Gas Exchange

Question 1

Adaptations of gas exchange

Answer 1

Large surface area

Thin so short diffusion pathway across the gas exchange surface.

Question 2

How do single called organisms exchange gases

Answer 2

Across their body surface.

They absorb and release gases by diffusion through outer surface.

They have a relatively large surface area, thin surface and short diffusion pathway so there’s no need for a gas exchange system as O2 can take part in a biochemical reaction soon as it diffuses.

Question 3

Gas exchange in fish

Answer 3

1. Fish use a counter current system for gas exchange.
2. Lower concentration of oxygen in water than air so fish have special adaptations.
3. Water containing oxygen enters mouth and passes out of gills.
4. Each gill made of lots of thin plates called gill filaments and so have a large surface area for gas exchange.
5. Gill filaments are covered in tiny structures called lamellae which increase the surface area.
6. Lamellae has lots of blood capillaries and thin surface layer of cells.
7. Blood flows through lamellae in one direction and water flows in the opposite direction - counter current system.

Question 4

Counter current system

Answer 4

Maintains a large concentration gradient between water and the blood. Oxygen concentration in water is always higher than in the blood, so as much oxygen as possible diffuses from water into blood.

Question 5

How does deoxygenated blood turn into oxygenated in fish

Answer 5

Flows in each gill arch, down inner side of each filament, across gill lamella and back. So it then becomes oxygenated.

Question 6

What happens to filaments when not wet

Answer 6

They stick together sí surface area becomes too small for efficient gas exchange

Question 7

Where do the gills lie

Answer 7

In a cavity in the pharynx between buccal cavity and oesophagus which is surrounded by a movable operculum.

Question 8

Describe and explain how counter current system leads to efficient gas exchange across gills?

Answer 8

1. Water and blood flow in opposite directions.
2. Maintains concentration gradient a long while length of gill.
3. Water has a higher concentration of oxygen than the blood that flows next to it.

Question 9

Which is a thicker lamellae not efficient

Answer 9

Longer diffusion distance do not efficient

Question 10

Why is a lamellae not efficient when it fuses

Answer 10

Surface area is reduced.

Question 11

Why is the direction of water and blood flow useful to a fish?

Answer 11

It has a concentration gradient maintained and more oxygen in the blood. More aerobic respiration to release energy for muscle contraction.

Question 12

Gill lamellae

Answer 12

The folds are kept supported and moist by the water that is continually pumped through the mouth and over the gills

Question 13

What do fish have that’s efficient in the lamellae

Answer 13

Fish also have an efficient transport system within the lamellae which maintains the concentration gradient across the lamellae.

Counter current system.

The arrangement of water flowing past the gills in the opposite direction to the blood (called countercurrent flow) means that they can extract oxygen at 3 times the rate a human can.

Question 14

Counter current system

Answer 14

As the blood flows in the opposite direction to the water, it always flows next to water that has given up less of its oxygen.

This way, the blood is absorbing more and more oxygen as it moves along. Even as the blood reaches the end of the lamella and is 80% or so saturated with oxygen, it is flowing past water which is at the beginning of the lamella and is 90 or 100% saturated.

Therefore, even when the blood is highly saturated, having flowed past most of the length of the lamellae, there is still a concentration gradient and it can continue to absorb oxygen from the water.

Question 15

Why is counter current system an advantage

Answer 15

Allows maximum oxygen to be absorbed by the blood from the water, by maintaining the concentration gradient the whole way through the gills.

This means fish can get enough oxygen without having to push large amounts of water through their gills, which would require a lot of energy, so the counter-current system is a more efficient way of increasing the amount of oxygen diffusing into the blood.

Question 16

Problem with insects

Answer 16

They lose water very easily through their body surface.

Question 17

Gas exchange in insects

Answer 17

1. Insects have microscopic air filled pipes called tracheae which they use in gas exchange.
2. Air moves into trachea thru spirackes

Question 18

What does insects use to move air in and out of spiracles

Answer 18

Rhythmic abdominal movements.

Question 19

What gives a large surface area in insects

Answer 19

Tracheae and tracheoles.

Tracheole lined with single layer of cells to minimise diffusion distance.

