The Oxygen Cascade II Flashcards
Steps in Oxygen Cascade
Convection (Advection)
VO2 = (VI x FIO2) - (VE x FEO2)
Diffusion
VO2 = DLO2(PAO2 - PcO2)
Convection
VO2 = Q (CaO2 - CvO2)
Diffusion
VO2 = DtO2(PcO2 - PtO2)
As a consequence of our absolute dependence
on aerobic metabolism, we have evolved:
• A large surface area for gas exchange (alveoli)
• An efficient transport system
(heart & circulation)
• An oxygen transport protein (haemoglobin)
Pulmonary capillary PO2 as a function of RBC transit time graph shows
Pulmonary capillary PO2 as a function of
RBC transit time
Line reaches 98% in one quarter of time of transit (by 0.25)
O2 is carried in the blood in two forms:
• As a gas in simple solution in the plasma,
i.e. physically dissolved
– (only 3 mL L-1 (100 mm Hg PO2)-1, since plasma sO2
is low)
• As oxy-haemoglobin in erythyrocytes (RBCs)
– (1.34 mL O2 g-1 Hb, ~ 200 mL if [Hb] is 150 g L-1)
Gases dissolved in solution obey Henry’s Law:
i.e.
the amount dissolved is proportional to the
partial pressure of the gas, and its solubility
c= solubity constant*P
Humans have the red-colored hemoglobin as their
_________ to increase the O2-carrying capacity of
the blood.
respiratory pigment
Hemoglobin is confined to the
• Increases the O2-carrying capacity of the blood
between
RBCs
65 - 70 x.
• Each RBC has about ____x 106 Hb molecules, and
each mL of blood contains ~5 X 109 RBCs.
300
Hb molecule made up of 4 subunits. Describe
(globin, 2 α & 2 β), each with 1
haem (a porphyrin compound) at the centre.
• Each haem contains ________ that combines with O2.
an iron atom (ferrous form, Fe2+)
• Hb carries up to ~_____mL O2 LBlood-1
200
Relaxed binding structure of haemoglobin
oxyhaemoglobin
Tight binding structure of haemoglobin
deoxyhaemoglobin
As the 4 haem groups unload O2, _______ binds (1:1)
strongly to the b subunits (globins).
2,3-DPG (2,3-BPG)
• Globin (i.e. the 4 subunits) can bind to
H+ and CO2.
• 2,3-DPG (2,3-BPG) 2,3-Diphosphoglycerate is a ______metabolite that
alters the?
glycolytic
the affinity of Hb for O2.
• 2,3-DPG is increased in blood by
hypoxia, low [Hb], and increased pH.
Under basal conditions the tissues require about 5 mLs
O2 per 100 mLs blood.
•To achieve this, PO2 must
less than 40 mm Hg.
During exercise the tissues require up to ~20 x more O2.
This achieved without a huge decr. PO2 because:
- Steep slope of HbO2 curve
* Increased tissue blood flow caused by the small drop ¯PO2. (Hypoxic vasodilation of tissue capillaries)
The range of PO2 values in the tissues is held tightly
between
40 - 15 mm Hg.
Haldane effect.LUNGS
Binding of Hb with O2 tends to displace
CO2 from the blood:
Bohr effect. TISSUES
Increase in blood [CO2] causes O2 to be
displaced from Hb:
Anaerobic threshold is a physiological indice of .
• Above this point ______accumulates in blood.
• Has a high correlation with an athlete’s
performance
lactate
endurance performance.
There are two ATP-generating systems,
glycolysis and
oxidative phosphorylation.
_______does not require O2 and has La− as its endproduct, because the equilibrium of the LDH reaction is
markedly in favor of La− .
• La− , then, is an immediate reservoir supplying pyruvate
to mitochondria for _____________
• Therefore, La− stands at the intersection of _____and _______metabolism of carbohydrate
fuel.
Glycolysis
complete oxidative combustion.
anaerobic and aerobic
2 ways Elimination of CO2
CO2 is excreted from the blood: • as CO2 in the lungs • as HCO3 - in the kidney CO2 is excreted from the body: • by exhalation • by micturition
_____ + ________ _H2CO3 H+ + HCO3-
CO2 + H2O
CO2 + H2O_H2CO3 catalysed by?
in RBCs by carbonic anhydrase
CA) to form carbonic acid (H2CO3
CO2 is transported in the blood by:
- ~ 7% as CO2 in simple solution (high sCO2)
- ~ 23% as HbCO2 (carbaminohaemoglobin)
- ~ 70% as HCO3-
• CO2 dissociation curve
is more linear, and never
reaches .
saturation
• CO2 content is
increased with
desaturation of Hb
(Haldane effect)
!
• CO2 content of whole
blood is ≈ _______ O2 content
3 x higher
than
Blood contains only a small part (~2.5 L) of total CO2 stored in the body:
• Content ~ 0.5 L CO2 Lblood-1 x Total blood volume (~ 5 L)
Total CO2 stored ~100L:
• Much of it dissolved in fat or stored in bone.
O2 stores are minute!
~approx?
1.5 L in blood + alveoli + myoglobin.
The six important, continuous phases of
respiration include:
- Bulk flow of air in/out of the lungs (ventilation).
- O2 and CO2 diffusion between alveoli & blood.
- O2 transport by blood (bulk flow or convection) to
the tissues. - Release of O2 from Hb & diffusion to cells.
- Use of O2 by cells & production of waste products
including CO2. - CO2 transport by blood where some diffuses out of
the blood and is exhaled
CO2 is excreted from the BODY by?
body:
• by exhalation
• by micturition
