## ratio of product / reactant

Discussion of all aspects of biological molecules, biochemical processes and laboratory procedures in the field.

Tiamaria
Garter
Posts: 7
Joined: Fri Jan 14, 2011 5:19 pm

### ratio of product / reactant

Hello Everyone.
I'm stuck on a few questions. But since they are long, I will post one at a time. I'm just working on a study workbook that was recommended for my biology class, but i can only get half way done the problems. I hope you can help.

1. For the reaction:

dihydroxyacetone phosphate <----> glyceraldehyde 3-phosphate
Delta G' = 1.8kcal/mol (I'll use this symbol ^ for delta)

What ratio of product/reactant must be maintained in order to keep the rxn going in a forward direction?

So this is what I've got so far ( and the back of the book shows the answer, but it doesnt show all the steps so it loses me near the end)

^G' < 0
^G' + 2.303 RT Log (glyceraldehyde 3-phosphate) / (dihydroxyacetone phoshate) < 0
1.8 kcal = 1800 cal

1800 cal/mol + (2.303) (1.987cal/mol K) (298K) log (glyceraldehyde 3-phosphate) / (dihydroxyacetone phoshate) < 0

1364 Log (glyceraldehyde 3-phosphate) / (dihydroxyacetone phoshate) < -1800cal/mol

Log (glyceraldehyde 3-phosphate) / (dihydroxyacetone phoshate) < -1800 / 1364

Log (glyceraldehyde 3-phosphate) / (dihydroxyacetone phoshate) < -1.32cal/mol

Then from here I dont know how to get rid of "log"

The final answer says it should be

(glyceraldehyde 3-phosphate) / (dihydroxyacetone phoshate) < 0.048 cal/mol

How did it go from -1.32 cal to 0.048 cal

JackBean
Inland Taipan
Posts: 5694
Joined: Mon Sep 14, 2009 7:12 pm
LOL, that's all what you need? Just convert logarithm to normal number?

log (10^x) = x
^ here means power, so you can have like:
log 100 = log (10^2) = 2
pretty simple, isn't it?

(of course, this is decimal logarithm, but the basis can be any)
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.

Tiamaria
Garter
Posts: 7
Joined: Fri Jan 14, 2011 5:19 pm
i still dont understand. can you break it down step by step for me.. i know i'm slow with this

how does that -1.32 get to be .048?

canalon
Inland Taipan
Posts: 3909
Joined: Thu Feb 03, 2005 2:46 pm