3.3.4.1 Mass Transport in Animals

Why do large organisms have transport systems?

they have a small surface area to volume ratio, so they need a specialised mass transport system to carry molecules between exchange surfaces and cells

What do mass transport systems ensure?

the efficient movement of molecules in an organism

What parts of a transport system may differ between organisms?

• whether there is a specialised medium (blood)

• whether a pump is neccessary

What factors change an organisms transport system?

• its surface area to volume ratio

• how active the organism is

When would an organism need a specialised transport system with a pump?

smaller surface area to volume ratio and more active the organism is

Why are mammals quite active

they generate their own body temperature, which requires a high metabolic rate due to respiration

Where is haemoglobin found?

erythrocytes

How has haemoglobin evolved?

it has evolved to make it efficient at loading oxygen in one set of conditions and unloading oxygen in another set

Describe the haemoglobin found in different types of organisms?

they are chemically similar and carry out the same function

What organisms is haemoglobin found?

mammals, vertabrates, starfish

What type of biological molecule is haemoglobin?

protein

Describe the structure of haemoglobin in depth

quaternary structure, 2 alpha chains, 2 beta chains, each with a prosthetic haem group

Describe the structure of 1 subunit of haemoglobin

contains a haem group with an iron Fe2+ ion

How many FE+ ions are in each heam group?

1

What gives haemoglobin a high affinity for oxygen?

Fe2+ ion

How many oxygen molecules can each haemoglobin molecule bind to when 100% saturated?

4

What does the binding of oxygen and haemoglobin form?

oxyhaemoglobin

What type of reaction is the one between haemoglobin and oxygen?

reversible

What is the equation for the formation of oxyhaemoglobin?

Hb + 4O2 → HbO8

Draw a diagram of haemoglobin

Give 2 terms for the binding of oxygen and haemoglobin?

• loading

• association

Where does the loading of oxygen happen in humans?

lungs

Give 2 terms to describe the releasing of oxygen from haemoglobin?

• dissociation

• unloading

Where does unloading of oxygen take place in humans?

respiring tissues

What type of graph is ysed to show the saturation of haemoglobin?

dissociation curve

Draw a dissociation curve for human saturation of haemoglobin with oxygen?

What is partial pressure of oxygen?

measure of oxygen concentration in the tissues

What is partial pressure of oxygen abreviated to?

pO2

What shape does a haemoglobin dissociation curve take?

sigmoid S shape

Why is it difficult for the first oxygen molecule to bind with haemoglobin at low partial pressure?

the haem groups are in the centre of the haemoglobin which makes it difficult for the oxygen to bind with it, resulting in low saturation

As partial pressure of oxygen increases, what happens to the hameoglobin molecule?

as the diffusion gradient is steeper, eventually an oxygen binds to the haemoglobin

What happens to the haemoglobin when the first oxygen molecule binds?

the shape changes making it easier for more oxygen molecules to associate with the other haem groups

Why is it easier for oxygen molecules 2 and 3 to bind with haemoglobin?

the shape is different

Why is it difficult for haemoglobin to become 100% saturated?

it is difficult for the last oxygen to diffuse and bind with the 4th haem group

Describe the conditions of the alveoli that result in oxygen loading?

• high pO2

• high affinity

• oxygen loads

Describe the conditions at respiring tissues that cause oxygen to unload

• low pO2

• low affinity

• high pCO2

• oxygen unloads

Why does carbon dioxide cause oxygen to unload?

it causes blood to become acidic and the haemoglobin binds to H+ ions instead as higher affinity, unloading O2

What does haemoglobin have a higher affinity to than oxygen?

H+

Apart from binding with oxygen, what is another purpose of haemoglobin?

pH buffer

What is partial pressure of carbon dioxide?

measure of carbon dioxide concentration in a cell

At higher pCo2, how is oxygen unloading affected?

oxygen unloads more readily

Why do cells have higher pCO2?

when they respire

At higher carbon dioxide levels, how does the dissociation curve shift?

to the right

What is the Bohr effect?

more oxygen is released when more carbon dioxide is being produced

What is the advantage of high CO2 resulting in more oxygen being unloaded?

when excersising and cells anaerobically respire the muscles are supplied with more oxygen

What may impact how an organisms haemoglobin is altered?

