10 Flashcards
what are the three functions of the CV system
- supply o2 and nutrients to tissues
- take away metabolic products like CO2
- Defense against microorganisms
what kind of dangerous chemical reaction is oxygen involved with
oxidazing agent (electron thief)
what is oxidation in terms of electron gain or loss
electron LOSS
but oxidising agents gain an electron
does oxidation release or require energy
release energy in the form of heat
what is reduction in terms of electron gain or loss
electron gain
but reducing agents lose an electron
what dictates whether an oxidation reaction is reversible or irreversible
the amount of energy released as a result.
if large energy, irreversible
is the oxidation of NAD reversible or irreversible=
reversible
the reaction from NADplus to NADH is an example of…
reduction reaction
the reaction from NADH to NADplus is an example of…
oxidation reaction
how do Anaerobic bacteria live in oxygen-poor environments
Use other oxidising agents such as sulphate, nitrate (NO3−), sulphur (S), etc
what is one unique feature of haemoglobin
can combine rapidly and reversibly with oxygen without becoming oxidised
what is the shape of RBC
biconcave disks 7 µm in diameter 2 µm thick. Volume of about 90 cu mm (1 cu mm = 1 femtolitre) 270 million hemoglobin molecules
pathology where RBC is smaller than usual
microcytic anemia
pathology where RBC is larger than usual
macrocytic anemia
what do RBC lack that most other cells have
nucleus and mitochondria bc maybe o2 would damage mitocondraia
where are RBC made
bone marrow
what are reticulocytes
immature RBC that are about to leave BM or have just left it
what percentage of circulating RBCs are reitculocytes
1-2%
how long after entering circulation to reticulocytes become RBC
a day
why are reticulocytes called that way
bc of reticualar mesh like network of rRNA that is visible under microscope.
why cant RBC live long
bc they lack mitochondria and nucleus so they cant divide
can reticulocytes carry O2
yes but not as well.
what would a high reticulocyte count indicate
lots of hemolysis going on or there a haemorrhage.
why do RBCs need to generate energy (ATP=
they require ATP to maintain their ion pumps
where do RBCs get their energy from
not mitochondria cause they don’t have one.
RBCs make ATP by glycolysis (glucose to pyruvate to lactic acid.
what’s better at generating energy, glycolysis made by RBCs or aerobic respiration made by all other cells
aerobic respiration
what’s the natural pH of RBCs and why
acidic because they get their energy by glycolysis which converts glucose to pyruvate to LACTIC ACID
how to RBCs uptake glucose
via Glut1 receptor: facilitated diffusion
NOT regulated by insulin
how to RBCs get NADPH and why do they need it
pentose phosphate pathway
NADPH helps counteract the oxidative stress
what three things are necessary for RBCs to survive
ATP (energy)
glucose
NADPH
antioxidants
what is the name of haemoglobin when its oxidised too much and therefore damaged
methaemoglobin
typical lifetime of a RBC
120 days
how are RBC degraded
ageing erythrocytes have high levels of methaemoglobin so this causes changes to their PM markers and so are recognised by phagocytes
can methaemoglobin carry oxygen
no
where does erythrocytes phagocytosis occur
bone marrow liver or spleen
The ability to transport oxygen without being oxidised depends on
the ability of the iron atom to be hexavalent (form six bonds with surrounding atoms).
what’s a ferrous ion
Fe plus plus
how many unpaired electrons in ferrous ion
6 electrons (4 on a plane and one above and one below)
what’s a heam group
porphyrin ring AND ferrous iron centre
what’s a porphyrin ring
The four iron electrons in the plane are held by four covalent bonds to nitrogen atoms
what do the four planar iron electrons bind to
nitrogen in porphyrin ring
what does the bottom electron pari up with
histidine
where does oxygen bind
weakly binds to top electron
why is the interaction between oxygen and the top electron only weak
because of steric hinderance caused by 3D structure (cannot get close enough to fully remove electron)
what is the structure of haemoglobin
four polypeptide units each with a HEAM group attached
what bonds link the four polypeptide chains in Hb
salt bridges
hydrogen bonds
hydrophobic interaction
what does oxygen bonding depend on
- interlocking of the heat subunits
2. partial pressur iof oxygen in solution
what happens to oxygen binding when the oxygen partial pressure is high
oxygen binds and you get oxyhemoglobin
in tehe lungs
what happens to oxygen binding when the oxygen partial pressure is low
oxygen DISSOCIATES and you get deoxyhemoglobin
in tissue
what’s haemoglobin with ferric ion called
methaemoglobin
why cant methaemoglobin carry oxygen
bc out of its 6 electrons, four are int he plane the one on the bottom is attached to histidine and the last one which would binds O2 binds the Ferric ion like the four int he middle
what enzyme may repair the damaged of methaemoglobin
methaemoglobin reductase but we don’t know how many times it can fix it
what substance does methaemoglobin reductase depend on
NADH
as the cell ages what happens to the level of methaemoglobin
increases
what percentage of our haemoglobin is methaemoglobin
1-2%
what would cause a high percentage of methaemoglobin in the blood indicate
genetic or exposure to some chemicals (Methaemoglobinemia)
what condition do alaskan inuits have a lot and how do they compensate
congenital deficiency of methaemoglobin reductase
They compensate for the defect by making more red blood cells than normal individuals (polycythemia). Thus the total oxygen carrying capacity of the blood is increased.
