VCE Biology Question Thread

[DJA]

Answering your first question: if you increase substrate concentration as you increase enzyme concentration, the reaction rate of the enzyme will increase in a linear fashion, assuming all other variables are kept constant. However, you may see a plateau because of product concentration, which forms almost an obstacle that limits the time interval in which the enzyme & substrate combine & react together, thereby reducing the activity rate of the enzyme.

So basically, the concentration of product surrounding the enzyme and substrate hinders the formation of the enzyme-substrate complexes-and this accounts for the plateau eventually?

[grannysmith]

So basically, the concentration of product surrounding the enzyme and substrate hinders the formation of the enzyme-substrate complexes-and this accounts for the plateau eventually?

Yes, think of it as "getting in the way" of the reactions

[DJA]

Yes, think of it as "getting in the way" of the reactions

Cheers!

Another question:
I was wondering regarding enzyme cofactors. I know that enzymes are entirely re-usable, but in the case of coenzymes which assist the catalytic function, (such as organic molecules, or ions) do these substances get 'used up' in the catalytic process (Do they bond to the substrate?

Or do the coenzymes merely play a role as a facilitator and don't actually COMBINE with the substrate and can thus be used repeatedly similar to the apoenzyme?

[alchemy]

Cheers!

Another question:
I was wondering regarding enzyme cofactors. I know that enzymes are entirely re-usable, but in the case of coenzymes which assist the catalytic function, (such as organic molecules, or ions) do these substances get 'used up' in the catalytic process (Do they bond to the substrate?

Or do the coenzymes merely play a role as a facilitator and don't actually COMBINE with the substrate and can thus be used repeatedly similar to the apoenzyme?

As far as I know, coenzymes are organic molecules required by certain enzymes to carry out catalysis. They do bind to the active site of the enzyme and participate in catalysis, however, they are not considered 'substrates' of the reaction. Like regular enzymes they are not changed or "used up" in the reaction. 
As for the relationship between a coenzyme and a cofactor, it is important to remember that a cofactor is a non-protein chemical compound whereas a coenzyme, as mentioned above, is an organic and loosely bound cofactor.

I probably missed out on a lot of other detail which you were after, as I only started studying this topic recently. Perhaps, someone else can expand on the above. Hope it helped though : )

[DJA]

As far as I know, coenzymes are organic molecules required by certain enzymes to carry out catalysis. They do bind to the active site of the enzyme and participate in catalysis, however, they are not considered 'substrates' of the reaction. Like regular enzymes they are not changed or "used up" in the reaction. 
As for the relationship between a coenzyme and a cofactor, it is important to remember that a cofactor is a non-protein chemical compound whereas a coenzyme, as mentioned above, is an organic and loosely bound cofactor.

I probably missed out on a lot of other detail which you were after, as I only started studying this topic recently. Perhaps, someone else can expand on the above. Hope it helped though : )

Thanks for the help!

FYI Sheldon, I believe that:
A cofactor simply describes the additional chemical component which can be either organic molecules (vitamin) OR inorganic ions (e.g. Ca2+ ions). So a cofactor is like a big branching term to describe the two types: coenzymes and prosthetic groups. So you are correct on that.
A coenzyme merely describes a type of cofactor that it is temporarily attached to the apoenzyme part.
A prosthetic group describes a cofactor which is permanently bound to the apoenzyme part.

**EDIT: Although Coenzyme often refers to any organic cofactor (to make things more confusing) after I did some research!**

[alchemy]

A coenzyme merely describes a type of cofactor that it is temporarily attached to the apoenzyme part.

Yep, that's what I meant by "loosely bound". Sorry for the confusion, if it caused any; I wasn't sure how to phrase that but I think you put it better ; )

[DJA]

Yep, that's what I meant by "loosely bound". Sorry for the confusion, if it caused any; I wasn't sure how to phrase that but I think you put it better ; )

**EDIT: Although Coenzyme often refers to any organic cofactor (to make things more confusing) after I did some research!**

[psyxwar]

For some reason in VCE biology there seems to be a dichotomy between coenzyme and cofactor, with the latter seemingly referring exclusively to inorganic substances and the former organic substances.

[DJA]

For some reason in VCE biology there seems to be a dichotomy between coenzyme and cofactor, with the latter seemingly referring exclusively to inorganic substances and the former organic substances.

wtf? just great..

Thanks VCE

[alchemy]

**EDIT: Although Coenzyme often refers to any organic cofactor (to make things more confusing) after I did some research!**

...it is important to remember that a cofactor is a non-protein chemical compound whereas a coenzyme, as mentioned above, is an organic and loosely bound cofactor.

Umm, yeah I mentioned that lol

[psyxwar]

wtf? just great..

Thanks VCE

Don't quote me on that as I'm not sure if that's VCAA's opinion on it, but every VCE level text/ resource I read seemed to suggest that.

[DJA]

Don't quote me on that as I'm not sure if that's VCAA's opinion on it, but every VCE level text/ resource I read seemed to suggest that.

Yeah I've been noticing a similar trend. cheers for the headsup

[SwagG]

Hey Guys,
Do we need to know how to draw the molecular diagrams of etc. glucose? If so, is there any method of drawing it or remembering it?
Thanks

[DJA]

Hey Guys,
Do we need to know how to draw the molecular diagrams of etc. glucose? If so, is there any method of drawing it or remembering it?
Thanks

No. You do not need to be able to actually draw the carbon hexagonal ring structure of glucose in Bio.

You do need to know how some of the side groups interact in that a condensation reaction (and an emission of H2O) allows glucose monomers to bond to form adisaccharide - maltose through a glycosidic bond.

[SwagG]

No. You do not need to be able to actually draw the carbon hexagonal ring structure of glucose in Bio.

You do need to know how some of the side groups interact in that a condensation reaction (and an emission of H2O) allows glucose monomers to bond to form adisaccharide - maltose through a glycosidic bond.

Thanks