marymochan

hmmm. I know this answer is a bit late, but I know that some PI's pay their students indirectly via work-study. For those who wish to learn, they sign a contract that allows the student to receive credits and for the faculty member to be paid as a teaching member of staff.

once you know the number of moles, you can divide by the number of ions dissociated to get the number of Na+ ions. for example, if you know that you have (53.2/58.44) moles total, you know that you have (53.2/58.44) moles of Na because each mole of NaCl dissociates into one mole Na and one mole Cl.

for every mole of nacl, you get one mole of na.

it's a 1:1 ratio, because of the way it dissociates

For parts A and B of this problem, use the following standard reduction potentials, free energies, and nonequilibrium concentrations of reactants and products:

atp=3.1mM

glucose=5.1mM

nad+=350micro M

Pi=5.9mM

pyruvate=62 micro M

nadh=15micro M

adp=220 micro M

co2= 15 torr

half reaction

NAD⁺ + H⁺ +2e^- --> nadh E⁰ (V)=-0.315

2 pyruvate+ 6H⁺ + 4e^----> glucose E⁰=-.590

pyruvate + nadh + 2H⁺ ---> ethanol + nad⁺ + co2

delta G^{' naught} =-64.4kJ/mol

adp+ h2o --> adp + Pi + H⁺

delta G'^naught=-30.5kj/mol

a) consider the last 2 steps in the alcoholic fermentation of glucose by brewers' yeast:

pyruvate + nadh + 2H⁺ ---> ethanol + nad⁺ + co2

calculate the nonequilibrium concentration of ethanol in yeast cells, if delta G=-38.3 kJ/mol for this reaction at pH=7.4 and 37 degrees C when the reactants and products are at the concentrations given above.

the correct answer is 0.527 M but I keep getting 1.53*10^-17 molar of ethanol. what am i doing wrong?

b)consider the degradation of glucose to pyruvate by the glycolytic pathway:

glucoset+ 2adp+ 2Pi + 2nad⁺ --> 2 pyruvate + 2atp + 2h2o + 2nadh + 2H⁺

calculate delta G for this reaction at pH 7.4 and 37 degrees C.

the correct answer is -62.4 kJ/mol but I am not getting the same numbers.

TIA

Basically, yes: http://www.scienceforums.net/topic/104-user-titles/

More here on the groups you reference: http://www.scienceforums.net/topic/67313-sfn-user-groups-and-their-significances/

thank you!

What books are you reading now?

 

Doesn't matter what kind, what subject, whatever. It'll just be fun to see what everyone's reading. I'd certainly like to get more reading material in.

 

I'll start: I'm currently starting The Blind Watchmaker, by Richard Dawkins, as I'm currently writing a report discussing evolution and I spotted it in the library while doing research.

Just finished Call of Cthulu and am working on a few other short stories by HP Lovecraft

What is the ranking system for the different member group titles? I've seen Senior group member, member. Is this achieved when you reach a certain number of posts?

if you have answer keys in the back of your textbooks, i'd recommend following those solution sets. if your school has free tutoring, i'd go to those before/after school programs. it's easy to mislead yourself if you don't have some sort of reference/guide. just do a bunch of problems using answer keys/guides/tutors to double check your work

the efficiency of a buffer in resisting changes in pH upon addition of base or acid is referred to as the buffer capacity. one way to define this quantity, which we shall call B, is B=dx/dpH, where x is the number of moles of base added to weak acid. Note that the HH equation may be rewritten as pH=pKa+ log (x/A₀-x)

where A₀ is the total concentration of acid.

obtain an expression for B, in terms of A₀ and the fraction of acid titrated, f, where f=x/A_0. hint: it's easiest to determine dpH/dx and take the reciprocal

this is problem 14 in ch 2 of biochemistry ed. 4

the correct answer is B=(A₀/2.303)f(1-f)

I thought the answer was just to take the pH formula and use it as the denominator and use the formula for x (derived from the formula for f) as the numerator.

TIA