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biology paper 1 > topic 3 - exchange of substances > Flashcards

topic 3 - exchange of substances Flashcards

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1
Q

why do single celled organisms diffuse easily

A

small surface area to volume ratio so distance of diffusion is smaller

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2
Q

adaptations of good exchange surfaces

A

-high surface area
-thin
-near blood supply

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3
Q

what do fish use for gas exchange

A

gills, which have an arch of gill filaments with lots of lamellae attached

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4
Q

what is the counter current exchange system in fish

A

blood and oxygen flow in opposite directions across the lamellae to maintain a steep diffusion gradient so the maximum amount of oxygen in the water can diffuse into the deoxygenated blood

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5
Q

how do fish ventilate

A

opens mouth to lower floor of buccal cavity so water flows in
shuts mouth so buccal cavity raises and increases pressure
water forced over gill filaments due to the pressure differences in the cavities

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6
Q

how do insects respire

A

muscle contraction forces oxygen through spiracles (small openings) in its tracheoles through diffusion

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7
Q

how do plants allow gas exchange

A

through stomata in leaves, no cell is far from stomata which reduces diffusion distance

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8
Q

structure of the cartilage in the lungs

A

supports the trachea and bronchi and prevents lungs from collapsing in the event of pressure drop from exhalation

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9
Q

structure of ciliated epithelium

A

present in bronchi, bronchioles and trachea, involved in moving mucus up to the throat where it can be swallowed to prevent lung infection

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10
Q

structure of goblet cells

A

secrete mucus in bronchi, bronchioles and trachea to trap bacteria with the help of lysozymes to break it down

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11
Q

structure of smooth muscle in lungs

A

ability to contract constricts the airway to control how much airflow goes to the alveoli

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12
Q

structure of elastic fibres

A

stretch when exhaling and recoil when inhaling controlling flow of air

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13
Q

process of inspiration

A

external intercostal muscles contract
internal intercostal muscles relax
ribs raise upwards
diaphragm contracts and flattens
volume inside thorax increases therefore pressure decreases compared to atmosphere

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14
Q

process of expiration

A

external intercostal muscles relax
internal intercostal muscles contract
ribs lower
diaphragm relaxes and raises upwards
volume inside thorax decreases therefore pressure increases compared to atmosphere

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15
Q

what is vital capacity

A

max volume of air that can be inhaled or exhaled in a single breath

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16
Q

what affects vital capacity

A

age, gender, height

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17
Q

what is tidal volume

A

the volume of air we breath in and out at each breath at rest

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18
Q

what is breathing rate

A

number of breaths per minute

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19
Q

how do you calculate breathing rate

A

use a spirometer graph and count peaks or troughs

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20
Q

what is the expiratory reserve volume

A

the volume of air that can be exhaled on top of the tidal volume eg during exercise

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21
Q

what is digestion

A

the hydrolysis of large biological molecules into smaller ones which can be absorbed across a membrane

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22
Q

how are carbohydrates digested

A

amylase in mouth breaks down polymers
maltase in ileum breaks down monosaccharides
sucrase and lactase break down disaccharides sucrose and lactose

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23
Q

how are lipids digested

A

lipases hydrolyse ester bond between fatty acids and monoglyceride
lipids are emulsified by bile salts from the liver
broken down in ileum

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24
Q

two advantages of bile salts

A

increase surface area of lipid
speed up reaction to break down lipids

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25
Q

how are proteins digested

A

endopeptidases- hydrolyse peptide bonds between specific amino acids in a polypeptide

exopeptidases- hydrolyse bonds at end of polypeptides

dipeptidases- break dipeptides into specific amino acids

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26
Q

how are lipids transported into epithelium cells

A

because they are polar they diffuse and are transported to endoplasmic reticulum where they are reformed to triglycerides, then move by vesciles into lymph system

