Psyxwar's Biology 3/4 Question Thread

[psyxwar]

A cytokine is a chemical signalling molecule that acts on specific cells which posess specific receptors to trigger a specific response.

Could be really wrong ^ though lol

Nah I think that's right, but I'm not sure if that's specific enough (since that's the same as a hormone). Then again, the more specific you get, the more wrong the definition seems to become...

[Yacoubb]

Nah I think that's right, but I'm not sure if that's specific enough (since that's the same as a hormone). Then again, the more specific you get, the more wrong the definition seems to become...

Perhaps, this one:

A cytokine is a signalling molecule that acts on specific cells of the immune system, which possess appropriate receptors, to trigger a specific response.

[Yacoubb]

I found this in the TSFX booklet:

Cytokines are groups of signalling molecules that are used extensively in communication between cells.

That sounds really vague but thats what they had!

[simpak]

Yup, it's vague because it's more accurate to say 'between cells' nonspecifically: cytokines can act on non-immune cells as well sometimes (eg endothelial cells), you guys have just only learnt of their communication in an immune context so I'm not sure that you would be penalised if you mentioned that they were involved in the communication between immune cells specifically.

[psyxwar]

Thanks. What would a good definition for signal transduction be?

I have something like "the transformation of one kind of signal into another, usually involving the amplification of said signal".

Most definitions I see seem to refer to signal transduction exclusively in the context of hormones, but even VCAA has questions asking about where signal transduction occurs between a postsynaptic and a presynaptic neurone.

Also, what type of molecules generally act as intermediate or relay molecules?

I was under the impression that this question refers to second messengers, hence non-protein molecules (eg. ions, cAMP). The answers seem to suggest (and this is from checkpoints) that it is proteins that act as relay molecules. Why?

[Yacoubb]

Thanks. What would a good definition for signal transduction be?

I have something like "the transformation of one kind of signal into another, usually involving the amplification of said signal".

Most definitions I see seem to refer to signal transduction exclusively in the context of hormones, but even VCAA has questions asking about where signal transduction occurs between a postsynaptic and a presynaptic neurone.

Also, what type of molecules generally act as intermediate or relay molecules?

I was under the impression that this question refers to second messengers, hence non-protein molecules (eg. ions, cAMP). The answers seem to suggest (and this is from checkpoints) that it is proteins that act as relay molecules. Why?

How about this:

Signal transduction refers to the  cell's receipt of a specific signalling molecule and the cascade of events that follow, resulting in the cell's response to this signal.

Would that be fine?

[Russ]

Mention amplification.

[Yacoubb]

Mention amplification.

That's what I thought but this was taken from a VCAA assessment report; would this be better.


Signal transduction refers to the cascade of events that follow the receipt of a signalling molecule by a cell, amplifying the number of molecules involved in the pathway to elicit a cellular response to that signal.

^ I just feel overly expressive there lol.

[simpak]

I would say 'molecular interactions' rather than 'events' because events is pretty vague and might sound like you're just trying to bullshit.

Re: psyxwar, your question about proteins: some of the molecules in a signalling cascade will be things like cAMP but other molecules involved in the cascade will be proteins.  A second messenger can be either of these things.  For instance, activation of adenylate cyclase (a protein) will cause the increase in cAMP inside many cells.  Sometimes VCAA will leave minor details out of the study design, so don't remember that specific example, it's just to illustrate that you do often require proteins to bring about these non-protein messengers.  Proteins will alter the functioning of each other in the pathway and also potentially interact with other non-protein molecules to eventually lead to some event or change.

[psyxwar]

Cheers.

In the following signal transduction pathway, what is the second messenger:

[some hormone] -> G Protein receptor -> G protein -> adenlyl cyclase -> cAMP

I'm not sure if it's G protein or cAMP. I know cAMP is the only 2nd messenger here, but I heard in 3/4 Bio g-proteins are also considered second messengers and the pathway itself terminates with cAMP.

[Yacoubb]

Cheers.

In the following signal transduction pathway, what is the second messenger:

[some hormone] -> G Protein receptor -> G protein -> adenlyl cyclase -> cAMP

I'm not sure if it's G protein or cAMP. I know cAMP is the only 2nd messenger here, but I heard in 3/4 Bio g-proteins are also considered second messengers and the pathway itself terminates with cAMP.

I'd say G-proteins because in this signal transduction pathway, the signal by [some hormone] is being relayed by the G-protein (i.e. the secondary messenger molecule) to then go on and activate adenylyl cyclase, to then eventually produce cyclic AMP.

[psyxwar]

I'd say G-proteins because in this signal transduction pathway, the signal by [some hormone] is being relayed by the G-protein (i.e. the secondary messenger molecule) to then go on and activate adenylyl cyclase, to then eventually produce cyclic AMP.

Yeah that's what I thought too, but by definition G-proteins cannot be second messengers. I went with G protein, but that's only because historically my school has been horribly inconsistent with the level of depth they see as acceptable. (this was a SAC question).

[Yacoubb]

Yeah that's what I thought too, but by definition G-proteins cannot be second messengers. I went with G protein, but that's only because historically my school has been horribly inconsistent with the level of depth they see as acceptable. (this was a SAC question).

Fair enough. I got 99 on a prac test for Bio on Homeostasis because I said cAMP for 2nd messenger molecule instead of G-protein (even though we were practically right?!). Oh well, just go with what VCAA has got in the assessment reports I reckon. They're the ones we need to assuage I guess!

What are you up to in Bio? We're nearly finished with Immunity. I'm frantically trying to finish this SAC 5 for Monday (luckily I have tomorrow off). Then Unit 3 *for now* is DONE!!

[psyxwar]

Fair enough. I got 99 on a prac test for Bio on Homeostasis because I said cAMP for 2nd messenger molecule instead of G-protein (even though we were practically right?!). Oh well, just go with what VCAA has got in the assessment reports I reckon. They're the ones we need to assuage I guess!

What are you up to in Bio? We're nearly finished with Immunity. I'm frantically trying to finish this SAC 5 for Monday (luckily I have tomorrow off). Then Unit 3 *for now* is DONE!!

Mm yeah. VCAA is where it's at. Why is 3/4 bio so different from real bio?!

We've finished immunity... technically (though I'd say very little of it was actually taught, rushed through it). We're up to the immunity SAC and that'll probably be something for me to do on the holidays. Yeah, it'll finally be over. loljk end of year exams.

[AbominableMowman]

Mm yeah. VCAA is where it's at. Why is 3/4 bio so different from real bio?!

We've finished immunity... technically (though I'd say very little of it was actually taught, rushed through it). We're up to the immunity SAC and that'll probably be something for me to do on the holidays. Yeah, it'll finally be over. loljk end of year exams.

We already started Unit 4, like before the mid year 'exams'  why are we so ahead.