VCE Biology Question Thread

[juntyhee]

Does the memory B cell immediately undergo clonal expansion after re-exposure to the same antigen? Or are they required to be activated by a Helper T cell? If so, how is this process faster than primary exposure?

[PhoenixxFire]

Does the memory B cell immediately undergo clonal expansion after re-exposure to the same antigen? Or are they required to be activated by a Helper T cell? If so, how is this process faster than primary exposure?

I’m not entirely sure if they require Th cell activation, from what I’ve read some do and some don’t.

If so it would still be faster simply because there’s more memory B cells. In the initial reaction there is only one naive B cell with the correct antigen specificity. More B cells with the correct specificity and more Th cells with the correct specificity means both would be activated faster, and would find each other faster.

[Monkeymafia]

The solutions for a prac exam say that, for the relationship between carbs, nucleic acids and proteins in synthesis of DNA polymerase, that RNA polymerase and other enzymes (respiratory enzymes) facilitate the joining of amino acids to form DNA polymerase.

Is this correct, as I thought only RNA polymerase is involved transcription and that no enzymes are involved in condensation?

[vox nihili]

The solutions for a prac exam say that, for the relationship between carbs, nucleic acids and proteins in synthesis of DNA polymerase, that RNA polymerase and other enzymes (respiratory enzymes) facilitate the joining of amino acids to form DNA polymerase.

Is this correct, as I thought only RNA polymerase is involved transcription and that no enzymes are involved in condensation?

Can you please quote the answer verbatim? I'm a bit hesitant to say what you've said (the first part at least) is correct. Enzymes are involved in the production of all biomacromolecules though.


RNA polymerase would be involved in the production of DNA polymerase (but not DNA).

[PopcornTime]

Can you please quote the answer verbatim? I'm a bit hesitant to say what you've said (the first part at least) is correct. Enzymes are involved in the production of all biomacromolecules though.


RNA polymerase would be involved in the production of DNA polymerase (but not DNA).

The exact question was: "Describe how carbohydrates, nucleic acids and proteins interact within a cell to form DNA polymerase."

And the solutions were:
"Carbohydrates, such as glucose provide the chemical potential energy that, via cell respiration, provides the ATP required for endergonic reactions such as protein synthesis.
Nucleic acids, such as the gene for DNA polymerase, provide the blueprint for the transcription (formation of mRNA) of the gene.
Proteins, such as RNA polymerase and other enzymes (respiratory enzymes) are required to facilitate the joining of amino acids to form the DNA polymerase."

Not sure about the wording of RNA polymerase facilitating the joining of amino acids to form the DNA polymerase.

[Monkeymafia]

Is this response ok for outline process of cell mediated immunity?

- APC engulfs pathogeb, processes it and displays antigenic fragments on mhc2 markers
- t helper cell binds to antigenic fragmrntd and secretes cytokined to have tc cells multiply
- tc cells produce granules that lyse pathogen membrane

[juntyhee]

The exact question was: "Describe how carbohydrates, nucleic acids and proteins interact within a cell to form DNA polymerase."

And the solutions were:
"Carbohydrates, such as glucose provide the chemical potential energy that, via cell respiration, provides the ATP required for endergonic reactions such as protein synthesis.
Nucleic acids, such as the gene for DNA polymerase, provide the blueprint for the transcription (formation of mRNA) of the gene.
Proteins, such as RNA polymerase and other enzymes (respiratory enzymes) are required to facilitate the joining of amino acids to form the DNA polymerase."

Not sure about the wording of RNA polymerase facilitating the joining of amino acids to form the DNA polymerase.

What exam is that from?

[PopcornTime]

Would anyone be able to confirm, based on past experience, whether unit 3 or 4 is more heavily tested on the exam?

[vox nihili]

Would anyone be able to confirm, based on past experience, whether unit 3 or 4 is more heavily tested on the exam?

They get an equal showing on the exam, but unit 3 SACs are worth more

[darkz]

They get an equal showing on the exam, but unit 3 SACs are worth more

I thought Unit 3 SACs were 16%, Unit 4 SACs 24% and Exam 60%?

[vox nihili]

I thought Unit 3 SACs were 16%, Unit 4 SACs 24% and Exam 60%?

Good pick up, got them mixed up!

[PhoenixxFire]

I thought Unit 3 SACs were 16%, Unit 4 SACs 24% and Exam 60%?

