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AL. AQA Biology > exchange > Flashcards

exchange Flashcards

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1
Q

Fick’s law

A

rate of diffusion = (SA x conc. gradient) /diffusion pathway

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2
Q

4 adaptations of specialised exchange surfaces to increase the rate of exchange

A
  • short diffusion pathway
  • large surface area
  • good blood supply
  • selectively permeable membrane
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3
Q

main adaptation of fish gills in regard to diffusion

A

countercurrent blood flow - concentration gradient is maintained all the way along the gill

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4
Q

adaptations of insects when more oxygen is required then provided by diffusion (2)

A
  • abdominal pumping - spiracles close, muscles pull skeletal plates of abdominal sections together, pumping air into air sacks deeper into the tracheoles
  • at rest water leaks across cell membranes of muscle cells, when are respiring anaerobically, produce lactate which lowers water potential of muscle cells so water moves from tracheoles to muscle cells drawing air in tracheoles closer to muscle cells, reducing diffusion distance for oxygen
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5
Q

ATP

A

product of respiration used directly by cells for energy

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6
Q

when red blood cell enters capillary…

A
  • slows slightly as is squashed, allowing more time for diffusion (pressure reduce)
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7
Q

tidal breathing

A

air goes in and out through the same route

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8
Q

pulmonary ventilation

A

air into the lungs per minute

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9
Q

eq. pulmonary ventilation

A

PV = TV (vital capacity) x BR (breathing rate)

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10
Q

mass transport system

A

a means by which materials are moved from exchange surfaces to other locations within the organism where the materials are required by cells, involves mass flow

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11
Q

structure of main fish gas exchange surface

A

gill filaments stacked in piles, with gill lamellae at 90 degrees to increase SA

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12
Q

adaptations for gas exchange in leaves (5)

A
  • diffusion takes place in gas phase which is more effective than in water
  • large air spaces - numerous interconnecting air spaces in mesophyll so gas readily comes into contact with mesophyll cells
  • large SA of mesophyll cells = rapid diffusion
  • many small pores - stomata - no cell is far from stomata = short diffusion pathway
  • stomata surrounded by guard cells so can be opened/closed when needed - controlling rate of gas exchange
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13
Q

insect adaptations to reduce water loss (4)

A
  • small SA:V to minimise area over which water is lost
  • waterproof covering over body - chitin exoskeleton covered by waxy cuticle
  • spiracles can be closed to reduce water loss (only at rest as conflicts with need for O2)
  • tracheae carry oxygenated air directly to tissues
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14
Q

xerophytes

A

adapted to live in areas without much water

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15
Q

adaptations of xerophytes (5)

A
  • thick waxy cuticle - waterproof barrier
  • rolling up leaves - traps air around stomata on lower epidermis (underside of leaf) and increases water potential of trapped air, reducing water potential gradient and reducing water loss
  • hairy leaves - (esp. lower epidermis) trap moist air next to leaf surface, reducing water potential gradient, reducing water loss
  • stomata in pits/grooves - trap air, reducing WPG
  • reduced SA:V of leaves - reducing area over which water loss can occur = slower rate of diffusion
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16
Q

mass transport system

A

a means by which materials are moved from exchange surfaces to other locations within the organism where the materials are required by cells - involved mass flow

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17
Q

open circulatory system

A

blood pumped by tubular, sac-like heart through short vessels into large spaces in the body cavity - blood bathes cells before reentering the heart through holes

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18
Q

closed circulatory system

A

blood pumped by heart through a series of arteries and veins - oxygen transported around body by blood and diffuses through capillary walls into cells

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19
Q

open circulatory systems useful for

A

the hydraulic movements of the body or its components

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20
Q

closed circulatory systems useful for

A

large, active animals where oxygen cannot easily be transported to the interior of the body - also allow more control over distribution of blood flow by contracting/dilating blood vessels

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21
Q

double circulatory system

A

where blood is pumped to the lungs separately to the body - pumped to lungs then returns to heart to be pumped around body