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27
Q

how much oxygen can one haemoglobin bind to

A

4 oxygen molecules

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28
Q

what is partial pressure of oxygen

A

greater the amount of dissolved oxygen in cells, greater the partial pressure

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29
Q

what happens when the partial pressure of oxygen increases

A

affinity of haemoglobin increases so more loading (occuring in the lungs)

30
Q

why does partial pressure of oxygen decrease and what happens to haemoglobin

A

respiration uses up oxygen therefore affinity of haemoglobin decreases so oxygen is released in respiring tissues

31
Q

how does the affinity of haemoglobin change depending on saturation

A

after haemoglobin binds to 1 oxygen, its affinity increases due to a change in shape so can bind to more oxygens easier

32
Q

what is positive cooperativity in haemoglobin

A

2nd and 3rd oxygens bind easier

33
Q

why is fetal haemoglobin more affinitive

A

by the time oxygen reaches the placenta, the oxygen saturation of the blood has decreased so the fetus needs to survive at a low partial pressure

34
Q

what happens to haemoglobin if carbon dioxide is present (Bohr effect)

A

affinity of haemoglobin decreases causing it to be released as carbon dioxide creates acidic conditions causing the haemoglobin to change shape making it easier to release oxygen

35
Q

4 common features of circulatory system

A

suitable medium- blood (mostly containing water so substances can easily dissolve in it)

means of moving the medium- often a pump eg heart to maintain pressure differences

mechanism to control flow around body- valves

close system of vessels-

36
Q

function of the aorta

A

LEFT and carries blood to body

37
Q

function of pulmonary artery

A

RIGHT and carries blood to lungs

38
Q

function of pulmonary vein

A

LEFT and brings back blood from lungs

39
Q

function of vena cava

A

RIGHT and brings back blood from body

40
Q

why is the heart myogenic

A

in right atrium there is a region of fibres called the sinoatrial node which is the pacemaker. this creates a wave of electrical stimulation to make the atria contract at roughly the same time

41
Q

how do the electrical signals get to the ventricles

A

reaches the atrioventricular node and passes down the bundle of His to the apex of the heart which branches into Purkyne fibres which carry the wave upwards causing the ventricles to contract at the apex

42
Q

what is cardiac diastole

A

atria and ventricles relax
elastic recoil lowers pressure inside the heart chambers
blood returns through vena cava and PV
pressure increases inside atria opening the atrioventricular valves
blood flows in ventricles

43
Q

what is atrial systole

A

the atria contract forcing blood into ventricles

44
Q

what is ventricular systole

A

atrioventricular valves close
semilunar valves open due to contraction of ventricles
blood leaves through aorta and PA

45
Q

structure and function of arteries

A

carries blood away from heart

thick walled - withstand high BP
elastic tissue - stretch and recoil for smooth blood flow
smooth muscle- vary blood flow
smooth endothelium- reduce friction and ease flow

46
Q

structure and function of arterioles

A

branch off arteries to feed blood into capillaries

thinner less muscular walls

47
Q

structure and function of capillaries

A

site of metabolic exchange

one cell thick-fast exchange of substance

48
Q

structure and function of venules

A

larger than capillaries but smaller than veins

49
Q

structure and function of veins

A

carry blood from the body to the heart

wide lumen- maximise blood to heart
thin walled- low pressure of blood
valves- prevent blood backflow
little elastic tissue or smooth muscle- less blood

50
Q

function of tissue fluid

A

hydrostatic pressure created when blood pumps through arterys forcing blood fluid out of the capillaries (tissue fluid)

tissue fluid water potential is positive compared to blood causing water to move down the water potential gradient from the tissue fluid to the blood by osmosis

remaining tissue fluid is carried back to lymphatic system, lymph fluid containing waste products and less oxygen

51
Q

what do lymph nodes in the lymph fluid do

A

filter out bacteria with the help of lymphocytes which destroy pathogens as part of the immune system defences

