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Author Topic: VCE Biology Question Thread  (Read 3570616 times)  Share 

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PhoenixxFire

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Re: VCE Biology Question Thread
« Reply #10125 on: April 20, 2018, 07:50:45 pm »
+1
These are the exact numbers I used:

Glycolysis:
C6H12O6 + 2ADP + 2Pi + 2NAD+ = 2 pyruvate + 2H2O + 2ATP + 2NADH

Krebs cycle:
2 Pyruvate + 2 ADP + 2 Pi + 8 NAD+ + 2 FAD = 6CO2 + 2 ATP + 8 NADH + 2 FADH2

Electron transport chain:
6O2 + 10 NADH + 2 FADH2 + 32 ADP + 32 Pi = 6H2O + 10 NAD+ + 2 FAD + 32 ATP

but as darkdzn said you definitely need to know the exact number of ATP, you might need to know the number of NAD, you don't need to know the number of FAD

The ATP difference is because 2 are used up in cellular respiration, and some cells (e.g. muscles) are more efficient so they make more. You can use either 36 or 38 - it doesn't matter.
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Scribe

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Re: VCE Biology Question Thread
« Reply #10126 on: April 20, 2018, 07:54:23 pm »
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Thank you very much darkdzn and PhoenixxFire!

A follow up question:
Is ATP an input of Glycolysis? Google tells me that an input of glycolysis is 2 ATP for an output of 4 ATP (net gain of 2 ATP). Is this true?

darkz

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Re: VCE Biology Question Thread
« Reply #10127 on: April 20, 2018, 07:55:57 pm »
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Thank you very much darkdzn and PhoenixxFire!

A follow up question:
Is ATP an input of Glycolysis? Google tells me that an input of glycolysis is 2 ATP for an output of 4 ATP (net gain of 2 ATP). Is this true?

Yes, you are correct - ATP is an input of glycolysis
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PhoenixxFire

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Re: VCE Biology Question Thread
« Reply #10128 on: April 20, 2018, 07:57:48 pm »
+1
Thank you very much darkdzn and PhoenixxFire!

A follow up question:
Is ATP an input of Glycolysis? Google tells me that an input of glycolysis is 2 ATP for an output of 4 ATP (net gain of 2 ATP). Is this true?
Yep, but just ignore it for VCE bio.

That’s the 2 ATP that causes variation in what people say the ATP output is. For VCE the study design says that you need to know the net output.
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darkz

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Re: VCE Biology Question Thread
« Reply #10129 on: April 20, 2018, 08:02:04 pm »
+1
Hi, so I just got my first biology SAC back for the year and I'm kind of confused about how my teacher has chosen to mark one of the questions. It was an experimental designs question, in which plants were placed in a container under different levels of light and the oxygen and carbon dioxide levels in the container were monitored. The questions stated that the aim was "to test the effect of light intensity on the photosynthetic rate of plants" and asked me to state the dependent variable. My answer was "photosynthetic rate of plants" and I've lost the marks because my teacher said that they were actually measuring oxygen and carbon dioxide levels. While I see that this is a valid answer, I cannot see how "photosynthetic rate" is not also a valid dependent variable, as it is, in fact, what was being measured. Thoughts?

Well the dependent variable is the variable being tested and measured within the experiment - so technically that would indeed be the oxygen and carbon dioxide levels. The reason for why I think your teacher didn't award the mark for saying the dependent variable was the photosynthetic rate because we weren't directly measuring that, rather that was something we could conclude and extrapolate from your results - so just a matter of being more precise, however I would say that it was a bit harsh
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PhoenixxFire

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Re: VCE Biology Question Thread
« Reply #10130 on: April 20, 2018, 08:05:47 pm »
+1
Hi, so I just got my first biology SAC back for the year and I'm kind of confused about how my teacher has chosen to mark one of the questions. It was an experimental designs question, in which plants were placed in a container under different levels of light and the oxygen and carbon dioxide levels in the container were monitored. The questions stated that the aim was "to test the effect of light intensity on the photosynthetic rate of plants" and asked me to state the dependent variable. My answer was "photosynthetic rate of plants" and I've lost the marks because my teacher said that they were actually measuring oxygen and carbon dioxide levels. While I see that this is a valid answer, I cannot see how "photosynthetic rate" is not also a valid dependent variable, as it is, in fact, what was being measured. Thoughts?
This is fairly harsh marking but your teacher is correct. The dependant variable is what you are actually measuring. You are not actually measuring the rate of photosynthesis you are measuring the levels of oxygen and co2. If there is any cellular respiration occurring that could also be affecting the levels, for example.
Its one of those things you just have to know, a bit of a tricky question but I would say it’s fair marking.


Also welcome to AN  ;D
« Last Edit: April 20, 2018, 08:07:56 pm by PhoenixxFire »
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PopcornTime

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Re: VCE Biology Question Thread
« Reply #10131 on: April 20, 2018, 08:14:37 pm »
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Questions about auxins:

Why do auxins move to the shaded region after being produced?
- to promote elongation of cells
- this allows for bending of the coleoptile towards light

If a coleoptile is cut from a plant and placed on an agar plate, how is auxin still able to diffuse (does it travel by diffusion?) onto the plate? How would meristem cells still be able to produce auxins, considering its vascular system, function, etc is "destroyed"?

