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Biology Y12 > gas exchange > Flashcards

gas exchange Flashcards

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1
Q

as size increases, internal and external stems are…?

A

needed to facilitate exchange of substances and heat.

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2
Q

small organisms have a large..?

A

surface ares to volume ratio

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3
Q

why do small animals loose heat more quickly?
also have a high..?

A

because of their large area to volume ratio
metabolism

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4
Q

larger organisms have a smaller…?

A

surface area to volume ratio

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5
Q

why do larger organisms have a higher demand for oxygen and glucose?

A

because they have more respiring cells

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6
Q

extra respiration means..?

A

extra waste products e.h co2 and heat

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7
Q

gas exchange in plants

A
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8
Q

what are dictyledonous plants?

A

plants that have mesophyl and stomata

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9
Q

what are the structures in a leaf and explain their roles?

A

waxy cuticle layer - prevents water loss by evaporation
upper epidermis - transparent to let light through
palisade mesophyll - main site of photosynthesis
spongy mesophyll - contain holes for gases to diffuse here, maintains conc gradient
stomata - holes formed by two gurad cells, main site of gas exchange
lower epidermis
xylem and phloem - transport sugar and water

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10
Q

why do plants need to go through photosynthesis?

A

so plants can use o2 for respiration to produce co2

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11
Q

where does oxygen and carbon dioxide come from during photosynthesis?

A

some carbon dioxide comes from respiration however most of it comes from the external air. in the same way some oxygen from photosynthesis is used in respiration but most of it diffuses out of the plant

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12
Q

explain what happens before photosynthesis when it’s dark?

A

oxygen diffuses into the lead

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13
Q

explain why plants have a fast, short diffusion pathway?

A

no living cell is far from the external air an therefore a source of oxygen and carbon dioxide

diffusion takes place in the gas phase which makes it more rapid than if it was in water

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14
Q

adaptions in a leaf?

A

large surface area - so absorbs as much sunlight as possible

thin - for light absorbtion , shorter diffusion pathway

transparent cuticle and epidermis - allows light to pass through for photosynthesis

long, narrow upper mesophyll cells and chloroplast - so collect sunlight

numerous stomata - for gas exchange, short diffusion pathway from one

stomata - opens and closes in changes to light intensity

may air spaces in lower mesophyll layer - allows rapid diffusion of co2 and o2

xylem and phloem - brings water and carries away sugar (glucose)

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15
Q

draw and label the stomata

A
  • chloroplast
  • nucleus
  • cell wall
  • vacoule
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16
Q

Explain why how oxygen and carbon dioxide enter and leave the stomata?

A

oxygen diffuses out of the stomata because there is a high concentration in the spongy mesophyll compared to the atmosphere, carbon dioxide diffuses into the stomata as its being constantly used in the palisade mesophyll, maintaining the conc gradient.

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17
Q

what causes stomata to open and close?

A

when carbon dioxide levels are low inside the plant, the guard cells gain water and become turgid, they curve out opening the stomata and allowing gases to diffuse in and out, water then evaporates through the stomata

high carbon dioxide levels cause guard cells to loose water, closing the stomata becoming flaccid.

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18
Q

what are xerophytic plants?

A

are plants which are adapted to survive in environments with limited water

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19
Q

how do plants limit water loss? what adaptions?

A

curled leaves - trap moisture to increase local humidity

hairs trap moisture- to increase local humidity

stomata sunken in - to trap moisture, more humid , less evaporation

thicker cuticle - to stop evaporation
longer root network - to reach more water

stomata - have ability to open and close when necessary to prevent water loss

smaller surface ares to volume ratio - slow rate of diffusion

20
Q

the rate of water uptake by a plant might not e the same as the rate of transpiration because..?

A
  • water is used for support/ turgidity
  • water used in photosynthesis
  • water used in hydrolysis
  • water produced during respiration
21
Q

gas exchange in insects

A
22
Q

why do insects have a high demand for oxygen?

A

because they are very active

23
Q

what is an insects exoskeleton made of?

A

a hard fibrous material for protection and a lipid layer to prevent water loss/ dehydration

24
Q

what is an insects system made up of?

A

trachea
tracheoles
spiracles

25
Q

what are spiracles?
What gases leave and enter?

A

round, valve like openings, running along the length of abdomen. oxygen and carbon dioxide enter and leave via the spiracles. trachea attaches to these openings

26
Q

role of spiracles?

A

controls water loss

27
Q

what is the trachea?

A

a network of internal tubes. the trachea tubes have rings within them to strengthen the tubes and keep them open

28
Q

what are the tracheoles?