52
Q

features of xylem tissue

A

-transport water and minerals
-long cylinders made of dead tissue with open ends
-xylem vessels contain pits which enable water to move sideways between the vessels
-thickened with lignin in spiral patterns to enable plant to remain flexible

53
Q

what is transpiration

A

the loss of water vapour from the stomata by evaporation

54
Q

how does light affect transpiration

A

more light- more stomata open for evaporation

55
Q

how does temperature affect transpiration

A

more heat- more kinetic energy, faster moving molecules so more evaporation

56
Q

how does humidity affect transpiration

A

more water vapour- water potential positive outside leaf so reduces water potential gradient

57
Q

how does wind affect transpiration

A

wind blows away humid air to maintain water potential gradient

58
Q

how does water move up a plant against gravity

A

cohesion tension theory
-cohesion
-adhesion
-root pressure

59
Q

how does cohesion help water molecules to travel up a plant

A

water is a dipolar molecule so can form hydrogen bonds with other water molecules
this makes the water molecules stick together and travel up the xylem as a CONTINUOUS column

60
Q

how does adhesion help water molecules to travel up a plant

A

water molecules stick to the xylem walls
narrower- more adhesion

61
Q

how does root pressure help water molecules to travel up a plant

A

as water moves into roots by osmosis it increases the volume of liquid inside root so the pressure increases, forcing water upwards

62
Q

describe steps of transpiration

A

1) water vapour evaporates out of stomata creating a lower pressure
2) more water is pulled up xylem to replace it due to negative pressure
3) cohesion of water molecules
4) adhesion
5) creating tension so column narrows

63
Q

what 2 key cells are in the phloem

A

sieve tube elements
companion cells

64
Q

features of sieve tube elements

A

living cells
dont contain nuclei
few organelles - makes it hollow so solution can be transported through

65
Q

what do companion cells do

A

provide ATP required for active transport of organic substances

66
Q

what are examples of the source and sink cells used in the phloem

A

source- photosynthesising cell
sink- respiring cell

67
Q

how does the source sink model work

A

1) source cells producing sucrose lowers water potential so water enters by osmosis
2) sink cells using up sucrose increases water potential so water leaves by osmosis
3) increases hydrostatic pressure in source cell
4) solution is forced to the sink cell via the phloem

68
Q

how does sucrose get from source to sieve tube element

A

1) sucrose diffuses down its conc gradient into the companion cell via facilitated diffusion
2) active transport of H+ occurs from the companion cell into the spaces within the cell walls using energy
3) this creates a conc gradient and therefore the H+ move down their conc gradient via carrier proteins into the sieve tubes
4) co transport of the sucrose with H+ occurs to transport sucrose into sieve tube element

69
Q

how does sucrose move through sieve tube element

A

1) increase of sucrose in sieve tube element lowers water potential
2) water enters sieve tube element from the surrounding xylem vessels via osmosis
3) increases hydrostatic pressure causing liquid to be forced to sink cell

70
Q

how does sucrose enter the sink cell

A

1) sucrose is used in respiration at sink
2) sucrose is actively transported into sink cell decreasing water potential
3) osmosis of water from the sieve tube element into sink cell
4) removal of water decreases the volume in sieve tube element so hydrostatic pressure decreases
5) movement of organic substances due to difference in hydrostatic pressure

71
Q

how do tracers work in providing evidence for translocation

A

plants are provided with radioactively labelled carbon dioxide which is used in photosynthesis to make sugars with the carbon in

thin slices of stem are cut and put on xray film which turns black when radioactive

this highlights where the phloem are and shows sugars are transported in the phloem

72
Q

how is the ringing experiment used to provide evidence for translocation

A

a ring of bark and phloem is removed from a tree trunk, the trunk will swell above the removed section

analysis of the liquid in this swelling shows it contains sugar, showing that when the phloem is removed sugar cannot be transported

biology paper 1 (4 decks)

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