Hi everyone,
Is anyone able to explain briefly what the difference in function is between the 5' methyl G cap and 3' poly A tail added during RNA processing, as I thought they both functioned to stabilise the mRNA strand but when I came across it in an exam paper it said that the methyl cap protects against attacks from enzymes (which I don't quite understand).
Thanks!
VCE Biology Questions Thread
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When the mRNA travels into the cytoplasm, a class of enzymes that break down RNA (conveniently called RNases) will be like "you've came to the wrong 'hood" and attempt to degrade the mRNA strand. Even in the absence of cytoplasmic RNases, mRNA isn't very stable on its own without modifications and can react with other chemicals in the cytosol. That's why you need the 7-methylguanosine cap to prevent premature degradation of the mRNA before it's translated
Does anyone know if the cell-mediated response has to occur before the humoral response in order to have T helper cell? Cause I have a question that asks if HIV stimulates a cell-mediated or humoral response and i am unsure.
I can't remember exactly, but here's my understanding:
- A T-helper cell is involved in stimulation of both the Cell Mediated and Humoral response.
- HIV attacks and destroys T-helper cells, preventing the production of 'immunity' to new antigens. (Stimulation of clonal expansion/differentiation in b/t cells)
My guess would be that it stimulates the cell-mediated response (it being a virus and all).... but I'm not 100% sure... Maybe someone else can help 
Why is glucose expressed as C₆H₁₂O₆ and not just CH₂O? Wouldn't that be simpler?
Do we need to know about the electron transport chain for the exam? Or if we do, how much do we need to know?
Okay, I'm not sure if this question makes complete sense but: do plant cells store energy as ATP or starch? What about animals? Do either of them store it as both?
Again, not sure if this completely makes sense but: I thought one gene coded for multiple amino acids but isn't an operon made of multiple genes that code for one amino acid? So what happened there?
Can substances that aren't inhibitors bind to the allosteric site? And does everything that binds to the allosteric site inhibit substrate from binding to the active site? Or are there some things that can bind without inhibiting?
Does all the energy created by photosynthesis need to go through cellular respiration to become ATP or can some of it - being chemical energy (glucose) be used as is?
How can you tell if a reaction is anabolic or catabolic bc e.g. photosynthesis is anabolic but it also involves the destruction of materials which would mean catabolic right?
What is the main difference between C4 and CAM plants?
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Why is glucose expressed as C₆H₁₂O₆ and not just CH₂O? Wouldn't that be simpler?
The second formula that you have listed is an empirical formula, whereas the first is the molecular formula. It is the molecular formula that actually tells us the amount of carbon, hydrogen and oxygen atoms in a glucose molecule. You need to make sure that you write the molecular formula as it helps us identify that the molecule you are talking about is glucose, and must be used when writing equations for photosynthesis/respiration.
In the future, please post all your questions in the one post as it makes it easier to answer them all 
I'm don't get how C4 and CAM plants lack photorespiration? If someone could explain this simply I would be super grateful! Thank you!!
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chimichurri If a reaction uses small molecules like CO2 and H2O to build larger ones like C6H12O6, then it's anabolic
Vice versa if a reaction uses up big molecules to make smaller ones
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chimichurri
ATP can't be stored, it's generated on demand from oxidation of glucose. Plants store energy as starch (amylose or amylopectin) whereas animals store energy as glycogen
PS to admins, is there a way to reply to multiple comments within the same post?
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No, (Adaptive) Cell-Mediated Responses and Adaptive Humoral Responses can develop simultaneously -- they can be activated at the same time.
You got a trick question (or alternatively a bad question) 
. Because:
Any pathogen able to stimulate an Adaptive Immune Response, can in theory, stimulate both responses. (note the "in theory" bit)
HIV is specifically good at suppressing Adaptive Immune Responses. They do this by targeting cells with the CD4 co-receptor (i.e. Helper T Cells).
Actually, Helper T cells also somewhat assist in Innate Immune Responses once they are activated because they can heighten macrophage aggressiveness etc... so really the Innate Immune System is also affected by HIV, technically, anyways, so I don't think that second bit matters so much for VCE.
If a virus is named the 'Human Immunodeficiency Virus', there is probably a good reason for it 
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chimichurri Do we need to know about the electron transport chain for the exam? Or if we do, how much do we need to know?
Yes, you will need to:
- Know that this is the final step (as far as VCAA is concerned anyways) of Cellular Respiration.
- Memorise it's inputs and outputs.
If a substance can bind to an allosteric site, it automatically makes that substance a non-competitive inhibitor.
It is just more efficient this way, especially in Eukaryotic cells with Mitochondria. In these Eukaryotes, glucose breakdown can be focused in specific areas of the cell.