Mass Transport Flashcards by Noah Dring

Describe the role of red blood cells & haemoglobin (Hb) in oxygen transport

Red blood cells contain lots of Hb
• No nucleus & biconcave → more space for Hb, high SA:V & short diffusion distance
• Hb associates with / binds / loads oxygen at gas exchango surfaces (lungs) where partial pressure of oxygen (po,) is high
• This forms oxyhemoglobin which transports oxygen
• Each can carry four oxygen molecule, one at each Haem group
• Hb dissociatos from / unloads oxygen near cells / tissues where pO, is low

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Describe the structure of haemoglobin

Protein with a quaternary structure
Made of 4 polypeptide chains
Each chain contains a Haem group containing an iron ion (Fe?*)

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Describe the loading, transport and unloading of oxygen in relation to the oxyhaemoglobin dissociation curve

Areas with low po2, - respiring tissues
• Hb has a low affinity for oxygen
So oxygen readily unloads / dissociates with Hb
So % saturation is low

Areas with high po, - gas exchange surfaces
Hb has a high affinity for oxygen
• So oxygenreadily loads / associates with Hb
So % saturation is high

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Explain how the cooperative nature of oxygen binding results in an S-shaped (sigmoid) oxyhemoglobin dissociation curve

Binding of first oxygen changes tertiary / quaternary structure of haemoglobin
This uncovers Haem group binding sites, making further binding of oxygens easier

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Describe evidence for the cooperative nature of oxygen binding

A low po, as oxygen increases there is little / slow increase in % saturation of Hb with oxygen
• When first oxygen is binding
• At higher po,, as oxygen increases there is a big / rapid increase in % saturation of Hb with oxygen
• Showing it has got easier for oxygens to bind

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What is the Bohr effect?

Effect of CO, concentration on dissociation of oxyhaemoglobin → curve shifts to right

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Explain effect of CO, concentration on the dissociation of oxyhaemoglobin

Increasing blood CO, eg. due to increased rate of respiration
Lowers blood ph (more acidic)
Reducing Hb’s affinity for oxygen as shape / tertiary / quaternary structure changes slightly
So more / faster unloading of oxygen to respiring cells at a given p02

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Explain the advantage of the Bohr effect

More dissociation of oxygen → faster aerobic respiration / less anaerobic respiration → more ATP produced

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Explain why different types of haemoglobin can have different oxygen transport properties

Different types of Hb are made of polypeptide chains with slightly different amino acid sequences
Resulting in different tertiary / quaternary structures / shape
So they have different affinities for oxygen

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Explain how organisms can be adapted to their environment by having different types of haemoglobin with different oxygen transport properties

Curve shift left
Hb has higher affinity for O2
• More O2 associates with Hb more readily
• At gas exchange surfaces where po, is lower Eg. organisms in low O, environments - high altitudes, underground, or foetuses

Curve shift right
Hb has lower affinity for 02
More O2 dissociates from Hb more readily
• At respiring tissues where more O, is needed
• Eg. organisms with high rates of respiration / metabolic rate (may be small or active)

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Describe the general pattern of blood circulation in a mammal

Closed double circulatory system - blood passes through heart twice for every circuit around body:
Deoxygenated blood in right side of heart pumped to lungs; oxygenated returns to left side
2. Oxygenated blood in left side of heart pumped to rest of body; deoxygenated returns to right

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Suggest the importance of a double circulatory system

• Prevents mixing of oxygenated / deoxygenated blood
• So blood pumped to body is fully saturated with oxygen for aerobic respiration
• Blood can be pumped to body at a higher pressure (after being lower from lungs)
Substances taken to / removed from body cells quicker / more efficiently

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Name the blood vessels entering and leaving the heart and lungs

• Vena cava - transports deoxygenated blood from respiring body tissues → heart
• Pulmonary artery - transports
deoxygenated blood from heart → lungs

Pulmonary vein - transports oxygenated blood from lungs → heart
• Aorta - transports oxygenated blood from heart → respiring body tissues

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Name the blood vessels entering and leaving the kidneys

• Renal arteries - oxygenated blood → kidneys
• Renal veins - deoxygenated blood to vena cava from kidneys ^

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Name the the blood vessels that carry oxygenated blood to the heart muscle

Coronary arteries - located on surface of the heart, branching from aorta

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Suggest why the wall of the left ventricle is thicker than that of the right

Thicker muscle to contract with greater force
• To generate higher pressure to pump blood around entire body

Atrial systole

Atria contract
• So their volume decreases, pressure increases
• Atrioventricular valves open when pressure in atria exceeds pressure in ventricles
• Semilunar valves remain shut as pressure in arteries exceeds pressure in ventricles
• So blood pushed into ventricles

