Mass Transport In Animals Flashcards by reyhana r

Describe the role of red blood cells and haemoglobin in oxygen transport

● Red blood cells contain lots of haemoglobin (Hb) - no nucleus, biconcave, high SA:V, short diffusion path
● Hb associates with / binds / loads O2 at gas exchange surfaces where partial pressure of O2 (pO2) is high
● This forms oxyhaemoglobin which transports O2 (each can carry 4O2- one at each Haem group)
● Hb dissociates from / unloads O2 near cells / tissues where pO2 is low

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Describe the structure of haemoglobin

Areas with low pO2 (respiring tissues):
● Hb has a low affinity for O2
● So O2 readily unloads / dissociates with Hb
● So % saturation is low
Areas with high pO2 (gas exchange surfaces):
● Hb has a high affinity for O2
● So O2 readily loads / associates with Hb
● So % saturation is high

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

● Protein with a quaternary structure
● Made of 4 polypeptide chains
● Each chain contains a Haem group containing an iron ion (Fe2+)

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Explain how the cooperative nature of oxygen binding results in an
S-shaped (sigmoid) oxyhaemoglobin 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 pO2 as oxygen increases there is little / slow increase in % saturation of Hb with oxygen
○ When first oxygen is binding
● At higher pO2, as oxygen increases there is a big / rapid increase in % saturation of Hb with oxygen
○ Showing it has got easier for oxygens to bin

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What is the Bohr effect?

Effect of CO2 concentration on dissociation of oxyhaemoglobin → curve shifts to right

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Explain effect of CO2 concentration on the dissociation of oxyhaemoglobin

1.Increasing blood CO2 eg. due to
increased rate of respiration
2. Lowers blood pH (more acidic)
3. Reducing Hb’s affinity for oxygen as
shape / tertiary / quaternary
structure changes slightly
4. So more / faster unloading of oxygen
to respiring cells at a given pO2
How the curve provides evidence for this:
At given po2 % saturation of o2 is lower

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Explain the advantage of the Bohr effect (eg. during exercise)

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 → 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 pO2 is lower
● Eg. organisms in low O2 environments - high
altitudes, underground, or foetuses
Curve shift right → Hb has lower affinity for O2
● More O2 dissociates from Hb more readily
● At respiring tissues where more O2 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:
1. 2. Deoxygenated blood in right side of heart pumped to lungs; oxygenated returns to left side
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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Draw a diagram to show the general pattern of blood circulation in a
mammal, including the names of key blood vessels
Name

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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 kidney

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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

Label a diagram to show the gross structure of the human heart (inside)

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 → 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 → volume
decreases, pressure increases
● Atrioventricular valves shut
when pressure in ventricles
exceeds pressure in atria
● Semilunar valves open when
pressure in ventricles exceeds
pressure in arteries
● So blood pushed out of heart through arteries

Diastole

● Atria & ventricles relax →
volume increases, pressure
decreases
● Semilunar valves shut when
pressure in arteries exceeds
pressure in ventricles
● Atrioventricular valves open
when pressure in atria
exceeds pressure in ventricles
● So blood fills atria via veins and 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

SL
valves
closed
● Pressure in [named] artery higher than
in ventricle
● To prevent backflow of blood from
artery to ventricles
SL
valves
open
● When pressure in ventricle is higher
than in [named] artery
● So blood flows from ventricle to artery
AV
valves
closed
● Pressure in ventricle higher than atrium
● To prevent backflow of blood from
ventricles to atrium
AV
valves
open
● When pressure in atrium is higher than
in ventricle
● So blood flows from atrium to ventricl

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)

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

Function– carry blood away from heart at high pressure ● Thick smooth muscle tissue → can contract and control / maintain 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 → withstand high pressure / stop bursting ● Smooth / folded endothelium → reduces friction / can stretch ● Narrow lumen → increases / maintains high pressure

Explain how the structure of arterioles relates to their function

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)

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 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 is a 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

Explain the formation of tissue fluid

1. 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 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 vein

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 ● High blood pressure (eg. caused by high salt concentration)→ high hydrostatic pressure ○ Increases outward pressure from arterial 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 The principles of analysis, interpretation and evaluation of data covered in ‘3.2 gas exchange also apply here