VCE Biology Question Thread

[Rishi97]

What score on the exam would you require for a study score of 45, given A+ SACs

Hard to estimate as it also depends on the strength of your cohort
Just keep trying your best and you will get the score you want! Good Luck !!!

[vox nihili]

Just a polite reminder that questions about scores should be directed elsewhere (Victorian Technical Score Discussion).

An even better idea would be to stop fretting over your scores. Unfortunately, no matter how much you know about your scores, such knowledge is unlikely to change them whatsoever. Just do your best and be hopeful that, at the end of the year, your best has been enough to do well.

[cosine]

Im currently massively struggling with cellular respiration, I have never done it before and no one is helping me so I am stressing out. Can someone just confirm my interpretation of the two stages of aerobic respiration, i would appreciate it a lot and if there's something wrong please let me know.

The first stage is glycolysis which occurs in the cytosol of the cell. A glucose molecule is broken down into 2 3C molecules called pyruvate. Some energy is initially released which is captured by ADP + Pi to form 2ATP. The remaining pyruvate molecules move into the mitochondrion where the second stage, the krebs cyle occurs. The pyruvate molecules react with a molecule known as coenzyme A, to produce CO2 and acetly coenzyme A. The coenzyme A enters the krebs cycle, where it is further broken down into another 2 molecules of CO2, and the energy released is used to produce ATP and five loaded carrier molecules (4NADH, FADH2).

Thank you a lot if you can help

[wobblywobbly]

Im currently massively struggling with cellular respiration, I have never done it before and no one is helping me so I am stressing out. Can someone just confirm my interpretation of the two stages of aerobic respiration, i would appreciate it a lot and if there's something wrong please let me know.

The first stage is glycolysis which occurs in the cytosol of the cell. A glucose molecule is broken down into 2 3C molecules called pyruvate. Some energy is initially released which is captured by ADP + Pi to form 2ATP. The remaining pyruvate molecules move into the mitochondrion where the second stage, the krebs cyle occurs. The pyruvate molecules react with a molecule known as coenzyme A, to produce CO2 and acetly coenzyme A. The coenzyme A enters the krebs cycle, where it is further broken down into another 2 molecules of CO2, and the energy released is used to produce ATP and five loaded carrier molecules (4NADH, FADH2).

Thank you a lot if you can help

Firstly, relax. You still have months to learn this stuff, and by the end of the year you'll be an expert. Secondly, you really need to just know inputs, outputs and location (It's a bit iffy with regards to whether you need to know exact numbers, my teacher recommends it). That's it. You don't need to know the intricate chemical processes that happens. I note that you haven't talked about the third stage of cellular respiration as well (Which I'm sure you know about). As for your interpretation, it seems correct, except for the fact that one NAD is produced as well as a CO2 when Acetyl CoA is formed, and three more NAD is released in the cycle, making it a total of four, instead of four in the end. Again, it's a technical point, and it's not going to be asked (of course, if your teacher puts it in the SAC, that's another issue, and you will need to learn it, even though it's not in the study design)

Here's exactly what you need to know:
Anaerobic process (Does not require oxygen):
1st stage -- Glycolysis -- Cytosol -- Breaking up glucose to make pyruvate
Inputs: Glucose, NAD, ADP + Pi
Outputs: 2 Pyruvate, NADH, 2 ATP

Aerobic processes below (Requires oxygen to proceed with the next two stages):
2nd stage -- Krebs Cycle -- Mitochondrial Matrix -- Turning pyruvate into carbon dioxide
Inputs: ADP+Pi, Pyruvate, NAD, FAD
Outputs: 2 ATP, CO2, NADH, FADH2

3rd stage -- Electron Transport Chain -- Mitochondrial Cristae -- The majority of ATP production, and where oxygen combines with hydrogen and electrons to make water.
Inputs: NADH, FADH2, O2
Outputs: NAD, FAD, 32-34 ATP, H2O

You should also know anaerobic respiration, where pyruvates formed in the first stage gets turned into ATP and lactic acid in animals, and in plants/yeast, it gets turned into ethanol, carbon dioxide and ATP.

Check out this link as well, if your stuck. Really good explanation (even if it goes out the SD slightly): http://www.vce.bioninja.com.au/aos-1-molecules-of-life/biochemical-processes/cell-respiration.html

[cosine]

Firstly, relax. You still have months to learn this stuff, and by the end of the year you'll be an expert. Secondly, you really need to just know inputs, outputs and location (It's a bit iffy with regards to whether you need to know exact numbers, my teacher recommends it). That's it. You don't need to know the intricate chemical processes that happens. I note that you haven't talked about the third stage of cellular respiration as well (Which I'm sure you know about). As for your interpretation, it seems correct, except for the fact that one NAD is produced as well as a CO2 when Acetyl CoA is formed, and three more NAD is released in the cycle, making it a total of four, instead of four in the end. Again, it's a technical point, and it's not going to be asked (of course, if your teacher puts it in the SAC, that's another issue, and you will need to learn it, even though it's not in the study design)

Here's exactly what you need to know:
Anaerobic process (Does not require oxygen):
1st stage -- Glycolysis -- Cytosol -- Breaking up glucose to make pyruvate
Inputs: Glucose, NAD, ADP + Pi
Outputs: 2 Pyruvate, NADH, 2 ATP

Aerobic processes below (Requires oxygen to proceed with the next two stages):
2nd stage -- Krebs Cycle -- Mitochondrial Matrix -- Turning pyruvate into carbon dioxide
Inputs: ADP+Pi, Pyruvate, NAD, FAD
Outputs: 2 ATP, CO2, NADH, FADH2

3rd stage -- Electron Transport Chain -- Mitochondrial Cristae -- The majority of ATP production, and where oxygen combines with hydrogen and electrons to make water.
Inputs: NADH, FADH2, O2
Outputs: NAD, FAD, 32-34 ATP, H2O

You should also know anaerobic respiration, where pyruvates formed in the first stage gets turned into ATP and lactic acid in animals, and in plants/yeast, it gets turned into ethanol, carbon dioxide and ATP.

