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A Level Bio > Chapter 7 - Mass Transport > Flashcards

Chapter 7 - Mass Transport Flashcards

1
Q

What does the affinity of haemoglobin for oxygen mean

A
  • the ability of haemoglobin to attract, or bind, oxygen
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2
Q

What does the saturation of haemoglobin with oxygen mean

A

When haemoglobin is holding the maximum amount of oxygen it can bind

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3
Q

What does the loading/ association of haemoglobin mean

A

The binding of oxygen to haemoglobin

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4
Q

What does the unloading/ dissociation of haemoglobin

A

When oxygen detaches or unbinds from haemoglobin

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5
Q

What does the oxyhemoglobin dissociation curve show

A

That oxygen is loaded in regions of high partial pressure of oxygen and unloaded in regions if low partial pressure

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6
Q

Explain why the oxyhemoglobin graph show that at low partial pressures, o2 is unloaded and saturation is low and why it is the opposite at high partial pressures

A

Due to the positive cooperative of the oxygen binding to the haemoglobin
As at low partial pressure it is difficult for the first O2 molecule to bind to the haemoglobin so requires a large increase in partial pressure (hence why the graph is steep at first)
Once the first O2 molecule binds the quaternary structure of the haemoglobin, it changes in shape, which increases the affinity for the next oxygen to bind so binding the rest of the oxygen molecules only require a small increase in partial pressure (hence why the graph begins to level off)

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7
Q

What is the Bohr effect

A

When carbon dioxide concentration causes the oxyhaemoglobin curve to shift to the right. So the affinity for oxygen decreases because the carbon dioxide dissolves in the blood to form carbonic acid causing pH to decrease and these acidic conditions changes the shape of the haemoglobin slightly decreasing affinity and therefore unloads more oxygen

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8
Q

What effect will low CO2 conc have in the oxyhemoglobin affinity curve

A

Makes it shift to the left as the pH will increase as less H+ ions are released into the blood so the Shape of haemoglobin will change and oxygen affinity increases and therefore more oxygen is loaded

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9
Q

Explain the difference between fetal haemoglobin and adult haemoglobin

A

The fetal haemoglobin has a higher oxygen affinity than the adult haemoglobin as the foetus cannot inhale or exhale, so it’s source of oxygen comes from the mother haemoglobin in the blood supply, so the fetal haemoglobin has to have a high o2 affinity in order to take oxygen from the mother’s haemoglobin

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10
Q

Explain the difference between llama haemoglobin and human haemoglobin

A

Llamas live at high altitudes where there is a low partial pressure of oxygen compared to humans so has a higher oxygen affinity

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11
Q

Explain the difference between dove haemoglobin and human haemoglobin

A

Dove has a lower oxygen affinity compared to humans as they have a faster metabolism for aerobic respiration to provide for contracting muscle (so will produce more co2 causing their oxygen affinity to decrease)

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12
Q

Explain the difference between earthworms haemoglobin and human haemoglobin

A
  • earthworms haemoglobin has a higher oxygen affinity than humans as they live underground where there is a low partial pressure of oxygen
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13
Q

Why do mammals have a double circulatory system

A

To mamaage the pressure if the blood flow

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14
Q

What does it mean by double circulatory system

A

That the blood passes through the heart twice in each circuit, with one circuit which delivers blood to the lungs and the other which delivers blood to the rest of the body

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15
Q

How does the closed double circulatory system work in mammals

A

1) the blood flows through the lungs at a lower pressure, this prevents damage to the capillaries in the alveoli and at low speed to enable more time for gas exchange
2) the oxygenated blood from the lungs then goes back through the heart to be pumped out at higher pressure to the rest of the body, this is important to ensure that the blood reaches all the respiring cells in the body

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16
Q

What are the key blood vessels

A
  • coronary arteries
  • pulmonary artery and vein (connected to lungs)
  • renal artery and vein (connected to kidneys)
  • vena cava, aorta, pulmonary artery and vein (connected to heart)
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17
Q

Role of coronary arteries

A

Supply heart with oxygenated blood

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18
Q

Properties of the cardiac muscle (thick muscular layer in heart)

A
  • myogenic, meaning can contract and relax without needing any stimulation from the nervous system or hormones
  • never fatigues as long as it has a supply for oxygen
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19
Q

What happened if coronary arteries become blocked

A
  • can cause coronary heart disease as the coronary arteries won’t receive oxygen and therefore won’t be able to respire so the cells in cardiac muscles will die, resulting in myocardial infarction (a heart attack)
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20
Q

Properties of the left and right atria (atrium)

A
  • elastic walls to stretch when blood enters
  • thinner muscular wall than ventricular as they do not need to contact as blood is only pumping to ventricles and not to the whole body
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21
Q

Properties of the left and right ventricles

A
  • thicker muscular walls to enable a bigger contraction, this creates a high blood pressure to enable blood to flow longer distances
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22
Q

Why does the right ventricle have a thinner muscular wall compared to the left ventrical

