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Biology > B7 - Mass Transport > Flashcards

B7 - Mass Transport Flashcards

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1
Q

Why do we need a circulatory system?

A

All cells need a constant supply of reactants for metabolism: oxygen and glucose
Microscopic organisms: can gain these directly through diffusion
Larger organisms: made of layers of cells → diffusion distance would be too far to supply all cells with these reactants
Have evolved mass transport systems - digestive, circulatory system

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2
Q

What is mass transport?

A

The bulk movement of gases or liquids in one direction, usually via a system of vessels & tubes to exchange site

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3
Q

Is a red blood cell a globular or fibrous protein?

A

Globular

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4
Q

What is the structure of haemoglobin?

A

Quaternary structure (4 polypeptide chains)
4 subunits (two α–globins and two β–globins) held together by disulphide bonds
Each subunit contains a haem prosthetic group: these contains Fe2+ which reversibly combine with oxygen molecules → forms oxyhaemoglobin

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5
Q

What is the equation for oxygen and haemoglobin?

A

Oxygen + Haemoglobin ⇌ Oxyhaemoglobin
4O2 + Hb ⇌ Hb4O2

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6
Q

What happens when oxygen binds with haemoglobin?

A

Bind of the first oxygen molecules causes conformational change in the structure of Hb → makes it easier for each successive O2 molecule to bind - this is called cooperative binding
This binding is reversed in tissues, as oxygen dissociates from Hb

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7
Q

What is partial pressure of oxygen (pO2)?

A

It is a measure of oxygen concentration

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8
Q

What is haemoglobin saturation?

A

When all four of its binding sites are taken up with oxygen

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9
Q

What is the affinity for oxygen?

A

The ease at which Hb associates and disassociates with oxygen

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10
Q

What is the oxygen dissociation curve?

A

When Hb, oxygen binds at different rates as the pO2 changes → results in a curve
Affinity changes at different pO2
1 - The first O2 molecule binds to Hb slowly
2 - Hb molecule undergoes conformational change → easier for the next two Hb subunits to bind O2 - what is this called?
3 - Hb molecule approaches saturation - takes longer for the last O2 to bind

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11
Q

What does a high concentration of oxygen mean for haemoglobin?

A

Hb loads all available subunits & has a high affinity for oxygen, Once saturated, oxygen does not dissociate easily here

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12
Q

What does a low concentration of oxygen mean for haemoglobin?

A

Hb has unloaded most of its oxygen & has a low affinity for oxygen

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13
Q

What does a medium concentration of oxygen mean for haemoglobin?

A

Small decrease in pO2 causes a large decrease in %saturation of Hb → leading to easy release of plenty of oxygen to the cells

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14
Q

What is the Bohr shift?

A

The changes in the oxygen dissociation as a result of carbon dioxide levels

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15
Q

What happens when the partial pressure of CO2 is high and why?

A

Hb’s affinity for oxygen is reduced because:
CO2 combines with water
Forms carbonic acid (which lowers the pH)
Carbonic acid dissociates into hydrogen carbonate ions & hydrogen ions
H+ ions bind to Hb →causes the release of oxygen (and therefore reduces the affinity of oxygen)

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16
Q

What does the Bohr shift look like on the oxygen dissociation curve?

A

The curve shifts to the right when CO2 levels increase
At any given pO2, the % saturation of Hb is lower at higher levels of CO2

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17
Q

What does the effect of altitude look like on the oxygen dissociation curve?

A

Higher altitude = curve shifted to the left
pO2 in the air is LOWER at higher altitudes
Llamas = have Hb that binds much more readily to oxygen
beneficial, as it allows them to obtain a sufficient level of oxygen saturation in their blood when the pO2 in the air is low

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18
Q

What does foetal Haemoglobin look like on the oxygen dissociation curve?

A

A foetus needs to obtain oxygen from its mother’s blood at the placenta
Foetal Hb therefore has a higher affinity for oxygen than adult Hb → can bind oxygen at low pO2 (In the placenta, where the mother’s Hb is dissociating w/ oxygen)
So the curve shifts to the left - at any partial pressure, foetal Hb has a higher %saturation than adult Hb

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19
Q

What is a closed circulatory system?

A

When blood is pumped around the body & is contained within a network of blood vessels

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20
Q

What is an open circulatory system?

A

When blood is not contained within blood vessels & is pumped directly into body cavities (Arthropods and molluscs)

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21
Q

What circulatory system do humans have?

A

Humans have a closed double circulatory system: in one circuit of the body, blood passes through the heart twice
Right side: deoxygenated blood is pumped to the lungs for gas exchange (Pulmonary system)
Left side: oxygenated blood returns to the heart, then is pumped at high pressure around the body (Systemic circulation)

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22
Q

What is the role of the pulmonary artery?

A

Carries deoxygenated blood away from the heart, towards the lungs

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23
Q

What is the role of the pulmonary vein?

