VCE Biology Question Thread

[alchemy]

2014 checkpoints page 177, question 2-22

Damn, I don't have that one.... But since they provided such a definition, all we can do is assume that it will be acceptable.

[Chang Feng]

Also about this. I just thought  then when enzymes are raised below or above temperatures (but not to the extent that it will denature), do bonds still break??? And if so how did they reform when temperate/ other deviation is returned to optimal temperature. If bonds don't break then how do enzymes lose their functions??  Thanks

[nerdmmb]

Also about this. I just thought  then when enzymes are raised below or above temperatures (but not to the extent that it will denature), do bonds still break??? And if so how did they reform when temperate/ other deviation is returned to optimal temperature. If bonds don't break then how do enzymes lose their functions??  Thanks

Enzymes only lose their conformational shape once they reach the critical temperature - the temperature above optimal temperature whereby bonds are broken and the enzyme therefore is unable to carry out its functions. Unless an enzyme is present to reverse the denatured enzyme's loss of tertiary structure, then the enzyme has been denatured permanently.

Enzymes can also be affected by fluctuating pH levels and chemical inhibition.
ln low temperatures, enzymes are not denatured however the speed at which they catalyse reactions are slowed down and when the temperature begins to increase so does the speed at which the enzyme catalyses the reaction.

[katiesaliba]

Also about this. I just thought  then when enzymes are raised below or above temperatures (but not to the extent that it will denature), do bonds still break??? And if so how did they reform when temperate/ other deviation is returned to optimal temperature. If bonds don't break then how do enzymes lose their functions??  Thanks

When enzymes are exposed to temperatures that are below their optimum, they become less effective and their reaction rate drops due to a loss of kinetic energy. This effect is completely reversible if heat is added. So no, bonds do not break when temperatures get cooler and thus enzyme structure does not change.

When temperatures surpass the optimum, the critical point is reached and enzyme's begin to denature due to bonds breaking (Van der Waal forces and hydrogen bonds<---according to Checkpoints 2014). Denaturing enzymes cannot be resurrected (without enzyme assistance); their conformational shape is permanently distorted due to changes made to their tertiary and quaternary structures. So just say that you heated up a solution of amylase and starch to 80 degrees celsius and then returned it to 37 degrees celsius. No catabolic reaction will be observed because the intense heat would have denatured the enzyme.

[vox nihili]

It's worthwhile noting that an enzyme does not denature the second it goes above its optimal temperature. It just means that the substrate(s) have too much kinetic energy sometimes and therefore they can't associate as well with the active site of the enzyme.

[alchemy]

Enzymes only lose their conformational shape once they reach the critical temperature - the temperature above optimal temperature whereby bonds are broken and the enzyme therefore is unable to carry out its functions.

When temperatures surpass the optimum, the critical point is reached and enzyme's begin to denature...

So just to confirm, these two statements aren't exactly accurate, right? The critical temperature and the point just after the optimal temperature peak are two different things? What about the effect of pH; are enzymes denatured right after the optimum peak?

Unless an enzyme is present to reverse the denatured enzyme's loss of tertiary structure, then the enzyme has been denatured permanently.

Can you explain how this occurs please? I don't remember reading about it.

[nhmn0301]

Strictly speaking, how come other enzymes come and reverse the denaturation process? Even though it seems like the only solution, however, if an enzyme reaches its critical temperature, others enzymes will get denatured as well. Hence, there's no way we can reverse the process. Please correct me if I'm wrong.

[Chang Feng]

Just wondering what exactly starts an inflammation. I know that serotonin stimulates vasodilation so more blood comes to infected site, hence phagocytes. But what causes serotonin to do this? Thanks

[Rishi97]

Has anybody done the osmosis sac?
If yes, what did it involve?
Our school is doing the osmosis prac on potatoes being placed in different solutions, so anyone done that?

[masonruc]

Has anybody done the osmosis sac?
If yes, what did it involve?
Our school is doing the osmosis prac on potatoes being placed in different solutions, so anyone done that?

Did that last year, from my memory you place the potatoes in different concentrated solutions so depending on what beaker the potato chunks are placed in they will either weigh less or more than prior to being placed in the solution. I think I used water for my control rather than the solutions (varied concentrations of salt) my teacher had made up.

[MM1]

What's a really good hypothesis for the potato sac? In just one line preferably? Cheers.

[Rishi97]

Did that last year, from my memory you place the potatoes in different concentrated solutions so depending on what beaker the potato chunks are placed in they will either weigh less or more than prior to being placed in the solution. I think I used water for my control rather than the solutions (varied concentrations of salt) my teacher had made up.

Thanks. Did u have to do a write up part of the sac as well?

[grannysmith]

What's a really good hypothesis for the potato sac? In just one line preferably? Cheers.

Mine will probably be along the lines of: The potato cylinders placed in the NaCl solutions will lose water and hence mass by osmosis, as they are hypotonic to the solutions. The potato cylinders placed in water will gain water and hence mass by osmosis, as they are hypertonic to the water.

Someone please correct me if I'm wrong.

[nhmn0301]

What's a really good hypothesis for the potato sac? In just one line preferably? Cheers.

You can find more information on page 42 of this thread, others have previously discussed it as well.

[grannysmith]

Also were do observations go in a scientific write up? In the discussion or results? Or do the results only contain graphs, etc?

Usually you'd present it as a graph/table in the results, and then you'd explain the underlying concepts pertaining to your results in the discussion.