O2 and CO2 in blood

Question 1

erythrocytes adaptations

Answer 1

• biconcave shape- large SA
• no nuclei- maximises haemeoglobin space
• contain haemoglobin- 4 haem groups
• haemoglobin + O2–> oxyhaemoglobin

Question 2

how does O2 bind to haemoglobin

Answer 2

• 1 oxygen binds to a haem group
• molecule changes shape, making it easier for the next oxygen to bind
• steep diffusion gradient is maintained untill all the haemoglobin is saturated with oxygen

Question 3

affinity of haemoglobin

Answer 3

• the tendency a molecule has to bind to oxygen
• when there is a high pO2, oxygen loads onto haemoglobin
• when there is a low pO2, oxygen unloads from oxyhaemoglobin

Question 4

what happens to oxygen in alveoli

Answer 4

• high O2 concentration
• high pO2
• high affinity
• oxygen loads

Question 5

what happens to oxygen in respiring tissue

Answer 5

• low O2 concentration
• low pO2
• low affinity
• oxygen unloads

Question 6

fetal haemoglobin

Answer 6

• fetal h. has higher affinity for oxygen than adult h.
• when mothers blood reaches placenta, O2 saturation has decreased as it has been used up by the body
• placenta has low pO2 so O2 unloads
• so fetal h. has to have a higher affinity for O2 so it takes up O2 in lower pO2 than adult h.

Question 7

the Bohr effect

Answer 7

• as partial pressure of CO2 increases, haemoglobin gives up O2 more easily

Question 8

the 3 ways that CO2 is transported from tissues to the lungs

Answer 8

• 5% dissolves in plasma
• 10-20% combines with haemoglobin to form carbominohaemoglobin
• 75-85% converted to hydrogen carbonate ions (HCO3-) in cytoplasm of RBCs

Question 9

how are hydrogen carbonate ions formed

Answer 9

• CO2 + water <–> H2CO3-(carbonic acid)
• carbonic acid dissociates to form hydrogen ions and hydrogen carbonate ions
• catalysed by carbonic anhydrase (RBCs)

Question 10

chloride shift

Answer 10

• negatively charged hydrogen carbonate ions move out of RBCs to plasma by diffusion down a conc. gradient
• negatively charged chloride ions move into RBCs
• maintains electrical balance of cell

Question 11

what happens with CO2 when blood reaches lung tissue

Answer 11

• hydrogen carbonate ions diffuse back into RBCs and react with H+ to form carbonic acid
• carbonic anhydrase catalyses reverse reaction- breaking down carbonic acid to CO2+H2O
• CO2 diffuses out of blood into lungs (which has low pCO2
• chloride ions diffuse out of RBCs into plasma down electrochemical gradient

Question 12

effect of increase of H+ ions in RBCs

Answer 12

• oxyhaemoglobin unloads its oxygen so that it can take up H+ ions (stops from increasing cell’s acidity)
• ## forms haemoglobinic acid