Lecture 6- Oxygen in blood and tissues

Question 1

is oxygen soluble in water

Answer 1

Oxygen is not very soluble in water

Solubility factor O2= 0.01 mmol/:/kPa

Less soluble than CO2

Question 2

[O2] dissolved =

Answer 2

partial pressure of Oxygen in alveoli x solubility coeffiecient of oxygen

= 13.3 x 0.01

Question 3

[O2] dissolved at a PaO2 of 13.3 kPa

Answer 3

(Solubility factor O2= 0.01 mmol/kPa) x (13.3 kPa)= so only 0.13 mmol/L O2 is dissolved in blood

Question 4

at rest how much oxygen do we need per minute

Answer 4

12 mmol

Question 6

oxygen binding to Hb features

Question 7

Haemoglobin features

Answer 7

binds 4 o2 reversibly

• haem molecule- iron at its centre

Question 8

States of hb

Question 9

tense state of Hb

Answer 9

The T state has a less of an affinity for oxygen than the R state. The T-state is the deoxy form of hemoglobin (meaning that it lacks an oxygen species) and is also known as “deoxyhemoglobin”.

Question 10

relaxed state

Answer 10

High affinity for oxygen in R state (relaxed)- easier for oxygen to bind

Question 11

What determines whether Hb is in T or R stat

Answer 11

PP of oxygen is the most important

Question 12

feature of hb which means the right amount of O2 is being carried by Hb

Answer 12

cooperativity

Question 13

Cooperativity of haemoglobin

Answer 13

Question 14

describe the oxygen haemoglobin dissociation curve

Answer 14

Question 15

kPa when Hb becomes saturated

Answer 15

9-10kPa

Question 16

viturally unsaturated below

Answer 16

1kPa

Question 17

half saturared at

Question 18

Saturation changes greatly over a

Question 19

Wide range of safe partial pressure oxygen- esp at rest- however…..

Answer 19

Though once past the safe region (zone A), rapid fall in the danger zone (zone B)

Question 20

Hb in arterial blood leaving the lungs

Answer 20

Alveolar pO2 ≈ 13.3 kPa (Hb saturated at around 9-10kPa) therefore Hb leaving the lungs well saturated

Question 21

how to calculate oxygen content of arterial blood

Question 22

what about oxygen content in an anaemic pt

Answer 22

if patient is anaemic though pO2 will be normal, and Hb saturation with oxygen 100% – O2CONTENTwillbelower

Fewer Hb, but all Hb will have 4 oxygen binded

Question 23

Summary: Oxygen in Blood and Tissues (part One)

Answer 23

• Oxygen poorly soluble in blood
• Therefore a carrier is required to which oxygen binds through a

chemical rxn – binding must be reversible

• Carrier is haemoglobin
• Saturation depends on partial pressure oxygen in blood
• Exhibits + cooperativity that facilitates picking up and carrying oxygen in oxygen rich environment – lungs! And then releasing oxygen in low oxygen environment – tissues!
• Haemoglobin is almost 100% saturated over a fairly wide range of oxygen partial pressure so we have a wide safety margin for oxygen levels
• Once past safety margin though saturation drops dramatically and delivery of oxygen to tissues compromised – tissue hypoxia

Question 24

Tissue pO2 depends on

Question 25

Haemoglobin saturation in venous blood

Answer 25

Question 26

a shift to the right on the oxygen dissociation curve represents

Answer 26

decreased affinity of the haemoglobin for oxygen and hence an increased tendency to give up oxygen to the tissues.

Question 27

what factors will push the oxygen dissociation curve to the right?

Answer 27

• increased temp
• decreased pH
• increased CO2
• increased 2,3 DPG

Question 28

what factors will push the oxygen dissociation curve to the right?

Answer 28

• decreased temp
• increased pH
• decreased CO2
• decreased 2,3 DPG