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Author Topic: VCE Biology Question Thread  (Read 3570292 times)  Share 

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Jay.C

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Re: VCE Biology Question Thread
« Reply #5055 on: April 26, 2015, 09:41:57 pm »
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Hey guys! Can someone please answer these for me.

Define signal transduction.

Outline the role of secondary messenger molecules.

Thanks.  :)
« Last Edit: April 26, 2015, 09:50:45 pm by Jay.C »
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cosine

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Re: VCE Biology Question Thread
« Reply #5056 on: April 26, 2015, 10:00:55 pm »
+1
Hey guys! Can someone please answer these for me.

Define signal transduction.

Outline the role of secondary messenger molecules.

Thanks.  :)

Signal transduction is the series of biochemical reactions that occur once the hormone-receptor complex has been formed, and the signal has been received by the target cell.

When protein-based hormones (hydrophillic) bind to their receptor proteins on the outer surface of the cell membrane, they stimulate the enzyme on the inner surface of the membrane which then activate a secondary messenger molecule, which will then endure signal transduction (activate other enzymes for the cellular response).

I just recently covered this topic, so my help might be rusty :3, hope it helped!
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Rishi97

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Re: VCE Biology Question Thread
« Reply #5057 on: April 27, 2015, 08:38:45 am »
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Signal transduction is the series of biochemical reactions that occur once the hormone-receptor complex has been formed, and the signal has been received by the target cell.

When protein-based hormones (hydrophillic) bind to their receptor proteins on the outer surface of the cell membrane, they stimulate the enzyme on the inner surface of the membrane which then activate a secondary messenger molecule, which will then endure signal transduction (activate other enzymes for the cellular response).

I just recently covered this topic, so my help might be rusty :3, hope it helped!

Good defintion! Maybe just mention G-proteins in there as well just to ensure u get full marks :)
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grannysmith

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Re: VCE Biology Question Thread
« Reply #5058 on: April 27, 2015, 09:08:49 am »
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Signal transduction is the series of biochemical reactions that occur once the hormone-receptor complex has been formed, and the signal has been received by the target cell.

When protein-based hormones (hydrophillic) bind to their receptor proteins on the outer surface of the cell membrane, they stimulate the enzyme on the inner surface of the membrane which then activate a secondary messenger molecule, which will then endure signal transduction (activate other enzymes for the cellular response).

I just recently covered this topic, so my help might be rusty :3, hope it helped!

Just remember to add that signal transduction leads to a cellular response!

Here are 3 points which summarise it:
1. Reception (the binding of the signalling molecule to its specific receptor)
2. Transduction (cascade of intracellular events which amplifies the original signal)
3. Response (leads to a cellular response).

cosine

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Re: VCE Biology Question Thread
« Reply #5059 on: April 27, 2015, 04:44:42 pm »
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Hey can someone list the steps in the pathway of a lipid soluble hormone and hydrophilic hormone. Thanks!
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heids

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Re: VCE Biology Question Thread
« Reply #5060 on: April 27, 2015, 05:02:37 pm »
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Hey can someone list the steps in the pathway of a lipid soluble hormone and hydrophilic hormone. Thanks!

Haven't read earlier responses in the thread, so I'm hoping this is what you want :)

Lipid soluble:
 - hormone diffuses through plasma membrane
 - binds with receptor in the cytosol
 - this directly interacts with the DNA, activating or suppressing a particular gene (in theory; I imagine in practice there are heaps of other molecules involved - I should research it :) )

Protein-based/hydrophilic:
 - hormone binds to plasma membrane receptor
 - this activates second messengers (e.g. G proteins, cAMP)
 - they then trigger a cascade of intracellular responses
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cosine

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Re: VCE Biology Question Thread
« Reply #5061 on: April 27, 2015, 06:29:08 pm »
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Haven't read earlier responses in the thread, so I'm hoping this is what you want :)

Lipid soluble:
 - hormone diffuses through plasma membrane
 - binds with receptor in the cytosol
- this directly interacts with the DNA, activating or suppressing a particular gene (in theory; I imagine in practice there are heaps of other molecules involved - I should research it :) )

Protein-based/hydrophilic:
 - hormone binds to plasma membrane receptor
 - this activates second messengers (e.g. G proteins, cAMP)
 - they then trigger a cascade of intracellular responses

For the bolded parts:
How does interacting with the DNA result in a cellular response, does the signal transduction result in the production of new enzymes to carry out the response?

Is that intracellular responses or intracellular enzymes which will carry out the response? or is it the same thing? :P

Also why is hydrophilic hormones faster (in terms of response) than the lipophillic hormones? Is it because the lipophillic ones have to enter the DNA and code for a new enzyme to be produced, and then carry the response, whereas the protein based ones directly target intracellular enzymes in the cytosol, hence the response is much quicker in general?

Thanks!
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cosine

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Re: VCE Biology Question Thread
« Reply #5062 on: April 27, 2015, 06:30:18 pm »
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Is homeostasis and the feedback systems part of the study design? I have heard differing reviews, help would be appreciated!
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Rishi97

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Re: VCE Biology Question Thread
« Reply #5063 on: April 27, 2015, 06:35:26 pm »
+1
Is homeostasis and the feedback systems part of the study design? I have heard differing reviews, help would be appreciated!

yes it is most definitely on the study design :)
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heids

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Re: VCE Biology Question Thread
« Reply #5064 on: April 27, 2015, 06:49:59 pm »
+1
How does interacting with the DNA result in a cellular response, does the signal transduction result in the production of new enzymes to carry out the response?
Genes can be either activated or suppressed; I don't know how much you know as this is unit 4 stuff.  So if a gene is activated, that means that mRNA is copied from it, and thus that protein production begins.  If a gene is suppressed, mRNA copying stops, so protein production stops.  So the hormone essentially controls production of a specific enzyme, and thus whether a specific reaction occurs or not.

