VCE Biology Question Thread

[ezferns]

I'm pretty sure the rise in glucose stimulates the pancreas to release glucagon, which converts glycogen in the liver to glucose. So the pancreas is stimulated. And I don't think homeostasis is achieved immediately after, but after a couple of cycles with the pancreas slightly overshooting the amount of glucagon or insulin released each time.

I would change just one thing with the second question: change 'affects' to 'effects' as it's a noun. Not sure how picky the examiners will be with that

Just gonna jump in here: a rise in glucose induces the release of insulin, which converts stops glycogen from being broken down. A FALL in glucose, on the other hand, induces the production of glucagon, which tells the liver to break down glycogen into glucose (among other things)

Whoooops my bad

[HasibA]

questions:
1) cofactors and coenzymes differ in the sense that cofactors are usually ions that help the enzyme to speed the rate of reaction, whereas coenzymes are more organic molecules that function the same way?
2) when defining an enzyme, is it okay just to mention the follow: organic,biological catalyst. enzymes are proteins. they help speed up the rate of reaction, by lowering the activation energy of a reaction [is this part necessary to mention for Biology?]. They don't get consumed when they perform their function, and hence are reusable.

ty guys

[solution]

questions:
1) cofactors and coenzymes differ in the sense that cofactors are usually ions that help the enzyme to speed the rate of reaction, whereas coenzymes are more organic molecules that function the same way?
2) when defining an enzyme, is it okay just to mention the follow: organic,biological catalyst. enzymes are proteins. they help speed up the rate of reaction, by lowering the activation energy of a reaction [is this part necessary to mention for Biology?]. They don't get consumed when they perform their function, and hence are reusable.

ty guys

1) Pretty much, yeah. However, coenzymes are used up in the reaction (eg. vitamins, ATP, NADH, etc.)
2) I would mention all of those things ESPECIALLY the lowering activation energy part (yes, it's apart of the course)

[HasibA]

1) Pretty much, yeah. However, coenzymes are used up in the reaction (eg. vitamins, ATP, NADH, etc.)
2) I would mention all of those things ESPECIALLY the lowering activation energy part (yes, it's apart of the course)

i see. thanks!

edit: more q's
which structure (primary, secondary, tertiary, quaternary) is most affected/ruined by denaturation? im thinking if an enzyme/protein has a quaternary structure, that'll be the first to go when denatured, followed by the tertiary structure. If it didn't have a quaternary structure- the tertiary structure would be affected, but would the secondary be affected?

also, covalent peptide bonds hold the primary structure of a protein. Hydrogen bonds hold the secondary structure, alongside covalent bonds, but what about tertiary/quaternary? im thinking tertiary has hydrogen bonds, ionic bonds , and disulfide bonds/bridges, but how are quaternary structures held up? thanks

edit again: more questions
how much do we need to know about drug design? basically the concept that certain drugs will be made to fight off x,y,z diseases/infections, and how  the drugs strcuture must be complementary etc.
? ty

[Hayley_turnham]

If B cells are capable of presenting antigens on their MHC II markers by themselves, why do they need the assistance of macrophages / T helper cells / cytokines etc to produce plasma cells?
  thanks

[blacksanta62]

is a GM food referring to genetically modified food? i thought this wasn't examinable (unless it's a SAC)?
but anyways, some uses of genetically modified food could include loading them with vitamins and nutrients, allowing for a complementary benefit of giving a wide array of people access to food with many nutrients/fibres/vitamins- potentially reducing the cost/need to get multivitamins/medication to treat malnourished/deficient people? is this what u mean?

Yes. Anymore suggestions?
Thanks

[sweetcheeks]

A potential is creating foods that can act like vaccines. Plants have the gene for specific antigens inserted into them (e.g tetanus), the gene is expressed, producing these antigens, which remain in the edible parts (fruits, leaves etc). When the food is consumed, the person gets a dose of the antigen and their immune system can produce B-memory cells.

It would be fantastic in places where there is low access to vaccines, as you could grow a large enough crop that could efficiently and effectively vaccinate a large proportion of people and provide food at the same time.

[blacksanta62]

Thank you sweetcheeks

[geminii]

i see. thanks!

edit: more q's
which structure (primary, secondary, tertiary, quaternary) is most affected/ruined by denaturation? im thinking if an enzyme/protein has a quaternary structure, that'll be the first to go when denatured, followed by the tertiary structure. If it didn't have a quaternary structure- the tertiary structure would be affected, but would the secondary be affected?

also, covalent peptide bonds hold the primary structure of a protein. Hydrogen bonds hold the secondary structure, alongside covalent bonds, but what about tertiary/quaternary? im thinking tertiary has hydrogen bonds, ionic bonds , and disulfide bonds/bridges, but how are quaternary structures held up? thanks

edit again: more questions
how much do we need to know about drug design? basically the concept that certain drugs will be made to fight off x,y,z diseases/infections, and how  the drugs strcuture must be complementary etc.
? ty

Just went to the Bio lecture today, so I'll try to remember as much as I can.
The tertiary structure is the one that is modified by denaturation. I'm not sure why, but that's as detailed as Thushan got. Hopefully someone can elaborate on this!

