respiratory 2

Question 1

describe the modifications to the Fick equation to describe diffusion for gases

Answer 1

V.O2 = k x A x (P2-P1)/D

V(dot)O2 = rate of transfer of certain volume of oxygen from one compartment to another
K = diffusion constant (oxygen is nonpolar gas, highly lipid soluble, can diffuse easily across alveolar membrane
A = surface area (high SA)
D = thickness of membrane (very thick in alveolar space)
P2-P1 = pressure gradient (gases move down a partial pressure gradient, which is the pressure gradient of a single gas within a mixture, depends on the mole fraction of that gas within the mix)

Question 2

what is alveolar partial pressure of oxygen? and how do u calculate it?

Answer 2

oxygen makes up 21% of 760 mmHg –> 160 mmHg
–> airways add in water, dilutes the oxygen (- 47), also diffusing CO2, which dilutes the oxygen –> by the time get to alveoli, PO2 = 100 mHg (so goes from 160 to 100)

Question 3

pulmonary capillary feeding blood to alveoli, ___ mmHg of oxygen in the alveolus, deoxygenated blood comes into pulmonary capillary at about ___…

Answer 3

100
40 mmHg (partial pressure gradient is 100-40=60)
huge pressure gradient, huge surface area, tiny thickness, huge permeability –> oxygen diffuses across alveoli into blood very very rapidly

Question 4

___ is one of the few examples in nature of a system that is 100% efficient…

Answer 4

alveoli and oxygen exchange

by the time blood leaves, it is 100% equilibrated, all the oxygen that can diffuse, does diffuse

Question 5

the same property that allows oxygen to diffuse so easily across alveolar membrane becomes a problem when getting oxygen to be carries in the blood (nonpolar, so diffuses easily, but blood is mostly water and oxygen is not very water soluble, so getting O2 to dissolve in bloos id hard), what drives oxygen into blood and what is the fix?

Answer 5

PO2 drives oxygen into blood, has to be carried in the blood by hemoglobin

Question 6

structure of hemoglobin

Answer 6

tetramer (4 subunits), each subunit contains a heme that is attached to a globular protein (heme consists of an iron atom bound to a big ring structure with 4 nitrogens that hold the iron in the middle) - 4 heme subunits and 4 irons

hemoglobin has 2 identical alpha chains and 2 identical beta chains that make up the tetramer

Question 7

every hemoglobin molecule can bind __ oxygens

Answer 7

4

Question 8

if hemoglobin has no oxygens on it, called ___
if has oxygens, called ___

Answer 8

deoxyhaemoglobin
oxyhaemoglobin

Question 9

hemoglobin binds ___ and ___ with oxygen, which is key to its function…

Answer 9

loosely & reversibly

oxygen sticks to iron, but not a strong bond (surrounding partial pressure of oxygen determines whether oxygen is bound to hemoglobin or if it comes off)
–> partial pressure is high in lungs, so oxygen binds to hemoglobin in lungs, then travels to metabolizing tissue and gives it up (surround PO2 is low, causing O2 to come off and diffuse into tissue)

Question 10

what color does hemoglobin turn when it binds with oxygen? in what range of wavelength? what about deoxyhaemoblogin?

b/c it changes color, hemoglobin is called a ___

Answer 10

red, 600nm

absorbs higher and looks blue/straw-colored
relationship is pretty linear

respiratory pigment (can measure the color of hemoglobin, will tell you how much oxygen is bound to it)

Question 11

hemoglobin binds oxygen when iron is in the ____ state, which represents a weakness b/c…

Answer 11

+2 ferrous state
weakness b/c our bodies are constantly creating oxidation, some will tend to oxidize this iron into the +3 ferric state - ferric iron hemoglobin is called methemoglobin (is brown, which does not bind oxygen, is functionally useless) –> fortunately in RBCs, also an enzyme called methemoglobin reductase which reduces the iron back to ferrous form

Question 12

the oxygen dissociation curve plots ___ vs ___

if half of the hemoglobin is bound to oxygen, said to be ___

Answer 12

% of hemoglobin saturation vs. surrounding partial pressure of oxygen

50% saturated

Question 13

the oxygen dissociation curve is this shape, ___, which gives hemoglobin molecules unique functional adaptations…

Answer 13

sigmoid shaped
the plateau of the curve (100–>70 mmHg) shows 100% hemoglobin is saturated at normal PO2, plateau functions as a safety factor, guarantees 100% of hemoglobin will be saturated even if alveolar PO2 drops below normal (if can’t get full amt of oxygen into your lungs, can still get full amt in blood) - this can happen at high altitudes with thinner oxygen

if curve were linear, would not have safety factor

Question 14

the slope of the oxygen dissociation curve functions in ____

as soon as PO2 drops below __, oxygen begins to come off hemoglobin and can be delivered to tissues

Answer 14

delivering the oxygen from the hemoglobin to the tissues

70 mmHg

normal systemic PO2 is 40mmHg, b/w 100 and 40mmhg, hemoglobin gives up 25% of its oxygen (b/c hemoglobin carries so much oxygen, that 25% is enough to sustain resting metabolism –> this leaves a huge amt of venous reserve ox oxygen that can be called upon in exercise

around 40mmHg, even a small decline in PO2 gives up a lot of oxygen (very steep)