A

Carries oxygenated blood away from the lungs, towards the heart

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24
Q

What is the role of the coronary arteries?

A

Deliver oxygen & nutrient-rich blood to the heart muscle, for aerobic respiration
Present on the surface of the heart
Important that they remain unblocked

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25
What is the role of the aorta?
Carries oxygenated blood out of the heart and to the rest of the body
26
What is the role of the vena cava?
Carries deoxygenated blood into the heart
27
What is the role of the renal artery?
Supplies the kidneys with oxygenated blood
28
What is the role of the renal vein?
Carries deoxygenated (and filtered) blood away from the kidneys, towards the heart
29
What is the heart protected by?
Pericardium - tough & fibrous sac
30
What is the left and right side of the heart separated by?
Left & right side separated by the septum (muscular tissue) Septum between the atria: interatrial septum Septum between the ventricles: interventricular septum
31
What is the role of the valves?
Valves maintain pressure & prevent the backflow of blood
32
What does it mean when a valve is open?
The pressure of blood behind them is greater than the pressure in front of them. So the chamber behind is contracting
33
What does it mean when a valve is closed?
The pressure of blood in front of them is greater than the pressure behind them. So the chamber behind is relaxed
34
What is the valve that separates the right atrium and the right ventricle?
The Atrioventricular / tricuspid valve
35
What is the valve that separates the right ventricle and the pulmonary artery?
Pulmonary valve
36
What is the valve that separates the left atrium and left ventricle?
Mitral / bicuspid valve
37
What is the valve that separates the left ventricle and the aorta?
Aortic valve
38
Where are the thickest and most muscular walls?
The left ventricle has the thickest walls, as blood has to be under high pressure to be pumped around the body
39
What is the contraction of the heart called?
Systole
40
What is the relaxation of the heart called?
Diastole
41
What happens when the heart muscles contracts?
Heart muscle contracts → volume decreases in the chamber → pressure increases
42
What happens when the heart muscles relax?
Heart muscle relaxes → volume increases in the chamber → pressure decreases
43
What is atrial systole?
Walls of atria contract Atrial volume decreases Atrial pressure increases Atrioventricular (AV) & Mitral valves OPEN Blood is forced into the ventricles Slight increase in ventricular pressure, as it is receiving the blood from the atria Ventricular diastole is occurring here, as the ventricles are yet to contract
44
What is ventricular systole?
Walls of ventricles contract Ventricular volume decreases Ventricular pressure increases Atrioventricular (AV) & Mitral valves are forced CLOSED Pulmonary and aortic valves OPEN Blood is forced into the arteries and out of the heart Atrial diastole is also occurring here, as blood begins to fill the atria again
45
What is diastole?
Walls of atria and ventricles both relax Pressure in the ventricles decrease Pulmonary and aortic valves CLOSE Atria continue to fill with blood (via the vena cava & pulmonary vein) Pressure in the atria rises again Atrioventricular (AV) & Mitral valves OPEN Blood also flows passively into the ventricles Atrial systole begins again
46
What occurs in the cardiac cycle (in the left side)?
Starts with the end of diastole where the atrium fills with blood Pressure is higher in the atrium, so the mitral valve opens Atrial systole then occurs, the LA contracts → increase atrial pressure Ventricular pressure increases slightly as it fills with blood Ventricular systole starts LV contracts → increases in ventricular pressure LA pressure drops, as the muscle relaxes Mitral valve close Ventricles continue to contract Pressure in the LV is higher than the aorta → Aortic valve opens → blood is forced into the aorta Diastole begins Left ventricle has been emptied of blood Left muscular wall relaxes → pressure falls → aortic valve closes Ventricles remain relaxes → ventricular pressure decreases Blood begins to flow into the relaxed atrium (via the pulmonary vein) → increase in pressure Relaxed atrium fills with blood → pressure in atrium increases → Mitral valve opens left ventricle expanded due to relaxing muscles LV volume increases, pressure decreases Blood slowly flows through the newly-opened mitral valve, into the LV This causes a brief decrease in ventricular pressure Pressure in the LA & LV increases slowly as they continue to fill w/ blood
47
What is cardiac output?
the vol. of blood pumped by the heart (both ventricles) per unit of time Cardiac output = heart rate x stroke volume
48
What is Coronary Heart Disease (CHD)?
Any condition that interferes with the coronary arteries which supply blood to the heart muscle
49
What are the main risk factors of CHD?
Genetic factors Age and sex High blood pressure Smoking High concentrations of low-density lipoproteins (LDLs)
50
What are arterioles?
Blood vessels which connect arteries to capillaries
51
How does the structure of arteries relate to its functions?
The walls contain thick layers of collagen, smooth muscle and elastic fibres, surrounding a narrow lumen Elastic fibres allow arteries to expand and recoil when the heart contracts and relaxes Arteries must withstand high pressures generated by heart contractions, and maintain that pressure when the heart is relaxes
52
How does the structure of veins relate to its functions?
Walls contain thinner layers of collagen, smooth muscle & elastic fibres, surrounding a larger lumen Also contain valves - prevent backflow of blood Veins receive blood that has passed through capillary networks (at a low pressure)
