VCE Biology Question Thread

[Mr West]

thanks.

I understand how it can be endocrine, since it can enter general circulation, but can you explain how it is paracrine or autocrine

cheers

edit: used the wrong term

[PhoenixxFire]

thanks.

I understand how it can be endocrine, since it can enter general circulation, but can you explain how it is paracrine or autocrine

cheers

edit: used the wrong term

So an example of this is the cytokines released by T helper cells. When a B cell that has bound its antigen finds a T helper cell that has been activated by an APC the Th cell will release cytokines. There cytokines cause both the Th cell and the B cell to divide and differentiate. The cytokines are released from the Th cell, and are acting on the Th cell so they are autocrine. They are also acting on a nearby cell (the B cell) so they are paracrine.

[PopcornTime]

Can someone help me with the following. Not sure how to answer 2nd and 3rd one. 

To quicken the ripening of bananas you can trap ethylene gas. How?
- gas chamber

What else could you do to help the fruit ripen quickly?


To stop fruit ripening CO2 gas is pumped in. Why?

[darkz]

Can someone help me with the following. Not sure how to answer 2nd and 3rd one. 

To quicken the ripening of bananas you can trap ethylene gas. How?
- gas chamber

What else could you do to help the fruit ripen quickly?


To stop fruit ripening CO2 gas is pumped in. Why?

To help the fruit ripen, you can physically damage the fruit - cut the skin etc as that will increase the amount of ethylene produced.

By increasing co2, concentration of o2 goes down, therefore rate of respiration goes down as well (which is what ethylene does - increases rate of respiration to ripen the fruit)

[PopcornTime]

What do we specifically need to know for the following study design dot points?

- molecular homology as evidence of relatedness between species including DNA and amino acid sequences, mtDNA (the molecular clock) and the DNA hybridisation technique

- the use of phylogenetic trees to show relatedness between species

- the evolution of novel phenotypes arising from chance events within genomes, specifically sets of genes that regulate developmental processes and lead to changes in the expression of a few master genes found across the animal phyla, as demonstrated by the expression of gene BMP4 in beak formation of the Galapagos finches and jaw formation of cichlid fish in Africa.

- The use of enzymes including endonucleases (restriction enzymes), ligases and polymerases

- Amplification of DNA using the polymerase chain reaction

- The use of gel electrophoresis in sorting DNA fragments, including interpretation of gel runs

-The use of recombinant plasmids as vectors to transform bacterial cells.

[peachxmh]

Why do antibiotics not work on fungi or yeasts? (or at least they don't work on some of them to my knowledge) I can only find stuff on why they don't work on viruses which I understand thx

[vox nihili]

Why do antibiotics not work on fungi or yeasts? (or at least they don't work on some of them to my knowledge) I can only find stuff on why they don't work on viruses which I understand thx

Do you have any thoughts about this? Why they don't work on viruses may give you a bit of an idea about why they don't work on fungi.

[peachxmh]

Do you have any thoughts about this? Why they don't work on viruses may give you a bit of an idea about why they don't work on fungi.

I've been told that antibiotics block metabolic pathways within a cell which doesn't affect viruses because they use a host cell to carry out these processes. I'm not sure how this translates into fungi though because don't they carry out their own metabolism? Correct me if I'm wrong haha

Edit: accidentally wrote antibodies instead of antibiotics whoops

[darkz]

I've been told that antibiotics block metabolic pathways within a cell which doesn't affect viruses because they use a host cell to carry out these processes. I'm not sure how this translates into fungi though because don't they carry out their own metabolism? Correct me if I'm wrong haha

Edit: accidentally wrote antibodies instead of antibiotics whoops

Well antibiotics are pretty much specifically designed to target specific parts of bacteria, for example, inhibiting the growth of bacteria cell walls by inhibiting specific enzymes like transpeptidase etc. However, fungi do not have such enzymes and furthermore, the composition of a fungus cell wall is different to that of a bacteria. To treat fungal infections, we would use an anti-fungal, which is specifically designed to target fungi. So likewise, antifungals would not be effective on bacteria.

[Mr West]

hey guys

is the overall process of signal reception, transduction and cellular response termed signal transduction?

I'm just confused how the overall process can share a name with a stage of it.

[PhoenixxFire]

hey guys

is the overall process of signal reception, transduction and cellular response termed signal transduction?

I'm just confused how the overall process can share a name with a stage of it.

The overall process is sometimes called signal transduction and sometimes called the very generic 'cell signalling'.

Transduction just refers to something being changed into another form. So the process transduction is change from a signal to a response whereas the step transduction is a change from an extracellular signal to an intracellular signal.

[Erutepa]

hey guys

is the overall process of signal reception, transduction and cellular response termed signal transduction?

I'm just confused how the overall process can share a name with a stage of it.

From my understanding of the stimulus respose model, I belive that signal transduction refers to the steps relaying the reception of a signal to the  effector.
In relation to biology the stimulus response model involves a signal (usually a molecule) which interacts with a receptor protein. This causes something to happen which results in the activation/production of an effector protein, which in turn brings about the response. Signal transuction, at least in my understanding, is what happens from the reception of a signal by the receptor protein to achive this effector protein.
Hope this helps and, if i am wrong, someone might be able to correct me.

[vox nihili]

From my understanding of the stimulus respose model, I belive that signal transduction refers to the steps relaying the reception of a signal to the  effector.
In relation to biology the stimulus response model involves a signal (usually a molecule) which interacts with a receptor protein. This causes something to happen which results in the activation/production of an effector protein, which in turn brings about the response. Signal transuction, at least in my understanding, is what happens from the reception of a signal by the receptor protein to achive this effector protein.
Hope this helps and, if i am wrong, someone might be able to correct me.

This is correct! Transduction is the passage of signal from the receptor tonthe thing that ultimately acts on the signal 

[peachxmh]

Hello again just wanted to very quickly clarify something - so MHC markers are only found on self-cells and not on foreign cells and they're essentially self-antigens, is that right? Then what do foreign cells have? Just other antigens that we don't need to know specifically about? Ty ty

[vox nihili]

Hello again just wanted to very quickly clarify something - so MHC markers are only found on self-cells and not on foreign cells and they're essentially self-antigens, is that right? Then what do foreign cells have? Just other antigens that we don't need to know specifically about? Ty ty

Not really. I think this is a really common misconception in VCE Biology and one that the course kind of encourages you to think about.


The immune system does not recognise self, it has no capacity to do so. It only recognises non-self. So it can recongnise molecular markers on the surface of pathogens (that do not exist on our own cells) and respond to them. Self is merely the absence of non-self.