A
  • As it Pumps blood to the lungs, so blood has to be at a low pressure to prevent damage to capillaries in the lungs and blood flows slowly allowing more time for gas exchange, this means that is has a thinner muscular wall compared to the left ventricle
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23
Q

Why does the left ventrical have thicker muscular walls compared to the right ventrical

A

Pumps blood to the body at high pressures to ensure blood reaches all the cells in the body, so therefore has a thicker muscular wall compared to the right ventricle to enable larger contractions of the muscle to create high pressure

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24
Q

Role of vena cava

A

Carries deoxygenated blood from the body to the right atrium

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25
Q

Role of pulmonary vein

A

Carries oxygenated blood from the lungs to the left atrium

26
Q

Role of pulmonary artery

A

Carries deoxygenated blood form the right ventricle to the lungs to become more oxygenated

27
Q

Role of aorta

A

Carries oxygenated blood from the left ventricle to the rest of the body

28
Q

Names of valves in heart and Where they are found

A

Semi lunar valve - in aorta and pulmonary artery
Atrioventricular valve - found between atrium and ventricles - Bicuspid valve (found on the left side) and Tricuspid valve (found in the right side)

29
Q

Role of septum

A

Separates the deoxygenated blood from the oxygenated blood to maintain a high concentration of oxygen in the oxygenated blood to maintain a concentration gradient to enable diffusion at respiring cells

30
Q

Roles of valves

A
  • enables blood to flow in one direction by opening when pressure is higher behind the valve and closing when the pressure is higher in front of the valve
31
Q

3 stages of cardiac cycle

A

1) Diastole
2) Atrial Systole
3) Ventricular systole

32
Q

What does systole mean

A

Contracting

33
Q

What does diastole mean

A

Relaxing

34
Q

What happens during diastole in the cardiac cycle

A

1) the atria and ventricular muscles are relaxed when the blood enters the atria via the vena cava and pulmonary vein
2) the blood flowing into the atria increases the pressure within the atria

35
Q

What happens during atria systole of the cardiac cycle

A

1) the atria muscular walls contract, increasing pressure further
2) this causes the atrioventricular valves to open and blood to flow into the ventricles
3) the ventricular muscle walls are then relaxed (ventricular diastole)

36
Q

What happens during ventricular systole in the cardiac cycle

A

1) the ventricular muscular walls contract, increasing the pressure beyond the pressure if the atria
2) this causes the atrioventricular valves to close and the semi lunar valves to open
3) the blood is pushed out of the ventricles into the arteries

37
Q

What is the cardiac output and stoke volume

A

Cardiac output = the volume of the blood which leaves one ventricle in one minute
Stroke volume = volume of blood that leaves the heart each beat

38
Q

How to work out cardiac output

A

Stroke volume x heart rate

39
Q

How do atrioventricular valves work

A
  • Open when pressure is higher in atria compared to ventricles
  • Close when pressure is higher in ventricles than in the atria
40
Q

How do semi lunar valves work

A
  • open when pressure is higher in ventricle than in arteries
  • closes when pressure is higher in arteries than ventricles
41
Q

how does the properties of arteries link to its function

A
  • very thick muscles layer so that constriction and dilation can occur to control the volume of blood
  • thick elastic layer to help maintain blood pressure, as the walls can stretch and recoil in response to the heart beat
  • thick walls to help prevent vessels from bursting due to the high pressure
  • no valves
  • narrow lumen to increase pressure
42
Q

Properties of veins

A
  • relatively thin muscle layer so it isn’t able to control blood flow (compared to arteries)
  • thin elastic walls as pressure is much lower
  • thin wall as the pressure is much lower so there is a low risk of bursting, plus the thinness means that the vessels are easily flattened which helps the flow of blood up to the heart
  • has valves
  • wide lumen
43
Q

properties of capillaries and how it is an advantage

A
  • narrow lumen, reduces flow rate giving more time for diffusion
  • single cell thick, reduces diffusion distance
  • small diameter gives a large surface area to volume ration and reduces diffusion distance
  • red blood cells in contact with the wall increases time for diffusion
  • fenestrations to allow large molecules through
  • flattened cells reduces diffusion distance
44
Q

Properties of arterioles

A
  • thick muscle layer (compared to arteries) to help restrict blood flow into the capillaries
  • thinner elastic wall than the arteries as the pressure is lower
  • thinner wall than arteries as pressure is lower
  • no valves
45
Q

Function of blood vessels

A
  • arteries - transports blood from the heart to the arterioles under high pressure
  • arterioles - transports blood from the arteries to the capillaries
  • capillaries - site of exchange of materials between blood and tissue fluid
  • veins - transports blood from the capillaries back to the heart
46
Q

Explain how tissue fluid is formed and how it may be returned to the circulatory system (6)

