Lecture 6- Oxygen in blood and tissues Flashcards

1
Q

is oxygen soluble in water

A

Oxygen is not very soluble in water

Solubility factor O2= 0.01 mmol/:/kPa

Less soluble than CO2

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2
Q

[O2] dissolved =

A

partial pressure of Oxygen in alveoli x solubility coeffiecient of oxygen

= 13.3 x 0.01

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3
Q

[O2] dissolved at a PaO2 of 13.3 kPa

A

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

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4
Q

at rest how much oxygen do we need per minute

A

12 mmol

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5
Q
A
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6
Q

oxygen binding to Hb features

A
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7
Q

Haemoglobin features

A

binds 4 o2 reversibly

  • haem molecule- iron at its centre
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8
Q

States of hb

A
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9
Q

tense state of Hb

A

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”.

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10
Q

relaxed state

A

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

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11
Q

What determines whether Hb is in T or R stat

A

PP of oxygen is the most important

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12
Q

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

A

cooperativity

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13
Q

Cooperativity of haemoglobin

A
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14
Q

describe the oxygen haemoglobin dissociation curve

A
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15
Q

kPa when Hb becomes saturated

A

9-10kPa

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16
Q

viturally unsaturated below

17
Q

half saturared at

18
Q

Saturation changes greatly over a

19
Q

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

A

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

20
Q

Hb in arterial blood leaving the lungs

A

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

21
Q

how to calculate oxygen content of arterial blood

22
Q

what about oxygen content in an anaemic pt

A

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

23
Q

Summary: Oxygen in Blood and Tissues (part One)

A
  • 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
24
Q

Tissue pO2 depends on

25
Haemoglobin saturation in venous blood
26
a shift to the right on the oxygen dissociation curve represents
decreased affinity of the haemoglobin for oxygen and hence an increased tendency to give up oxygen to the tissues.
27
what factors will push the oxygen dissociation curve to the right?
* increased temp * decreased pH * increased CO2 * increased 2,3 DPG
28
what factors will push the oxygen dissociation curve to the right?
* decreased temp * increased pH * decreased CO2 * decreased 2,3 DPG