The Oxygen Cascade II Flashcards
(36 cards)
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.