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Biology AS > Transport > Flashcards

Transport Flashcards

1
Q

Haemoglobin structure

A

haemoglobin is a protein with quaternary structure - it is formed of 4 polypeptide chains, each of which is associated with a haem group (which contains an Fe2+ ion)

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2
Q

What are the haemoglobins?

A

a group of chemically similar molecules found in many different organisms.

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3
Q

How many O2 molecules can each Hb transport?

A

4

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4
Q

Where is haemoglobin found?

A

in red blood cells

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5
Q

where does the loading and unloading of oxygen from haemoglobin occur?

A

Haemoglobin loads oxygen in regions of high pO2- the lungs.

Haemoglobin unloads oxygen is respiring tissues, where pO2 is low.

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6
Q

what is the role of haemoglobin?

A

to transport oxygen from the lungs to respiring tissues.

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7
Q

How does Haemoglobin differ between species?

A

Each species produces a haemoglobin with a slightly different primary structure. The molecule therefore has slightly different tertiary and quaternary structures, and so different oxygen binding properties. The haemoglobin molecules of different species can have a high or low affinity for oxygen.

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8
Q

High vs low affinity for oxygen of haemoglobin

A

Haemoglobins with a high affinity for oxygen take up oxygen more easily, but release it less easily. The converse is true for haemoglobins with a low affinity for oxygen.

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9
Q

What does the affinity of haemoglobin for oxygen depend on?

A

the partial pressures of O2 and CO2

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10
Q

Why is the oxyhaemoglobin dissociation curve S-shaped?

A

due to the cooperative nature of oxygen binding - the binding of the first oxygen causes a shape change in haemoglobin which makes the binding of further oxygens easier. As haemoglobin becomes saturated, it is harder for more oxygen molecules to bind as fewer binding sites are available.

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11
Q

Describe why the oxyhaemoglobin dissociation curve has regions with different gradients

A

The steep section in the middle of the curve is where it is easier for oxygen to bind - a small change in pO2 leads to a large increase in percentage saturation. The shallower parts of the curve are where it is harder for oxygen to bind.

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12
Q

Describe the link between the position of the oxyhaemoglobin dissociation curve and the affinity of haemoglobin for oxygen

A

The further left the curve is, the greater the affinity of haemoglobin for oxygen. O2 is loaded readily but unloaded less easily.

The further to the right the curve, the lower the affinity of haemoglobin for oxygen. O2 is loaded less readily but unloaded more easily.

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13
Q

Describe the Bohr effect. why is this important? + OxyHb curve shift

A

Oxygen is unloaded from haemoglobin more readily at higher partial pressures of CO2.
Respiring cells produce CO2 and require oxygen for respiration.
Rate of oxygen unloading increases - so the oxyhaemoglobin dissociation curve shifts to the right.

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14
Q

For what kinds of organisms is it an adaptation for the oxyhaemoglobin dissociation curve to be shifted to the left?
Why is this important?

A

species that lives in an environment with a lower pO2 - e.g. at high altitude or depleted oxygen environment
Haemoglobin has a higher affinity for oxygen and more oxygen is loaded.

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15
Q

For what kinds of organisms is it an adaptation for the oxyhaemoglobin dissociation curve to be shifted to the right?

A

very active species - so more oxygen is unloaded in respiring tissues for aerobic respiration.

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16
Q

Why do multicellular organisms require a specialised transport system?

A

to carry raw materials from specialised exchange organs to body cells - important as surface area to volume ratio is low.

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17
Q

What is the purpose of the double circulatory system in mammals?

A

when blood passes through the lungs, its pressure is reduced. If it were to travel to the rest of the body straight away, the low pressure would make circulation very slow. Blood is returned to the heart to increase its pressure before going to the rest of the body, so substances are delivered quickly. This is important due to the high metabolism of mammals.

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18
Q

double circulatory system meaning

A

blood passes through the heart twice in each full circuit of the body.

