VCE Biology Question Thread

[juntyhee]

Are g-proteins secondary messengers? If not, what are they?

[vox nihili]

Are g-proteins secondary messengers? If not, what are they?

Not technically because they don't expand the message. I don't think this level of detail is strictly required to VCE though.

I guess I'd just call a G-protein a G-protein, but in a sense they could be an intermediary. To my knowledge, there's no term we'd use to describe that kind of set up. G-proteins are so well known by people working in the field that I guess using such a term would be unnecessary.

[darkz]

Are g-proteins secondary messengers? If not, what are they?

Just letting you know, g-proteins are not in the biology study design anymore. In my opinion, they do not really act as secondary messengers per se, however do aid in the production of secondary messengers. So basically, GTP activates the G-Protein which then activates another protein called adenylate cyclase, which catalyses the production of cyclic AMP from ATP (substrate). A cascade is then produced etc.

[TheBigC]

Are g-proteins secondary messengers? If not, what are they?

This has already been answered well previously, however I'd like to add my five cents worth.

- G-proteins are often coupled with receptors, whereby they act as intermediary molecules that, upon ligation of the receptor they are coupled to, are activated (through GTP (guanosine triphosphate) replacing previously bound GDP ('' '' diphosphate)). Ultimately, the G-protein is merely another protein involved in signal transduction such that it acts to then activate another protein or molecule etc.

Just letting you know, g-proteins are not in the biology study design anymore. In my opinion, they do not really act as secondary messengers per se, however do aid in the production of secondary messengers. So basically, GTP activates the G-Protein which then activates another protein called adenylate cyclase, which catalyses the production of cyclic AMP from ATP (substrate). A cascade is then produced etc.

Also, I would just like to highlight that what Darkdzn is referring to here is merely (I was wrong - it is used for many other pathways: cleared up by Vox Nihili below) the epinephrine pathway involving a GPCR (G-Protein Coupled Receptor), this does not always occur with G-proteins: they often activate various other enzymes (not only adenylate cyclase) etc.

[vox nihili]

Also, I would just like to highlight that what Darkdzn is referring to here is merely the epinephrine pathway involving a GPCR (G-Protein Coupled Receptor), this does not always occur with G-proteins: they often activate various other enzymes (not only adenylate cyclase) etc.

This discussion has become completely irrelevant to VCE, but just to preempt that there might be some disagreement about this statement I’ll jump in here. Skip this post if you’re a VCE student.



This is not the “epinephrine pathway”. Many GPCRs act via adenylate cyclase, certainly not just some adrenoceptors (receptors that respond to adrenaline). There are actually different classes of adrenoceptors, which involve different types of G-proteins.

Other ligands that operate via adenylate cyclase include:

ADH
GHRH/GHIH
TSH
CRH
ACTH
LH
FSH
Glucagon
PTH
hCG
Calcitonin

And heaps heaps more.

Another minor point: the term epinephrine is an unusual term in Australia. We use adrenaline instead.

The reason epinephrine exists is because adrenaline is a copyright term in the US, so to avoid having to acknowledge the copyright in academic works, US academics called it epinephrine. They share the same etymology ad=on, renal=kidneys. Επι/epi=on, νεφρός/nephros=kidneys...the former being in Latin, the latter in Greek.

[TheBigC]

This discussion has become completely irrelevant to VCE, but just to preempt that there might be some disagreement about this statement I’ll jump in here. Skip this post if you’re a VCE student.



This is not the “epinephrine pathway”. Many GPCRs act via adenylate cyclase, certainly not just some adrenoceptors (receptors that respond to adrenaline). There are actually different classes of adrenoceptors, which involve different types of G-proteins.

Other ligands that operate via adenylate cyclase include:

ADH
GHRH/GHIH
TSH
CRH
ACTH
LH
FSH
Glucagon
PTH
hCG
Calcitonin

And heaps heaps more.

Another minor point: the term epinephrine is an unusual term in Australia. We use adrenaline instead.

The reason epinephrine exists is because adrenaline is a copyright term in the US, so to avoid having to acknowledge the copyright in academic works, US academics called it epinephrine. They share the same etymology ad=on, renal=kidneys. Επι/epi=on, νεφρός/nephros=kidneys...the former being in Latin, the latter in Greek.

