blood

Question 1

outline how the structure of red blood cells is related to their function

Answer 1

• contain respiratory pigment haemoglobin allowing oxygen to be transported to respiring tissues
• biconcave shape to increase surface area so more oxygen diffuses through the membrane , the thin centre reduces diffusion distance
• they have no nucleus so there is more room for haemoglobin maximising oxygen carried at one time

Question 2

what is plasma

Answer 2

a pale yellow liquid which is 90% water containing solutes such as food molecules, waste products, hormones and plasma proteins

Question 3

define affinity

Answer 3

the degree to which molecules are attracted to one another

Question 4

define co-operative binding

Answer 4

the increasing ease with which haemoglobin binds itself to the third oxygen molecules

Question 5

outline the structure of haemoglobin

Answer 5

• quaternary protein
• contains 4 haem groups
• each haem group contains an iron
• one oxygen can bind to each iron so 4 oxygen molecules can bind to 1 Hb molecule

Question 6

Outline how oxygen binds to haemoglobin

Answer 6

1) the first oxygen attaches to the haemoglobin causing a change is shape, this increases the ease for the second oxygen to bind
2) the second oxygen attaches causing another change in shape making it easier for the third molecule to bind
3) the third bound molecule does not induce a shape change so it takes increased partial pressures of oxygen to bind the 4th molecule

Question 7

what does co-operative binding do

Answer 7

allows haemoglobin to pick up oxygen rapidly in the lungs

Question 8

why does affinity of oxygen increase when partial pressures of oxygen increase

Answer 8

as ppO2 increases, the diffusion gradient into the hemoglobin also increases increasing the ease of oxygen to bind to a haem group

Question 9

outline the oxygen dissociation curve

Answer 9

• oxygen affinity of Hb is high at high partial pressures of oxygen and oxyhemoglobin does not release its oxygen ( this means oxygen is released to muscles that don’t require it)
• oxygen affinity decreases as the partial pressure of oxygen decreases and oxygen is readily released ( partial pressures in working muscles will be low so oxygen is released allowing aerobic reparation)

Question 10

draw and explain the oxygen dissociation curve in the lungs

Answer 10

1) PPO2 is low so it is hard for the oxygen to reach the haem group so saturation of Hb is low as the diffusion gradient is less
2) as PPO2 increases the likelihood of the first oxygen associating increases, as the diffusion gradients increases, and when it does associate it changes the configuration of Hb increasing ease of biding for the second oxygen and then the third, therefore saturation of Hb increases dramatically
3) the third oxygen doesn’t change the configuration of Hb therefore it is harder for the fourth molecule to associate so requires very high PPO2 for this to occur

Question 11

draw and explain the oxygen dissociation curve in respiring muscles

Answer 11

1) as partial pressures of oxygen drop- the oxygen dissociates more readily
2) at higher PPo2 the oxygen does not readily dissociate
3) as ppO2 drops the affinity for oxygen decreases and oxygen is more readily released
4) therefore at low ppo2 in working muscles oxygen is more readily released allowing aerobic respiration

Question 12

explain why the oxygen dissociation curve in foetal Hb shifts to the left

Answer 12

• the fetus must absorb oxygen from the mother’s placenta
• the fetal Hb has a greater affinity for oxygen compared to the adults at the same ppO2
• their blood flows close in the placenta so oxygen is transferred at any ppO2
• this means the % of saturation of the fetus’s blood is higher than the mother so it moves to the left

Question 13

why is it important that foetal Hb has a higher affinity than adults

Answer 13

by the time the mothers blood reaches the placenta oxygen saturation has decreased

Question 14

explain the transport of oxygen in other animals that live in areas with low oxygen

Answer 14

eg a llama

• with increased altitudes, the ppO2 in the atmosphere decreased
• this means the O2 dissociation curve is also to the left
• the Hb must have a higher affinity for oxygen at lower ppO2 so it loads oxygen more readily into the lungs and releases oxygen when ppO2 is low

Question 15

what effect does carbon dioxide have on the oxygen dissociation curve

Answer 15

if co2 conc increases the Hb releases oxygen more readily- therefore dissociation of oxygen occurs at lower partial pressures of oxygen so the curve is moved to the right

Question 16

define the Bohr effect

Answer 16

the movement of the oxygen dissociation curve to the right at high ppCO2 because data given oxygen PPo2 hemoglobin has a lower affinity for oxygen