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19
Q

pattern of blood circulation - start at the vena cava, include heart chambers and some organs

A 
⇒Vena cava 
⇒ (right atrium and ventricle) 
⇒ pulmonary artery 
⇒ lungs 
⇒ pulmonary vein 
⇒ (left atrium and ventricle) 
⇒ aorta 
⇒ renal artery 
⇒ (kidney) 
⇒ renal vein (body) 
⇒ vena cava again
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20
Q

where and what does the right side of the heart pump blood?

A

deoxygenated blood, to the lungs

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21
Q

where and what does the left side of the heart pump blood?

A

oxygenated blood, to the body

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22
Q

role and structure of atria and ventricles

A

chambers of the heart with muscular walls (contract to pump blood). Blood passes into the atria first, then the ventricles. Ventricles have thicker muscular walls than atria as atria only have to pump blood a short distance to the ventricles, while ventricles pump blood to the lungs/ rest of the body.

23
Q

purpose of valves

A

to prevent backflow of blood

24
Q

what valves are there in the heart?

A

atrioventricular valves - between atria and ventricles

semilunar valves - between ventricles and arteries

25
Q

which vessels supply blood to the heart muscle?

A

coronary arteries

26
Q

Describe the vessels entering and leaving the heart

A
  • Aorta - connected to the left ventricle, carries oxygenated blood to all parts of the body except the lungs.
  • Vena cava - connected to the right atrium, carries deoxygenated blood back from all tissues except the lungs.
  • Pulmonary artery - connected to the right ventricle, carries deoxygenated blood to the lungs, where it is oxygenated and CO2 is removed.
  • Pulmonary vein - connected to the left atrium, brings oxygenated blood back from the lungs.
27
Q

in which of the vessels entering and leaving the heart is blood pressure highest? lowest?

A

pressure is highest in the aorta and lowest in the vena cava

28
Q

why does the left side of the heart have a thicker muscular wall than the right?

A

as the right side pumps blood to the lungs whereas the left side pumps blood a much further distance to the body.

29
Q

why do ventricles have thicker muscular walls than arteries?

A

as they require stronger contractions to pump blood a further distance.

30
Q

how is high pressure needed to pump blood out of the heart and around the body created in the left ventricle?

A

the muscular wall contracts.

31
Q

what are the 3 stages of the cardiac cycle?

A

atrial systole, ventricular systole, diastole

32
Q

what happens during atrial systole? the cardiac cycle

A
  • The ventricles relax and the atria contract, decreasing atrial volume so increasing pressure in the chambers - this forces blood into the ventricles.
  • The AV valves are open in this stage.
33
Q

what happens during ventricular systole? the cardiac cycle

A
  • The atria relax.
  • The ventricle walls contract at the same time, thereby decreasing ventricular volume and increasing ventricular pressure.
  • Ventricular pressure exceeds atrial pressure, so the AV valves close to prevent backflow of blood.
  • When ventricular pressure is higher than arterial pressure, the semilunar valves open and blood is forced from the ventricles to the arteries.
34
Q

what happens during diastole? the cardiac cycle

A
  • Atria and ventricles both relax.
  • Pressure is higher in the arteries than the ventricles so the SL valves close to prevent backflow.
  • Blood returns to the atria via the vena cava and pulmonary vein.
  • The atria fill, and the pressure in them rises.
  • When atrial pressure>ventricular pressure, the AV valves open, so blood flows into the ventricles passively.
  • The atria then contract and the whole cycle starts again.
35
Q

artery structure related to function

A
  • thick muscular layer so can constrict to maintain high pressure
  • thick elastic layer so wall can stretch and recoil with every heartbeat.
  • no valves - blood is always under high pressure so won’t flow backwards.
36
Q

arteriole structure related to function

A
  • thinner walls than arteries as blood pressure isn’t as high.
  • there is still a fairly thick muscle layer to allow constriction of the lumen to control the movement of blood into capillaries.
37
Q

vein structure related to function

A
  • Elastic and muscle layers are thinner - as pressure is lower
  • The wall is thin - there is no need for a thick wall since pressure in veins is too low to cause bursting. This also means veins can be flattened easily.
  • Valves - to stop the backflow of blood, which could occur due to the low pressure.
  • Blood flow through veins is helped by the contraction of body muscles surrounding them.
38
Q

capillary adaptations for exchange

A
  • Found very near cells so there is a short diffusion pathway.
  • Walls are one cell thick, which also shortens the diffusion pathway.
  • Blood flow here is slower, to allow more time for exchange.
39
Q

where does exchange directly with cells occur?