• environment

• activity

• size

How does haemoglobin adapt for organisms that live in an environment with low pO2?

higher affinity to oxygen

Why does the haemoglobin of organisms in lower pO2 have a higher affinity to oxygen?

not much oxygen available so the haemoglobin must be very good at loading any oxygen available

Where does the dissociation curve for an organism in a low pO2 environment shift?

left

Draw a dissociation curve for a human, an organism in low pO2 and an organism with high activity levels?

How does the haemoglobin alter for organisms with a high activity levels?

lower affinity to oxygen

Why do organisms with a high activity level have a lower affinity to oxygen?

so they can unload oxygen more easily

Where does the dissociation curve shift for organisms with a high rate of activity?

right

Describe the haemoglobin of a smaller mammal

lower afinity

Why do smaller animals have a high oxygen demand?

they have a higher metabolic rate for their temperature

Why do smaller organisms have haemoglobin with a lower affinity to oxygen?

so the oxygen can be unloaded more easily

Where does the dissociation curve of a smaller mammals’s haemoglobin shift to?

right

What makes our circulatory system closed?

blood is confined in vesseks

What makes our circulatory system double?

blood passes twice thrugh the heart for each complete circuit of the body

What does the blood transport?

respiratory gases, products of digestion, metabolic waste products, hormones

Draw a diagram of the circulatory system

Where does the pulmonary artery carry blood to and from?

from heart, to lungs

Where does the pulmonary vein carry blood to and from?

from lungs to heart

Where does the aorta carry blood to and from?

from heart to body

Where does the vena cava carry blood to and from?

from body to heart

Where does the renal artery carry blood to and from?

from aorta to kidneys

Where does the renal vein carry blood to and from?

from kidneys to vena cava

Draw an internal diagram of the heart?

Draw an external diagram of the heart

What is the function of the right side of the heart?

pumps deoxygenated blood to the lungs

Where does the left side of the heart pump blood to?

oxygenated blood to body

How many chambers does the heart have?

4

Compare the wall thickness of atria to ventricles?

ventricle walls much thicker

Why do the ventricles need thicker muscle walls?

they push blood out of the heart rather than into aother chamber

Compare the thickness of the muscle of right and left ventricles?

left ventricles are thicker

Why should the left ventricle wall muscle be thicker?

needs to generate higher pressure- contract more powerfull to ump blood to entire body

What is the function of the septum?

separates the 2 sides of the heart and maintains the different pressures

Why is the septum of foetus incomplete?

mixes deoxygenated blood wit oxygenated

Which blood vessels carry blood (and oxygen) to the heart?

coronary artery

What is the purpose of arteries?

carry blood away from the heart to the rest of the body

What do arteries divide into?

arterioles which form a network throughout the body

What is the artery made of?

• small lumen

• endothelium

• elastic fibres

• smooth muscle

• collagen fibres and fibrous proteins

What is the purpose of the smooth lumen in the artery?

reduces friction and is folded so it can unfold when the lumen stretches

what is the purpose of the collagen fibres and fibrous proteins in arteries?

the thick wall can withstand high pressures

What is the purpose of the elastic tissue in arteries?

allows the wall to stretch and recoil - maintains diastolic pressure

What does the elastic tissue in arteries allow for the maintenance of?

diastolic blood pressure

How is friction in the arteries reduced?

by having a smooth endothelium

How is the artery endothelium specialised?

it is folded so it can stretch when the lumen stretches

What is the function of the smooth muscle in arteries?

allows contraction and vasoconstriction (narrowing of the lumen) - enables the blood to be directed to different areas of the body in demand

What is the result of the contraction of smooth muscles in arteries?

vasoconstriction

What is the function of veins?

carries blood from the rest of the body to the heart

What tissues are veins made of?

• endothelium

• elastic fibres

• smooth muscle

• collagen fibres

Compare the pressures of arteries, veins and capillaries

• arteries

• capillaries

• veins

What is the purpose of the vein’s large lumen?

lower blood pressure

Describe the collagen, muscle and elastic tissue composition of veins to arteries?

the vein walls have less collagen, smooth muscle and elastic tissue as they do not need to perform the roles of an artery

What is the function of valves?

they prevent backflow of blood

How is blood moved back to the heart?

pressure is exerted by movement/ contraction of the muscles. There is also some residual pressure from the contraction of the left ventricle wall

Describe the structure of capillaries?

• they have a very narrow lumen

• 1 cell thick endothelium

Describe the pressure gradient across capillaries?

high at the arteriole end and lower at the venous end

Describe the walls of capillaries?

1 cell thick- single layer of flattened endothelial cells