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March 30, 2024, 12:31:48 am

Author Topic: VCE Biology Question Thread  (Read 3571769 times)  Share 

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katiesaliba

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Re: VCE Biology Question Thread
« Reply #3285 on: October 10, 2014, 07:04:28 pm »
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Hi,
Could someone explain me the differences between signalling molecules and signal transduction?
These two ideas are really confusing me..

Thanks :)

Signalling molecules initiate a cellular response. Examples include hormones and neurotransmitters. Signal transduction, however, is the process by which the signalling molecules instigate the response-the cascade of enzymes that bring about a cellular response.   

So, to give an analogy, signalling molecules are like teachers giving students (or cells) a bunch of practice exams (instructions). If students complete the exams, then signal transduction has occurred and they'll score well (response). If not, then a response will not happen (receptor doesn't bind to signalling molecule) and students will therefore fail.

Okay, so my analogy was terrible ahaha but I hope that it clarifies things a little :') 
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katiesaliba

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Re: VCE Biology Question Thread
« Reply #3286 on: October 10, 2014, 07:36:54 pm »
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Q. Explain, with the use of a diagram, how the message is transmitted along the axon of the post-synaptic neuron.

A. Once a received signal is potent enough to overcome threshold (activation) energy, an axon will enter absolute refractory, depolarising (sodium voltage-gated channels open and sodium rushes in) and repolarising (potassium rushes out due to the opening of potassium voltage-gated channels) consequentially to propagate an action potential along an axon. The message is transmitted through the diffusion of sodium ions down the axon and back-flow is prevented due to the relative refractory period entered by an axon during hyperpolarisation.

(I haven't drawn a diagram, but I would do so in the exam)

Can someone please edit my answer to make it more concise.  Thanks!




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vox nihili

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Re: VCE Biology Question Thread
« Reply #3287 on: October 10, 2014, 07:42:07 pm »
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Q. Explain, with the use of a diagram, how the message is transmitted along the axon of the post-synaptic neuron.

A. Once a received signal is potent enough to overcome threshold (activation) energy, an axon will enter absolute refractory, depolarising (sodium voltage-gated channels open and sodium rushes in) and repolarising (potassium rushes out due to the opening of potassium voltage-gated channels) consequentially to propagate an action potential along an axon. The message is transmitted through the diffusion of sodium ions down the axon and back-flow is prevented due to the relative refractory period entered by an axon during hyperpolarisation.

(I haven't drawn a diagram, but I would do so in the exam)

Can someone please edit my answer to make it more concise.  Thanks!

Delete the point about threshold (it's not actually called activation energy I don't think) because it doesn't add anything to your response. Don't talk about absolute refractory either (honestly have no idea what that is, so please tell me:))

Something like: when a stimulus of sufficient size reaches a neurone, voltage gated sodium channels open up. This causes an influx of sodium into the cell and the rapid local depolarisation. This depolarisation event causes adjacent voltage gated sodium channels to open, thus propagating the signal down the axon. Action potentials are unidirectional because areas of membrane enter a refractory period after depolarisation, which means that they are unable to generate another action potential for a short time.
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shivaji

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Re: VCE Biology Question Thread
« Reply #3288 on: October 10, 2014, 07:57:37 pm »
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What are some ethical issues about therapeutic cloning?

Can it be that most of the stem cells used come from embryos, and this is potentially taking a human life?
Or taking adult stem cells are an invasive and painful act. (like extacting bone marrow cells)

shivaji

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Re: VCE Biology Question Thread
« Reply #3289 on: October 10, 2014, 08:56:04 pm »
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what exactly does a germline cell refer to?
is it the cells which give rise to gametes (those in the gonads) or the gametes themselves?

vox nihili

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Re: VCE Biology Question Thread
« Reply #3290 on: October 10, 2014, 09:01:52 pm »
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what exactly does a germline cell refer to?
is it the cells which give rise to gametes (those in the gonads) or the gametes themselves?

Pretty sure it's thecells that give rise to the gametes, or maybe both?
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flares

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Re: VCE Biology Question Thread
« Reply #3291 on: October 10, 2014, 09:40:06 pm »
+1
Signalling molecules initiate a cellular response. Examples include hormones and neurotransmitters. Signal transduction, however, is the process by which the signalling molecules instigate the response-the cascade of enzymes that bring about a cellular response.   

