VCE Biology Question Thread

[PhoenixxFire]

1. correct me if I'm wrong, but I think the 2013-2016 exams were out of 220 marks, indicating a significantly lower A+ cutoff last year (79%) compared to 2016's 85%

Got a couple of questions from VCAA 2017:

2. Is the reason chloroplasts have double membranes due to the outer membrane arising from endocytosis, or due to cyanobacteria having double membranes themselves? Seen differing views of this in the textbook and online
On MCQ 12 one of the incorrect options was that chloroplast and bacteria "store chlorophyll in their outer membrane".
Not sure if the reason it's incorrect is because the bacteria don't have an outer membrane or because they store chlorophyll in their inner membrane.

3. In the 2017 exam for the question (9c) about selection of bacterial cells which have been successfully transformed, I noticed the solutions didn't say anything about the tetracycline gene being disrupted as a method for selecting bacteria (which have taken up the recombinant plasmids (containing the foreign gene), rather than just any plasmids. Would we just have to interpret the question as implying that ALL of the plasmids being inserted are recombinant?

1. Yep you're right. Not something I ever realised haha. I actually wrote out a different response to that, but then I looked at the grade distributions and thought they were the same. It's fairly likely that the cutoff will go up this year now that people know what the new format looks like.

2. It's from endocytosis. That's one of the things that is used as evidence of the endosymbiotic theory.

3. Yeah given they've said in the question that they made plasmids with the inserted human gene, they're just asking about how to identify which bacteria took up the plasmids.

If I a question asks why there’s a great genetic variation in African than non-African populations, could we say that since Homo Sapiens migrated out of Africa, they could have been subject to the founders effect, hence having a low genetic diversity, whereas the Homo Sapiens in Africa were not? How else could I go about answering this?

Yeah, it's an example of founders effect. If you get a question on that worth more than 1 mark, make sure you say what the founders effect is (that all the individuals evolved from a limited gene pool etc.)

[EllingtonFeint]

Question 6
Plants growing in soil with low levels of nitrogen may be unable to produce sufficient molecules of
A. ribonucleic acids.
B. triglycerides.
C. cellulose.
D. sucrose.

The answer is a.
But is this relevant to the current study design?

-Are autoantibodies relevant currently also?

-do we need to know about feedback mechanisms?

[PhoenixxFire]

1. Question 6
Plants growing in soil with low levels of nitrogen may be unable to produce sufficient molecules of
A. ribonucleic acids.
B. triglycerides.
C. cellulose.
D. sucrose.

The answer is a.
But is this relevant to the current study design?

2. -Are autoantibodies relevant currently also?

1. Yep it’s relevant. It’s just asking you to recognise that RNA has a nitrogenous base.

2. Yep. You don’t need to know them in detail, just know that they play a role in autoimmune disorders.

[EllingtonFeint]

1. Yep it’s relevant. It’s just asking you to recognise that RNA has a nitrogenous base.

2. Yep. You don’t need to know them in detail, just know that they play a role in autoimmune disorders.

So pretty much just antibodies that attack self antigens?

And are the feedback mechanisms relevant for this exam?

[PhoenixxFire]

1. So pretty much just antibodies that attack self antigens?

2. And are the feedback mechanisms relevant for this exam?

1. Yep

2. If you mean things like maintaining homeostasis etc then no. You do need to know the stimulus - response model, but only in relation to signal transduction.

[EllingtonFeint]

So ATP is made from ADP + P and also sunlight as an original source of energy, true?
What other sources of energy help in this reaction in different cells (like animal cells)...? Does that make sense?  I think I’m just confused cos the 2012 diagram was probably photosynthesis and not cellular respiration.


Also any difference between MHC Class I and Class II molecules?

[Sine]

So ATP is made from ADP + P and also sunlight as an original source of energy, true?
What other sources of energy help in this reaction in different cells (like animal cells)...? Does that make sense?  I think I’m just confused cos the 2012 diagram was probably photosynthesis and not cellular respiration.


Also any difference between MHC Class I and Class II molecules?

Yes sunlight is the primary source of energy for photosynthesis (as per 2012 sunlight is the "original' source). It is really mainly important to know the main inputs and outputs of photosynthesis along with the site that this occurs.

MHC I - are on all nucleated cells (basically all cells except mature RBCs)
MHC II - are on APCs (antigen presenting cells)

[EllingtonFeint]

Could the difference in protein production between two different cells be explained by regulatory genes?

[PhoenixxFire]

Could the difference in protein production between two different cells be explained by regulatory genes?

Yes, but it’s not in the VCE study design so just stick with either different transduction pathways or alternative splicing (depending on the question)

[Robot10]

Here are a few Qns I have

1. Is chlorophyll a pigment containing enzymes or a protein embedded in the thylakoid membrane?

2. With the peptide bond, is it the bond between the Carbon of one amino acid and Nitrogen of the next amino acid?
A solution to an exam paper circled the Carbon double bonded to Oxygen along with the Carbon bonded to Nitrogen as being the peptide bond.

3. For a particular qn, it asked for the impact of using a large sample size.

The answer was that Increasing sample size increases validity of results, but I thought a large sample size increases reliability.

  4. When the Lac repressor is bound to the operator, is it true that RNA polymerase cannot bind to the promoter or can it bind but not move forward and transcribe the structural genes due to the repressor protein?
Thanks

[sophiie]

the purpose of lymph nodes?
do they help filter lymph fluid and are they site of antigen-presenting cells

[Robot10]

the purpose of lymph nodes?
do they help filter lymph fluid and are they site of antigen-presenting cells

Yes and Lymph nodes are also the site of clonal selection and clonal expansion.

[EllingtonFeint]

Do we need to know about continuous and discontinuous variation?


Do we also need to know DNA replication? Like drawing it, identifying all stages and about Okazaki fragments?

[Ellyjayne27Ellyjayne2]

Does anyone have a list of all the possible techniques used to determine relatedness between species? Eg. gel electrophoresis

[EllingtonFeint]

Does anyone have a list of all the possible techniques used to determine relatedness between species? Eg. gel electrophoresis

There are also molecular homology, DNA hybridisation and molecular clock, I think