Also worth noting that whilst U4 is worth more, each area of study is worth the same amount (U3 has 2 AOS, U4 has 3 AOS)

[PhoenixxFire]

Is this response ok for outline process of cell mediated immunity?

- APC engulfs pathogeb, processes it and displays antigenic fragments on mhc2 markers This does happen, but you should talk about it in humoral immunity not cell mediated.
- t helper cell binds to antigenic fragmrntd and secretes cytokined to have tc cells multiply Yes, but the Tc cell needs to have bound to its antigen on MHC1 for it to multiply
- tc cells produce granuleszymes that lyse pathogen membrane The pathogen doesn't have a membrane - it's in a cell. It also doesn't lyse the membrane, although complement proteins do lyse bacterial membranes in innate immumity. It induces apoptosis - if it lysed membranes it would trigger inflammatory responses throughout the body and that would be a mess!

You've combined elements of several immunity processes here.

When talking about cell mediated immunity you should just talk about it, not humoral immunity (unless the question also asks for humoral immunity.)
1. Tc cells attempt to bind to peptide fragments presented on MHC1 markers.
2. If a Tc cell can bind to a fragment, it indicates that that fragment is non-self. You should adapt this to the specific question you are asked, eg. due to a virus
3. This Tc cell is now selected and when cytokines are released from an activated Th cell it will proliferate and differentiate into memory Tc and active Tc cells.
4. The memory Tc cells will remain in the body to fight against subsequent infection by the same pathogen, the active Tc cells will travel throughout the body attempting to bind to peptide fragments presented on MHC1.
5. When they can bind they will release granzymes (including perforin) that induce apoptosis in the infected cell.

Hey everyone,

I performed quite poorly (55/75) on the Unit 3 practice exam I just completed and realised that my expression is terrible as in writing answers irrelevant to the question or unnecessary to be awarded a mark. How can I improve on this? I have no idea of where to even begin.

I lost a couple of marks on experimental design questions too. Are there any online resources I can read up on?
 
Have a great day all!

Are you aware when you're writing it that your answers are irrelevant or do you realise later?
If you're aware then you're probably doing it because you don't know the content as well as you should.

If not then you could try writing dot point answers(although I'm not a fan of them they do seem to help some people).

Go through any questions you have - start with easy ones that you know you know the answers too - it doesn't matter if they are textbook questions or past SACs or whatever. Answer them and then go through and cross out everything that you didn't need to include, ignoring how disjointed it makes your answer seem. Then answer them again just using the information that you didn't cross out.

Also try underlining or highlighting key words in your questions for example if your questions is:
1. Explain what happens to a pre-mRNA strand before it leaves the nucleus of a cell.

Then you would underline
1. Explain what happens to a pre-mRNA strand before it leaves the nucleus of a cell.

So that gives you your boundaries - the question only wants to know about the time period after transcription is finished to when it leaves the nucleus and it only wants to know about the pre-mRNA strand not anything else that's going on at the same time.
Don't try and explain everything around the question - just explain directly what it is asking you to explain.

[Scribe]

Could someone check if this is right?

eg.
[DNA] Coding/non-template strand - TAT GCT ATC AGC
[DNA] Template strand - ATA CGA TAG TCG
[mRNA] Complementary strand - UAU GCU AUC AGC
[tRNA] Anticodon strand - AUA CGA UAG UCG
Amino acids - ILE ARG STOP SER

[PhoenixxFire]

Could someone check if this is right?

eg.
[DNA] Coding/non-template strand - TAT GCT ATC AGC
[DNA] Template strand - ATA CGA TAG TCG
[mRNA] Complementary strand - UAU GCU AUC AGC
[tRNA] Anticodon strand - AUA CGA UAG UCG
Amino acids - ILE ARG STOP SER

The anticodon strand isn't actually a strand - its on the end of each tRNA molecule so they're not joined into a strand.

I think you've used your tRNA anticodon's to figure out what your amino acids are? The way (most) amino acid tables are drawn, you need to use your mRNA strand to work out the amino acids not the tRNA.

A group of 3 bases that codes for an amino acid is called a codon (hence tRNA being called an anticodon). Whatever table you are using to convert RNA into amino acids will probably say '1st base of codon' or somthing like that - that's how you know that you need to use mRNA to read it, if it says anticodon or triplet then you need to use tRNA/DNA.

so the amino acids would be
tyr-ala-ile-ser