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Lecture

Biology 2601A/B Lecture Notes - Respiratory Pigment, Sigmoid Function, Sipuncula


Department
Biology
Course Code
BIOL 2601A/B
Professor
Brent Sinclair

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Organismal Lecture 18
Gas Exchange 4: Blood
Gases Dissolve in Liquids
He same as having air bubbles
Pressure of the liquid (Pliquid) is proportional to pressure of the air (Pair)
The amount of gas in a solution is dependent upon
o 1. Temperature
o 2. Salinity
o 3. Type of gas
Gases that have reacted chemically will not contribute to partial pressure in a solution
Blood Must be Thicker than Water
The solubility of O₂ in water (especially warm salty water) is not enough to provide O₂ to active
tissues
Most organisms have to, therefore, use respiratory pigments to reversibly bind O₂ and have
them transport it to the tissues
o An example of a respiratory pigment is haemoglobin
o By taking this O₂ out oof solution, O₂ carriers help to maintain the PO₂ gradient across
the respiratory surface, improving O₂extraction
At the tissues, mitochondrial O₂ consumption ↓’s the PO₂ of the blood, causing O₂ to dissociate
from the oxygen carrier, and allowing it to then diffuse down its PO₂ gradient into the cells
Respiratory Pigments
diffusion will be dependent upon the
properties of the solution as well as
the [O] of the air
ed partial pressure in the blood
allows for of O diffusion from the
air
Once the O molecules are bound to
the respiratory pigment they are no
longer considered part of the solution

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What it Means to have a Respiratory Pigment
In comparison to water, there is much more carrying
capacity of the respiratory pigments to carry O,
allowing the organism to better pull O out of the
water/air and deliver large amounts to the tissues
Respiratory Pigments
Most are proteins; can either be in solution or enclosed in red blood cells (usually for
vertebrates)
Hematocrit is the proportion of total blood volume that is occupied by red blood cells
We can use Hematocrit to measure O carrying capacity in the blood
This is done by centrifuging the whole blood and measuring the proportion of solids (cells)
o This is a pretty good measure of blood O carrying capacity in vertebrates
Components of a Respiratory Pigment
When considering haemoglobin, it is made up of 4 subunits (2 α and 2 β subunits = tetramer)
Within each subunit, heme groups are non covalently bound to the molecule and contain a iron
ion at the centre
Haemoglobin plays a role in O transport and storage
Kinds of Respiratory Pigments (**ON EXAM***)
1/ Fe means these
pigments require 1 iron ions
to bind to 1 O molecule
1/ 2Fe mean these
pigments require 2 iron ions
to bind to 1 O molecule
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