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22
Q

‘heart is myogenic’ meaning

A

its contractions are initiated from within the muscle itself rather then nervous impulses from outside

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23
Q

where is initial stimulus for contraction from

A

Sinoatrial node (SAN) in wall of right atrium

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24
Q

‘describe how a heartbeat is initiated and coordinated’ [5]

A
  • the SAN sends out an impulse of electrical excitement which spreads out across atria causing them to contract
  • non-conductive tissue layer (atrioventricular septum) stops the impulse being transmitted to the ventricles immediately
  • the wave enters the AVN which, after a short delay (allowing time for the atria to empty and the ventricles to fill), conveys a wave of electrical excitement between the ventricles
  • the Bundle of His conducts wave through atrioventricular septum to the branching fibres of purkyne tissue
  • the wave is released from tissue, causing quick contraction of the ventricles, from the bottom of the heart upwards
25
Q

features of an artery (9) [incl. pressure values]

A
  • thick muscular wall
  • much elastic tissue
  • small lumen relative to diameter
  • capable of constriction
  • non-permeable
  • valves in aorta + pulmonary artery only
  • high pressure (10-16kPa)
  • blood moves in pulses
  • flows quickly
26
Q

features of a vein (9) [incl. pressure values]

A
  • thin muscular walls
  • little elastic tissue
  • large lumen relative to diameter
  • not capable of constriction
  • not permeable
  • valves through all veins
  • low pressure (1 kPa)
  • no pulse
  • flows slowly
27
Q

features of a capillary (6) [incl. pressure values]

A
  • only endothelium walls
  • links arteries and veins
  • blood Changes from oxygenated to deoxygenated
  • blood pressure reducing (4-1 kPA)
  • slow flow
  • permeable
28
Q

contents of tissue fluid

A
  • glucose
  • amino acids
  • fatty acids
  • ions in solution
  • oxygen
29
Q

role of tissue fluid

A

a means by which materials are exchanged between blood and cells - the immediate environment of cells

30
Q

formation of tissue fluid

A
  • as blood pumped through arteries to capillaries, high pressure is created at the arterial end of capillaries
  • high pressure causes tissue fluid to move out of blood plasma, out of capillaries, although opposed by 2 forces:
      • hydrostatic pressure of tissue fluid outside capillaries
      • lower water potential of the blood due to plasma proteins that cause water to move back into the blood within capillaries

however, combined effect of all forces creates overall pressure which pushes tissue fluid out of capillaries

31
Q

ultrafiltration

A

type of filtration under pressure - pressure is only great enough to force small molecules out fo capillaries, leaving behind all cells/proteins in the blood as too large to cross membranes

32
Q

2 ways tissue fluid moves back into blood

A
  • directly via capillaries, as a result of wp gradient and osmosis
  • lymphatic system
33
Q

how does tissue fluid return to blood 1 - (directly)

A
  • loss of tissue fluid from capillaries reduces hydrostatic pressure inside them
  • by the time it has reached venous end of capillary network, hydrostatic pressure is lower then that of tissue fluid around it
    ∴ tissue fluid forced into capillaries by high hydrostatic pressure
  • ALSO - plasma has lost water but still contains proteins ∴ has a lower water potential then tissue fluid
    ∴ tissue fluid moves back by osmosis down WP gradient
34
Q

how does tissue fluid return to blood 2 - (lymphatic system)

A
  • remaining 5% of tissue fluid drains into lymphatic capillary
  • carried by vessels which gradually get bigger (pumped by the contracts on skeletal muscles) + hydrostatic pressure of exiting lymph at other end
  • drains back into bloodstream via 2 ducts close to heart
35
Q

SAN

A

sino atrial node

36
Q

AVN

A

atrio ventricular node

37
Q

passage of blood through heart

A

vena cava - right atrium - right ventricle - pulmonary artery - [LUNGS] - pulmonary vein - left atrium - left ventricle - aorta - [BODY]

38
Q

process (summarised) of control of heartbeat

A

SAN - atria - AVN - [DELAY] - nerves - bundle of His - nerve - purine tissue - ventricles