what subunits make up normal adult Hb
2 alpha 2 beta (alpha2beta2)
how do different forms of Hb differ
Diff amino acid sequence and so diff steric hinderance
what subunits make up normal fetus Hb
2 alpha 2 gamma (alpha2gamma2)
how does maternal oxygen go to fetus across placenta
fetal hb has higher affinity for O2 than maternal Hb. so leaves moms oxyhemoglobin to come to babysit deoxyhemoglobin
what molecule enhances the ability of RBCs to release oxygen in hypoxic tissues.
2,3 DPG (2-3 diphosphoglycerate)
Small separate molecule bound loosely to Hb
When beta subunits start to deoxygenate, it binds to them more tightly, moves into the centre of the haemoglobin and increases the rate of oxygen release.
What is percent saturation
The proportion of haemoglobin that is bound to oxygen
written as % Hb saturation or often for arterial blood as SaO2
how can percent saturation be measured
pulse oximeter
normal oxygen saturation values
between 96% and 99%, and should be above 94%.
how is hypoxemia defined
An SaO2 (arterial oxygen saturation) value below 90% is
is oxygen saturation the same as tissue oygenation=
no bc that depends on ability to unload oxygen
oxygen unloading is described by what curve
Oxygen-haemoglobin dissociation curve.
whats the shape of O2 dissociation curve
‘s’shaped, flat at high pO2 and steep at medium and low pO2
whats the temperature like of heavily metabolising tissue vs slowly metabolising tissue
Heavily metabolising tissue heats up;
slowly metabolising tissue is colder than normal.
whats the effect of heat on Hb curve
heat moves it to the right (unloading MORE O2 at any given time
whats the effect of pH on Hb curve
heavily metabolising tissue make a lot of CO2 so it becomes more acidic and moves it to the right (unloading MORE O2 at any given time
whats the Bohr shift
shift of oxygen dissociation curve caused by pH changes
which of myoglobin or hemoglobin has a higher affinity for oxygen
myoglobin
whats myoglobin
form of hb found in muscle
Whats rhabdomyolysis.
When myoglobin is released from damaged muscle tissue. The released myoglobin is filtered by the kidneys but is toxic to the renal tubular epithelium and so may cause acute renal failure.
what makes muscles look red
myoglobin
whats the myoglobin dissociation curve shape
exponential
how do muscles get o2
As oxygenated blood goes through muscle capillaries you get transfer of o2 from hemoglobin to myoglobin.
what does the amount of blood carried depend on
hematocrits (percentage of blood which is red blood cells)
what a normal hematocrits percentage
45%
how is hematocrits controlled
via erythropoietin
which is continually released from interstitial cells in the kidney; when the kidney is hypoxic, erythropoetin secretion is increased. Thus this is a negative feedback loop. There is some evidence that erythropoetin secretion is inhibited by a rise in pulmonary arterial pressure
when can synthetic EPO be useful
in treating anaemia resulting from chronic kidney disease, from the treatment of cancer (chemotherapy & radiation), and from other critical illnesses (heart failure).
what kind of feedback is EPO
negative
what enzyme converts carbon dioxide to bicarbonate in red blood cells
carbonic anhydrase
whats the chloride shift
when cl enters RBCs to maintain cellular neutrality because bicarbonate just left the cell.
why does CO2 leave as bicarbonate not as CO2
bc co2 is not dissolvable in water and bicarbonate is
how does released bicarbonate make it to the lugs
via veins
does bicarbonate get released as is from the alveoli
no it gets converted to CO2 by CA in the lungs
what percentage of CO2 from tissues is carried to lungs as carbaminohaemoglobin
23%
what are the two forms that CO2 can be carried to the lungs as
bicarbonate
carbaminohaemoglobin
whats the most important mechanism by cwhich CO2 leaves the lungs
via bicarbonate