53
How does the structure of arterioles relate to its functions?
Have a lower proportion of elastic fibres and a large number of muscle cells - allows them to contract and close their lumen to stop blood flow They can contract and partially cut off blood flow to specific organs
54
How does the structure of capillaries relate to its functions?
Capillaries have thin walls with pores which allows blood plasma to leak out, and form tissue fluid They form networks called capillary beds Have a very small lumen - forces blood to travel slowly → diffusion more likely to occur Capillary walls are made from a single layer of endothelial cells - reduces diffusion distance for carbon dioxide and oxygen, between the blood and tissues of the body
55
What is tissue fluid used for?
It bathes all cells in this fluid Exchange of substances between cells and blood occurs via the tissue fluid
56
How does tissue fluid form?
Arterial end of the capillary: the increased hydrostatic pressure forces molecules OUT of the capillary Protein remain the blood, which creates a water potential gradient between the capillary and tissue fluid Venous end of the capillary: hydrostatic pressure decreases → less fluid is pushed out, some water begins to flow back into the capillary Overall, more fluid leaves the capillary than returns, leaving tissue fluid behind to bathe cells
57
How does some of the tissue fluid get back to the heart?
The lymph capillaries - these are separate from the circulatory system Larger molecules that can’t leave through capillary walls enter the lymphatic system as lymph, through small valves Lymph moves around large lymphatic vessels by compression and backflow is prevented by valves Lymph eventually re-enters the bloodstream through veins close to the heart Plasma proteins that have escaped the blood are returned to the blood via the lymph capillaries - this prevents the water potential being lowered and impairing water reabsorption
58
What is the structure of the xylem?
Made of dead cells → forms a long, hollow tube (no pores between cells) Contain lignin - for structural support
59
How does the movement of water occur?
Evaporation of water vapour from the leaves and the cohesive and adhesive properties exhibited by water molecules The water potential gradient drives water movement - Plant roots take up water from the soil, up plant stems, then out into the atmosphere via the leaves and stomata
60
What is transpiration?
Transpiration is the loss of water vapour via the stomata by diffusion
61
What is transpiration important for?
Cooling the plant via evaporative cooling Helps to uptake mineral ions Provides turgor pressure to provide support to the leaves
62
What is the transpiration stream?
Water evaporates out of the stomata The water vapour lost by transpiration lowers the water potential in the air spaces surrounding the mesophyll cells Water in the mesophyll cell walls evaporates into these air spaces → causes a transpiration pull as there is a water gradient Water goes up the xylem vessels by cohesive + adhesive forces, to replace the water lost from the mesophyll cells
63
Does stomata being open increase the rate of transpiration?
Yes
64
What does high air movement do to transpiration rate?
Increases the rate of transpiration, maintains gradient
65
What does high humidity do to transpiration rate?
Decreases the rate of transpiration, weaker concentration gradient
66
What does high light intensity do to transpiration rate?
Increases the rate of transpiration, stomata open
67
What does high temperature do to transpiration rate?
Increases the rate of transpiration, molecules move faster and evaporation is quicker
68
What is the structure of the phloem?
Made of living cells + pores between cells
69
What is translocation?
Translocation within phloem tissue is the transport of assimilates (e.g., sucrose) from source to sink, which requires ATP
70
What are assimilates transported in?
Phloem saps
71
What is the mass flow hypothesis?
This hypothesis was the model used to explain the movement of assimilates in the phloem tissue
72
What is the mass flow hypothesis mechanism?
Sucrose is actively loaded into the sieve elements at the source which lowers the water potential of the sap Water moves into the sieve elements by osmosis from xylem Hydrostatic pressure increases at the source Sucrose is unloaded from the sieve elements at the sink which decreases the hydrostatic pressure, water goes back to xylem The difference in pressure creates a gradient, causing a mass flow of water containing dissolved substances (the phloem sap)
73
What is the tracer and ringer experiment?
Involves the removal of a ring of the phloem from the stem of the plant, while leaving the xylem intact After ringing, the plant is exposed to a radioactive tracer (normally 14CO2) to investigate the rate & direction of translocation
74
What is the evidence supporting the mass flow hypothesis?
When the phloem sieve tube is punctured, phloem sap oozes out, suggests that it is under pressure Phloem sap taken from near a source has a higher sucrose concentration than sap taken from near a sink, suggests that different water potentials would result in osmosis into & out of the tubes
75
What is the evidence against the mass flow hypothesis?
Amino acids appeared to travel more slowly than sucrose The mass flow hypothesis states should be flowing at the same rate Some scientists have conducted experiments that detected different substances moving in opposite directions The mass flow hypothesis states everything should be flowing in one direction

Biology (21 decks)

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