Question 15

this feature of the oxygen dissocation curve, ___, is the surrounding PO2 value at which 50% of the hemoglobin is saturated with oxygen

Answer 15

P50- used as a measure of the oxygen affinity for hemoglobin, this is how attractive hemoglobin is for oxygen(how easily the O2 binds)

Question 16

P50 and oxygen affinity are ___ related…

Answer 16

inversely
the lower the P50, the higher the oxygen affinity (low P50, takes very little oxygen to saturate hemoglobin b/w hemoglobin has such a strong affinity for it)

high P50 –> takes high PO2 to saturate hemoglobin b/c less attractiveness

Question 17

hemoglobin represents a whole ___, they adapt to their specific ___, one of the big differences is in their ____

describe an example

Answer 17

family
environments
oxygen affinities

maternal vs. fetal hemoglobin

fetal has lower P50, so higher oxygen affinity than maternal (adaptive b/c fetus gets its O2 from maternal blood circulation across the placenta, allows fetus to pull O2 from her), fetal and maternal are synthesized from 2 diff genes: during development, gene for fetal is on and maternal is off, during birth it switches

Question 18

myoglobin has a really high ____

Answer 18

oxygen affinity (P50 around 2.5mmHg), very efficient at pulling oxygen off circulation to the tissue its found in

ultimately, oxygen given up to mitochondria –> used to make ATP (inside mitochondria, PO2 is basically zero)

Question 19

the shape of myoglobin curve is ___

Answer 19

hyperbolic, diff shape b/c the curve is a result of the diff molecular structure of the 2 molecules

Question 20

hemoglobin has 4 subunits, each binds an oxygen, when it binds, it changes shape…

Answer 20

exists in 2 conformations (T, tense state- deoxy state, does not allow oxygen to bind) or the (R, relaxes state- oxy state, allows O2 to bind)

4 subunits cooperate with each other in positive way using property of cooperativity (first O2 binds to first subunits slowly, after it binds, it changes shape from T to R, b/c subunit connected to adjacent subunits, change in shape of 1st subunit changes shape of the others, making it easier for the 2nd oxygen to bind, and so on

Question 21

structure of myoglobin

Answer 21

monomer (no subunits to interact, no cooperativity - load the molecule and that is all

Question 22

hemoglobin starts in the veins, where PO2 is ___, goes to right atrium & right ventricle –> goes to lungs where its oxygenated in capillaries, here it is ____, then leaves fully oxygenated at 100 mmHg –> gets to systemic capillaries where it gives off oxygen to the systemic tissues and goes back to __mmHg

Answer 22

40
fully equilibrated, 100mmHg
40

Question 23

the first reason hemoglobin gives off its oxygen is b/c surrounding PO2 is low, there are ___ changes in the systemic capillary blood that speed up this process, these changes are called ___

Answer 23

chemical
allosteric effects (other sites other than the iron where the oxygen binds)

Question 24

allosteric effects do not effect the ___ directly, they bind other parts of the hemoglobin molecule –> ___ of the molecule which lowers oxygen affinity of the hemoglobin and makes it ___ for the oxygen to come off and be delivered to tissues

Answer 24

iron
alter configuration
easier

Question 25

what is the first allosteric effect that helps hemoglobin give up its oxygen easier

Answer 25

direct effect- if you are a metabolizing tissue, producing a lot of CO2 (CO2 in systemic capillaries goes up), CO2 can bind to hemoglobin directly, it binds to the amino end terminal of the protein –> this type of hemoglobin with bound CO2 called carbaminohemoglobin, the more CO2 bound to it –> the lower the oxygen affinity

Question 26

what is the second allosteric effect that helps hemoglobin give up its oxygen easier

Answer 26

indirect effect- CO2 chemically reacts with water to form carbomic acid –> produces more protons (in systemic capillaries, pH does down)
- the protons can also bind to the hemoglobin molecule (stabilizes salt bridges b/w the diff subunits and also within the subunits) –> changes shape of molecule, reduces oxygen affinity (low pH shifts curve to the right, called the Bohr effect- lower affinity and higher P50)

Question 27

what is the third allosteric effect that helps hemoglobin give up its oxygen easier

Answer 27

since low Po2 in systemic capillaries and lots of metabolic activity, increases amt of energy produced by anaerobic glycolysis –> results in increase in 2,3-DPG (2,3-BPG), this also binds hemoglobin b/w the 2 beta subunits and sticks them together, stabilizes them in favor of the T state, and lowers oxygen affinity and makes it easier for hemoglobin to give up its oxygen

Question 28

this poisoning is colorless, odorless, and tasteless gas, it directly competes with oxygen for binding of ___, it has this affinity for hemoglobin

Answer 28

carbon monoxide, CO
iron
200x greater affinity for hemoglobin than oxygen (sticks to iron 200x stronger than oxygen, binding is almost irreversible)