So, to give an analogy, signalling molecules are like teachers giving students (or cells) a bunch of practice exams (instructions). If students complete the exams, then signal transduction has occurred and they'll score well (response). If not, then a response will not happen (receptor doesn't bind to signalling molecule) and students will therefore fail.

Okay, so my analogy was terrible ahaha but I hope that it clarifies things a little :')

Not bad of an analogy hahaha :)
And yes, it does make my viewpoint on signal transduction and signalling molecules a little clearer, thanks for that :)
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shivaji

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Re: VCE Biology Question Thread
« Reply #3292 on: October 10, 2014, 10:31:08 pm »
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would you desribe the position of the foramen magnum in hus to be at the centre of the base of the skull, and in animals at the back of the base of the skull?

vox nihili

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Re: VCE Biology Question Thread
« Reply #3293 on: October 10, 2014, 10:54:04 pm »
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would you desribe the position of the foramen magnum in hus to be at the centre of the base of the skull, and in animals at the back of the base of the skull?

Could say that the foramen magnum is behind the brain of primates and at the bottom of the brain of humans. It's not true that the foramen magnum is in the same place for all animals.
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katiesaliba

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Re: VCE Biology Question Thread
« Reply #3294 on: October 11, 2014, 12:24:28 am »
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Delete the point about threshold (it's not actually called activation energy I don't think) because it doesn't add anything to your response. Don't talk about absolute refractory either (honestly have no idea what that is, so please tell me:))

Something like: when a stimulus of sufficient size reaches a neurone, voltage gated sodium channels open up. This causes an influx of sodium into the cell and the rapid local depolarisation. This depolarisation event causes adjacent voltage gated sodium channels to open, thus propagating the signal down the axon. Action potentials are unidirectional because areas of membrane enter a refractory period after depolarisation, which means that they are unable to generate another action potential for a short time.

Thanks so much! :) Why wouldn't it be called the activation energy out of curiosity?

I don't really understand the logistics behind it, but I know that absolute refractory occurs during depolarisation and repolarisation to prevent action potentials from firing regardless of stimulus strength. I think it's due to the increased voltage/threshold required to initiate an action potential during that phase, but I'm not sure! I just came across it during my study and learnt the basics :) 
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shivaji

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Re: VCE Biology Question Thread
« Reply #3295 on: October 11, 2014, 09:13:59 am »
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Does the swelling from inflammation result fr leaky capillaries or vasodilation which brings more blood to the site?

Also, what causes the itchiness from inflammation?

walkec

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Re: VCE Biology Question Thread
« Reply #3296 on: October 11, 2014, 10:27:36 am »
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Does the swelling from inflammation result fr leaky capillaries or vasodilation which brings more blood to the site?

Also, what causes the itchiness from inflammation?

I believe the swelling occurs due to vasodilation  :)

grannysmith

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Re: VCE Biology Question Thread
« Reply #3297 on: October 11, 2014, 11:03:23 am »
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Does the swelling from inflammation result fr leaky capillaries or vasodilation which brings more blood to the site?

Also, what causes the itchiness from inflammation?
Leaky capillaries causes an accumulation of fluid in the tissues, causing the swelling. This fluid carries phagocytes to the sites of infection.

Itchiness/pain is probably a result of increased pressure on surrounding nerves due to that swelling.

vox nihili

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Re: VCE Biology Question Thread
« Reply #3298 on: October 11, 2014, 01:34:10 pm »
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Thanks so much! :) Why wouldn't it be called the activation energy out of curiosity?

I don't really understand the logistics behind it, but I know that absolute refractory occurs during depolarisation and repolarisation to prevent action potentials from firing regardless of stimulus strength. I think it's due to the increased voltage/threshold required to initiate an action potential during that phase, but I'm not sure! I just came across it during my study and learnt the basics :)

Not sure why to be honest. They call it "threshold potential". It's not really an energy that's being supplied, rather, a difference in energies.

Oh yeah, I see what you're talking about. It's got to do with the sodium voltage gates closing and the potassium gates opening, they all take a while to spring back to normal :)
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soli

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Re: VCE Biology Question Thread
« Reply #3299 on: October 11, 2014, 01:48:29 pm »
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In terms of the exam, is there a difference between selective breeding and artificial selection?