Transport of gases C3 Flashcards
what is blood?
an aqueous medium which allows for gas exchange and the delivery of important molecules such as glucose and oxygen
what is plasma?
straw-coloured fluid in blood
it comprises blood cells
is blood a tissue
yes
what does plasma contain?
90% water with a range of dissolved materials which are:
proteins
glucose
clotting factors like fibrinogen
mineral ions
hormones
antibodies
dissolved CO2
what else does plasma do?
transport dissolved materials
distributes heat around body
what are the three types of blood cells?
leucocytes - white blood cells for immunity
thrombocytes - platelets for blood clotting
erythrocytes - red blood cells for oxygen transport
what two groups can leucocytes be divided into?
granulocytes
agranulocytes
what are granulocytes?
they have granular cytoplasm and lobed nuclei meaning the cell has more space and is more flexible
their function is to engulf pathogens by phagocytosis
what are agranulocytes?
they produce antibodies and antitoxins, have a clear cytoplasm and spherical nucleus
the antibodies/antitoxins are made of protein so these cells have RER and SER and Golgi body
what are erythrocytes filled with?
the pigment haemoglobin (Hb)
what three features do erythrocytes have to allow them to efficiently transport oxygen?
biconcave shape allows a greater surface area for diffusion
no nucleus and few organelles so there is more space to fit haemoglobin
flexible elastic membrane to squeeze through narrow capillaries
what is haemoglobin?
a complex globular protein with a quaternary structure consisting of four folded polypeptide chains
at the centre of each polypeptide is a haem group which contains iron (Fe2+)
each haem group is a binding site for one oxygen molecule
how is oxyhaemoglobin formed?
one molecule of haemoglobin can bind to four molecules of oxygen
what intermolecular bonds can be found in Hb?
hydrogen bonds
disulphide bridges
ionic bonds
the reaction between haemoglobin and oxygen is reversible and can be represented in the form of an equation. what is this equation?
Hb + 4O2 (double-headed arrows) Hb.O8
define affinity
the degree to which one molecule (haemoglobin) is chemically attracted to another molecule (oxygen)
define saturation
the percentage of oxygen bound to haemoglobin
define association/loading
the uptake of oxygen by haemoglobin to form oxyhaemoglobin in the lungs
define dissociation/unloading
the release of oxygen at the respiring tissues to form haemoglobin
how is oxygen transported?
oxygen diffuses into red blood cells and associates with haemoglobin to form oxyhaemoglobin
oxygen concentration is measured by partial pressure (kPa)
when the partial pressure of oxygen is high eg in the lungs, haemoglobin has a high affinity for oxygen and so oxygen associates with haemoglobin to form oxyhaemoglobin
when the partial pressure of oxygen is low eg in the respiring tissues, haemoglobin has a low affinity for oxygen and so oxygen dissociates from oxyhaemoglobin, forming haemoglobin
list 4 ways in which the shape of the haemoglobin dissociation line differs from the theoretical line
haemoglobin line is s-shaped
actual line rises much more steeply between 2kPa and 7kPa/steeper in the middle
theoretical line shows no flattening on top
haemoglobin shows higher saturation throughout
what is cooperative binding?
describes the ease with which a haemoglobin molecule binds a second and a third oxygen molecules, compared with the first and fourth
describe cooperative binding with haemoglobin
as haemoglobin is a protein, any molecule that associates with it will cause a slight change in shape
once the first molecule of o2 is associated with haemoglobin, it causes a change in shape that makes the second and third binding sites more available, increasing haemoglobin affinity for oxygen
the 2nd and 3rd o2 molecules associate more easily than the first
it is then more difficult for an oxygen molecule to associate with the last binding site
therefore the binding of o2 to Hb is not directly proportional to oxygen concentration
as a result the line of the o2 dissociation curve is not straight but instead a sigmoid curve (s-shaped)
describe the sigmoid graph
start - at very low ppo2 it is difficult for haemoglobin to load oxygen
in respiring tissues, the ppo2 is low because oxygen is being used up in aerobic respiration
the oxygen then unloads from oxyhaemoglobin (dissociates)
oxygen affinity decreases as ppo2 decreases
this means that it is readily released to meet respiratory demands
a very small reduction in the ppo2 leads to o2 unloading from oxyhaemoglobin rapidly
haemoglobin’s affinity for oxygen is high at high partial pressures of oxygen
haemoglobin loads oxygen in the lungs, where the ppo2 is high
the haemoglobin becomes saturated with o2 and forms oxyhaemoglobin
o2 is transported in this form to respiring tissues such as muscles
how does a pulse oximeter estimate the o2 saturation in your blood?
