VCE Biology Question Thread

[vox nihili]

Following on from the previous question, can someone explain clearly the signal transduction of hydrophilic (protein) hormones? My textbook (Nature of Biology) explains the role of G proteins different to what other sources say, and I'm quite confused, so a clear explanation would be wonderful.

Thanks

There's no single pathway. There are heaps of different signal transduction pathways that can be used. The basics are that the receptor is activated and different proteins in the cell transmit that signal via a signalling cascade.

[Rob16]

Not a content related question, but which notes do people recommend to get out of the TSFX, A+ or connect notes for bio?

[Elizawei]

Not a content related question, but which notes do people recommend to get out of the TSFX, A+ or connect notes for bio?

I personally liked the A+ notes, it had a good summary of the notes and the sample questions and definitions were quite good as well. I've heard TSFX is very good, but their stuff is a bit pricey

[thefrog]

It's me again Just wondering if someone could briefly explain how negative feedback works in this scenario (see attachment). If thyroxine is deficient, does this mean that the negative feedback would cause the hypothalamus to produce more TRH so that eventually more thyroxine is produced? Likewise, if there is too much thyroxine, the hypothalamus would decrease its production of TRH? Thanks in advance!

[vox nihili]

It's me again Just wondering if someone could briefly explain how negative feedback works in this scenario (see attachment). If thyroxine is deficient, does this mean that the negative feedback would cause the hypothalamus to produce more TRH so that eventually more thyroxine is produced? Likewise, if there is too much thyroxine, the hypothalamus would decrease its production of TRH? Thanks in advance!

Yes

[Maddie Trinh]

This might sound like a stupid question but as a neuron transmits information in the form of neurotransmitters across a nerve-muscle junction does it stimulate transduction pathways in the muscle cell or does it somehow help the muscle to produce an electrical potential and then somehow respond in some way?
It's a classic case of confusion of some people saying this and others saying something else XD.

Thanks in advance

[vox nihili]

This might sound like a stupid question but as a neuron transmits information in the form of neurotransmitters across a nerve-muscle junction does it stimulate transduction pathways in the muscle cell or does it somehow help the muscle to produce an electrical potential and then somehow respond in some way?
It's a classic case of confusion of some people saying this and others saying something else XD.

Thanks in advance

Way beyond VCE, but basically it starts an action potential in the muscle, which triggers the release of calcium in the muscle cell and which then allows the muscle to contract.

[RamseyBolton]

Describe how a signal is transferred across the synapse. (4 Marks)

[Maddie Trinh]

Way beyond VCE, but basically it starts an action potential in the muscle, which triggers the release of calcium in the muscle cell and which then allows the muscle to contract.

Wow, thanks for the quick reply.

Describe how a signal is transferred across the synapse. (4 Marks)

I love this part of the course as it involves tying in your knowledge from all the previous topics you learnt so far in bio. For the purpose of this question I'm assuming the target cell is a neuron but it's pretty much the same for an effector
Essentially there is a build up of sodium ions (Na+) at the axon terminals in a neuron causing nearby calcium ion channels to open up allowing calcium ions (Ca2+) to rush into the neuron. This occurs as an electrical impulse travels down a neuron towards the axon terminals. (Essentially these channels are voltage gated, meaning that they open in response to certain charges in the neuron as an electrical impulse travels down a neuron generating action potentials. Hence, as an action potential is generated, sodium ions rush into the neuron causing the inside of the neuron to become depolarised or positive which causes the calcium ion channels to open. Luckily, you don't need to know whatever I wrote in the brackets and its just a little background information)

This causes vesicles containing neurotransmitters to move towards the pre-synpatic membrane, where they fuse with the neuron's cell membrane to secrete their contents into the synapse through a process known as exocytosis.

The neurotransmitters then net passively diffuse across the synapse (meaning they move from an area of high concentration from the neuron which released them to an area of low concentration to the next neuron) where they bind to specific receptors on the post synaptic membrane causing sodium ion channels to open on the target cell. Sodium ions then flood into the next neuron allowing the impulse to be carried on.

At the end of this process, neurotransmitters are either recycled and taken up by the neuron which released them through endocytosis or broken down by neighboring enzymes in the area.

Anyway hoped that help

[johnhalo]

Why do protein hormones take a shorter amount of time than lipid-soluble hormones to produce a response?

[vox nihili]

Why do protein hormones take a shorter amount of time than lipid-soluble hormones to produce a response?

Hmmm they don't always, not sure it's part of the VCE course. But it's basically because lipid-soluble hormones are typically responsible for transcriptional responses, whereas protein hormones, generally, complete their actions by modulating enzymes etc.

How do yeast store energy? As glucose or glycogen?

Glycogen. Glucose is not a storage molecule.

[RamseyBolton]

@maddie trinh
Thank you for such a detailed response
I shall flay no members of ur house.
Have a safe journey to kings landing.

Ramsey BOLTON

[girlz_love123]

Hey guys,

Does anyone have the vcaa practice exams for biology unit 3 from 1997-2001 unit 4 from 1999-2001?
If you have any other practice exams from external companies please post them or send them to me
Thanx

[nhmn0301]

Am I correct in saying that, ATPase breaks down ATP into ADP + Pi to produce energy, while ATP synthase requires energy to produce ATP from ADP + Pi? Also, I see ATPase being used in place of ATP synthase, what's the deal with that?

Yes ATPase is an enzyme that helps with the breakdown from ATP to ADP + Pi.
ATPsynthase or FoF1-ATPase (or F-ATPase) is used interchangeably in describing the mechanism that helps to produce ATP. The reason why call the same mechanism that produces ATP as FoF1-ATPase is because this enzyme can also catalyse the reverse reaction, which is breaking down ATP to yield ADP+pi. Think about the formation and breakdown of ATP as equilibrium, you have both forward and backward reaction. Fyi, the hydrolysis of ATP to ADP + Pi is spontaneous and so very favourable whilst the formation of ATP is highly non-spontaneous and thats why we need energy to drive this reaction as you said. The energy that causes this enzyme to function is a proton gradient that was set up by other complexes within the Electron transport chain, and so when there is an absence of this proton gradient, ATPsynthase will catalyse the reverse reaction (i.e performing its ATPase activity).
NB: the Fo and F1 are just the name of the structures that make up ATPsynthase. You dont need to worry too much about this amount of details in VCE from what I recalled.

[mtDNA]

How exactly does Calcium act as a second messenger molecule in the presynaptic neuron? Specifically, how does it allow the release of neurotransmitters from the synaptic terminal into the synapse? My teacher mentioned something about calmodulin, but never really explained properly. I know the specifics aren't required for the VCE syllabus, but I feel as though it would be a major help in understanding neuronal function in relation to signal transduction...
Thanks!