VCE Biology Question Thread

[Calebark]

So, from what you've said, a limiting factor is something that makes the rate of photosynthesis plateau? If that's the case, if all factors are constant for photosynthesis, would you say that there are no limiting factors?


P.S thank you for replying!! This was really helpful, since I've found a way to approach this barrier of mine—limiting factors   

Yes, anything that causes the rate to plateau is a limiting factor. If all the factors you learn about in VCE (like light intensity, CO2 concentration, temperature, etc) are high enough, the rate would still plateau, as there are only so many enzymes in a plant cell that can operate at once. In this case, you could say that the number of enzymes necessary for photosynthesis is the limiting factor.



No worries at all

[coolkat3378]

Pretty much, you need to
-cut 20 leaf disks and place in a syringe
-add approx 1.5g of sodium bicarbonate to 300ml of water, with 2 drops of liquid detergent and stir gently (ensuring there are no bubbles)
-draw 15-20ml of the sodium bicarbonate/detergent solution into the syringe (leaf disks should float)
-hold the syringe upwards and expel the air; stop before the solution comes out of the tip.
using your index finger to seal the tip of the syringe , create a vacuum by pulling on plunger (10 sec)
- simultaneously , release index finger; some leaf disks should begin to sink.

Then, pt 2
-add remaining solution to 2 small beakers and separate 10 disks in each
-use one beaker, exposed to light and one exposed to no light while using the timer
-record observations ; wanting to see how long it will take for all disks to rise to the top (with light exposure)

My question is, what would the DV and IV (and CV) be in this case? I have an idea but need reassurance. Thanks

Mod edit: You already posted this in another thread, so I deleted one and left this one here. Please only ask the question in one place -- Calebark

[Calebark]

Pretty much, you need to
-cut 20 leaf disks and place in a syringe
-add approx 1.5g of sodium bicarbonate to 300ml of water, with 2 drops of liquid detergent and stir gently (ensuring there are no bubbles)
-draw 15-20ml of the sodium bicarbonate/detergent solution into the syringe (leaf disks should float)
-hold the syringe upwards and expel the air; stop before the solution comes out of the tip.
using your index finger to seal the tip of the syringe , create a vacuum by pulling on plunger (10 sec)
- simultaneously , release index finger; some leaf disks should begin to sink.

Then, pt 2
-add remaining solution to 2 small beakers and separate 10 disks in each
-use one beaker, exposed to light and one exposed to no light while using the timer
-record observations ; wanting to see how long it will take for all disks to rise to the top (with light exposure)

My question is, what would the DV and IV (and CV) be in this case? I have an idea but need reassurance. Thanks

The thing that causes the leaf discs to rise is the production of oxygen (which is a good measure of the rate of photosynthesis). If there is more oxygen being produced, the discs will rise faster, so we can use that to measure oxygen production. Given that one beaker is exposed to light and one is not, we are seeing if light affects the rate of oxygen production.

IV: Light intensity
DV: Time for discs to float

What do you think the CV would be?

(At ATAR Notes, we encourage our users to give us their thoughts before we give answers, so we can better help them learn rather than just providing an answer, so next time if you could walk us through your thought process so far, that'd be grouse!)

[FabAsianZung]

Outcome 1
Explain the dynamic nature of the cell in terms of key cellular processes including regulation, photosynthesis and cellular respiration, and analyse factors that affect the rate of biochemical reactions.

Can anyone explain what "dynamic nature" and "regulation" means in this key point for the study design first SAC?

Additionally, can you guys give me examples of questions that will highly likely appear in this SAC

A thanks beforehand. 

[darkz]

In my opinion, the dynamic nature simply refers to the interlinking of the processes, and how they all work together. For the regulation bit, since the main regulatory ideas you learn in AOS 1 are about gene regulation, it'd probably be about that e.g. about the lac opeon etcetera.

[PolySquared]

Hey guys

Why are are muscular skeletal cells high in protein?

What problems can arise if the golgi apparatus breaks down?

[PhoenixxFire]

Hey guys

1) Why are are muscular skeletal cells high in protein?

2) What problems can arise if the golgi apparatus breaks down?

1) what is the importance of proteins? Here I think the question wants you to recognise that enzymes are a type of protein and then further recognise that enzymes are necessary for the generation of ATP which is required in higher quantities in muscle cells than in other types of cells.

2) As far as I know the problem is that it won’t work. This means that there won’t be enough proteins and the follow on effects from that - it could also cause molecules that aren’t supposed to be in the cytosol to be released which could cause other problems.

[Oxmacro]

Hey guys,

I'm sorry if this has already been asked before/earlier, but I just wanted to clarify the 'Inputs' and 'Outputs' of each stage of Photosynthesis and Cellular Respiration. I've just seen varied answers between textbooks/webpages, so I was wondering what VCAA expects in the exam. If you could give both the chemical and worded equations, with the amount of each molecule utilised/produced, that would be amazing!

Thanks in advance!!

[PhoenixxFire]

Hey, you're probably getting a different amount of water molecules from different sources. This is because water is both an input and an output of photosynthesis so some equations include it in both and some only include the net input. Either equation is fine to use.