A

the trachea branch into smaller tubes, deeper into the abdomen of the insect. these extend throughout all tissue in the insect to deliver oxygen to all respiring tissue

29
Q

there are three methods of moving gases in the tracheal system
1. gases moving by diffusion?

A

along a concentration gradient. when cells are respiring, oxygen is used up and so its concentration towards end of the tracheoles falls. this creates a concentration gradient that causes gaseous oxygen to diffuse from the atmosphere along the trachea and tracheoles to the cells.

carbon dioxide is produced by cells during respiration which creates a diffusion gradient in the opposite direction. this causes gaseous carbon dioxide to diffuse along the tracheoles and trachea from the cells to the atmosphere.

as diffusion in air is much more rapid than water, respiratory gases are exchanged quickly by this method

30
Q

second method of gas exchange?

A

mass transport. the contraction of muscles in insects can squeeze the trachea enabling mass movements of air in and out. this further speeds up the exchange of respiratory gases

31
Q

third method of gas exchange?

A

the end of the tracheoles are filled with water.

during periods of major activity, the muscle cells around the tracheoles respire and cary out anaerobic respiration. this produces lactate, which is soluble and lowers the water potential of the muscle cells.

water therefore moves into the cells from the tracheoles by osmosis. the water in the ends of the tracheoles decrease in volume and doing so draws water further into them.

this means that the final diffusion pathway is in a gas rather than a liquid phase and therefore diffusion is more rapid.

this increases the rate at which air is moved into the tracheoles but leads to greater water evaporation

32
Q

Terrestrial insects live on land. explain one problem for them?

A

water easily evaporates from the surface of their bodies and they can become easily dehydrated

33
Q

describe how some terrestial insects are adapted to limit water loss?

A

small SA to volume ratio to minimise the area over which water is lost

waterproof covering around their body surfaces. rigid outer skeleton of chitin that is covered with a waterproof cuticle

spiracles can be closed to reduce water loss. this conflicts with the need for oxygen so occurs largely when the insect is at rest.

34
Q

how are insects adapted for efficient diffusion?

A
  • large number of tracheoles - increases the surface area
  • walls of tracheoles are thin and short - distance between spiracles and tracheoles- short diffusion pathway
  • use of oxygen and production of carbon dioxide sets up steep diffusion gradients
35
Q

gas exchange in fish

A
36
Q

where do fish get their oxygen from?

A

from the surrounding water. this is because oxygen dissolves in water.

37
Q

why do fish need to be specially adapted to maintain diffusion?

A

because there is 30x less oxygen in water than in air

38
Q

fick’s law?

A

diffusion ∝ SA x difference in conc.
/length of diffusion path

39
Q

what is the operculum?

A

a protective, bony flap

40
Q

describe the structure of the gills

A
  • four layers of gills on both sides of their head - bony arch- v- shape
  • the gills are made up of a stack of gill filaments
  • each gill filament is covered in gill lamellae positioned at right angles to the filament
    which increases the surface area of the gills.
41
Q

how is water passed along fish gills?

A

water is taken in through the mouth and forced over the gills and out through an opening on each side of the body

42
Q

Describe fully the ventilation process in a bony fish

A
  1. Mouth opens (operculum is closed)
  2. The buccal cavity floor is lowered
  3. This increases the volume and decreases the pressure of the buccal cavity compared to outside
  4. Water rushes into the mouth down a pressure gradient
  5. Opercular cavity expands
  6. The buccal cavity floor is raised
  7. The pressure inside the buccal cavity is now higher than in the opercular cavity
  8. Water moves from buccal cavity over the gills into the opercular cavity
  9. The mouth is now closed and the operculum opens
  10. The sides of the opercular cavity move inwards, increasing the pressure
  11. Water rushes out of the fish through the operculum
43
Q

what is Countercurrent flow?

A

the flow of water in the gill lamellae and the flow of blood within them are in opposite directions - ensures more gas exchange takes place

44
Q

the arrangement of the counter current flow mean that…?

A
  • blood is already well loaded with oxygen, meets water which has its maximum concentration of oxygen. therefore diffusion of oxygen from the water to the blood takes place
  • blood with little oxygen in it meets the water, which has had most, but not all, of its oxygen removed. Again, diffusion of oxygen from the water to the blood takes place
45
Q

what does the Countercurrent system ensure?

A

ensures equilibrium is not reached
ensures that a diffusion gradient is maintained across the entire length of the gill filament

46
Q

DONE!!

A

Biology Y12 (20 decks)

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