VCE Biology Question Thread

[PopcornTime]

What’s your concern? It should look roughly like that

Well the question is, how would one explain why a temp, enzyme activity graph looks like this (positive parabola): https://bhs-methods10.wikispaces.com/068fulltpform

rather than this (negative parabola): http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/proteins/proteinsrev3.shtml

Would it just be cause the axis are switched?

[vox nihili]

Well the question is, how would one explain why a temp, enzyme activity graph looks like this (positive parabola): https://bhs-methods10.wikispaces.com/068fulltpform

rather than this (negative parabola): http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/proteins/proteinsrev3.shtml

Would it just be cause the axis are switched?

Nah, axis switch wouldn’t do that...not really sure I get that question to be honest, really bizarre question.

[darkz]

Nah, axis switch wouldn’t do that...not really sure I get that question to be honest, really bizarre question.

I'm pretty sure he is asking why a temp/enzyme activity graph he has looks like the red line (concave up, increasing) in the screenshot below instead of the blue one (concave down, increasing).

Edit: To be honest, I have no idea why its concave up, increasing, however I suppose if is was from an experiment you did in class where you collected your own data it might have been slightly skewed depending on your accuracy etc?

[PopcornTime]

How can reactions occur without the presence of enzymes, such as starch to maltose in presence of amylase?

Is it just due to natural collisions between substrate molecules; how would product formation work if it was not lock and key/induced fit?

Also, can all reactions occur without enzyme presence, its just that these reactions would occur too slowly?

[darkz]

How can reactions occur without the presence of enzymes, such as starch to maltose in presence of amylase?

Is it just due to natural collisions between substrate molecules; how would product formation work if it was not lock and key/induced fit?

Also, can all reactions occur without enzyme presence, its just that these reactions would occur too slowly?

So enzymes decrease the activation energy of a reaction thus making the reaction occur at a much faster rate. By removing enzymes, the reactions can indeed still occur, however of course they would be way too slow to be able to maintain life. The binding of the substrates to an active site for product formation would simply decrease the activation energy to bind them together - so therefore without enzymes, they would solely rely on collisions, but would be very slow as the activation energy is significantly higher. As for starch to maltose without the presence of amylase, the enzyme decreases the activation energy to break the bonds, so without enzymes, it would just take much longer to reach the required activation energy etc.

[Mr West]

slightly confused

can someone please explain NADP's role in the light dependant stage of photosynthesis.

also my teacher says that NADP is a positively charged carrier molecule, and that NADPH is aswell. is this true?

cheers

[darkz]

slightly confused

can someone please explain NADP's role in the light dependant stage of photosynthesis.

also my teacher says that NADP is a positively charged carrier molecule, and that NADPH is aswell. is this true?

cheers

So NADP+ acts as an electron acceptor (or electron carrier) in the light dependent stage of photosynthesis. Thus, it "accepts" or "carries" the hydrogen ions and electrons released from the splitting of the water molecule to form NADPH. I know that NADP+ is positively charged, but I'm pretty sure that NADPH is neutral - not positively charged

[TheAspiringDoc]

So NADP+ acts as an electron acceptor (or electron carrier) in the light dependent stage of photosynthesis. Thus, it "accepts" or "carries" the hydrogen ions and electrons released from the splitting of the water molecule to form NADPH. I know that NADP+ is positively charged, but I'm pretty sure that NADPH is neutral - not positively charged

Minor detail
It accepts electrons from the the dependent stage, and donates them to the light independent stage.
It’s a pretty cool process.

[PopcornTime]

Why would the optimum pH of an intracellular enzyme not be the same as pH of its intracellular surroundings?

[darkz]

Why would the optimum pH of an intracellular enzyme not be the same as pH of its intracellular surroundings?

This is because the enzyme may be operated within a certain organelle which is enclosed by a membrane e.g. chlorplast. Therefore, the optimum pH for it can be different from the intracellular pH as the enclosure essentially separates the internal/external environment creating "compartments" where different environmental conditions can be set

[PopcornTime]

This is because the enzyme may be operated within a certain organelle which is enclosed by a membrane e.g. chlorplast. Therefore, the optimum pH for it can be different from the intracellular pH as the enclosure essentially separates the internal/external environment creating "compartments" where different environmental conditions can be set

I thought it would be because cells require enzymes to catalyse reactions at different speeds, so since pH's are not similar, products would be formed at a "correct" rate (as different enzymes won't be working at their optimum). Thoughts?

[MAGGOT]

Do we need to know what kinds of neurotransmitters there are and the functions of each

[PhoenixxFire]

Nope. Just very generally how they work.

[PopcornTime]

When polypeptide chains are produced at free ribosomes, how, are they "converted" into intracellular enzymes? Would it just be post-translation modifications and do we need to know about these (it was referred to in the 2017 examiners report)?

[PhoenixxFire]

When polypeptide chains are produced at free ribosomes, how, are they "converted" into intracellular enzymes? Would it just be post-translation modifications and do we need to know about these (it was referred to in the 2017 examiners report)?

It’s not really converted. An enzyme is just a protein with a specific structure. There are molecules (enzymes I think) that fold the polypeptide into its tertiary shape. I’m pretty sure that’s all you need to know. What specifically did it say on the examiners report?