Biology Unit 3 Questions Megathread

[vexx]

are all coenzymes (the temporarily bound cofactors) organic?

i believe they are.

edit, beaten..

[HERculina]

ok thanks guys.
'the apoenzyme is the protein portion of the functionally active enzyme' (biozone answers)
but i thought that the apoenzyme wouldnt work without its cofactor? so how can it be 'functionally active' :/
also, would it be right to say that; prosthetic group = inorganic cofactors and then coenzyme group = organic cofactors? (as well that one is permanent and the other temporary)
or can prosthetic be organic as well

[dooodyo]

Why is it 36 or 38 ATP and not 37 produced during aerobic respiration?

[shinny]

Why is it 36 or 38 ATP and not 37 produced during aerobic respiration?

Not particularly VCE level knowledge, but it's because in the brain, liver, heart and kidneys, a certain shuttle molecule exists which doesn't elsewhere which brings the NADH made in glycolysis from the cytoplasm into the mitochondria so it can be reduced in the electron transport chain. Therefore you get more ATP. Keep in mind that these are all theoretical maximums. Apparently you get nowhere near 36-38 ATP.

[scocliffe09]

ok thanks guys.
'the apoenzyme is the protein portion of the functionally active enzyme' (biozone answers)
but i thought that the apoenzyme wouldnt work without its cofactor? so how can it be 'functionally active' :/
also, would it be right to say that; prosthetic group = inorganic cofactors and then coenzyme group = organic cofactors? (as well that one is permanent and the other temporary)
or can prosthetic be organic as well

the terms you ask about are less to do with whether the compounds are organic or not and more to do with their function. Cofactors can (depending on whose definition you take) include both organic and inorganic compounds.
prosthetic groups and coenzymes are both types of cofactors and are both usually organic - prosthetic groups bind tightly (usually permanently) to the enzyme whereas coenzymes bind loosely to the enzyme - coenzymes enter the reaction as a cosubstrate, are changed by the reaction and released. examples of coenzymes include ATP, NAD, FAD and coenzyme A; examples of prosthetic groups (I don't think these are even on the VCE course just btw, but for interest's sake...) include the Heme group (e.g. Haemoglobin) and the Flavin group.

EDIT: also with regard to apoenzymes (Which I also think are not on the course), they are functionally active once they have their cofactor - without the cofactor they are inactive - just be careful how you interpret Biozone's terminology.

[a/b]

Hey guys, one of the Checkpoints questions included:
"Why is it advantageous for starch and glycogen to be large and not soluble?
Both are needed as energy stores inside the cell. They are large and soluble and therefore form solid grains inside cells. These grains do not interfere with metabolic reactions taking place in cells and do not affect the osmotic gradient."

This is the first time I've come across 'starch/glycogen grains.' What are they made of exactly?

Also, I was looking over some Neap Smartstudy questions and they referred to microscopes a few times but I've read before that we don't need to know about them? Is Neap being vague, or should I actually learn about the electron etc. microscopes?

Thanks !

[shinny]

This is the first time I've come across 'starch/glycogen grains.' What are they made of exactly?

They're made of...starch/glycogen respectively

EDIT: Wait so did you understand the rest of Checkpoints' explanation? Basically since they're insoluble, they don't dissolve within the cytoplasm and will form solid masses i.e. the grains. The reasons for this occurring are pretty much as Checkpoints has said. As for the microscopes, they might get mentioned often as part of the stimulus material but I think all you need to know is what organelles are visible under a light and electron microscope.

[a/b]

LOL, I know haha but are the grains like, covered in anything? Or is it just that since starch/glycogen is insoluble, it can just float around in the cytoplasm? Idk how to explain my question -.-

But thanks

[shinny]

LOL, I know haha but are the grains like, covered in anything? Or is it just that since starch/glycogen is insoluble, it can just float around in the cytoplasm? Idk how to explain my question -.-

But thanks

Well yeh, they just float around I guess. They don't need to be covered in anything (such as a phospholipid bilayer vesicle etc.) because they're already soluble.

[a/b]

Haha, thanks for that

[Christiano]

Would 'catalase will breakdown hydrogen peroxide at differing rates due to factors, such as temperature and pH, affecting the rate of reaction' be a suitable one mark hypothesis statement when experimenting the rates of reactions of catalase in liver with hydrogen peroxide?

[WhoTookMyUsername]

possibly. if your teacher is very harsh he would expect a more detailed explanation that enzyme action and reaction rates will decline as pH and temp vary away from the optimum, though if he is more lenient (or she) they will give you full mark

[dooodyo]

hey guys I have a question,

" when plant and animal cells are placed in a saline solution why does the plant cell retain its shape
whilst the animal cell doesn't ?"

I thought that the plant cell wouldn't really retain its shape since the presence of the cellulose cell
wall merely maintains its shape whilst the plasma membrane shrivels.

[HERculina]

hm well  wen the plant cell undergoes plasmolysis, the plama membrane may shrival but the cell wall doesnt shrink too with it. it stays the same in size and shape if you look at the wall, its only inside the contents are squished together and changed in shape.
 

[WhoTookMyUsername]

^That's it

Not a great question though, as the plant cell really doesn't retain its shape