VCE Biology Question Thread

[J_Rho]

What is VCAA's definition of an allergen?

Adding onto what darkz said, in the 2019 examiners reports allergen is described as as "allergens contribute to the allergic response", other than that allergens are always used with reference to the allergic response and mast cells and students have not (in the past) been required to define an allergen.

[elena1510]

For our SAC, we need to do an experiment at home due to coronavirus ( and I was just wondering if anyone had any good ideas for what to test? It has to be on Unit 3, I was originally going to do enzymes at school but now I'm stuck on what to do

[tigerclouds]

Hi!
I would like to ask about photosynthesis. If the input of H20 in the light-dependent stage is 12, thus 24 hydrogens, why is there only 12NADPH coenzyme as an output. Isn't there supposed to be 24NADPH in the output as NADPH is a carrier of hydrogen?  Or is some carried in the 12ATP that is also a output of the light independent stage?

Thanks in advance! =)

I've been thinking about this question for ageeeeessss and can't find a definite answer. Could it be that some hydrogen ions are kept in the thylakoid to create the hydrogen gradient that drives ATP Synthase? Or does it have anything to do with NADP+ accepting 2 electrons instead of one?
Help guys!

[Ionic Doc]

Quick Question

How does an increase in Carbon Dioxide, decrease the rate of cellular respiration?

[darkz]

I've been thinking about this question for ageeeeessss and can't find a definite answer. Could it be that some hydrogen ions are kept in the thylakoid to create the hydrogen gradient that drives ATP Synthase? Or does it have anything to do with NADP+ accepting 2 electrons instead of one?
Help guys!

Did you account for the \(6H_2O\) produced?
Ref below

Quick Question

How does an increase in Carbon Dioxide, decrease the rate of cellular respiration?

Well if an environment was 50% oxygen and 50% carbon dioxide and we increase the concentration of carbon dioxide to 99%, then the concentration of oxygen will decrease to 1%, which would mean that there is a greater chance of carbon dioxide 'blocking' the mechanism of using oxygen.

[Ionic Doc]

Well if an environment was 50% oxygen and 50% carbon dioxide and we increase the concentration of carbon dioxide to 99%, then the concentration of oxygen will decrease to 1%, which would mean that there is a greater chance of carbon dioxide 'blocking' the mechanism of using oxygen.

Ohh, so if there's more carbon dioxide there is less oxygen in the environment and that's how respiration would decrease.

Thanks @darkz 

[tigerclouds]

Did you account for the \(6H_2O\) produced?

Could you please elaborate? I'm not sure I understand how that explains the 12NADPH

[darkz]

Could you please elaborate? I'm not sure I understand how that explains the 12NADPH

Ahh yeh, my bad, misread (disregard).
\[ADP = C_{10}H_{15}N_{5}O_{10}P_{2}\]
\[ATP = C_{10}H_{16}N_{5}O_{13}P_{3}\]
Based on the above, that would explain where the extra protons are going. But obviously, for any purpose related to VCE, you won't be required to explain where these protons are going, nor be required to remember the number of NADPH produced etc.

[tigerclouds]

Ahh yeh, my bad, misread (disregard).
\[ADP = C_{10}H_{15}N_{5}O_{10}P_{2}\]
\[ATP = C_{10}H_{16}N_{5}O_{13}P_{3}\]
Based on the above, that would explain where the extra protons are going. But obviously, for any purpose related to VCE, you won't be required to explain where these protons are going, nor be required to remember the number of NADPH produced etc.

Ohhh ok, so since hydrogen is being added to ADP to form ATP, after 12 cycles that would constitute for the 12 protons. So of the 24 hydrogens that are initially split from water, 12 are relayed onto NADP+ to form NADPH and the other 12 are used to drive the production of ATP from ADP. Correct?
Thank you for your reply!

[darkz]

Ohhh ok, so since hydrogen is being added to ADP to form ATP, after 12 cycles that would constitute for the 12 protons. So of the 24 hydrogens that are initially split from water, 12 are relayed onto NADP+ to form NADPH and the other 12 are used to drive the production of ATP from ADP. Correct?
Thank you for your reply!

Yes

[natalie03]

could someone please help define wet weight, my teacher said it could be on my upcoming sac and would love someone to define and help explain it. Thanks

[J_Rho]

could someone please help define wet weight, my teacher said it could be on my upcoming sac and would love someone to define and help explain it. Thanks

Hi Natalie,
I have never come across this term but a quick google search came up with this definition from Green facts - Wet weight definition

The plant, animal, or other material containing the chemical of interest is not dried to remove water. The amount of the chemical found in subsequent analysis is expressed as the weight of chemical divided by the total weight, including any water present, of the material which once contained it.

and this from BioBlast- Wet Weight
Wet weight of a tissue or biological sample, obtained after blotting the sample to remove an arbitrary amount of water adhering externally to the sample.

[ajka0002]

Hi
I was wondering if someone could pls explain what this process is or what the images are (image attached). It relates to the cellular signals topic.
Thanks

[tigerclouds]

Hi guys,
With regards to photosynthesis and cellular respiration, the study design states that "details of the biochemical pathway mechanisms are not required" so how much do we actually need to know about the two processes? Like do we need to understand the steps in the Krebs cycle or the steps in the Calvin cycle? Or do we just need to remember the inputs and outputs?

[SS1314]

Hi
I was wondering if someone could pls explain what this process is or what the images are (image attached). It relates to the cellular signals topic.
Thanks

From what I can discern from the  images, the first image is illustrating autocrine signalling, the second image is illustrating paracrine signalling and the third image is illustrating endocrine signalling.

Autocrine signalling refers to signalling involving a cell that is both the producer of the ligand and the target cell, eg. cytokines.

Paracrine signalling refers to signalling involving two cells close to each other in which the producer of the ligand excretes  it and it  passes through a small gap and reaches the target cell. An example of this type of signalling would be neurotransmitters which pass through a small gap called the synaptic cleft (or gap) and are released by pre-synaptic neurons.

The final image is illustrating endocrine signalling which refers to signalling molecules that are excreted by a cell and act on a cell that is quite far away. Endocrine signalling molecules travel through the bloodstream, hence the illustration of the blood vessel. An example of this could be animal hormones that are secreted by endocrine glands and circulate around the blood.

Hope this helps

Hi guys,
With regards to photosynthesis and cellular respiration, the study design states that "details of the biochemical pathway mechanisms are not required" so how much do we actually need to know about the two processes? Like do we need to understand the steps in the Krebs cycle or the steps in the Calvin cycle? Or do we just need to remember the inputs and outputs?

Just need to know the inputs and outputs of EACH stage. However, I remembered some parts of the stages because it was taught in class.

Mod Edit: Merged double post