Question 20

For efficient gas exchange

Answer 20

1. Thin permeable surface over large areas

2. Balance the need of exchanging materials

Question 21

How do u reduce water loss

Answer 21

1. Water proof covering.
2. Small surface area: volume.
3. Close spiracles using muscles and tiny hairs around it - reduces evaporation

Question 22

Insects structure

Answer 22

1. Tracheae. Supported by cartilage to prevent collapse.
2. Tubes branch to tra helped and extend throughout its body therefore oxygen can be delivered direct to respiring tissues.
3. Movement of oxygen/ air along trachea is due to diffusion gradient and muscles in the insect contracting.

Question 23

How does oxygen move into gas exchange system when insect at rest

Answer 23

Due to concentration gradient. The concentration gradient maintained because the tracheoles dip into the respiring tissue.

Oxygen used in respiration and establish a concentration gradient so oxygen diffuses in.

Oxygen diffused into respiring cells and tissues from tracheae.

Question 24

Which plants exchange gases at the surface of the mesophyll cells

Answer 24

Dicotyledonous plants

Question 25

What's the waste gas produced when plants use CO2 for photosynthesis What about when its respiration

Answer 25

Oxygen Co2

Question 26

What's the main gas exchange surface in plants How are they well adapted

Answer 26

Surface of the mesophyll cells in the leaf. They're well adapted for their function as they have a large surface area

Question 27

What do you gases move in and out of

Answer 27

Special pores in the epidermis called stomata

Question 28

What does the stomata do

Answer 28

Opens to allow gas exchange and close if there is too much water loss

Question 29

What controls the opening and closing of the stomata

Answer 29

Guard cells

Question 30

How do plants reduce water loss

Answer 30

Stomata kept open during the day to allow gas exchange. Water enters guard cells making them turgid and that opens the stomatal pore. Guard cells close if plants get dehydrated and become flaccid. xerophytes are adapted to warm dry and windy conditions

Question 31

Adaptations of an xerophytic

Answer 31

Stomata sunk in pits. Trap moist air and reduce conc. gradient of water between leaf and air. So that reduces water diffusing out of the leaf and evaporating away. Hairs trap moist air around the stomata. Curled leaves with stomata inside, protecting them from wind. Wind increase rate of diffusion and evaporation. Reduced number of stomata so fewer places for water to evaporate from. Wavy waterproof cuticles on leaves and stems to reduce evaporation.

Question 32

Plants similar to insects as

Answer 32

No. Of cells far from external air. Diffusion takes place in air.

Question 33

Why might the rate of water uptake not be the same as rate of transpiration

Answer 33

1. Used in photosynthesis | 2. Used for support

Question 34

What are lungs

Answer 34

Specialised organs for gas exchange.

Question 35

What do humans need in their body

Answer 35

Oxygen in the blood And to get rid of co2 made by respiring cells.

Question 36

Use of gas exchange system in humans

Answer 36

Remove co2 and put oxygen in blood

Question 37

Order of human gas exchange system

Answer 37

1. Trachea 2. Bronchus / Bronchi 3. Bronchioles 4. Alveoli 5. Intercostal muscles and external 6. Rib cage 7. Lungs 8. Diaphragm 9. Thorax 10. Abdomen

Question 38

Trachea

Answer 38

Flexible airway supported by cartilages so don't collapse. Walls made of muscles and lined with ciliates epithelium and globlet cells.

Question 39

Bronchi

Answer 39

Two divisions of trachea. Lead to each lung supported by cartilage and contain muscles. Produce mucus

Question 40

Bronchioles

Answer 40

Series of branching tubes. Muscle walls with epithelium cells lined across it.

Question 41

Alveoli

Answer 41

Minute air sacs - gas exchange and end of bronchioles. Made of epithelial and elastic so stretch when fill with air and spring back when breathe out.

Question 42

Ribcage

Answer 42

Support and protect lungs

Question 43

Volume of o2 required and volume of co2 needed to be removed is high in mammals because

Answer 43

Large no. Of cells Maintain high body temp so high metabolic and respiratory rates

Question 44

Why are lungs inside body

Answer 44

Would lose water and dry outside the body Air not dense enough to support and protect delicate structure

Question 45

Pulmonary ventilation

Answer 45

Total vol. of air taken into lungs in a given time PV (dm3/min) = TV (dm3) x VR (per min) TV usually 0.5 VR no. Of breathes in a min.

Question 46

What is ventilation

Answer 46

Breathing in and out. Inspiration and expiration.

Question 47

What is ventilation controlled by

Answer 47

Diaphragm, internal and external intercostal muscles and ribcage.

