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Biology A level AQA > Chapter 7 - Mass transport > Flashcards

Chapter 7 - Mass transport Flashcards

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1
Q

what is the quarternary structure of haemoglobin?

A

four polypeptides, each associated with a haem group which contains Fe 2+ which can combine with one molecule of oxygen each

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2
Q

what is the term for taking up oxygen in haemoglobin?

A

loading and unloading

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3
Q

what is the role of haemoglobin? (2)

A
  • readily associate with oxygen at gas exchange (high partial pressure)
  • readily dissociate at low partial pressures such as respiring tissues
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4
Q

why are their different haemoglobin in different animals?

A

different partial pressure e.g. high altitude

different dissociating required e.g. lugworms

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5
Q

explain the shape of oxygen dissociation curves (4)

A
  • difficult for first molecule to bind = shallow curve gradient
  • first molecule binding changes the shape making it easier for subsequent molecules to bind
  • positive cooperativity, the gradient steepens
  • lower probability of oxygen binding when oxygen is highly loaded means gradient levels off
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6
Q

what are the effects of CO2 on haemoglobin? (3)

A
  • reduced affinity for oxygen
  • release oxygen more readily at high CO2 conc. ,e.g. respiring tissues
  • slightly acidic, CO2 changes shape of haemoglobin
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7
Q

state the sequence of vessels in the heart from the vena cava to the aorta (12)

A
  • vena cava
  • right atrium
  • atrioventricular valve
  • right ventricle
  • semi-lunar valve
  • pulmonary artery
  • (lungs)
  • pulmonary vein
  • left atrium
  • atrioventricular valve
  • left ventricle
  • semi-lunar valve
  • aorta
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8
Q

name the 3 stages of the cardiac cycle

A

diastole
atrial systole
ventricular systole

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9
Q

what are the valves in veins and what do they do?

A

pocket valves prevent backflow

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10
Q

what is the action of diastole? (3)

A
  • blood returns to atria through vena cava and pulmonary vein
  • when pressure exceeds that in the ventricles the semi-lunar valves open allowing blood to drain into ventricles by gravity
  • semi-lunar valves remain open until the pressure in the atria has decreased below that of the ventricles
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11
Q

what is the action of atrial systole?

A

both atria contract at the same time along with further recoil of the ventricles, forcing the remaining blood in the atria into the ventricles

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12
Q

what is the action of ventricular systole? (2)

A
  • ventricles contract together, AV valves shut
  • pressure within ventricles rises further forcing the semilunar valves of aorta open due to higher pressure in ventricles
  • (creates high pressure for blood to go round whole body and back)
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13
Q

state the cardiac output calculation

A

heart rate x stroke volume = cardiac output

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14
Q

name the types of blood vessels (4)

A
  • arteries
  • arterioles
  • capillaries
  • veins
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15
Q

what are capillaries made from?

A

lining layer/epethelial cells

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16
Q

name the structures of arteries arterioles and veins (5)

A
  • tough fibrous outer layer
  • muscle layer - contraction for blood pressure
  • elastic layer - recoil
  • endothelium - reduce friction
  • lumen - cavity
17
Q

compare the main function of arteries to that of capillaries (2)

A
  • arteries carry blood around whole body by maintaining constant high blood pressure
  • capillaries, allow diffusion due to short diffusion pathway
18
Q

outline tissue fluid formation (2)

A
  • hydrostatic pressure created by pumping of the heart and narrow capillaries
  • at arteriole end of capillaries hydrostatic pressure forces tissue fluid into surrounding cells
19
Q

what forces resist the formation of tissue fluids? (2)

A
  • hydrostatic pressure of surrounding cells and fluid outside
  • lower water potential of blood due to plasma proteins
20
Q

outline the return of tissue fluid to the circulatory system (5)

A
  • reduced hydrostatic pressure at venous end due to loos of fluid
  • tissue fluid forced back into capillaries
  • capillaries have lower water potential
  • water moves down water potential gradient
  • remainder absorbed into lympatic capillaries which drain into the blood
21
Q

name the process of water loss through evaporation in plants

A

transpiration

22
Q

how does water move up the stem into the leaves?

A

in a continuous column of water up the xylem (caused by cohesion) known as transpiration pull, cohesion tension theory

23
Q

what is the function of the xylem?

A

to carry water up the stem from the roots (transport of water)

24
Q

what is the evidence in support of cohesion tension theory? (2)

A
  • change in diameter of tree trunks e.g. after rain
  • if xylem is broken, column of water is broken and water no longer passes upwards, in addition the the fact air is drawn in showing tension
25
Q

what is the function of the phloem?

A

transport of organic molecules

26
Q

what theory governs the mechanism of translocation?

A

mass-flow hypothesis

27
Q

outline the process by which sucrose enter sieve elements (3)

A
  • sucrose is manufactured and diffuses down conc. gradient into companion cells
  • hydrogen ions are actively transported from companion cells into spaces in the cell wall
  • hydrogen ions diffuse back down concentration gradient into the phloem through specific co-transport proteins with sucrose
28
Q

outline the process of mass flow through sieve elements (4)

A
  • lower water potential in the sieve element, water moves in from xylem
  • causes greater hydrostatic pressure
  • inverse is true at sink with respiring cells
  • mass flow of sucrose solution down hydrostatic pressure gradient to sink
29
Q

by what process does the sucrose leave the sieve elements once at the sink?

A

active transport

30
Q

what is the evidence to support mass flow? (5)

A
  • sap released from sieve tubes when cut shows pressure
  • conc. of sucrose higher in leaves
  • downward flow only occurs in day when leaves are photosythesising
  • sucrose increase in leaves results in sucrose increase in phloem
  • companion cells contain many mitochondria for active transport
31
Q

evidence questioning mass flow? (3)

A
  • unclear function of sieve plates
  • not all solutes move at same speed
  • sucrose delivered at same rate to all regions
32
Q

types of xylem/phloem experiments (2)

A
  • ringing experiments

- tracer experiments

33
Q

what is the evidence that translocation occurs in the phloem? (3)

A
  • phloem cut, organic molecules come out
  • plants given tracer CO2 show tracer in phloem after a short time
  • removal of a ring of phloem on a plant leaves sugars building up above the ring
34
Q

outline a ringing experiment on a tree and the expected results (2)

A
  • remove ring of protective layer and phloem

- area immediately above ring swells with sugars

35
Q

outline a tracer experiment and the expected results (4)

A
  • radioactive carbon absorbed by plant and incorporated into sugars
  • after some time thin slices of plant take and placed over X-ray photography film
  • were film is blackened shows where radioactive isotope in sugars is
  • these correspond with where the phloem is

Biology A level AQA (19 decks)

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