VCE Biology Question Thread

[vox nihili]

Haha, seems like so many of us have enzyme-related questions x]

Does anyone know if exergonic reactions still need addition of energy at the beginning, given that they actually release energy ?? ;x

Absolutely they do. You need energy to start a reaction. If this didn't occur, then everything would just disintegrate and bonds would never exist. Think about what would happen if you didn't need an activation energy for an exergonic reaction, it'd just be a straight down slope to the lowest form: individual atoms.

If that confused you, look at it this way: you need a spark to start a fire. That's an energy input, to get a much bigger output. You must, however, input extra energy to start a reaction though.

[RazzMeTazz]

Does the salinity affect enzyme catalysed reactions?

I thought I read this somewhere...

[vox nihili]

Does the salinity affect enzyme catalysed reactions?

I thought I read this somewhere...

Yes, salts can disturb protein binding. Completely irrelevant for VCE though

[RazzMeTazz]

Ohh okay thankyou!

[RazzMeTazz]

How would an increased surface area to volume ratio, increase the rate of enzyme action?

 

[Scooby]

To an extent, yes. Consider cellular respiration; although it is deemed an exergonic reaction, 2 ATP molecules are required to drive the Krebs cycle, which produces a net total of 2 ATP.

2 ATP molecules are invested in the preparatory phase of glycolysis (not the Krebs cycle) and 4 are produced in the pay-off phase

[DJA]

What are the effect of limiting Cofactors and Coenzymes from enzymes which require them to function normally?

What would a graph look like say for limiting the % conc of cofactors and coenzymes to 0% to increasing it?
Will the enzyme activity rise and plateau or what? How does this work?

And thus are cofactors and coenzymes limiting factors in enzyme-mediated reactions? (Is this correct terminology? - How would you refer to reactions which require enzymes to occur - I know all reactions in living organisms need enzymes to occur but how would I word this?)

(SORRY for the stream of consciousness questions - I'm thinking as I type...)

[grannysmith]

What are the effect of limiting Cofactors and Coenzymes from enzymes which require them to function normally?

What would a graph look like say for limiting the % conc of cofactors and coenzymes to 0% to increasing it?
Will the enzyme activity rise and plateau or what? How does this work?

And thus are cofactors and coenzymes limiting factors in enzyme-mediated reactions? (Is this correct terminology? - How would you refer to reactions which require enzymes to occur - I know all reactions in living organisms need enzymes to occur but how would I word this?)

(SORRY for the stream of consciousness questions - I'm thinking as I type...)

Well, considering they are necessary for some enzymes to function, limiting them would decrease enzyme activity. In a way, they could be limiting factors, although I'm uncertain as to whether this would be asked in an exam.

Enzyme-mediated reaction sounds legitimate.

[RazzMeTazz]

What is an apoenzyme?

[alchemy]

What is an apoenzyme?

The protein component of the enzyme, by itself. A coenzyme attaches onto the apoenzyme to form the holoenzyme (active enzyme).

[RazzMeTazz]

The protein component of the enzyme, by itself. A coenzyme attaches onto the apoenzyme to form the holoenzyme (active enzyme).

Oh okay thanks!
What about when cofactors bind with an enzyme to activate it?
Is the enzyme referred to as an apoenzyme in this case as well?

[alchemy]

Oh okay thanks!
What about when cofactors bind with an enzyme to activate it?
Is the enzyme referred to as an apoenzyme in this case as well?

Yes.

[RazzMeTazz]

Why do chemical reactions occur in a biochemical pathway?

Is it so that the amount of energy released can be controlled, so that not too much energy is released all at once?

[grannysmith]

Why do chemical reactions occur in a biochemical pathway?

Is it so that the amount of energy released can be controlled, so that not too much energy is released all at once?

One reason is that enzymes are substrate-specific, and there is no uber-enzyme which can catalyse every single reaction

[vox nihili]

Why do chemical reactions occur in a biochemical pathway?

Is it so that the amount of energy released can be controlled, so that not too much energy is released all at once?

Yeah complex biochemical pathways allow you to be very precise with various physiological levels etc. So the more complex it is, the more control the system has in some ways. It also makes everything even out as well, so you're getting endothermic reactions that are fuelled by exothermic reactions etc. (as you suggested).

In respiration, the reason that you get those steps is also what you suggested, the energy release would be too high. If you just catalysed the production of CO2 and water from glucose, you'd boil the cell. It's massively exothermic, so it needs to be taken in steps.