by sending infrared light into capillaries in your finger
then measures how much light reflected off the gases
the o2 saturation of Hb measured in a healthy person is 98/99%. Why is it not 100%
some o2 used by respiring cells in the alveoli
the rate of blood flow through the pulmonary capillaries is still too fast for all o2 to diffuse into the blood
what does foetal haemoglobin’s o2 dissociation curve look like and what does it mean?
curve shifted to the left of the adult curve
means it has a higher affinity for o2 therefore can load o2 from the mother’s blood at all partial pressures of o2
why doesn’t a baby retain its foetal haemoglobin once it is born?
foetal haemoglobin’s high affinity for o2 means that it doesn’t efficiently give it up at respiring tissues
adult haemoglobin needs a lower affinity for o2 than foetal so that o2 can pass from mothers to their foetuses
what happens to ppo2 at high altitudes?
drops
with an increase in altitude, there is a drop in atmospheric pressure and therefore a reduction in the ppo2
since llamas live in high altitudes, how do they compensate for the low ppo2? and what happens to the o2 dissociation curve?
a llama’s haemoglobin has a higher affinity for o2 and therefore picks up o2 more readily at the lungs
curve is shifted to the left
why do animals living in high altitudes have more red blood cells?
more haemoglobin to carry o2
where do lugworms live and how do they get o2?
they live in burrows in the sand on the seashore
they absorb o2 from the seawater they pump through their burrows
to cope with the low o2 conc. of seawater they have a dissociation curve shifted to the left meaning they have a high affinity for o2 so the Hb more readily takes up o2
what is myoglobin?
a tertiary structured protein that is more stable than haemoglobin
acts as an o2 store in the muscle tissues
less affected by ppco2 than Hb
what does ‘myo’ mean?
muscle
what is the shape of myoglobin’s dissociation curve?
shifted very far to the left of haemoglobin
when is myoglobin used?
at every partial pressure of o2, myoglobin has a higher percentage o2 saturation than Hb
if ppo2 becomes very low, oxymyoglobin unloads its o2 eg very strenuous exercise
ensures that o2 can be stored in the muscles for periods of low ppo2
describe the Bohr Effect
when the ppco2 is high due to co2 production in respiring tissues eg contracting muscle, the conditions inside the red blood cells become more acidic
this causes haemoglobin to change shape slightly and so haemoglobin now has a lower affinity for o2, unloading this o2 to the respiring tissues more readily
what does the Bohr Effect dissociation curve look like?
s-shaped curve is shifted to the right
what percentage of CO2 dissolves in blood plasma?
5%
where does the CO2 move from and to?
from respiring cells
to capillary
what percentage of co2 binds to haemoglobin in the red blood cell?
10%
what is formed as a result of the 10% of co2 and haemoglobin bound together?
carbamino-haemoglobin
what percentage of co2 binds to water in the red blood cell?
85%
what is formed as a result of 85% of carbon dioxide and water bound?
carbonic acid (H2CO3)
what enzyme catalyses the reaction between 85% of co2 and water?
carbonic anhydrase
what does the carbonic acid dissociate into?
H+
HCO3-
ions
what do the HCO3-ions do after?
the ions diffuse down their conc. gradient into plasma
what do the HCO3- ions bind to in the plasma?
Na+ ions
What is formed as a result of HCO3- ions and Na+ ions?
sodium hydrogen carbonate (NaHCO3)
what happens as a result of the accumulation of H+ ions in the red blood cell?
causes a fall in pH so cytoplasm becomes more acidic
alters the haemoglobin, reducing its affinity for oxygen
what does H+ ions combine with in the red blood cell?
with haemoglobin
what does the reaction between H+ ions and haemoglobin form?
haemoglobinic acid (HHb)
what does the reaction between H+ ions and haemoglobin do to the oxygen?
releases it
what is the equation between H+ ions and haemoglobin?