Question 48

Inspiration

Answer 48

1. External intercostal and diaphragm muscles contract. 2. Rib cage up and out 3. Diaphragm muscle flat and down 4. Volume of thorax increases 5. Pressure inside decreases 6. Air drawn in (air flows from high pressure to low down trachea and into lungs) down the pressure gradient 7. Inspiration is an active process and requires energy

Question 49

Expiration

Answer 49

1. External intercostal and diaphragm muscles relax. 2. Ribcage down and in 3. Diaphragm curved and up 4. Volume in thorax decreases 5. Pressure increases 6. Air forced down pressure gradient and out of lungs. 7. Normal expiration is a passive process and doesn't require energy. It can be forced though where he external intercostal muscle relaxes and the internal intercostal muscles contract

Question 50

Antagonistic

Answer 50

Opposing intercostal muscles during time of expiration being forced.

Question 51

Where does gaseous exchange happen in humans

Answer 51

In the alveoli

Question 52

Alveoli

Answer 52

Air sacs where gas exchange occurs in lungs.

Question 53

What is each alveoli made up from

Answer 53

single layer of thin, flat cells called alveolar epithelium

Question 54

Adaptations of alveoli

Answer 54

1. Huge No. of Alveoli in lungs so big surface area for oxygen and carbon dioxide exchange. 2. Large surface area: volume ratio so speeds up gas exchange 3. Short diffusion pathway one cell thick so thin surface 4. Close contact with blood vessels and increase diffusion 5. Narrow so increase diffusion time as red blood cells slow down and have to squeeze through in a single file = keeps distance to diffusion 6. Steep concentration gradient of oxygen and carbon dioxide between alveoli and capillaries maintained by constant ventilation of lungs with air and blood flow. 7. Thin layer of fluid provides quicker diffusion as moist.

Question 55

What is the alveoli surrounded by

Answer 55

Capillaries

Question 56

What acts as a mass transport

Answer 56

The constant flow of internal medium (blood).

Question 57

When does diffusion happen quicker in alveoli

Answer 57

When surface is moist and large surface area

Question 58

How does gas exchange happen in the alveoli // describe how oxygen in the air reaches capillaries surrounding alveoli in the lungs

Answer 58

1. Oxygen from air moves down the trachea, bronchi, bronchioles and alveoli down a pressure gradient. 2. Oxygen diffuses out of alveoli, across alveolar epithelium To the capillary endothelium and then the capillary itself down a diffusion gradient into haemoglobin in the blood.

Question 59

How does alveoli try to maintain a conc. gradient

Answer 59

1. Blood needs to be taken away quickly. 2. Movement of blood away and replaced with low conc. 3. Ventilation of the lungs.

Question 60

Name two similarities and two differences between the gas exchange of an insect and a mammal

Answer 60

They both have a large surface area, Thin gas exchange surface, and a moist gas exchange surface. Concentration gradient achieved by ventilation. The difference is in mammals there is a transport circulatory system. Not in insects. Also respiratory surface in mammals is the alveoli, but in insects it is the junction between the tracheoles and the respiring tissues

Question 61

Suggest why gill lamella would not provide an efficient gas exchange surface on land

Answer 61

The surface area is reduced. The gills dry out. Prevents oxygen dissolving on the surface of the gills. No longer supported by water so the gills stick together with surface tension

Question 62

Smaller body mass means

Answer 62

Larger surface area to volume ratio

Question 63

Give two features of gills that allow efficient gas exchange

Answer 63

Counter current system which maintains concentration gradient. Thin epithelium cell for short diffusion

Question 64

Why would small animals such as worms not need gills

Answer 64

Large surface area to volume ratio so diffusion occurs over body surface

Question 65

Explain how the structure of the gas exchange system of an insect insures that there is a large surface area for gas exchange

Answer 65

Many branched tracheoles.

Question 66

Give one way in which the transport of oxygen to a muscle in an insect is different from that in a fish

Answer 66

Blood is not involved in insects

Question 67

What give gills a large surface area

Answer 67

Lots of lamella on filaments

Question 68

Why do some fish underwater sway

Answer 68

Provide more water over the surface which maintains a concentration gradient

Question 69

Xerophytes adaptations

Answer 69

1. Hairs so trap water vapour and water potential gradient decreased. 2. Stomata in pits so trap water vapour and water potential gradient decrease. 3. Thick cuticle layer so increased diffusion distance. 4. Waxy cuticle so reduces evaporation. 5. Folded leaves so trap water vapour and water potential gradient decreased. 6. Spines and needles. so reduces surface area to volume ratio.