VCE Biology Question Thread

[vox nihili]

How do receptors develop tolerance to hormones i.e in type 2 diabetes? I know that this can be caused by aging, but what other ways can this be onset?

Irrelevant to the VCE course

Diabetes isn't really an example of tolerance either. It's a pathological process that operates by a different mechanism to normal tolerance pathways.

[Scribe]

1) How is self-distinguished from non-self? Is it just that leukocytes of the immune system have receptors that are able to distinguish antigens on the surface of the body's own cells and molecules as self?
2) Is self-distinguished from non-self through cell surface antigens or through MHC markers, or both?
3) What is the difference between an antigen and MHC? Are MHCs antigens?

Thanks!

[Azim.m]

Why is the expression of lactase in E.coli limited when both glucose and lactose are present? Is this relevant to study design?

[EllingtonFeint]

So catalysts lower activation energy. True?

[darkz]

So catalysts lower activation energy. True?

Yes, catalysts reduce the activation energy required for reactions to occur

[Robot10]

Why is the expression of lactase in E.coli limited when both glucose and lactose are present? Is this relevant to study design?

Lactose is converted into galactose and glucose. The main aim of this conversion process is to obtain glucose, that can be used for aerobic cellular respiration. Hence if there is enough glucose present in E.coli bacteria, they do not require any more glucose and therefore don’t need to break down  lactose and hence the expression of the structural genes involved in the metabolism of lactose is reduced.

[vox nihili]

1) How is self-distinguished from non-self? Is it just that leukocytes of the immune system have receptors that are able to distinguish antigens on the surface of the body's own cells and molecules as self?
2) Is self-distinguished from non-self through cell surface antigens or through MHC markers, or both?
3) What is the difference between an antigen and MHC? Are MHCs antigens?

Thanks!

1. Leukocytes have receptors that can identify foreign antigens. They don't need to have receptors for self, because self is just the absence of non-self!
2/3. MHC molecules just hold digested antigens up so that T-cells can see them. MHC molecules are not antigens, they hold antigens. The digested component of the antigen held in the MHC is called the epitope.

[jondempsey17]

For the 2018 study design, are we expected to know the specifics of the electron transport chain such as Oxygen being the final electron acceptor and the H+ gradient that forces lots of ATP to be produced??

[PhoenixxFire]

For the 2018 study design, are we expected to know the specifics of the electron transport chain such as Oxygen being the final electron acceptor and the H+ gradient that forces lots of ATP to be produced??

Nope, the study design specifies that details of biochemical pathways are not required. Just need to know inputs, outputs, and location. (Also welcome to AN )

[lacitam]

For the 2018 study design, are we expected to know the specifics of the electron transport chain such as Oxygen being the final electron acceptor and the H+ gradient that forces lots of ATP to be produced??

don't think so.
just know that all electron carriers from prev stages go to this area, donate electrons to pump h+ to intermembrane space, then to atp synthase where atp is formed. oxygen comes and picks up electrons and h+ to form water

[joanna120728]

Would appreciate if someone could give feedback to my questions for 2017 sample exam (my teachers don't have answers unfortunately):

1) Q9di (4 marks)
Explain how plasmids can be used to transfer the two genes into the cells of the new strain of rice.
- The 2 genes and plasmid are cut using the same restriction enzymes, leaving the same complementary sticky ends
- Some plasmids will join to both genes when they are mixed together
- DNA ligase seals these joins
- The plasmid is then inserted into the new strain of rice (do we have to say how the plasmid is inserted into the rice cells, is bacteria transformation involved in this?)

2) 10e Describe a modern method that is used to quickly identify a pathogen. (1 mark)
-ELIZA test detects antibodies made against antigens of a specific pathogen
- DNA probes and fluorescent light used to bind to a specific target sequence in the DNA,  if it glows then the pathogen is present (is this how DNA probes work? how much detail do we need to know?)
- is there any other types of tests that can be used? 

[C14M8S]

Would appreciate if someone could give feedback to my questions for 2017 sample exam (my teachers don't have answers unfortunately):

1) Q9di (4 marks)
Explain how plasmids can be used to transfer the two genes into the cells of the new strain of rice.
- The 2 genes and plasmid are cut using the same restriction enzymes, leaving the same complementary sticky ends
- Some plasmids will join to both genes when they are mixed together
- DNA ligase seals these joins
- The plasmid is then inserted into the new strain of rice (do we have to say how the plasmid is inserted into the rice cells, is bacteria transformation involved in this?)