H+ + HbO8 makes HHb + 4O2
HbO8 = oxyhaemoglobin
where does the released oxygen go as a result of the reaction between H+ ions and haemoglobin?
it diffuses out of the red blood cells into the respiring tissues
what happens as a result of the movement of HCO3- ions out of the red blood cell into the plasma?
HCO3- ions are negatively charged and their movement out the red blood cell is balanced by the movement of negatively charged chloride ions, Cl-, in the red blood cell from the plasma
by what method of transport do Cl- ions come in the red blood cell?
facilitated diffusion
why is it important that the movement of HCO3- ions is balanced by the arrival of Cl- ions?
to maintain the electrochemical neutrality of the red blood cells
what is this movement of HCO3- ions out the cell balanced by Cl- ions in the cell called?
the chloride shift
how does the transport of co2 link to the Bohr effect?
the formation of carbonic acid and fall in pH inside the red blood cells explain the effect:
the high conc. of co2 produced by actively respiring tissues reduces the affinity of haemoglobin for o2 and therefore enables cells requiring more o2 to obtain it by promoting the dissociation of o2 from oxyhaemoglobin in the red blood cells
the more o2 produced the more acidic the conditions will be and so more o2 will dissociate from the oxyhaemoglobin
how are capillaries adapted to being the site of exchange between the blood and body cell/respiring tissues?
endothelial cells are one cell thick so they have a short diffusion pathway, they also have thin permeable walls and a large cross-sectional area
capillaries are very close to respiring tissues
blood flows slowly allowing time for gas exchange of materials
describe the capillary network
oxygenated blood from arteriole
network of capillaries over the body cells
there is also tissue fluid and a lymphatic system
amongst the tissues there is a lymphatic vessel
deoxygenated blood to venule
what else does blood contain?
large colloidal plasma proteins
what molecules do cells require?
o2
glucose
amino acids
what are waste substances that need to be removed?
urea
co2
how is tissue fluid formed?
at any capillary bed, fluid aka water and small molecules, is forced out through gaps between cells in the capillary walls
what does tissue fluid do?
bathes the cells and allows exchange of gases and nutrients
what happens at the arterial end of the capillary?
reference to tissue fluid
blood is under pressure because contraction of the left ventricle, creating a high hydrostatic pressure and forcing fluid through gaps in the capillary walls
the outward flow of fluid is opposed by osmotic pressure which is water trying to move back into the blood by osmosis
however as the hydrostatic pressure is greater than osmotic pressure, there is a net flow of fluid out of the blood
molecules dissolved in the tissue fluid move by diffusion and facilitated diffusion into the cells down their conc. gradient
what happens at the venous end of the capillary?
reference to tissue fluid
tissue fluid contains waste substances that have diffused out of the cells which can diffuse back into the blood in the capillaries down a conc. gradient
there is now a much lower hydrostatic pressure due to friction between the blood and the capillary wall and due to the lower volume of fluid in the capillaries
water potential in the blood is lowered due to the presence of plasma proteins therefore osmotic pressure is now greater than hydrostatic pressure and so there is a net movement of water back into the blood in the capillaries by osmosis.
what percentage of tissue fluid flows back into the capillaries?
90%
where does the tissue fluid that doesn’t flow back into the capillaries go?
around 10% drains into lymphatic capillaries found amongst the tissues
this remaining lymph eventually returns to the blood in the circulatory system
what two things are the lymphatic system involved in?
the absorption of lipids in the small intestine
the formation of lymphocytes and the prevention of disease
what does accumulation of tissue fluid cause?
causes swelling under the skin also known as oedema
annotate a diagram to show the formation of tissue fluid;
label lymph vessel, lymph blood, tissue fluid, arterial and venous end of capillary
using arrows to show the direction of flow due to high or low hydrostatic pressure and high or low osmotic pressure in the capillary
show where water potential is high and low in the capillary
show the direction of flow of fluid out of the capillary and back in
https://puppeteer.cognitoedu.org/coursesubtopic/b3-alevel-aqa_oTVXDIaF
https://myedspace.co.uk/blog/post/tissue-fluid-a-level-biology-explained
look in diagram in booklet page 17
kwashiorkor is a severe form of malnutrition when there is not enough protein in the diet
why is oedema the main symptom?
fluid isn’t moved from the tissues, so more water retention/loss of balance between hydrostatic and osmotic pressure across capillary blood vessel walls