A

1) as blood enters the capillaries the hydrostatic pressure of blood is high at arterial end of the capillary
2) causes water and soluble molecules pass out
3) large proteins and molecules remain
4) this lowers the water potential and hydrostatic pressure
5) water moves back into the venule end of the capillary by osmosis
6) lymphatic system absorbs any excess tissue fluid which returns to the circulatory system

47
Q

What is tissue fluid

A

Fluid containing water, glucose, amino acids, ions and oxygen which batches the tissues

48
Q

Properties of two key cells in the phloem tissue

A

1) sieve tube elements- are living cells with few organelles but no nucleus
2) companion cells - provide ATP for active transport f organic substances

49
Q

How does translocation occur - mass flow hypothesis

A

1) photosynthesis will occur in the chloroplast of the leaves creating organic substances e.g sucrose
2) this creates a high concentration of sucrose at the source cell (the leaves), therefore sucroses diffuses down a concentration into the companion cells via facilitated diffusion
3) active transport of hydrogen ions occur form the companion cells into the spaces within the cell walls of the companion cell using ATP
4) this creates a concentration gradient and therefore the hydrogen ions move down the concentration gradient via co transporter proteins into the sieve tube elements and the co transport of sucrose with the H+ ions occurs via the co transport proteins to transport the sucrose into sieve tube elements
5) the increase of sucrose in the sieve tube elements lowers the water potential causing water to move into the sieve tube elements from the xylem by osmosis
6) this increase in water volume in the sieve tube elements increases the hydrostatic pressure causing liquid to be forced towards the sink cells (root cells), where there is a low hydrostatic pressure

50
Q

What happens in the sink cells

A

Sucrose is used in respiration at the sink or stored mass insoluble starch

51
Q

Why is there a low hydrostatic pressure at the sink cells (last step of mass flow hypothesis)

A

1) more sucrose is actively transported into the sink cell, which causes the water potential to decrease
2) this results in osmosis of water from the sieve tube elements into the sink cell (some water also returns to the xylem)
3) the removals of water decreases the volume in the sieve tube element and therefore the hydrostatic pressure decreases

52
Q

Evidence/Investigations to show that sugars are transported in the phloem

A
  • Tracers
  • Ringing experiment
  • aphids - as they feed on plants by penetrating the phloem and extracting the contents in the sieve tube elements
53
Q

How do tracers work

A

1) Plants are provided with only radioactively labelled carbon dioxide and over time this is absorbed into the plant and used in photosynthesis to create sugars which all contain the radioactively labelled carbon dioxide
2) Thin slices from the stems are then cut and placed on the x rays film and the stem that contains the sugars turn black and this highlights where the phloem is showing that the sugars are transported in the phloem

54
Q

How does the ringing experiment work

A

1) a ring of bark and phloem are removed off a tree trunk, resulting in the trunks to swell above the removed section
2) analysis of the liquid in this swelling shows it contains sugar, and this shows that when the phloem is removes the sugars cannot be transported and therefore proves that the phloem transports sugars

55
Q

Factors affecting transpiration

A
  • Light intensity- increases rate of transpiration as more light will cause more stomata to open, which increases the surface area for the evaporation of water
  • temperature - increases rate of transpiration as more heat means faster kinetic energy, so faster moving molecules and therefore more evaporation
  • humidity - decreases rate of transpiration as more water vapour in the air means that the water potential outside is higher than inside the leaf therefore it reduces the water potential gradient so less evaporation occurs
  • wind - increases rate of transpiration as more wind will blow away the air containing the water vapour, maintaining the water potential gradient
56
Q

What are the factors that contribute to the cohesion tension theory (how water moves up the xylem)

A
  • cohesion
  • adhesion
  • root pressure
57
Q

How does cohesion contribute to the cohesion tension theory

A
  • water is dipolar which enables hydrogen bonds to form between the different water molecules, this creates cohesion between water molecules (they stick together) , therefore water travels up the xylem as a continuous water column
58
Q

How does adhesion (also known as capillarity) contribute to the cohesion tension theory

A
  • Adhesion of water is when water sticks to other molecules and so the water adheres to the xylem walls
  • the narrower the xylem the bigger the impact of adhesion
59
Q

How does root pressure contribute to the cohesion tension theory

A
  • as water moves into the root by osmosis it increases the volume of liquid inside the root and therefore the pressure inside the root increases, this is known as root pressure
  • this increase in pressure in the roots forces water above it upwards (positive pressure)
60
Q

Explain the cohesion tension theory (how water moves up the xylem)

A

1) Water vapour evaporates out of the stomata on leaves, this loss in water volume creates a lower pressure
2) when this water is lost by transpiration more water is pulled up the xylem to replace it (negative pressure)
3) due to hydrogen binds between the water molecules, the water molecules are cohesive, which creates a continuous column of water within the xylem
4) water molecules also adhere to the walls of the xylem, which helps pull the water column upwards
5) as this column of water is pulled up the xylem it creates tension, pulling it he xylem into become narrower, increasing the impact of adhesion

A Level Bio (15 decks)

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