Lecture 6 - Carriage of O2 and CO2 in the blood

Question 1

In what 2 forms is oxygen carried in the blood

Answer 1

dissolved in the blood

combined with haemoglobin

Question 2

What is the relationship between temperature and proportion of gas dissolved?

Answer 2

amount of gas dissolved in solution is proportional to the temperature.
more dissolves at a lower temperature and depends on partial pressure also.

Question 3

Volume of O2 in blood is

Answer 3

solubility (0.0232) x PO2 (Partial pressure)

Question 4

Oxygen saturation equation

Answer 4

oxy haemoglobin/ (deoxy +oxy haemoglobin)

Question 5

Volume of oxygen carrying haemoglobin

Answer 5

Saturation x concentration of haemoglobin (14) X hufners constant (1.39)

Question 6

What are the different structures of haemoglobin

Answer 6

Primary, secondary, tertiary and quartenary

Question 7

Primary structure of

Answer 7

141-146 AA’s per chain

Question 8

Secondary

Answer 8

globular structure

Question 9

tertiary structure

Answer 9

crevice for haem and O2 binding

Question 10

Quartenary structure

Answer 10

hb A 4 chains - 2 alpha and 2 beta chains

Question 11

what does one haemoglobin molecule comprise of

Answer 11

4 globin chains
4 haem groups
4 iron atoms
4 oxygen molecules

Question 12

What is the molecular basis of o2 binding?

Answer 12

o2 binding occurs in a crevice of haem
when in relaxed form (oxygenated) - o2 can access the binding site
when in a tense form (deoxygenated) - O2 is pushed out

Question 13

Hb- O2 dissociation curve concept

Answer 13

the tense nature of deoxyhaemoglobin makes it difficult for oxygen to bind and so starts off having a low saturation. as oxygen molecules one by one the saturation shoots up, the oxy hb is relaxed and O2 binding sites become available to acces. this eventually happens until there is maximum saturation and curve levels off.

Question 14

whys is systemic blood only 97% saturated?

Answer 14

because of a mix in the blood that crosses the pulmonary capillaries

Question 15

What causes a right shift in haemoglobin dissociation curve?

Answer 15

Carbon dioxide
Acid (decrease in pH)
Diphospho-glycerate increase 
Exercise 
Temperature increase

Question 16

What shifts the dissociation curve to the left?

Answer 16

an increase in pH
A decrease in temperature
a decrease in DPG

Question 17

What happens in thalassaemia

Answer 17

absent globin chain

Question 18

Defective blobin chain

Answer 18

sickle cell disease (HbS)

single amino-acid defect

Question 19

Defective Fe atom (Fe3+)

Answer 19

Methaemoglobin

Drug induced: metHb does not carry oxygen

Question 20

Wrong ligand

Answer 20

CO Hb
smoking/house fires
CO blocks O2 binding site

Question 21

What is a buffer?

Answer 21

a solution that can minimise changes in the Free H+ concentration and therefore in pH

Question 22

Example of a buffer

Answer 22

usually a weak acid and its base in equilibrium

Question 23

Blood buffer systems in the body

Answer 23

includes proteins - carboxyl and amino groups at each end of the chain and basic?acidic

bicarbonate, plasma proteins, haemoglobin and phosphate

Question 24

Normal Blood pH

Answer 24

7.35-7.45, H+ concentration 35-45 nmol-1

Question 25

in what 3 forms is CO2 carried in the blood?

Answer 25

1. dissolved in the blood
temperature dependent 
at 37 degrees = 3ml CO2 per dl of blood
2. Carbamino compounds
- bound to R-NH2 groups on proteins. includes terminal amino group and side chains of lysine and arginine  - 4ml 
3. as carbonic acid/bicarb
= 45 ml CO2

Question 26

how is carbonic acid formed in the blood and broken down?

Answer 26

formed from co2 and water and is broken down by carbonic anhydrase into H+ ions and HCO3-

Question 27

How are H+ ions and HCO3- handled from breakdown of carbonic acid buffered?

Answer 27

H + buffered by Hb ions.

HCO3- pumped out of RBC’s in exchange for a chloride ion (Hamburger shift)

Question 28

What happens in the CO2 dissociation curve and the haldane effect

Answer 28

since deoxygenated blood binds more H+ than oxyhaemoglobin, and forms carbamino groups readily, binding of O2 to haemoglobin reduces its affinity for CO2 which is the haldane effect. consequently, venous blood carries more CO2 than arterial blood.

Question 29

What is Henderson-Hesselbalch equation

Answer 29

Measure of pH in a biological system, assuming all CO2 is converted into H2CO3 and using law of mass action, equation can be rearranged to:

pH= pK (6.1) + log10 [HCO3-]/[CO2]

Question 30

Compensatory systems of acid base balance?

Answer 30

Respiratory: blood pH regulates ventilation and so controls PCO2 - rapid response

Renal: excretion of H+ in urine controlled by pH - slow response

Question 31

What is pK in hendersons eqution?

Answer 31

6.1

Question 32

What is alkalosis

Answer 32

pH greater than 7.45

Question 33

What does respiratory alkalosis involve

Answer 33

low PC02, normal HCO3-. Hyperventilation (Anxiety, iatrogenic

Question 34

What is metabolic alkalosis

Answer 34

normal PCO2, high HCO3-
Loss of H+ - eg. vomitting
abuse of antacid remedies

Question 35

Normal ranges of P02 and PC02

Answer 35

PO2 - 10 - 13.33
pCO2 - 4.67 -6
HCO3- - 22-26 mmol/L

Question 36

Respiratory acidosis

Answer 36

less than pH 7.35
High PCO2, high HCO3- - renal compensation
Ventilatory failure

Question 37

Metabolic acidosis

Answer 37

low HCO3- and low PCO2-
Respiratory compensation
Renal failure, diabetic ketoacidosis, shock, poor tissue perfusion