So (this is hypothetical, obviously untrue example) let's say that we need more ATP produced in muscle cells because the person has started jogging.  A specific enzyme is involved in one of the steps of ATP production.  So a hormone might be sent to muscle cells, it goes to the DNA, activates a gene segment so the enzyme is produced, and therefore the enzyme can start working to produce ATP.  When ATP isn't needed so much, another hormone can be sent to suppress the gene, stop this enzyme production, and thus stop ATP production.

Quote
Is that intracellular responses or intracellular enzymes which will carry out the response? or is it the same thing? :P
Yup, same thing.

Quote
Also why is hydrophilic hormones faster (in terms of response) than the lipophillic hormones? Is it because the lipophillic ones have to enter the DNA and code for a new enzyme to be produced, and then carry the response, whereas the protein based ones directly target intracellular enzymes in the cytosol, hence the response is much quicker in general?
My guess is (though I'm not sure) that hydrophilic hormones trigger a lot of second messengers - so with the lipophilic, one individual molecule travels through and works directly, whereas with hydrophilic lots and lots of other molecules are triggered to begin working, so the response is faster.  Dunno.
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Re: VCE Biology Question Thread
« Reply #5065 on: April 27, 2015, 07:51:13 pm »
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Two questions

1. How would you define the cascade effect in signal transduction?
2. What is the benefit of having both excitatory and inhibitory synapses?

Thanks

grannysmith

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Re: VCE Biology Question Thread
« Reply #5066 on: April 27, 2015, 07:52:22 pm »
+1
For the bolded parts:
How does interacting with the DNA result in a cellular response, does the signal transduction result in the production of new enzymes to carry out the response?

Is that intracellular responses or intracellular enzymes which will carry out the response? or is it the same thing? :P

Also why is hydrophilic hormones faster (in terms of response) than the lipophillic hormones? Is it because the lipophillic ones have to enter the DNA and code for a new enzyme to be produced, and then carry the response, whereas the protein based ones directly target intracellular enzymes in the cytosol, hence the response is much quicker in general?

Thanks!
Actually, it's the opposite. Generally, lipophilic signalling molecules carry out a faster response than hydrophilic ones, as they can pass through the plasma membrane directly and then trigger signal transduction, whereas hydrophilic signalling molecules must first bind to a membrane receptor, activating second messengers which relay the message causing an event cascade. The latter process tends to take longer IN GENERAL.

HOWEVER, this is different to the duration of the response; hydrophilic signalling molecules tend to bring about a cellular response which involves the activation of enzymes etc. whereas lipophilic ones tend to act on DNA (gene expression: transcription/translation) which would be a much more sustained response.

I was profoundly surprised when I found this out last year :p

cosine

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Re: VCE Biology Question Thread
« Reply #5067 on: April 27, 2015, 08:00:14 pm »
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Two questions

1. How would you define the cascade effect in signal transduction?

Thanks

The cascade (relay) effect in signal transduction can be defined as the series (or relay, or cascade) of biochemical reactions that occur after a hormone-receptor complex has been formed, that is, once a hormone binds to it's specific protein receptor, it triggers a relay of more reactions that will eventually lead to the cell's response. You can think of the signal transduction as multiple enzymes catalysing reactions and causing certain molecules to be produced/not produces which will have a profound effect on the cell, thus that is the cell's response.
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cosine

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Re: VCE Biology Question Thread
« Reply #5068 on: April 27, 2015, 08:01:50 pm »
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Actually, it's the opposite. Generally, lipophilic signalling molecules carry out a faster response than hydrophilic ones, as they can pass through the plasma membrane directly and then trigger signal transduction, whereas hydrophilic signalling molecules must first bind to a membrane receptor, activating second messengers which relay the message causing an event cascade. The latter process tends to take longer IN GENERAL.

HOWEVER, this is different to the duration of the response; hydrophilic signalling molecules tend to bring about a cellular response which involves the activation of enzymes etc. whereas lipophilic ones tend to act on DNA (gene expression: transcription/translation) which would be a much more sustained response.

I was profoundly surprised when I found this out last year :p

Cheers grannysmith, appreciate it.

You know when the cell's response has been achieved, how does the response come to a stop? Is it that intracellular enzymes break down one of the signalling molecules of signal transduction, and how exactly does this affect the duration of the response?
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grannysmith

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Re: VCE Biology Question Thread
« Reply #5069 on: April 27, 2015, 08:10:43 pm »
+1
Cheers grannysmith, appreciate it.

You know when the cell's response has been achieved, how does the response come to a stop? Is it that intracellular enzymes break down one of the signalling molecules of signal transduction, and how exactly does this affect the duration of the response?
Yeah, pretty much. There'd be regulatory enzymes which stop the reaction from happening any further. You can think of it as being a linked system: if you can stop one section of it, you can stop the whole system from occurring. So in context, either the signalling molecule is broken down, or the relay molecules within the cell are terminated.

Two questions

1. How would you define the cascade effect in signal transduction?
2. What is the benefit of having both excitatory and inhibitory synapses?

Thanks
1. The significance of a cascade effect is that a single signalling molecule can exert a profound effect within a cell through the activation of a multitude of relay molecules. A single molecule can activate thousands upon thousands of other molecules within the cell, which then gives rise to a cellular response. You wouldn't need to define the 'cascade effect'; however, it's essentially the activation of relay molecules which subsequently initiates a chain reaction of more reactions.
 
2. Well, not everything is to be excited about! And yet, excitation is necessary for the proper functioning nervous system. So basically, both types of synapses are required to regulate the nervous system.
« Last Edit: April 27, 2015, 08:13:29 pm by grannysmith »