Help with Biochem

[deleted647690]

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Hi guys,
I have a biochem final coming up and I'm having trouble with enzyme kinetics stuff. I am having a hard time understanding kcat,Km, how these values are affected by inhibitors/how that translates to reciprocal plots. Also having a hard time understanding why kcat/km is the rate at low substrate concentration, while kcat represents high concentration rate. Does anybody know of any helpful online resources, like videos, that explain these concepts well? I found these lectures on youtube called "AK lectures", but they are sort of long and become hard to follow because I lose focus. Maybe it's just the nature of the material.

Not sure if this is inappropriate for this forum.

 

[Glandzburg]

I always use the Moof University videos on YouTube for biochem (even helpful in medical school!).

 

[robin911]

The best advice I can give you is to go and speak with the professor during office hours. Youtube videos help, but a professor can give you the answers that you are looking for without any ambiguity. Sometimes, I have kicked myself in the foot after listening to an entire video lecture on youtube and realizing only 1/4 of the video is relevant to what I needed to know for the exam. Although, there are definitely some great videos out there.

If your prof has office hours, I would start there or with a TA. If that is not helpful, find a classmate. Study buddies help tremendously.
If all of this fails, reread your notes and homework.

You are already taking the best step, which is asking for help. SDN may have some brilliant people but in the end, it is your prof who is grading your exam so I would look to them for help. 🙂

 

[Lawpy]

Hi guys,
I have a biochem final coming up and I'm having trouble with enzyme kinetics stuff. I am having a hard time understanding kcat,Km, how these values are affected by inhibitors/how that translates to reciprocal plots. Also having a hard time understanding why kcat/km is the rate at low substrate concentration, while kcat represents high concentration rate. Does anybody know of any helpful online resources, like videos, that explain these concepts well? I found these lectures on youtube called "AK lectures", but they are sort of long and become hard to follow because I lose focus. Maybe it's just the nature of the material.

Not sure if this is inappropriate for this forum.

I look at this graph

And consult online videos via Khan Academy or Lehninger's supplemental materials where necessary

 

[DoctorSynthesis]

I look at this graph

And consult online videos via Khan Academy or Lehninger's supplemental materials where necessary

this confused me till i realized it was a lineweaver burk plot lol

 

[amazing tekkers]

AK Lectures are awesome. Watch it at 2x speed.

Also would highly recommend Khan Academy.

 

[Govols22]

Moof

 

[FCMike11]

A saturated conditions, the velocity will be determined by how efficient the enzyme is (can only bind so many enzymes for x amount of substrate) - kcat. At low concentrations, velocity will be determined by how specific the enzyme is for the substrate (Km). kcat/km ratio will be the determination at other concentrations.

 

[Satire5Texul]

Some particular things that come to mind:

V system: same affinity in R and T state. But different Kcat. This means in T (tense) and R (relaxed) states the enzyme has same affinity, but once the sbustrate binds its different turnover numbers.

Its not sufficient to just use Kcat. Lots of variables and not always best represented. You want to use kcat/km. This is kind of like why we use charge/mass ratio on Electrophoresis, rather than just one of these. the ratio is a good comparison.

Make sure you can derive these from equation. Unless you dont need calculators, you can count on doing some math with MkM.

Km and affinity also has reverse relationship. Glucokinase in liver which readily turns over glucose at high concentration, has a high Km. But it has low affinity for glucose. In other words, if you have low km, you have high affinity (hexokinase).

PM if you have any questions. Happy to help.

I tried to provide some gems of knowledge that took me personally some time to get (sometimes even after test and during review).

sharing some bookmarks:

http://chemwiki.ucdavis.edu/Biologi...nzymatic_Kinetics/Michaelis-Menten_Kinetics_1

http://www.ncbi.nlm.nih.gov/books/NBK92007/

http://plantphys.info/plant_physiology/enzymekinetics.shtml

https://www.rose-hulman.edu/~brandt/Chem330/Inhibition_kinetics.pdf

http://themedicalbiochemistrypage.org/enzyme-kinetics.php

https://ww2.chemistry.gatech.edu/~lw26/bCourse_Information/3511/stud_comp/chap12_17.pdf