VCE Biology Question Thread

[cosine]

That's an exergonic reaction, they've stuffed up.

Don't bump things you've only posted 9 minutes ago please.

Agreed. The differences are covered in very little detail.

Sorry I just bumped it because it went on the previous page and thought no one would see it. My apologies.

Epinephrine = adrenaline by the way, those funny Americans just spell it differently.

The answer is quite complicated. In this case, it's that the receptors (and the signal transduction pathways) are different. Both receptors are distinct, both bind adrenaline, and both activate different signal transaction pathways.

This isn't true.

For VCE Biol, what are we meant to know about these receptors. Because as you say it's complicated, for VCE should we just say the hormones act on specific target tissue/cells that exhibit complementary receptors to initiate a specific cellular response?

I remember a question asking why a hormone was able to initiate a response in liver cells, but not other cells. Would this be because the liver cells possessed the receptors that would be able to bind to the hormone, but the other cells don't?

And actually another question i had troubles with ages ago asked why a hormone had an effect in one tissue that was different to another tissue culture in the same organism. What would you say the appropriate answer be in terms of VCE?

Thanks

[mahler004]

For VCE Biol, what are we meant to know about these receptors. Because as you say it's complicated, for VCE should we just say the hormones act on specific target tissue/cells that exhibit complementary receptors to initiate a specific cellular response?

I'll let someone who's more familiar with the course field these questions.

I remember a question asking why a hormone was able to initiate a response in liver cells, but not other cells. Would this be because the liver cells possessed the receptors that would be able to bind to the hormone, but the other cells don't?

That's a reasonable answer.

[tashhhaaa]

Agreed. The differences are covered in very little detail.

Just know that:
CNS = Central Nervous System and is comprised of the brain and spinal cord, and the interneurones that interconnect sensory and motor neurones.
PNS = Peripheral Nervous System and is comprised of the sensory and motor neurones. Basically all the nervous mechanisms outside the brain and spinal cord. 

thanks guys!!!

also just another query, in the FAQs VCAA says this regarding action potentials

Spoiler

However, students are expected to understand in general terms that there are some membrane proteins that allow the passage of ions that would ordinarily be stopped by the lipid bilayer of the membrane, and that electrical transmission through an axon is facilitated by Na+/K+ pumps on the membrane. They are also expected to know that Ca2+ ions are involved in neurotransmitter release into a synapse, with further details not required. Students are expected to recognise that nerve transmission is an ‘all-or-nothing’ response, that electrical transmission occurs through the axon, that there is a ‘refractory’ or ‘resting’ period during which the neuron does not respond to incoming stimuli, and that the impulse is transmitted across a synapse to another neuron via neurotransmitters.

if I just re-worded/dot pointed that info is that really all they want us to know?!

it seems to good to be true?

[vox nihili]

Sorry I just bumped it because it went on the previous page and thought no one would see it. My apologies.

For VCE Biol, what are we meant to know about these receptors. Because as you say it's complicated, for VCE should we just say the hormones act on specific target tissue/cells that exhibit complementary receptors to initiate a specific cellular response?

I remember a question asking why a hormone was able to initiate a response in liver cells, but not other cells. Would this be because the liver cells possessed the receptors that would be able to bind to the hormone, but the other cells don't?

And actually another question i had troubles with ages ago asked why a hormone had an effect in one tissue that was different to another tissue culture in the same organism. What would you say the appropriate answer be in terms of VCE?

Thanks

Yes, you should know that the same hormone can bind different receptors and therefore have different effects. That's why they used to make you go through the fight/flight response.

thanks guys!!!

also just another query, in the FAQs VCAA says this regarding action potentials

Spoiler

However, students are expected to understand in general terms that there are some membrane proteins that allow the passage of ions that would ordinarily be stopped by the lipid bilayer of the membrane, and that electrical transmission through an axon is facilitated by Na+/K+ pumps on the membrane. They are also expected to know that Ca2+ ions are involved in neurotransmitter release into a synapse, with further details not required. Students are expected to recognise that nerve transmission is an ‘all-or-nothing’ response, that electrical transmission occurs through the axon, that there is a ‘refractory’ or ‘resting’ period during which the neuron does not respond to incoming stimuli, and that the impulse is transmitted across a synapse to another neuron via neurotransmitters.

if I just re-worded/dot pointed that info is that really all they want us to know?!

it seems to good to be true?

