VCE Biology Question Thread

[Billuminati]

Which inhibitory neurotransmitter is used by neurons of the CNS to suppress the sensation of pain?
A endorphins
B acetylcholine
C Adrenalin
D serotonin

Would this be d

I'm pretty sure it's endorphins, cuz they activate opioid receptors. Serotonin can both promote and suppress pain, so it's not a strictly pain-killing neurotransmitter

[Chocolatepistachio]

in the equation for the krebs cycle where did the 2H20 come from isn't there only one also where did the COA-SH come from isnt there 3 and isnt there 4 H+

[Domek]

in the equation for the krebs cycle where did the 2H20 come from isn't there only one also where did the COA-SH come from isnt there 3 and isnt there 4 H⁺

Hi Chocolatepistachio,

Please refer to the attached diagram.
During the Krebs cycle a total of 3 H₂O are consumed and 1 H₂O is produced. Therefore, a net of 2 H₂O are consumed.
CoA-SH is removed twice and added once during the course of the Kreb's cycle, so there is a net of 1 CoA-SH produced.
Not sure about the H⁺.

[yr12_vcestudent]

Can someone pls explain to me the process of C4, C3 and CAM plants-photosynthesis 
THANKS

[Domek]

Can someone pls explain to me the process of C4, C3 and CAM plants-photosynthesis 
THANKS

Hi there,
C3 photosynthesis
CO₂ undergoes the Calvin cycle. In the first step of the cycle, the enzyme rubisco catalyses the production of a 3-carbon compound, 3-PGA. Hence the name C3 photosynthesis.

Process of C4 photosynthesis
CO₂ enters a mesophyll cell in a leaf, where the enzyme PEP carboxylase catalyses the reaction of CO₂ with PEP (3-carbon compound) to form oxaloacetate (4-carbon compound). Oxaloacetate is then converted to malate, which is transported into the bundle sheath cells.
In the chloroplast of bundle sheath cells, malate is decarboxylated (carboxyl group is removed), producing CO₂ and pyruvate (3-carbon compound). This reaction also generates NADPH.
The CO₂ generated by the previous step undergoes the Calvin cycle. Pyruvate is transported back into the chloroplast of the mesophyll cells where it is converted into PEP to complete the cycle.

Process of CAM photosynthesis
Everything occurs in the mesophyll cells.
During the night, stomata are open and CO₂ enters the mesophyll cells where it is converted into malate (via the same process as in C4 photosynthesis). The malate is then stored the vacuole of the mesophyll cells.
During the day, stomata are closed. In the cytosol of mesophyll cells, CO₂ is liberated from malate and then undergoes the Calvin cycle in the chloroplast. Also in the chloroplast, pyruvate is converted into PEP. PEP then moves back into the cytosol.

To see some nice diagrams and a more detailed explanation please have a look at this Khan academy article: https://www.khanacademy.org/science/biology/photosynthesis-in-plants/photorespiration--c3-c4-cam-plants/a/c3-c4-and-cam-plants-agriculture

[Chocolatepistachio]

Some living cells were maintained in a culture medium under aerobic conditions. They were supplied with glucose labelled with radioactive carbon-14, which of the following is likely to be true?
A carbon-14 atoms would be found in NADPH
B carbon-14 atoms would be found in ATP
C carbon-14 atoms would be found in carbon dioxide produced by the cells
D carbon d-14 atoms would be found in pyruvate

Would this be d

[Domek]

Some living cells were maintained in a culture medium under aerobic conditions. They were supplied with glucose labelled with radioactive carbon-14, which of the following is likely to be true?
A carbon-14 atoms would be found in NADPH
B carbon-14 atoms would be found in ATP
C carbon-14 atoms would be found in carbon dioxide produced by the cells
D carbon d-14 atoms would be found in pyruvate

Would this be d

Actually, I think it would be C. If the cells are in an aerobic medium, they will undergo aerobic respiration which involves the Krebs cycle. Therefore the carbon-14 containing pyruvate produced by glycolysis would be converted into acetyl-CoA, which would then enter the Krebs cycle. As the Krebs cycle produces carbon dioxide, the radioactive carbon atoms would leave the Krebs cycle as carbon dioxide.

[Chocolatepistachio]

Thanks
how would you answer this question
if someone could help with this question

[Domek]

Thanks
how would you answer this question
if someone could help with this question

This looks like a question from a university subject! At least, this kind of stuff wasn't covered in VCE Biology when I did it. There's potentially multiple correct answers to this question, so if you like, have a go at answering it and I'll try give you some feedback.

[Chocolatepistachio]

So would you use the p1000 pipette and set it to 180
Not sure when to go to first or second stops

[Chocolatepistachio]

Why doesnt methionine involve disulfide bonding even though it has sulfur why does the positioning of the sulfur group next to the methyl not allow it to whereas cysteine residues are involved with disulfide bonds

[Domek]

So would you use the p1000 pipette and set it to 180
Not sure when to go to first or second stops

You're on the right track. Because you want to transfer 1080 無 I would first use the p1000 pipette to transfer 1000 無 as the p1000 pipette has an accurate range of 200-1000 無. To transfer the remaining 80 無 I would use the p200 pipette which has a range of 20-200 無. In each case I would set each pipette to the desired volume, and place the appropriate tip on the pipette. Then I would press the plunger down to the first stop, insert the pipette vertically into the solution and slowly lift my thumb of the plunger to allow the pipette to aspirate the solution. To dispense the solution into the test tube, I would gently place the pipette tip against the test tube wall at an angle and drag the tip slightly up along the wall, with the plunger pressed to the second stop so that the last amount of liquid comes out.

[Chocolatepistachio]

Which of the following amino acids is not inside an alpha helix?
A alanine
B glycine 
C phenylalanine
D proline

Would this be both c and d

[Rose34]

Hello,

Does anyone from previous years recommend a website where I can find free questions for each topic in units 3&4 bio? I want a website that helps with SAC practice and Exams as well.
Also, can anyone advice me of how to get full answers on long answer questions? Is there a specific structure I should be following? Last year I lost most marks becuase I could not write the answer well even though I knew the concept. (since I do legal when we see questions like "discuss, evaluate.." we know that we should be defining any key words in the question and give advantages and disadvantages as well as a conclusion, so I was wondering if there is something like this in bio too)

Thanks in advance,
Rose.

[Frostflake]

Hi !!

Could someone tell me what topics from 1/2 are needed for 3/4? I'm in year 10 and I'm not taking 1/2 bio this year but I want to take 3/4 next year so I was wondering what topics to study on my own. Also, do you think getting a score above 40 or even 45 is achievable if you haven't done 1/2? Thanks!