Is there an advantage of coleoptiles bending towards light?

darkz

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Re: VCE Biology Question Thread
« Reply #10132 on: April 20, 2018, 08:20:48 pm »
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Questions about auxins:

Why do auxins move to the shaded region after being produced?
- to promote elongation of cells
- this allows for bending of the coleoptile towards light

If a coleoptile is cut from a plant and placed on an agar plate, how is auxin still able to diffuse (does it travel by diffusion?) onto the plate? How would meristem cells still be able to produce auxins, considering its vascular system, function, etc is "destroyed"?

Is there an advantage of coleoptiles bending towards light?

I'm not sure about all the details of why Auxin moves into the shade region - but what we're told is that the sunlight repels the auxin causing it to move into the shaded region. From there, the auxin produces an enzyme which removes the cross bridges between the cellulose fibres in the cell wall of the plant cell and there is the creation of an imbalance in the ion concentration allowing water to enter the cell and expand the cell wall making the cell expand and elongate (because the cross bridges are no longer there the cell wall can expand). Because the cells on the shaded part are longer, and the cells on the side closer to the sun are shorter, this means that it will curve towards the sun as the left is longer than the right. (Just think about how the unequal growth makes it turn towards the sun)

I don't believe that the meristems are still producing auxin when they are cut off. The reason for why the auxin is able to diffuse into the agar jelly is because they're hydrophilic, so any remaining auxin diffuses on

And the bending of the coleptile towards the light just serves as an advantage for the plant - such that it can maximise photosynthesis/capture of light

Edit: As PhoenixxFire said, a lot of this isn't relevant to the study design so you won't see it on the end of year exam - but then again it's just some interesting background info etcetera for extra interest and just helps you to understand it a bit better :P
« Last Edit: April 20, 2018, 08:52:13 pm by darkdzn »
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PhoenixxFire

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Re: VCE Biology Question Thread
« Reply #10133 on: April 20, 2018, 08:47:41 pm »
0
Questions about auxins:

Why do auxins move to the shaded region after being produced?
- to promote elongation of cells
- this allows for bending of the coleoptile towards light

If a coleoptile is cut from a plant and placed on an agar plate, how is auxin still able to diffuse (does it travel by diffusion?) onto the plate? How would meristem cells still be able to produce auxins, considering its vascular system, function, etc is "destroyed"?

Is there an advantage of coleoptiles bending towards light?
You don't need to know this level of detail for VCE bio. The only study design dot relating to auxin is:

• the sources and mode of transmission of various signalling molecules to their target cell, including plant and
animal hormones, neurotransmitters, cytokines and pheromones

From that I would say you just need to know where they are created and how they move. I don't know if you even need to know about specific plant hormones - you definitely don't need to know about specific neurotransmitters and they are listed equally. I would learn their general function though as most teachers seem to be teaching at least that much.

I don't know if your teachers are just teaching you too much detail or if you are learning this on your own but definitely don't worry about it, it will not be on the exam.

Also if you know that the question you're asking is not VCE relevant, please write that so that other people don't freak out. If you don't know whether its relevant I'll tell you so don't worry about it.

Edit: @darkdzn Definitely interesting and feel free to talk about it, I just didn't want anyone else to read this and think that they had to know all of it.
« Last Edit: April 20, 2018, 08:59:36 pm by PhoenixxFire »
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PopcornTime

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Re: VCE Biology Question Thread
« Reply #10134 on: April 20, 2018, 09:06:02 pm »
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Also, how would one explain why the line graph of temperature and enzyme activity is upright (looks like this https://bhs-methods10.wikispaces.com/068fulltpform).

Even if temperature is x axis and y axis is enzyme activity (abritrary units).

Would flipping data values solve this?

vox nihili

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Re: VCE Biology Question Thread
« Reply #10135 on: April 20, 2018, 10:24:12 pm »
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Also, how would one explain why the line graph of temperature and enzyme activity is upright (looks like this https://bhs-methods10.wikispaces.com/068fulltpform).

Even if temperature is x axis and y axis is enzyme activity (abritrary units).

Would flipping data values solve this?

Not sure what you mean by upright? There are two parabolae on that page.

You should actually get a "bell curve", with the "point" pointing upwards.
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PopcornTime

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Re: VCE Biology Question Thread
« Reply #10136 on: April 21, 2018, 01:29:09 am »
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Not sure what you mean by upright? There are two parabolae on that page.

You should actually get a "bell curve", with the "point" pointing upwards.

1st graph (positive parabola).

PopcornTime

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Re: VCE Biology Question Thread
« Reply #10137 on: April 21, 2018, 11:49:52 am »
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Do roots not grow in high auxin concentration due to being adapted over time to grow in low auxin concentration or is there another reason?

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Re: VCE Biology Question Thread
« Reply #10138 on: April 21, 2018, 12:15:27 pm »
+1
Yes. Root growth is inhibited under high concentrations of auxin as naturally over time they have evolved to deal with  low concentrations of auxin that is synthesised in the apical meristem and diffuses down the plant. As the auxin diffuses down the plant the auxin molecules are dispersed to the different plant cells and the concentration of auxin therefore reaching the roots is much lower than the auxin reaching the upper part of the plant. If high concentrations of auxin is applied to the root, the root is unable to recognise this high level of auxin that is provided which  has an inhibitory effect, reducing the growth of roots. If too much auxin is applied to either the roots or shoot, an inhibitory effect on growth is observed.

vox nihili

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Re: VCE Biology Question Thread
« Reply #10139 on: April 21, 2018, 12:18:30 pm »
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1st graph (positive parabola).

What’s your concern? It should look roughly like that
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