Biochem/Physio

[toothfairy2011]

Could someone help me out with this question?

Assuming that P50 = 26 torrs, under conditions where pO2 = 30 torrs, the average # of O2 molecules bound per hemoglobin molecule is closest to:

A. 0.5
B. less than 1
C. almost 2
D. greater than 2
E. greater than 3

The answer is D.

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[impaction]

Could someone help me out with this question?

Assuming that P50 = 26 torrs, under conditions where pO2 = 30 torrs, the average # of O2 molecules bound per hemoglobin molecule is closest to:

A. 0.5
B. less than 1
C. almost 2
D. greater than 2
E. greater than 3



P50 is the pressure at which half the sites are saturated,
Hb carries at the most 4 molecules of oxygen. so ath half the pressure it will carry half.
so at 26 torrs , it will carry half the molecules i.e. 2,
now at 30 torrs it will carry almost 2

 

[porcelain258]

Could someone help me out with this question?

Assuming that P50 = 26 torrs, under conditions where pO2 = 30 torrs, the average # of O2 molecules bound per hemoglobin molecule is closest to:

A. 0.5
B. less than 1
C. almost 2
D. greater than 2
E. greater than 3

The answer is D.

p50 is the pressure of oxygen at which half of the Hb chains in each Hb molecule is bound to o2
4 molecules of o2 normally bind to 1 Hb molecule (having 4 chains)
Since given p50 is 26 torrs
and30 torrs is greater than that , so more than 2 molecules of oxygen shd bind to each Hb molecule

 

[impaction]

p50 is the pressure of oxygen at which half of the Hb chains in each Hb molecule is bound to o2
4 molecules of o2 normally bind to 1 Hb molecule (having 4 chains)
Since given p50 is 26 torrs and it is greater than 30 torrs which is acc to the conditions ,so more than 2 molecules shd be bound to each Hb molecule

yeah it will be 2.
but there is nothing like 2.1 or 2.2 molecules attatched because it will either be 2 or 3.
so the answer should be 2,
btw from where did u get this question

 

[porcelain258]

yeah it will be 2.
but there is nothing like 2.1 or 2.2 molecules attatched because it will either be 2 or 3.
so the answer should be 2,
btw from where did u get this question

i think i have seen this q in the released papers and and the ans (greater than 2) is acc to the key

 

[porcelain258]

Could someone help me out with this question?

Assuming that P50 = 26 torrs, under conditions where pO2 = 30 torrs, the average # of O2 molecules bound per hemoglobin molecule is closest to:

A. 0.5
B. less than 1
C. almost 2
D. greater than 2
E. greater than 3

The answer is D.

can u pls confirm the ans acc to tthe key

 

[skabbaraju]

can u pls confirm the ans acc to tthe key

The answer is almost 2. use the following formula:
((p50)e 2.3) / ((p50)e 2.3 + (p02)e 2.3)
This is a released question.

 

[porcelain258]

The answer is almost 2. use the following formula:
((p50)e 2.3) / ((p50)e 2.3 + (p02)e 2.3)
This is a released question.

hey thanks skabbaraju
but i didn't understand the formula......can u pls explain
actually when i did this q in the released papers, my own understanding also gave me this ans. but then changed my mind after looking at the key
really , wrong answers in the keys totally misguide us ..something shd be done about that

 

[impaction]

hey thanks skabbaraju
but i didn't understand the formula......can u pls explain
actually when i did this q in the released papers, my own understanding also gave me this ans. but then changed my mind after looking at the key
really , wrong answers in the keys totally misguide us ..something shd be done about that

i will give u simple clue.....
almost 2 means close to 2,
2.1 & 1.9 are both almost 2

 

[porcelain258]

i will give u simple clue.....
almost 2 means close to 2,
2.1 & 1.9 are both almost 2

thanks impaction
i think i got the point

 

[armorshell]

The answer D is correct. If O2 saturation is HIGHER then P50, there are going to be MORE O2 molecules bound ON AVERAGE. This means that most hemoglobin molecules will have 2 O2 bound, but a certain percentage of them will have 3 O2 bound, meaning the MEAN hemoglobin molecule has GREATER THAN 2 O2 bound.

Almost 2 does not mean "in the vicinity of 2." Almost, nearly, approaching, etc... all mean less than.

 

[porcelain258]

now what

 

[passiondentistr]

principle allosteric regulator of pyruvate metabolism in liver?
ATP
NAD
citrate
cAMP
Acetyl coA

which one is responsible for initiating cross bridge cycling in smooth muscle?
myosin ATPase
myosin kynase
myosin reductase
myosin phosphatase

 

[toothfairy2011]

Thanks very much for the replies. FYI the question is from a released exam and the answer is definitely D, according to the booklet.

 

[toothfairy2011]

Answer to passiondentistr's questions:

1. ATP
2. myosin ATPase

Others agree?

 

[shuntyman]

principle allosteric regulator of pyruvate metabolism in liver?
ATP
NAD
citrate
cAMP
Acetyl coA

which one is responsible for initiating cross bridge cycling in smooth muscle?
myosin ATPase
myosin kynase
myosin reductase
myosin phosphatase

 

[passiondentistr]

yeah agree wit shuntyman!