39
Q

high affinity for oxygen

A

takes up easily but releases less easily

40
Q

low affinity for oxygen

A

takes up less easily but releases more easily

41
Q

explain shape of oxygen dissociation curve

A
  • shape of molecule makes it different for first oxygen to bind to a site as they are closely united ∴ low oxygen partial pressure, little oxygen binds on ∴ gradient of curve = shallow
  • binding of first molecule changed quaternary structure, causing shape to change, making easier for oxygen to bind ∴ requires smaller increase in partial pressure to get 2nd O2 to bind then 1st O2 ∴ gradient increases
  • after binding of 3rd molecule, although theoretically should be easier due to changing of quaternary structure, ore difficult as probability of collisions reduced as most binding sites occupied ∴ gradient flattens again
42
Q

the further left the oxygen dissociation curve…

A

the higher the oxygen affinity

43
Q

the further right the oxygen dissociation curve…

A

the lower the oxygen affinity

44
Q

effect of increasing CO2 conc on oxygen affinity

A

makes it lower as more CO2 increases acidity of blood, causing haemoglobin to change shape

45
Q

higher pH = … affinity

A

higher affinity - oxygen more easily loaded

46
Q

lower pH = … affinity

A

lower affinity - oxygen less easily loaded but more easily released ∴ oxygen more easily released at respiring tissues ∴ more active the tissue, the more oxygen unloaded

47
Q

structure of xylem vessels

A

long, tube-like structures formed from dead cells (vessel elements ) joined end to end

48
Q

transpiration stream

A

continuous column of water in the vessels due to cohesion-tension
(transpiration –> water loss from leaves, cohesion between water molecules due to polarity and H-bonds mean water is pulled upwards)

49
Q

how is water transported up xylem

A
  • water evaporated from mesophyll cells into air spaces, and out through stomata
  • water potential In mesophyll is lowered so water enters from neighbouring cells (ultimately from xylem)
  • more water molecules are drawn up as a result of cohesion-tension, creating a transpiration stream up the xylem
  • mineral ions actively transported I -> lower WP -> water In by osmosis = high HS pressure
50
Q

where is the phloem located on vascular bundle

A

on the outside

51
Q

source of phloem-transported materials

A

leaves

52
Q

sink of phloem-transported materials

A

tips of roots and shoots and roots where sugars converted to starch

53
Q

how does transportation in the phloem occur

A
  • solutes produces In leaf diffuse into companion cell and are then transported into the phloem by active transport
  • creating a low water potential, ∴ water moves into phloem by osmosis from xylem, creating high hydrostatic pressure
  • at the sink glucose is used in respiration/converted to starch ∴ solute diffuses out of phloem, creating a high water potential
    ∴ water moves back into xylem by osmosis, creating a low hydrostatic pressure
  • the solution ∴ moves down the phloem, down the hydrostatic pressure gradient, from source to sink
54
Q

role of companion cells

A

carry out living functions for sieve tube elements - eg. provide energy for AT

55
Q

translocation

A

movement of solutes in a plant from source to sink

56
Q

how is conc. gradient at sink maintained?

A

enzymes change solutes to ensure conc is lower then at source

57
Q

evidence supporting mass flow theory (4)

A
  • if rig of bark cut (including phloem but not xylem) from woody stem, bulge forms above the ring - fluid in bulge has HIGHER conc of sugars hone fluid below ring ∴ downwards flow of sugars
  • radioactive tracer used to track movement of organic substances - eg. CO2 containing radioactive 14C
  • pressure investigated using aphids - mouthpieces left in so sap comes out - faster nearer leaves = pressure gradient
  • metabolic inhibitor (stops ATP production) introduced, translocation stops - evidence active transport is involved.
58
Q

why does the aortic pressure increase at start of relaxation period?
- importance?

A
  • gradually pressure falls (not below 12KPa) because of elasticity of the aortic wall creating RECOIL ACTION
  • especial for blood to be continually delivered to tissues

AL. AQA Biology (18 decks)

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