*SAT Subject Test Biology E/M June 2016 Discussion Thread*

first level has 1% of the sun energy, goes down to the fourth level, should that be 0.001%

Plus it was product formation over time so if the product rate is consistently high, how would the substrate all be used up?

@apple349 I c where u r coming from, but I think u overthought it cuz it said biomass which is made by producers, so the sun would not matter.

At least that’s wut I think, but idk cuz I’m dumb

@Lebronjamesisbad First of all, active sites can’t get used up. Second of all, there isn’t an infinite amount of substrate, and the level of substrate doesn’t increase, either. The answer that substrate got all used up is perfectly logical. Third, if all the active sites got filled up, that would mean that the enzyme takes at least 5 seconds to catalyze the reaction, because the period of time that enzyme activity dropped was from seconds 7 to 12. However, if that is the case, then why was a larger amount of product produced in the first 7 seconds? Wouldn’t it be a flat line from 0 to 5 seconds?

@Apple349 It didn’t talk about energy. The question was asking what percent of the phytoplankton’s biomass would be transferred to the end.

@Lebronjamesisbad do you remember what the question was exactly like? i thought that it only asks about energy. I could be wrong

It said biomass if I recall correctly

Bruh @mastersuperfan it was time vs. product, so if all the substrate was used up, then y would the concentration of products still be high, wouldn’t it go down if substrate decreases, and it goes up initially because u r just adding substrates at time 0

Plus in any reaction doesn’t it usually increase in the beginning then flatlines?

At least most reactions

“y would the concentration of products still be high, wouldn’t it go down if substrate decreases”

I don’t understand what you’re saying. The substrate becomes the product, so as the substrate decreases, the product increases. Just because there’s no substrate doesn’t mean that there’s no product; just the opposite, in fact.

Ugh u need substrate to make the product tho

So r I saying that enzymes can make a product with no substrate?

Sry I meant to say r u saying

Perhaps you misunderstood the graph. The line does not represent the amount of product being produced every second, but rather the TOTAL product produced by that point. Since the product doesn’t simply disappear from the solution, it accumulates, and thus the line only goes upward. If the line is near the top but is flat, no more product is being produced.

I mean I can’t misunderstand the graph when the exact same question was in the pr

i mean I c where u r coming from, but I really don’t think the graph said total product formation vs time

Cuz I remember the word they used was longer than total

Also I just read online that the rate of a reaction is not affected by the amount of substrate, so y would the substrate being gone affect it then…

That’s reaction kinetics and it varies from reaction to reaction. If all the active sites were used up, the line would have had a non zero slope, but this graph had a slope of zero at the end, so all of the substrate was used up because no more product was created.