haemoglobin- mass transport in animals

describe the structure of proteins (5)

• Polymers of amino acids, joined together by peptide bonds formed in condensation reactions.

• Primary structure: specific sequence of amino acids in a polypeptide chain.

• Secondary structure: the polypeptide chain folds into an alpha helix or beta-pleated sheet due to hydrogen bonding.

• Tertiary structure: further folding of a single polypeptide chain due to interactions between R groups- hydrogen bonds, ionic bonds, disulfide bonds.

• Quaternary structure: two or more polypeptide chains associate together to form a functional protein.

what elements are proteins made up of

carbon, hydrogen, oxygen, nitrogen, sulphur

what does haemoglobin ( a transport protein ) carry?

oxygen

what is the monomer making up proteins

amino acids

how many naturally occurring amino acids are there

20

structure of amino acids

a carboxyl group -cooh. an amine group- nh2. a variable group- r

structure of haemoglobin

globular protein, 4 peptide chains, each w one haem group.

structure is curled up: hydrophilic side chains face outwards, hydrophobic side chains face inwards

makes haemoglobin soluble and is therefore good transport for blood

where is haemoglobin transported

red blood cells

why is haemoglobin soluble

structure is curled so that hydrophilic side chains face outwards and hydrophobic side chains face inwards. therefore it is good for transport in the blood

the structure of haem is the same in all haemoglobin, but the globin chains vary between species. what causes this change in protein structure between species?

different primary sequences of amino acids = different hydrogen bonding in secondary structure, different ionic and disulphide bonding in tertiary and quaternary structures

reversible reaction for haem group combining with oxygen molecule

Hb + 4O2 = 4Hb(O2)

what is partial pressure (po2)

a measure of oxygen concentration- pO2 is high in the lungs and lower in body tissues like muslce

what does affinity depend on?

the pO2- higher affinity in low PP, low affinity in high PP

oxygen associates (loads) with haemoglobin to form oxyhaemoglobin where there is a _____ pO2?

high

oxygen dissociates (unloads) from oxyhaemoglobin where there is a _____ pO2?

lower, e.g muscles

what is the saturation

how much oxygen being carries

haemoglobin binds _____ with oxygen so is a good transporter of oxygen

reversibly

what is the affinity of haemoglobin for oxygen at a gas exchange surface? e.g. lungs, gills

high pO2 in the medium (water/air), so oxygen associates/loads with Hb

what is the affinity of haemoglobin for oxygen at respiring tissues? e.g. muscles

low pO2, haemoglobin has low affinity for oxygen, oxygen unloads from haemoglobin. high pCO2 = haemoglobin change shape and unload oxygen

what is an oxygen dissociation curve

relationship between the saturation of haemoglobin with oxygen and the partial pressure of oxygen

what is the % saturation of haemoglobin

the percentage of haemoglobin associated with oxygen at a given pO2

what does % saturation of Hb depend on?

pO2 of the environment

explain how oxygen is loaded, transported and unloaded in the blood

haemoglobin carries O2- has a high affinity of O2

haemoglobin found in red blood cells

loading in lungs at high oxygen concentration

oxygen unloads at respiring cells/tissues at low oxygen concentration

unloading linked to higher carbon dioxide concentration

Hb reaches nearly 100% oxygen saturation even when partial pressure is lower than atmospheric partial pressure of 21kPa. why is this and what is the advantage of this?

in alveoli, pO2 is less than 21kPa as alveolar air contains a lot of water vapour and high CO2

pO2 is around 15kPa which is still high enough to saturate almost 100% of the Hb

the blood system carries red blood cells through a PV into the heart, then pumped out to body tissues. explain why Hb does not unload its oxygen before it reaches the capillaries in the tissues

walls of arteries, veins and arterioles are too thick to allow gaseous exchange. the pO2 around the red blood cells remains constant so the Hb remains saturated

if the curve on an O2 dissociation graph is further to the left, what is the affinity?

higher affinity- holds more oxygen

if the curve on an O2 dissociation graph is further to the right, what is the affinity?

lower affinity- spends more oxygen

why is it important for a baby to develop haemoglobin after birth

start to breathe air/become more active, must release oxygen more readily at tissues.

doesn’t need to take up O2 at low pO2- air has a pO2 of approx 21kPa

what is the bohr effect on a graph

a curve to the right of a normal dissociation curve

why does the bohr effect occur

high concentration of carbon dioxide and an increase in temperature

in active tissues, what percentage of oxygen is unloaded

45%

in active tissues, more than 45% of oxygen is unloaded. an active tissue is respiring and producing CO2. why is more oxygen unloaded?