 

[passiondentistr]

each is necessary for viral antigen recognition by CD4 helper cells EXCEPT ?
-viral replication in host cell
-cleavage of viral proteins into small peptides
-transport of viral peptides to a cell surface by MHC Class ll
-binding of T cells TCR to a MHC class ll bound viral peptide
-internalization of virus progein by antigen presenting cell

greatest blood to left coronary art. during ?
-eartly systole
-late syst
-early diast
-late diast

 

[porcelain258]

each is necessary for viral antigen recognition by CD4 helper cells EXCEPT ?
-viral replication in host cell
-cleavage of viral proteins into small peptides
-transport of viral peptides to a cell surface by MHC Class ll
-binding of T cells TCR to a MHC class ll bound viral peptide
-internalization of virus progein by antigen presenting cell

greatest blood to left coronary art. during ?
-eartly systole
-late syst
-early diast
-late diast

 

[shuntyman]

ach is necessary for viral antigen recognition by CD4 helper cells EXCEPT ?
-viral replication in host cell
-cleavage of viral proteins into small peptides
-transport of viral peptides to a cell surface by MHC Class ll
-binding of T cells TCR to a MHC class ll bound viral peptide
-internalization of virus progein by antigen presenting cell

greatest blood to left coronary art. during ?
-eartly systole
-late syst
-early diast
-late diast

 

[skabbaraju]

principle allosteric regulator of pyruvate metabolism in liver?
ATP
NAD
citrate
cAMP
Acetyl coA

which one is responsible for initiating cross bridge cycling in smooth muscle?
myosin ATPase
myosin kynase
myosin reductase
myosin phosphatase

1. Acetyl coA
2. Myosin kinase as far as I know.

 

[skabbaraju]

ach is necessary for viral antigen recognition by CD4 helper cells EXCEPT ?
-viral replication in host cell
-cleavage of viral proteins into small peptides
-transport of viral peptides to a cell surface by MHC Class ll
-binding of T cells TCR to a MHC class ll bound viral peptide
-internalization of virus progein by antigen presenting cell

greatest blood to left coronary art. during ?
-eartly systole
-late syst
-early diast
-late diast

1. I would agree with shuntyman.
2. late diastole

 

[impaction]

each is necessary for viral antigen recognition by CD4 helper cells EXCEPT ?
-viral replication in host cell
-cleavage of viral proteins into small peptides
-transport of viral peptides to a cell surface by MHC Class ll
-binding of T cells TCR to a MHC class ll bound viral peptide
-internalization of virus progein by antigen presenting cell

greatest blood to left coronary art. during ?
-eartly systole
-late syst
-early diast
-late diast

 

[porcelain258]

Lt and Rt coronary arteries recieve their blood from ascending aorta....so volume of blood shd be greater in coronary arteries when pressures and volume r greater in aorta which is during late systole...

 

[Catfish]

greatest blood to left coronary art. during ?
-eartly systole
-late syst
-early diast
-late diast

I know it's diastole for sure. I read it in multiple places, saying that's when the coronaries arteris are filled (maybe in the decks too?). But don't know why (never looked it up). Can someone explain please?

 

[porcelain258]

during late diastole heart's left ventricular chamber contains max. volume blood but not the left coronary artery becoz these arteries(lt and rt coronary arteries ) r supplied by the aorta
anybody who is very clear about this can pls confirm the answer..
btw passiondentistr , do u have this ans in the key....if yes pls do confirm

 

[njsmahal]

when the pressure in the chambers is high, that is systole, the arteries are shut and the blood doesnt flow into them as the muscles are constricted, but whne the heart is in diastole, the muscles expand adn so the coronary arteries also open up and heart gets the blood supply. thats why if there is hypertension it is a predisposing factor to ischemic heart disease due to high pressure. and so is the prolonged exercise effect on heart.

 

[njsmahal]

thsi also makes sense as during high pressure systole if these arteries are open they would be damaged as they are not that strong. so these arteries are kept shut to protect them from damage... easy way to remember

 

[porcelain258]

hey guys
I actually needed to brush up my physio fundamentals.....finally i got to clear my doubt by myself
the ans is late diastole becz of less coronary vascular resistance during this phase as compare to systole when the intramyocardial vessels r collapsed shut and CVR is high
during diastole the intramyocardial pressures drop allowing the vessels to reopen .....hence, the increased coronary volumes during diastole

 

[porcelain258]

thsi also makes sense as during high pressure systole if these arteries are open they would be damaged as they are not that strong. so these arteries are kept shut to protect them from damage... easy way to remember

hey thanks
i just saw ur post......

 

[SM156]

During contraction of the ventricular myocardium (systole), the subendocardial coronary vessels (the vessels that enter the myocardium) are compressed due to the high intraventricular pressures. However the epicardial coronary vessels (the vessels that run along the outer surface of the heart) remain patent. Because of this, blood flow in the subendocardium stops. As a result most myocardial perfusion occurs during heart relaxation (diastole)