Ahh. Fair. Thanks for the clarification Vox. Apologies to darkdzn, I probably jumped in too swiftly there.

When I used to go through Campbell Biology, an American textbook, the action of adenylate cyclase was highlighted to occur via the 'epinephrine' signalling pathway, though I had assumed that it was primarily restricted to this path... I should have done more research on it it seems.

[vox nihili]

Ahh. Fair. Thanks for the clarification Vox. Apologies to darkdzn, I probably jumped in too swiftly there.

When I used to go through Campbell Biology, an American textbook, the action of adenylate cyclase was highlighted to occur via the 'epinephrine' signalling pathway, though I had assumed that it was primarily restricted to this path... I should have done more research on it it seems.

You never need to apologise here for making a mistake. If you don't make mistakes, how else do you learn?

Plus, in this case too, you've gone well beyond the course and indulged all of our interests in Biology, so big props to you.

[PopcornTime]

Is this list ok?

Steroid Hormones:
- testosterone
- oestrogen
-progesterone

Protein hormones:
- insulin
- glucagon
- glycogen
- epinephrine (adrenaline)

Amino acid derivative?

[sweetiepi]

Is this list ok?

Steroid Hormones:
- testosterone
- oestrogen
-progesterone

Protein hormones:
- insulin
- glucagon
- glycogen
- epinephrine (adrenaline)

Amino acid derivative?

I'm not an expert in biology, but from my understanding, glycogen is a polysaccharide (a sugar), and not a protein hormone (however, glycogen does contain the protein glycogenin), otherwise that list looks a-okay to me!

(Correct me if I'm wrong, I was covering glucose and glycogen in a pharmacology unit just before and I may be a tad confused <3 )

[darkz]

I'm not an expert in biology, but from my understanding, glycogen is a polysaccharide (a sugar), and not a protein hormone (however, glycogen does contain the protein glycogenin), otherwise that list looks a-okay to me!

(Correct me if I'm wrong, I was covering glucose and glycogen in a pharmacology unit just before and I may be a tad confused <3 )

Yeh, I'm pretty sure you're correct. Glucagon is the hormone which is secreted when low blood glucose levels are detected, so then glycogen is then broken down in the cell into glucose which is released into the bloodstream to increase the blood glucose level back to the norm value

[vox nihili]

I'm not an expert in biology, but from my understanding, glycogen is a polysaccharide (a sugar), and not a protein hormone (however, glycogen does contain the protein glycogenin), otherwise that list looks a-okay to me!

(Correct me if I'm wrong, I was covering glucose and glycogen in a pharmacology unit just before and I may be a tad confused <3 )

You're absolutely right Glycogen is basically animals' version of starch.

Is this list ok?

Steroid Hormones:
- testosterone
- oestrogen
-progesterone

Protein hormones:
- insulin
- glucagon
- glycogen
- epinephrine (adrenaline)

Amino acid derivative?

Thyroid hormone is the classic amino acid derivative

[Poet]

What is meant by B cell self tolerance? Where in the body does testing for self-tolerance occur?
I'm not finding any clear answers.

[PhoenixxFire]

It means that B cells that react to self antigens are destroyed. It occurs during maturation in the bone marrow. When it doesn't happen properly we get autoimmune diseases. T cells are also tested for self tolerance, but for them it's in the thymus.

[TheBigC]

What is meant by B cell self tolerance? Where in the body does testing for self-tolerance occur?
I'm not finding any clear answers.

Hey there.

'Self-tolerance' is a concept that can be attributed to both B cells and T cells, whereby it describes a process where B and T cells are ensured to be non-reactive toward self-antigens. The method through which this is able to occur involves B cells and T cells being exposed to self antigens in specific tissues. If they react to them, they are eliminated (undergo apoptosis etc.), however, if not - then they are considered 'mature naive cells'. These mature naive cells are considered 'self-tolerant' or un-reactive toward self antigens and are able to exit their respective sites of maturation.

In terms of location, this process of maturation occurs in the thymus for T cells (T for thymus) and in bone marrow for B cells (B for bone). I hope this helped.

[Abi21]

Hi,
So at my school, were are currently doing the AOS3 poster production research task (some schools do it in unit 4). I was wondering, because my school is doing it in unit 3, will it contribute to my unit 3 sac ranking and grade or is there a separate grade for AOS3 research task?
Thanks in advance