gradient into the blood

Question 23

What is parallel flow?

Answer 23

Water and blood flow in the same direction

Question 24

Why is parallel flow less efficient?

Answer 24

Only maintained along half the lamella so water cant diffuse when saturations are the same in the blood and water so reach equilibrium

Question 25

Where does most gas exchange happen in the plant?

Answer 25

In the leaves

Question 26

What two processes do plants perform?

Answer 26

Photosynthesis and respiration

Question 27

What two things make diffusion fast in plants?

Answer 27

No living cells are far from air and it takes place in the gas phase so more rapid

Question 28

How is the leaf adapted for exchange?

Answer 28

1. Very thin so short diffusion pathways 2. Large surface area to volume ratio 3. Stomata so gas can come into contact with mesophyll cells and they can open and close due to the guard cells

Question 29

How is the leaf adapted to reduce water loss?

Answer 29

Stomata closes so reduces water loss by transpiration

Question 30

What are some adaptations of xerophytic plants to reduce water loss?

Answer 30

1. Stomata in pits or grooves to trap moist air reducing water potential gradient 2. Rolling up leaves protects lower epidermis traps region of air so no water potential gradient 3. Hairy leaves trap moist air reducing water potential gradient 4. Reduced surface area to volume ratio for example needles, cacti, holly, desert plants

Question 31

How are the lungs adapted for gas exchange?

Answer 31

1. Large surface to volume ratio 2. Reduced heat loss as it is internal 3. Thin alveoli and capillary walls reduces diffusion pathway 4. Concentration gradient due to capillaries always moving blood away 5. Moist 6. Pigment transports co2 and o2 7. Contains squamous epithelium

Question 32

What is the trachea and how is it prevented from collapsing?

Answer 32

A flexible airway lined with ciliated epithelium and goblet cells supported by rings of cartilage to prevent collapse when we breathe in

Question 33

What is the bronchi and how is it prevented from collapsing?

Answer 33

Where trachea splits in two lined with cilia supported with cartilage to prevent collapse

Question 34

What are bronchioles?

Answer 34

Made up of muscle lined with epithelium cells so they can constrict to control the flow of air in and out of the alveoli

Question 35

What are alveoli and why do they have elastic fibres?

Answer 35

Minute air sacs at the end of the bronchiole lined with epithelium and elastic tissue so that they can stretch and fill with air then spring back

Question 36

What is the pathway of blood from the alveolus to the blood?

Answer 36

Moves across epithelium cells of alveolus then down a concentration gradient through the endothelial cells in the capillaries which are just 1 cell thick

Question 37

What two ways makes diffusion between alveolus and blood so rapid?

Answer 37

1. Pulmonary capillaries are thin so red blood cells are slowed down to fit through so more time for diffusion 2. Distance reduced red blood cells are flattened against the capillary walls

Question 38

What are the 6 ways alveoli are adapted for efficient gas exchange?

Answer 38

1. Red blood cells are slowed through pulmonary capillaires allowing more time for diffusion 2. Distance reduced red blood cells are flattened against capillary walls 3. Walls of alveoli and capillaries are thin diffusion pathway is short 4. Alveoli and pulmonary capillaries have large SA 5. Breathing constantly ventilated lungs and heart pumps blood around alveoli maintaining a steep concentration gradient 6. Blood flow through the pulmonary capillaries maintains a concentration gradient

Question 39

What is correlation?

Answer 39

When a change in 1 or 2 variables is reflected by a change in another variable

Question 40

What is causation?

Answer 40

When it is scientifically proven that one variable directly causes something else

Question 41

What are the risk factors for lung disease?

Answer 41

Smoking, air pollution, genetic makeup, infections, occupation

Question 42

How does asthma effect the lungs?

Answer 42

Muscle walls of bronchi contract and walls secrete more mucus so diameter of airway is reduced so flow of air is reduced

Question 43

What happens in inspiration?

Answer 43

External intercostal muscles contract while internal intercostal muscles relax Ribcage moves upwards and outwards Diaphragm contracts and flattens Thoracic volume increases so pressure decreases Air moves into lungs from atmosphere down a pressure gradient Active process

Question 44

What happens in expiration?

Answer 44

External intercostal muscles relax while internal intercostal muscles contract Ribs move downwards and inwards Diaphragm relaxes and becomes dome shaped Thoracic volume decreases so pressure increases Air moves out if lungs down a pressure gradient Passive process Energy only needed for forced expiration

Question 45

What is ventilation?

Answer 45

When air is constantly moved in and out of the lungs called inspiration and expiration to maintain a diffusion gradient across the alveolar epithelium

Question 46

What is the equation for pulmonary ventilation rate?

Answer 46

Tidal volume x breathing rate

Question 47

What is tidal volume?

Answer 47

Volume of air normally taken in at each breath

Question 48

What is breathing rate?

Answer 48

Number of breaths taken in a minute