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Lecture 3

BIOB32H3 Lecture Notes - Lecture 3: Myoglobin, Hemolymph, Nfkb1


Department
Biological Sciences
Course Code
BIOB32H3
Professor
Steve Joordens
Lecture
3

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BIOB32 Lecture 3
Slide 4
- Similar pattern as nutrition and digestion when it comes to variation in
respiratory systems
- If you are a small organism, diffusion is good enough
- But if you are larger you need something that will distribute oxygen and
nutrients through the tissues of the body
o Includes conductive and convective steps
Slide 5
- This is what we usually think of when we think of a circulatory system that is
carrying respiratory gasses
- In our case we are talking about a closed system in that the blood never
leaves the vessel and the gasses need to diffuse out of the vessels
- See that we have lower pressure in the pulmonary system because it has to
do with how much pumping has to be done to get blood through that part of
the system
o This is a relatively short circuit compared to the systemic circulation
system.
o Coming from our heart to lung is shorter (pulmonary system) than
heart to toes per say (systemic system) and therefore a lower
pressure differential is needed for sufficient flow
- See differences in the construction in the vessels having to do with just
downstream of the hear or upstream of the heart
- In arteries, since the pump is generating pressure, this is a high pressure
pump of this high pressure system so we see relatively thick, elastic walls
that are designed to resist these changes in pressure, to buffer them
o Why are they so elastic? Each heart beat is increasing the pressure
and so we want that evened out and relatively even flow and so this
can stretch and recoil a little to buffer those pressure changes
o On the other end of the system we have lost a lot of that pressure, we
lost it as we were pushing blood through this network of very thin
capillaries and have thinner compliant walls. If we take a pint of blood
out, it shrinks down a little and picks up the volume of blood that was
lost
Slide 6
- So in many insect and invertebrates we have an open circulatory system
- Have a heart that is drawing in hemolymph (their version of blood) from
sinuses throughout the animal
- The hemolymph bathes the tissues directly
- In insects in particular, this circulatory system does not play a very
important role in the respiration per say but does play an important role in
getting nutrients such as sugar, hormones, around the body but it is the
tracheal system in particular that is responsible for delivering oxygen to
various tissues especially the active flight motor tissues
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- Have openings on the side of the insect and tubes that are airfilled through
part of their journey and at the back end are filled with fluid and so the air is
literally diffusing in there
- Have a separation in the circulatory and respiratory systems unlike it is in us
Slide 7
- In vertebrates it is RBC as well as WBC and platelets
o Carry hormones and other nutrients
- Invertebrates
o Don’t see something equivalent to RBC or pigments that carry oxygen
o In some invertebrates though the circulatory system does play this
role
Arthropods, spiders, etc
In this case, the respiratory pigments would be in hemoglobin
and it would be floating free in the plasma
o As we have WBC, many invertebrates have hemocytes which are part
of the immune system in these invertebrates
Slide 8
- In vertebrate blood we fraction this
- Where are the platelets and WBCs found?
o Found in the buffy coats
Slide 9
- Hemoglobin has a heme group which has an iron molecule in there and iron
molecule oxidizes
- It is the binding of oxygen to the iron molecule of the heme group
- Hemeoglobin has 2 alpha subunits and 2 beta subunits and each subunit has
one heme group and when oxygen is bound be call this oxyhemoglobin ad
when oxygen in not bound and all 4 subunits are dissociated from oxygen we
call this deoxyhemoglobin
- Like many proteins, there can be allosteric regulation… that is the binding of
things to non-active sites that causes changes in the performance of this
protein and what it does
o In this case the binding of protons and CO2 to certain amino acids as
well as other compounds causes slight conformational changes that
changes the affinity of this protein for oxygen
o The binding of oxygen can also change the affinity for this protein for
the binding of CO2 molecules
Slide 10
- Because we are dealing with large multicellular animals, we are dealing with
multiple diffusive and multiple convective steps.
- By convection we mean the bulk flow of fluids and this usually involves a
pump or pressure gradient
o Could be by a pump like a heart or could be by the contraction of
muscles around veins
- Diffusive step at the lung, diffusing oxygen and CO2 from the blood, then we
convectively move things like out hemoglobin through the blood throughout
the system at which point we once again must rely on diffusion for that O2
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bound to hemoglobin to dissociate and to diffuse into that extracellular fluid
and subsequently to the cells of the various tissues of the body and vice versa
with C02 diffusing back in the other direction
- We have a further diffusion step here with myoglobin in many of our cells
and this has a heme group associated with it and it is a single subunit but it
does a similar kind of job.
o It reversibly binds oxygen and then that way if can help buffer oxygen
levels within our tissues then it can be a stores source of oxygen for
short-term needs in the absence of sufficient delivery via the
circulatory system
- The end destination of oxygen is mitochondria and the CO2 are produced as
part of the citric acid cycle diffusing back in the other direction
Slide 11
- Hemoglobin and Myoglobin, as we do with enzymes, we can ascribe a similar
kind of variable here… it is not a enzymatic reaction in that oxygen is not
fundamentally changed into a product, but it binds to an active site reversibly
the way that substrate product do to an enzyme
- We can describe the affinity of these proteins for oxygen using a similar kind
of concept called P50
- P50 is the partial pressure at which pigment is 50% saturated
- The units here are in partial pressure
- We notice that here that there are 2 curves being shown, one is sigmoidal
and one is hyperbolic. This relates to enzyme function as well
- Hemoglobin has the sigmoidal curve and Myoglobin has the Hyperbolic
curve… why?
o Cooperativity
o Because myoglobin has one subunit it cannot exhibit cooperativity
Slide 12
- Things like crabs and spiders
- Don’t contain a heme group but contains copper
- Hemocyin, rather than having reddish tint when oxygen is bound to it, has a
bluish tint
- These are horseshoe crabs and every year they are picked up from the east
coast, brought into labs and drained of their blood, not enough to kill them,
and then re-released
- They harvest the blood to extract coagulogen. A protein that coagulates to
trap bacteria
- Because the hemolymph is bathing in the fluids here, the bacteria if it gets
into the circulatory system of a horseshoe crab, it can easily get right to the
tissues and the cells whereas if a bacteria gets right into our blood, the first
line of defense is the WBC which will hopefully get to the bacteria before it
can make their way out of our circulatory system and into our tissues. So this
does the job of trapping that bacteria very rapidly before it can make it to the
broad tissue
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