VCE Biology Question Thread

[PhoenixxFire]

Hi, are stromatolites trace fossils? Or do they actually contain fossilised bacteria? Different sources say different things so I'm a bit confused. Thanks!

Stromatolites are chemicals produced by bacteria as a reusult of metabolic pathways - so they are trace fossils.

[Seno72]

Hey peeps.

1) Why is mtDNA used in molecular homology? What are the advantages and disadvantages of it?

2) Also since we need to know how rational drug design works, do we need to the specifics of Neuraminidase enzyme (like that the substrate is sialic Acid) or just that it basically allows virus particles to leave the host cell?

3) When an organ transplant is rejected, is it because of the cytotoxic T cells recognising the organ transplant cells as non self and then attack them by releasing granzymes that initiate apoptosis or do we talk about the humoral response?

[margecaitl]

Just wondering about antigens, if they initiate an antibody generating response, do the MCH1 markers prevent that response happening in your own body (to your own cells)? OR are MCH1 the antigens?

[chrisjudd00]

1) Why is mtDNA used in molecular homology? What are the advantages and disadvantages of it?
mtDNA is used as firstly it does not undergo recombination during meiosis. There is alos quite a high yield of mtDNA in cells and also mitochondrial DNA does not undergo the reapair mechanisms that nuclear DNA has. Thus the mutations will accumulate more quickly and substantially in mtDNA, which is important for molecular clocks where they use the rate of mutation accumulation to determine relatedness between species.

2) Also since we need to know how rational drug design works, do we need to the specifics of Neuraminidase enzyme (like that the substrate is sialic Acid) or just that it basically allows virus particles to leave the host cell?
Neurimidinase cuts the connection between the heamagluttin the cell's receptor. If the Relenza binds to the neurimidinases' active site then it cannot perform this function meaning the virion is contained to that cell, making it easier to destroy. 

[Seno72]

32. (so 36 total for aerobic respiration)

You may be able to get away with writing slightly different amounts, however DO NOT write a range (eg 32-36) VCAA will not like it (they see it as taking multiple guesses to the answer - if you forget just pick one).

How about writing 36/38 ATP instead of 36-38 ATP (because in certain cells it can vary)?

[PhoenixxFire]

How about writing 36/38 ATP instead of 36-38 ATP (because in certain cells it can vary)?

I would still not do it. I was told by my teacher that VCAA will not accept it. Also recent studies show some cells produce 40.

[PhoenixxFire]

Just wondering about antigens, if they initiate an antibody generating response, do the MCH1 markers prevent that response happening in your own body (to your own cells)? OR are MCH1 the antigens?

MHC1 molecules do neither. They present a peptide fragment (that was produced inside the cell) for inspection by Tc cells. These peptide fragments are antigens that may either be self (expressed from our own DNA) or non-self (expressed as a result of viral DNA/mutated DNA (eg. cancer)).

Not in study design
MHC 1 can trigger a Tc cell to release cytotoxic enzymes if the Tc cell's CD8 receptor (located next to the T cell receptor (the T cell receptor is the one that binds to peptide fragments.) cannot bind to the MHC 1 molecule. This is why transplants are rejected - it also is used to find cancerous cells. In this case The MHC 1 molecule would be the antigen. - But we do not need to know this.

[margecaitl]

MHC1 molecules do neither. They present a peptide fragment (that was produced inside the cell) for inspection by Tc cells. These peptide fragments are antigens that may either be self (expressed from our own DNA) or non-self (expressed as a result of viral DNA/mutated DNA (eg. cancer)).

Not in study design
MHC 1 can trigger a Tc cell to release cytotoxic enzymes if the Tc cell's CD8 receptor (located next to the T cell receptor (the T cell receptor is the one that binds to peptide fragments.) cannot bind to the MHC 1 molecule. This is why transplants are rejected - it also is used to find cancerous cells. In this case The MHC 1 molecule would be the antigen. - But we do not need to know this.

Okay, thanks

[Seno72]

I would still not do it. I was told by my teacher that VCAA will not accept it. Also recent studies show some cells produce 40.

Thanks mate. So if I wrote this, would this get a mark for VCAA standards:

6O2 + C6H12O6 ----->  6CO2 + 6H2O + 38 ATP

[psl123]

Hi, if anyone can correct me where i'm going wrong with transduction pathways of neurotransmitters and hydrophilic signals that would be greatly appreciated

Neurotransmitters-
Sodium ions diffuse into neuron, potassium ions diffuse out creating the action potential that drives the electrical signal across the neuron
Calcium ions enter axon terminal
Vesicle containing neurotransmitters are stimulated by electrical impulse to move toward the plasma membrane and exocytose the neurotransmitters out of the axon terminal into the synaptic cleft
The neurotransmitters attach to complementary receptors on the post-synaptic neuron and diffuse into the neuron, repeating the process again

Hydrophilic signalling molecules-
bind to complementary plasma membrane receptor on target cell
This activates the intracellular part of the receptor to activate an enzyme in the plasma membrane that catalyses production of the second messenger molecule. Second messenger molecule activates the first enzyme of the enzyme cascade, that then activates the next enzyme and this repeats to amplify the signal until it reaches the nucleus where the specific cellular response occurs (like synthesis of a specific protein)

[waldo]

How do GMO's and transgenic organisms increase crop resistance? And what are the social, biological and ethical implications associated with them? I've always had trouble getting my head around this point in the study design.

[Seno72]

How do GMO's and transgenic organisms increase crop resistance? And what are the social, biological and ethical implications associated with them? I've always had trouble getting my head around this point in the study design.

GMOs increase are genetically modified to become resistant to pests (due to addition of certain genes to their genome that deter pests and insects).

Social Implication: (of GMOS and transgenic organisms)
• It is against certain aspects of religion.

Biological Implication:
• It can harm the biodiversity as GMOs may target and kill beneficial insects such as bees.
• The use of GM crops can result in potential gene flow between GM crops and related wild species, resulting in pesticide resistant weeds that can pose a threat to GM crops.

Ethical Implications
• Is it against nature to alter the genome of crops to make them become genetically modified?

[PhoenixxFire]

Thanks mate. So if I wrote this, would this get a mark for VCAA standards:

6O2 + C6H12O6 ----->  6CO2 + 6H2O + 38 ATP

If it asks for a balanced chemical equation you need to say
38ADP + 38Pi + 6O2 + C6H12O6 ----> 6CO2 + 6H2O + 38ATP
Otherwise yes.

[Apricot]

Are homo sapien pelvic girdles wider than Australopithecus or were theirs wider? Diagrams and vcaa 2013 suggest that Australopithecus had a wider pelvic girdle but i thought wider pelvic girdle helped more with bipedalism. Can someone please clarify what would be the reason for Australopithecus having a wider pelvis?

[smamsmo22]

Just wondering; are cytokines transported through tissue fluid..or the blood? Or through a different pathway? Thanks