It's true. They've dumbed it down heaps

[cosine]

Yes, you should know that the same hormone can bind different receptors and therefore have different effects. That's why they used to make you go through the fight/flight response.

So it's not the hormone binding to other tissues with the same receptor, they have different receptors that are able to both bind to the hormone, and because the receptors are different, the signal transduction cascade will be different also?

So same receptor = same response
Different receptor = different cellular response?

[Acid]

Hi! This is a 2004 vcaa question.
In this species a male locust has a diploid number of 15.
 What is the chromosome number of each of the two daughter cells produced during a mitotic division in
a male?
The answer is 15. Is it because the question is asking for the products of  mieosis 1 by mentioning "two daughter cells" because meiosis actually produces 4 daughter cells?
I'm confused...
Any help would be appreciated!

[cosine]

Hi! This is a 2004 vcaa question.
In this species a male locust has a diploid number of 15.
 What is the chromosome number of each of the two daughter cells produced during a mitotic division in
a male?
The answer is 15. Is it because the question is asking for the products of  mieosis 1 by mentioning "two daughter cells" because meiosis actually produces 4 daughter cells?
I'm confused...
Any help would be appreciated!

It says mitotic division, hence is talking about the division of the nucleus during the cell cycle, mitosis. I think you have mixed it up with meiosis?

[katiesaliba]

So it's not the hormone binding to other tissues with the same receptor, they have different receptors that are able to both bind to the hormone, and because the receptors are different, the signal transduction cascade will be different also?

So same receptor = same response
Different receptor = different cellular response?

You are expected to know that hormones bind to specific receptors and therefore only initiate a response in tissues that possess the complementary receptors. Furthermore, you need to know that lipid-soluble hormones bind with their respective receptor molecules inside the cell and that peptide hormones use a secondary messenger system to initiate a cellular response. That's pretty much it. Don't worry about discrepancies in enzyme cascades between different tissues.

Hi! This is a 2004 vcaa question.
In this species a male locust has a diploid number of 15.
 What is the chromosome number of each of the two daughter cells produced during a mitotic division in
a male?
The answer is 15. Is it because the question is asking for the products of  mieosis 1 by mentioning "two daughter cells" because meiosis actually produces 4 daughter cells?
I'm confused...
Any help would be appreciated!

You've confused meiosis with mitosis. This is a classic VCAA type question - they mention the sex so that you immediately think that it's meiosis!

[cosine]

Warning, images attached are of 2014 exam, so if you don't want to look at them please disregard it (cant attach pics to spoilers, sorry)

Spoiler

Question 27: It specifically says that they are two distantly related plants, so would this not mean an example of divergent evolution if these two species diverged from this related ancestor? o.O

Question 11: I have no idea why it's D, but I was able to cancel out the other options as they were contradictory to the info given. Can someone explain why it's actually D? I will provide statements of why I think the other answers are incorrect, can you also let me know if my assumptions are correct, or whether I fluked this question ?

A. When the trap is opening, potassium ions accumulate in the motor cells by diffusion: This was a bit ambiguous to me, because initially the ions all diffused out, and so when the trap actually closed, there would be a higher concentration of ions outside the cells, so as the trap is INITIALLY opening, the ions would be diffused into the motor cells facilitated by proteins. However, over some time, the concentration inside the cells would be greater than the outside as stated in the stem of question, so this would be active transport. Any suggestions ?

B. When the trap is opening, water accumulates in the motor cells by active transport: When the trap is opening, water does not undergo active transport because as the ions move back into the cells, the water would naturally diffuse into the cells to reach equilibrium? Not sure about this one..

C. When the trap is closing, potassium ions leave the motor cells because of the pressure in the surrounding cells: The ions move out because they are triggered to do so..