more co2, haemoglobin has a reduced affinity, higher dissociation for oxygen

DESCRIBE what is happening at the bottom of the oxygen dissociation curve

at lower partial pressure, theres a little increase in saturation of haemoglobin

DESCRIBE what is happening in the middle of the oxygen dissociation curve

small change in pO2 can result in a large change in the percentage saturation of the blood- steep gradient

DESCRIBE what is happening at the top of the oxygen dissociation curve

at higher partial pressures, there is little change in the saturation

EXPLAIN what is happening at the bottom of the oxygen dissociation curve

first molecule of oxygen combines with haemoglobin and slightly distorts it. the joining is quite slow

EXPLAIN what is happening at the middle of the oxygen dissociation curve

after the haemoglobin has changed shape a little, becomes increasingly easy for the second and third oxygen to join = cooperative binding

EXPLAIN what happens at the top of the oxygen dissociation curve

flattens off at the top because joining the fourth oxygen is more difficult- fewer sites available to bind to

what is the bohr effect

at lower PH values, oxygen dissociates from Hb more readily.

useful in tissues- cells respiring aerobically faster so need more oxygen.

increases rate of oxygen disassociation and the curve shifts to the right.

so, saturation of blood with oxygen at a given partial pressure is lower because more oxygen is being released

effects of carbon dioxide on the lungs

• CO₂ concentration is low bc diffuses from the blood into the alveoli and is exhaled.

• The low CO₂ concentration increases haemoglobin's affinity for oxygen (the Bohr effect in reverse).

• haemoglobin loads/binds oxygen more readily

effects of carbon dioxide on the tissues

• CO₂ conc high because CO₂ is produced during respiration.

• The high CO₂ concentration decreases haemoglobin's affinity for oxygen (Bohr effect).

• This causes haemoglobin to release (unload) oxygen more readily.

• The released oxygen can then be used for aerobic respiration by the cells.

effects of carbon dioxide on protein structure of Hb

• Carbon dioxide dissolves in the blood and forms carbonic acid, lowering pH.

• The decrease in pH alters the bonding within the haemoglobin molecule.

• This causes a slight change in the tertiary structure (shape) of haemoglobin.

• The change in shape reduces haemoglobin's affinity for oxygen.

• Oxygen is therefore released (dissociates) more readily in tissues with high carbon dioxide concentrations.

the effect of carbon dioxide concentration on the function of haemoglobin

• High partial pressure of CO₂.

• Reduced affinity of haemoglobin for oxygen.

• Increased oxygen unloading/dissociation.

• More oxygen delivered to actively respiring tissues.

• Respiration produces CO₂, increasing pCO₂ in tissues.

exam q: describe and explain the effect of increasing carbon dioxide concentration on the dissociation of oxyhaemoglobin

more oxygen unloading by decreasing blood pH

how does blood temperature affect dissociation

increased blood temperature reduces haemoglobins affinity for O2.

more oxygen is delivered to warmed-up tissue

more oxygen is loaded from haemoglobin at tissue level

an increase in blood temperature makes the dissociation curve shift in which direction?

to the right

how does the size of an animal affect dissociation

smaller animals high metabolic rate, need oxygen to be released readily in the tissues

haemoglobin has a lower affinity for oxygen

how does altitude affect dissociation (e.g. llamas)

live at higher altitudes where there is lower partial pressure of oxygen. haemoglobin has a higher affinity for oxygen than similar lowland animals so that it can bind to any oxygen that is available

how does higher altitude shift of the dissociation curve

shifts to the left

how do sand burrows (intertidal) affect dissociation

there is low partial pressure of oxygen in a burrow. need higher affinity haemoglobin as picks up oxygen more readily but releases it less readily.

which way does the dissociation curve shift for sand burrows

to the left

do organisms with less oxygen in their environment need haemoglobin with a low or high affinity?

high affinity

what does low affinity mean

dont take up oxygen easily but release it more readily

what does high affinity mean

take up oxygen very easily but dont release it as readily

why do animals with a high metabolic rate need haemoglobin with a low affinity for oxygen

to that oxygen is released more easily at the respiring tissues

what is foetal haemoglobin

oxygen dissociates from maternal haemoglobin in placenta and foetal haemoglobin loads with oxygen. curve further left

what do higher affinity haemoglobins have and what does it do

myoglobin- red pigment in slow twitch muscles adapted for aerobic respiration.

has an even higher affinity for oxygen than haemoglobin, only releasing it at very low partial pressures

stores oxygen

what is this

haemoglobin

what is this

myoglobin