As for your second question, I'm not sure but would also like to know the answer!

[Calebark]

Primary structure has peptide bonds -- these are covalent bonds, so are quite strong, and are not broken during denaturation.

Secondary structure has hydrogen bonds, which are significantly weaker than covalent bonds. These are broken during denaturation. Tertiary structure has hydrogen bonds, ionic bonds, and disulphide (disulfide??) bridges, which are broken during denaturation.

Well, this is what I remember, so now I have a question to make sure I am correct, oops. Ionic bonds are stronger than covalent bonds, but tertiary structure can be destroyed, but primary structure cannot. Why is this? Is it because the ionic bond couldn't form an ionic lattice, so it'd be weaker?

[vox nihili]

Primary structure has peptide bonds -- these are covalent bonds, so are quite strong, and are not broken during denaturation.

Secondary structure has hydrogen bonds, which are significantly weaker than covalent bonds. These are broken during denaturation. Tertiary structure has hydrogen bonds, ionic bonds, and disulphide (disulfide??) bridges, which are broken during denaturation.

Well, this is what I remember, so now I have a question to make sure I am correct, oops. Ionic bonds are stronger than covalent bonds, but tertiary structure can be destroyed, but primary structure cannot. Why is this? Is it because the ionic bond couldn't form an ionic lattice, so it'd be weaker?

I suspect you're looking into it too deeply. Just remember that secondary and tertiary structure are disrupted in denaturation.



Beyond Biology: as far as the ionic bonds go, it depends on what disrupts it. pH tends to be very good at disrupting ionic bonds, for instance. It's all relative and hugely complicated so don't worry about it

A potential is creating foods that can act like vaccines. Plants have the gene for specific antigens inserted into them (e.g tetanus), the gene is expressed, producing these antigens, which remain in the edible parts (fruits, leaves etc). When the food is consumed, the person gets a dose of the antigen and their immune system can produce B-memory cells.

It would be fantastic in places where there is low access to vaccines, as you could grow a large enough crop that could efficiently and effectively vaccinate a large proportion of people and provide food at the same time.

Interesting idea. Fairly sure it's never been done though!

The only vaccine that I can think of that's disseminated that easily is the polio vaccine. The virus they give in the vaccine is still alive, and can still be spread around (but doesn't do damage )

If B cells are capable of presenting antigens on their MHC II markers by themselves, why do they need the assistance of macrophages / T helper cells / cytokines etc to produce plasma cells?
  thanks

They present antigens so that T-cells specific to that antigen (which the B-cell is also specific to) can bind the B-cell and give it help to become a plasma cell. A b-cell won't become a plasma cell unless a T-helper cell has told it to do so. Part of that is via that MHC interaction I just described, part of it is also the cytokines that the T-cell secretes in order to tell it what to do. 

[Gogo14]

1) Pretty much, yeah. However, coenzymes are used up in the reaction (eg. vitamins, ATP, NADH, etc.)
2) I would mention all of those things ESPECIALLY the lowering activation energy part (yes, it's apart of the course)

I would argue that coenzymes are not used up in the reaction. Coenzymes are just organic cofactors. They maybe, however, used up to allow the reaction to occur (e.g. ATP provide energy), but not in the actual reaction itself.

p.s. Vox, I really liked it when you asked us consolidating questions.  Is it possible to continue that/ make a new thread for that?pllllzz

[vox nihili]

I would argue that coenzymes are not used up in the reaction. Coenzymes are just organic cofactors. They maybe, however, used up to allow the reaction to occur (e.g. ATP provide energy), but not in the actual reaction itself.

p.s. Vox, I really liked it when you asked us consolidating questions.  Is it possible to continue that/ make a new thread for that?pllllzz

Will try to chuck the odd question in every so often. Here's the first:

Explain why penicillin can be used to kill bacteria without killing the humans who take it

[Calebark]

Explain why penicillin can be used to kill bacteria without killing the humans who take it

-Penicillin works by damaging the cell wall of bacteria
-The cell wall is composed of peptidoglycan
-Peptidoglycan is not found in human cells, so penicillin has no effect

[Gogo14]

Will try to chuck the odd question in every so often. Here's the first:

Explain why penicillin can be used to kill bacteria without killing the humans who take it

Pretty much been answered well by calebark, also I don't know much about penicillin so:
Penicillin is an antibiotic which acts as a growth inhibitor to bacteria. It does this by interfering with the normal function/ growth of bacterial cells, and by considering that bacterial cells are prokaryotes and humans eukaryotes. The human cells will be structurally different to bacterial cells, therefore, penicillin will be able to kill bacterial cells but not human cells due to its specificity.