Photosynthesis
12 Water + 6 Carbon dioxide = Glucose + 6 Oxygen + 6 Water
12H2O + 6CO2 = C6H12O6 + 6O2 + 6H2O

OR

6 Water + 6 Carbon dioxide = Glucose + 6 Oxygen
6H2O + 6CO2 = C6H12O6 + 6O2

Cellular respiration
Glucose + 6 Oxygen + 36 ADP + 36 Pi = 6 Carbon dioxide + 6 Water + 36 ATP
C6H12O6 + 6O2 + 36 ADP + 36Pi = 6CO2 + 6H2O + 36 ATP

I've included the ATP on both sides of the equation - if it asks for a balanced equation you need to put it on both sides, not just put ATP as an output. It's not always necessary to include it though, you should ask your teacher whether they want you to for the SAC.


For the individual stages theses are the equations I used:

Photosynthesis
Light dependent stage:
12H2O + 12NADP = 6O2 + 12NADPH2

Light independent stage:
24NADPH2 + 6CO2 = 24NADP + C6H12O6 + 6H2O

Cellular respiration
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

The FAD/FADH2 are probably unnecessary but my teacher taught them to me - If you haven't covered them then leave it out (they're another type of carrier molecule, like NADH)

[Oxmacro]

Hey, you're probably getting a different amount of water molecules from different sources. This is because water is both an input and an output of photosynthesis so some equations include it in both and some only include the net input. Either equation is fine to use.

Photosynthesis
12 Water + 6 Carbon dioxide = Glucose + 6 Oxygen + 6 Water
12H2O + 6CO2 = C6H12O6 + 6O2 + 6H2O

OR

6 Water + 6 Carbon dioxide = Glucose + 6 Oxygen
6H2O + 6CO2 = C6H12O6 + 6O2

Cellular respiration
Glucose + 6 Oxygen + 36 ADP + 36 Pi = 6 Carbon dioxide + 6 Water + 36 ATP
C6H12O6 + 6O2 + 36 ADP + 36Pi = 6CO2 + 6H2O + 36 ATP

I've included the ATP on both sides of the equation - if it asks for a balanced equation you need to put it on both sides, not just put ATP as an output. It's not always necessary to include it though, you should ask your teacher whether they want you to for the SAC.


For the individual stages theses are the equations I used:

Photosynthesis
Light dependent stage:
12H2O + 12NADP = 6O2 + 12NADPH2

Light independent stage:
24NADPH2 + 6CO2 = 24NADP + C6H12O6 + 6H2O

Cellular respiration
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

The FAD/FADH2 are probably unnecessary but my teacher taught them to me - If you haven't covered them then leave it out (they're another type of carrier molecule, like NADH)

Thanks a lot! Just a question, in the Light Dependent Stage of Photosynthesis, ATP is also produced; but is used up in the Independent Stage, do you know the specific amount, or is that not required? Other than that, everything matches my understanding; thanks for that!

[PhoenixxFire]

Thanks a lot! Just a question, in the Light Dependent Stage of Photosynthesis, ATP is also produced; but is used up in the Independent Stage, do you know the specific amount, or is that not required? Other than that, everything matches my understanding; thanks for that!

Hey,
I don't know the specific numbers and I've never had to include it.

The cellular respiration dot point of the study design specifically refers to ATP yield

Cellular respiration key knowledge

• the location of, and the inputs and outputs of, glycolysis including ATP yield (details of the biochemical pathway mechanisms are not required)
• the main inputs and outputs of the Krebs (citric acid) cycle and electron transport chain including ATP yield (details of the biochemical pathway mechanisms are not required)

whereas the photosynthesis key knowledge dot point does not

photosynthesis key knowledge dot point

• inputs and outputs of the light dependent and light independent (Calvin cycle) stages of photosynthesis in C3 plants (details of the biochemical pathway mechanisms are not required)

So it is highly unlikely that you need to know it.

[HighSchoolerRS]

Hi guys! I was wondering, in an experiment testing fermentation in yeast, would the control group be repeating the experiment without yeast?

[PhoenixxFire]

Hi guys! I was wondering, in an experiment testing fermentation in yeast, would the control group be repeating the experiment without yeast?

It depends what you are trying to measure? Are you measuring the rate of fermentation? If so what is your experimental condition? What's your IV and DV?

The control group would only be repeating it without yeast if your experiment is testing whether yeast can ferment - I doubt that is the entire experiment so that is probably not going to be the control.

[HighSchoolerRS]

It depends what you are trying to measure? Are you measuring the rate of fermentation? If so what is your experimental condition? What's your IV and DV?

The control group would only be repeating it without yeast if your experiment is testing whether yeast can ferment - I doubt that is the entire experiment so that is probably not going to be the control.

The experiment involves us making a yest+sucrose solution, putting paraffin oil on top of it and then placing it in a water bath for 10 minutes before using an inverted measuring cylinder to measure the volume of gas produced. If the control group involves removing the factor that causes change, I am confused as to what it may be.

[PhoenixxFire]

The experiment involves us making a yest+sucrose solution, putting paraffin oil on top of it and then placing it in a water bath for 10 minutes before using an inverted measuring cylinder to measure the volume of gas produced. If the control group involves removing the factor that causes change, I am confused as to what it may be.

The most likely experimental variable is probably the sucrose which would mean that your control is exactly the same but the yeast is in normal water not sucrose.

It could be that you are measuring whether yeast can ferment, but that is a pretty useless experiment.

If it were the sucrose solution it also seems strange that you would only have one experimental condition - I would expect several tests, each with a different sucrose concentration (and the control as plain water) to see which causes the fastest rate of fermentation.

It's probably best to ask your teacher what you are supposed to be comparing.