A

in and out of the tissue fluid surrounding cells

40
Q

describe how tissue fluid is formed and returned to the circulatory system

A
  • high hydrostatic pressure in the capillaries (at the arterial end) compared to in tissue fluid forces water and small molecules out.
  • large proteins remain in the capillary
  • at the venule end, there is low water potential in the capillary due to the high concentration of plasma proteins
  • water enters by osmosis
  • excess tissue fluid is drained via the lymphatic system.
41
Q

how is excess tissue fluid returned to the circulatory system?

A

drained via the lymphatic system and returned at the lymph nodes

42
Q

function of capillaries

A

to exchange metabolic materials between the blood and body cells.

43
Q

capillary structure

A

narrow lumen and thin endothelial lining - no muscles or valves.

44
Q

capillary beds

A

networks of capillaries in a tissue

- large numbers of capillaries here increase the surface area for exchange.

45
Q

cohesion-tension theory - transport of water in the xylem

A
  • water evaporates from the leaf via the stomata (=transpiration)
  • this creates tension, pulling more water into the leaf.
  • there is cohesion between water molecules due to hydrogen bonding, so the whole column of water in the xylem is pulled upwards.
  • water enters the stem through the roots.
46
Q

mass flow theory - translocation of solutes in the phloem

A
  1. solutes are actively transported from the sieve tube into companion cells.
  2. this decreases the water potential in the sieve tube.
  3. water moves into the sieve tube by osmosis, down a water potential gradient.
  4. this increases pressure in the sieve tube at the source end.
  5. this leads to a mass flow of solutes from source to sink, down a pressure gradient.
  6. at the sink, solutes are unloaded to be used or stored.
    opposite processes to source occur at the sink.
47
Q

name a source and a sink in translocation

A

source - leaves

sink - storage organs, fruit

48
Q

function of arteries

A

transport blood quickly under high pressure from the heart to the rest of the body.

49
Q

function of arterioles

A

to carry blood, under lower pressure than in arteries, from arteries to capillaries, and to control the flow of blood.

50
Q

function of veins

A

carry blood from capillaries/ organs back to the heart under low pressure.

51
Q

return of tissue fluid to the circulatory system (3)

A
  • hydrostatic pressure is lower in the capillaries than in the tissue fluid at the venule end
  • water potential in the capillary is lower than in the tissue fluid due to the high concentration of plasma proteins.
  • water enters the capillaries by osmosis, down a WP gradient.
  • excess tissue fluid returns via the lymphatic system.
52
Q

2 methods of investigating translocation in plants

A

radioactive tracer and ringing experiments

53
Q

what happens in ringing experiments? How can the movement of substances be determined?
to investigate translocation

A

part of a plant (leaf) is supplied with an organic substance with a radioactive label - containing a radioactive isotope.
The radioactive substance will be incorporated into organic substances produced by the leaf (via photosynthesis) which are transported around the plant by translocation.

The movement of substances can be determined via autoradiography. The plant is killed and placed on photographic film - radioactive substance is present where film turns black.
Results show translocation from source to sink over time.

54
Q

what happens in radioactive tracer experiments? What does this show?
to investigate translocation

A

The outer protective layer and phloem are removed from the full circumference of a section of stem. Over time, the section of stem above the missing ring swells with liquid rich in sugars.

Non-photosynthetic tissue below the ring withers and dies as sugars are no longer transported to this region. The tissue above the ring continues to grow.

This shows that the phloem rather than the xylem are responsible for the translocation of sugars.

Biology AS (10 decks)

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