2) 10e Describe a modern method that is used to quickly identify a pathogen. (1 mark)
-ELIZA test detects antibodies made against antigens of a specific pathogen
- DNA probes and fluorescent light used to bind to a specific target sequence in the DNA,  if it glows then the pathogen is present (is this how DNA probes work? how much detail do we need to know?)
- is there any other types of tests that can be used?

There's a set of sample answers compiled by vox nihili here
I've got a series of questions too -
1) Are Natural Killer cells considered to be a part of cell-mediated immunity?
2) How much do I need to know about aneuploidy and assortment of alleles for the dotpoint on mutations?
3) How much should I know about the change in earth's lifeforms with time? Is it just a general outline of how life has become more complex?
4) Are there any useful resources that I can use aside from practice exams to specifically improve with phylogenetic trees that aren't aimed at year 7 students?
5) What are everyone's go-to examples for ethical dilemmas with gene cloning, genetic screening and DNA profiling?
6) What does the syllabus mean by 'the use of scientific knowledge to identify a pathogen?'

[Azim.m]

How could the same genetic sequence produce different proteins?

[PhoenixxFire]

I've got a series of questions too -
1) Are Natural Killer cells considered to be a part of cell-mediated immunity?
2) How much do I need to know about aneuploidy and assortment of alleles for the dotpoint on mutations?
3) How much should I know about the change in earth's lifeforms with time? Is it just a general outline of how life has become more complex?
4) Are there any useful resources that I can use aside from practice exams to specifically improve with phylogenetic trees that aren't aimed at year 7 students?
5) What are everyone's go-to examples for ethical dilemmas with gene cloning, genetic screening and DNA profiling?
6) What does the syllabus mean by 'the use of scientific knowledge to identify a pathogen?'

1. No. Cell-mediated immunity is adaptive, natural killer cells are innate.
2. Pretty sure you just need to know about the different types of mutations and how to recognise them/write them (so 2n+1, 3n, etc.)
3.Just a general outline, you don't need to know specific dates, just know what order life evolved in (so single celled -->multicellular, prokaryotes-->eukaryotes
4. Not that I'm aware of.
5. Reduced genetic diversity and associated consequences for natural selection, 'playing god', effects on other people (so if a kid has a hereditary disease e.g. huntingtons, do you tell the parents they also have it?),
6. Stealing this answer yet again
The 'scientific knowledge' is the tests below.

There are actually a few ways to identify a pathogen (bacteria or virus, in this case)
Bacteria:
- agglutination test (with specific antibodies)
- precipitation test (to see if a bacterial colony precipitates in the blood of an infected person)
- Western blot test (used to separate and identify proteins specific to a bacteria)
- ELISA (enzyme-linked immunosorbent assay, which is used to detect and count substances such as antibodies, hormones, enzymes and antigens, which indicates the type of bacteria we might be looking for)

Virus (these things are smaller, so we have to use more precise techniques to kinda sort them out)
- ELISA
- X-ray crystallography (which is used to determine the atomic and molecular structure of crystals, can be used to identify viruses of specific shapes and sizes)
- Electron microscope (these things let you see really small things so you can see viruses with this)

How could the same genetic sequence produce different proteins?

Most likely alternative splicing (there are other ways but that's the one in VCE)

Do we need to know about light chains and heavy chains and parts of an antibody for the exam, cos I haven’t really learnt much about that at all 

You need to be able to draw and label an antibody (light chains, heavy chains, variable region, constant region, disulphide bridges, antigen binding sites)

Ughhh, my images aren’t passing security checks... what do I do?
The other times when I upload images I literally have to compress the image with an app, save to photos, upload to ‘files’, then upload onto here... how do I skip the hassle no an iPad??

And now the pics are getting rejected 

Easiest way is probably to upload them to an image sharing site like imgur then click the little drop down arrow on the top right (on the web version, doesn't seem to work properly on the app) then click 'get share links' and copy the one that says BB code and paste it into here.

[C14M8S]

1) What is the 'functional importance' of the four levels of protein structure aside from tertiary and quartenary proteins actually doing things?
2) What's the difference between RNA processing and transcription? Would I just refer to the post-transcriptional modifications as RNA processing?
3) How does temperature affect the rate of photosynthesis? I've heard mixed things about this.
4) Where do pheromones originate from usually (i.e what glands)?