Ventricular systole

Ventricles contract
• So their volume decreases, pressure increases
• Atrioventricular valves shut when pressure in ventricles excoods pressure in atria
• Semilunar valves open when pressure in ventricles excoods pressure in arteries
• So blood pushed out of heart through arteries

Diastole

Atria & ventricles relax
• So their volume increases, pressure decreases
• Semilunar valves shut when pressure in arteries exceeds pressure in ventricles
• Atrioventricular valves opon when pressure in atria exceeds pressure in ventricles
So blood fills atria via veins & flows passively to ventricles

Explain how graphs showing pressure or volume changes during the cardiac cycle can be interpreted, eg. to identify when valves are open / closed

Semilunar valves closed
Pressure in artery higher than in ventricle
• To prevent backflow of blood from artery to ventricles

Semilunar valves open
• When pressure in ventricle is higher than in named artery
• So blood flows from ventricle to artery

Atrioventricular valves closed
• Pressure in ventricle higher than atrium
• To prevent backflow of blood from ventricles to atrium

Atrioventricular valves open
• When pressure in atrium is higher than in ventricle
So blood flows from atrium to ventricle

How can heart rate be calculated from cardiac cycle data?

Heart rate (beats per minute) = 60 (seconds) / length of one cardiac cycle (seconds)

Explain how the structure of arteries relates to their function

Thick smooth muscle tissue
Can contract and control / maintain / withstand blood flow / pressure

Thick elastic tissue
Can stretch as ventricles contract and recoil as ventricles relax, to reduce pressure surges / even out blood pressure / maintain high pressure

Thick wall
Withstands high pressure / prevents bursting

Smooth / folded endothelium
Reduces friction / can stretch

Narrow lumen
Increases / maintains high pressure

Explain how the structure of arterioles relates to their function

Function - (division of arteries to smaller vessels which can) direct blood to different capillaries / tissues

Thicker smooth muscle layer than arteries
• Contracts → narrows lumen (vasoconstriction) → reduces blood flow to capillaries
Relaxes → widens lumen (vasodilation) → increases blood flow to capillaries
• Thinner elastic layer → pressure surges are lower (as further from heart / ventricles)

Describe the equation for cardiac output

Cardiac output (volume of blood pumped out of heart per min)
= stroke volume (volume of blood pumped in each heart beat) x heart rate (number of beats per min)

Explain how the structure of veins relates to their function

Function - carry blood back to heart at lower pressure • Wider lumen than arteries → less resistance to blood flow Very little elastic and muscle tissue - blood pressure lower Valves → prevent backflow of blood

Explain the formation of tissue fluid

At the arteriole end of capillaries: Higher blood / hydrostatic pressure inside capillaries (due to contraction of ventricles) than tissue fluid (so net outward force) 2. Forcing water (and dissolved substances) out of capillaries 3. Large plasma proteins remain in capillary

Explain how the structure of arterioles relates to their function

Function - (division of arteries to smaller vessels which can) direct blood to different capillaries / tissues Thicker smooth muscle layer than arteries • Contracts → narrows lumen (vasoconstriction) → reduces blood flow to capillaries Relaxes → widens lumen (vasodilation) → increases blood flow to capillaries • Thinner elastic layer → pressure surges are lower (as further from heart / ventricles)

Suggest and explain causes of excess tissue fluid accumulation

Low concentration of protein in blood plasma • Water potential in capillary not as low → water potential gradient is reduced • So more tissue fluid formed at arteriole end / less water absorbed at venule end by osmosis • Lymph system may not be able to drain excess fast enough High blood pressure (eg, caused by high salt concentration) → high hydrostatic pressure • Increases outward pressure from arteriole end AND reduces inward pressure at venule end So more tissue fluid formed at arteriole end / less water absorbed at venule end by osmosis Lymph system may not be able to drain excess fast enough

What is a risk factor? Give examples for cardiovascular disease

An aspect of a person's lifestyle or substances in a person's body / environment • That have been shown to be linked to an increased rate of disease • Examples - age, diet high in salt or saturated fat, smoking, lack of exercise, genes

Explain the return of tissue fluid to the circulatory system

At the venule end of capillaries: 1. Hydrostatic pressure reduces as fluid leaves capillary (also due to friction) 2. (Due to water loss) an increasing concentration of plasma proteins lowers water potential in capillary below that of tissue fluid 3. Water enters capillaries from tissue fluid by osmosis down a water potential gradient 4. Excess water taken up by lymph capillaries and returned to circulatory system through veins

Explain how the structure of capillaries relates to their function

Function - allow efficient exchange of substances between blood and tissue fluid (exchange surface) Wall is a thin (one cell) layer of endothelial cells Reduces diffusion distance Capillary bed - large network of branched capillaries Increases surface area for diffusion Small diameter / narrow lumen Reduces blood flow rate so more time for diffusion Pores in walls between cells Allow larger substances through