Please help me understand this question and the mark scheme.Watch
Explain the results shown in the graph.
I was wondering why the answer is in terms of starch and not amylase?
Yes i understand that amylase is the enzyme in this reaction but if there was a limited amount of amylase then the reaction wouldnt occur as it has done in the graph.
So i am surprised that there is no reference to the importance of amylase in the mark scheme eg all active sites of amylase been occupied by starch so reaction stops .Without amylase starch wouldnt beable to convert to maltose- its not used up but its active sites are so after 25 minutes it says no starch left- so how do we know its not because all active sites are occupied???
Also why is the ase underlined-is it just to show its an enzyme or another reason?If the point is being rejected by the mark scheme then why underline it?
Very confused by this answer, and so it is very frustrating as i do understand the topic but not how the q is marked.
On top of this, you determine enzyme saturation on a graph of rate against substrate concentration. When the graph plateaus, it doesn't mean that the reaction has stopped - it just means that the rate can't increase any faster. Since the enzyme isn't used up the reaction will continue to proceed and form product, but at a constant rate. In this questions case, this is a graph of increasing product against time. Since there is no increase in the concentration of product after a certain time point - that means the reaction has stopped.
Hope this helps.
The “ase” is underlined to emphasise that it’s an enzyme and therefore can’t be used up in the reaction.
When there is less substrate left the reaction rate slows down because the enzyme is going to be finding less starch to hydrolyse. It’s not because of the enzyme.
I think you’re maybe over complicating enzymes in your head. You clearly understand how they work but they cannot be used up. Maybe look over your notes again?
So when the graph plateaus it means
1.The reaction hasnt stopped but cant increase any faster
2.The reaction has stopped
How do i know which one is the case?
If a reaction exists in equilibrium, then when the graph plateaus there will still be some exchange, but the concentration of substrate and product will remain the same, so the reaction is essentially finished because it won't go any further.
Does that make sense?
If the enzyme is saturated, it's important to remember the reaction hasn't stopped. It's just proceeding at a constant rate.