Check out this link as well, if your stuck. Really good explanation (even if it goes out the SD slightly): http://www.vce.bioninja.com.au/aos-1-molecules-of-life/biochemical-processes/cell-respiration.html

I love you. Thanks so much you literally are a legend!

For the inputs of krebs cycle, did you forget coenzyme A? And the outputs of glycolysis, is it 2NADH molecules or just 1?

Once again, thank you!

[wobblywobbly]

I love you. Thanks so much you literally are a legend!

For the inputs of krebs cycle, did you forget coenzyme A? And the outputs of glycolysis, is it 2NADH molecules or just 1?

Once again, thank you!

I didn't forget it, technically speaking, pyruvates are the one that enters the process. Coenzyme A is just part of the cycle, and isn't really an imput because it isn't changed i.e. it is reused (though all this stuff is outside the VCE course) Output of glycolysis is 2 NADH per glucose.

[Apink!]

What does it mean when lipid "aggregates"?
I have my notes here and it tells me that the polymer bonding type rarely bonds but form aggregates but I don't understand this 

Also don't lipids have covalent bonds between glycerol and fatty acids?
so shouldn't the polymer bonding type also include covalent bonding?

Thank you so much

[cosine]

What does it mean when lipid "aggregates"?
I have my notes here and it tells me that the polymer bonding type rarely bonds but form aggregates but I don't understand this 

Also don't lipids have covalent bonds between glycerol and fatty acids?
so shouldn't the polymer bonding type also include covalent bonding?

Thank you so much

Lipids do not form polymers. This is because the glycerol backbone and the fatty acid chains are seperated in nature, and when they bind together, the condensation reaction occurs (a water molecule is released), hence lipids do not form polymers. The bond between glycerol and fatty acids are called ester bonds.

Hope it helps

[mahler004]

What does it mean when lipid "aggregates"?
I have my notes here and it tells me that the polymer bonding type rarely bonds but form aggregates but I don't understand this 

Also don't lipids have covalent bonds between glycerol and fatty acids?
so shouldn't the polymer bonding type also include covalent bonding?

Thank you so much

It's not really worded that well and beyond VCE AFIAK. Lipids can non-covalently interact to form aggregates in solution (look up micelles and bicells.) These are not polymers.

[Arithmetic]

Tonight I was performing the leaf disc and photosynthesis experiment for a science assignment. I followed the method (suction of oxygen in the leaf discs, and placing them in bicarbonate solution.) I was shining white light on the leaf discs, but still after a long time none of the discs had floated? Does anyone know why? I followed the exact method written, but I noticed that the leaves were waxy and hard in texture could this have affected my results?

Many Thanks.

[caitlynharbrow]

Hello, I'm about to do a prac in biology that relates to photosynthesis and cellular respiration. We are using 4 test tubes filled with Bromothymol. two test tubes A and C will have Edola in them whereas B and D don't. A and B are left in the sun where C and D are put in a dark place.
What is this testing? what questions could I be asked?

[Rishi97]

Hello, I'm about to do a prac in biology that relates to photosynthesis and cellular respiration. We are using 4 test tubes filled with Bromothymol. two test tubes A and C will have Edola in them whereas B and D don't. A and B are left in the sun where C and D are put in a dark place.
What is this testing? what questions could I be asked?

Hey
Since C and D are put in a dark place, it sounds like you will be testing the effect of light on photosynthesis. You may be asked hypothesis questions such as what you expect will happen (will oxygen be produced or not?). As photosynthesis cannot occur in the dark, cellular respiration must be occuring. You may also be asked questions such as which was the control and why you need a control. I have no idea what Edola is but if it a carbon source, you can expect that test tubes in A and C will have a greater rate of photosynthesis as an important input is carbon dioxide.
As you cant specifically measure rates of oxygen/carbon dioxide produced, you will have to just observe the colour changes that occur in the solution due to the indicator. It will change colour depending on the pH of the solution.

[caitlynharbrow]

What does a colour change from blue to yellow indicate about a change pH and carbon dioxide level in the vial?
How would I approach this question? referencing to the information I gave above

[kimmytaaa]

Hi Guys does anyone know what the second process of fermentation and explain the process of it?

[MagicGecko]

What does a colour change from blue to yellow indicate about a change pH and carbon dioxide level in the vial?
How would I approach this question? referencing to the information I gave above

With respect to bromo blue, under acidic conditions (less than 7, e.g ph of 6 or 5 etc), it turns yellow. This is due to a large amount on CO2. But when there is a low concentration of CO2, the ph of the solution will be greater than 7 (around 7.5, 7.6 etc) and this causes bromo blue to well actually be blue.
So to summarise:
High CO2 - Low pH - yellow
Low CO2 - Higher pH - blue