D. When the trap is closing, water leaves the motor cells via osmosis: Because the motor cells were turgid, when the ions diffuse outside the cell, the water would naturally want to reach equilibrium too so it would diffuse out to maintain equilibrium?

[Maca 13]

Warning, images attached are of 2014 exam, so if you don't want to look at them please disregard it (cant attach pics to spoilers, sorry)

Spoiler

Question 27: It specifically says that they are two distantly related plants, so would this not mean an example of divergent evolution if these two species diverged from this related ancestor? o.O

Question 11: I have no idea why it's D, but I was able to cancel out the other options as they were contradictory to the info given. Can someone explain why it's actually D? I will provide statements of why I think the other answers are incorrect, can you also let me know if my assumptions are correct, or whether I fluked this question ?

A. When the trap is opening, potassium ions accumulate in the motor cells by diffusion: This was a bit ambiguous to me, because initially the ions all diffused out, and so when the trap actually closed, there would be a higher concentration of ions outside the cells, so as the trap is INITIALLY opening, the ions would be diffused into the motor cells facilitated by proteins. However, over some time, the concentration inside the cells would be greater than the outside as stated in the stem of question, so this would be active transport. Any suggestions ?

B. When the trap is opening, water accumulates in the motor cells by active transport: When the trap is opening, water does not undergo active transport because as the ions move back into the cells, the water would naturally diffuse into the cells to reach equilibrium? Not sure about this one..

C. When the trap is closing, potassium ions leave the motor cells because of the pressure in the surrounding cells: The ions move out because they are triggered to do so..

D. When the trap is closing, water leaves the motor cells via osmosis: Because the motor cells were turgid, when the ions diffuse outside the cell, the water would naturally want to reach equilibrium too so it would diffuse out to maintain equilibrium?

I'm pretty sure its convergent evolution because they are 'distantly related' and belong to 'different families', meaning that a common ancestor would have been a long time ago (therefore not being divergent evolution). Also, because they then give you information about shared characteristics in similar environments, meaning that it is most likely convergent evolution.

[warya]

for q27, I think you had to examine the diagram. They seem different in basic structure but have both developed the spines or whatever due to encountering similar selection pressures as a result of living in the same environment (analogous=convergent). If they didn't include the diagram, it would've been a dog question though

[cosine]

for q27, I think you had to examine the diagram. They seem different in basic structure but have both developed the spines or whatever due to encountering similar selection pressures as a result of living in the same environment (analogous=convergent). If they didn't include the diagram, it would've been a dog question though

But guys isn't the definition of convergent evolution: Two species that do not share a common ancestor? Clearly these two species do, meaning they diverged from the same ancestor? Am I missing something? Like yeah tbh the diagram supports convergent, but the info given supports divergent?

[Maca 13]

For Q11, your reasoning for D being the correct answer is right (I'm pretty sure).

But guys isn't the definition of convergent evolution: Two species that do not share a common ancestor? Clearly these two species do, meaning they diverged from the same ancestor? Am I missing something? Like yeah tbh the diagram supports convergent, but the info given supports divergent?

I think its because the question is trying to say that they shared a common ancestor too long ago to be considered divergent evolution (considering that they're also giving you analogous structures and saying that they're 'distantly related')?

[warya]

But guys isn't the definition of convergent evolution: Two species that do not share a common ancestor? Clearly these two species do, meaning they diverged from the same ancestor? Am I missing something? Like yeah tbh the diagram supports convergent, but the info given supports divergent?

I mean, if you really get into it, we all share a common ancestor as we all arose from bacteria, so I guess that's something we are expected to recognise and apply to this q

[StupidProdigy]

But guys isn't the definition of convergent evolution: Two species that do not share a common ancestor? Clearly these two species do, meaning they diverged from the same ancestor? Am I missing something? Like yeah tbh the diagram supports convergent, but the info given supports divergent?

Well you have to judge where to draw the line, because everything has a common ancestor if you go all the way back to the first ever organism of life. Things just differentiated from that. So although the two cacti had a distant ancestor, we should assume this ancestor existed millions of years prior or something like that. They'd say 'recent' if they wanted to imply otherwise. Hope that helps!!