VCE Biology Question Thread

[solution]

Does phospholipid bilayer refer to the plasma membrane, or just the phospholipids of the membrane?

Will this answer gain full marks? "What structural properties of the phospholipid bilayer enables it to carry out its function?" 2 marks

Phospholipids have a hydrophobic head and hydrophobic tail, allowing small hydrophobic molecules to pass through the phospholipids. The bilayer contains transport proteins allowing hydrophilic molecules to pass through the plasma membrane.

[gameboy99]

Does phospholipid bilayer refer to the plasma membrane, or just the phospholipids of the membrane?

Will this answer gain full marks? "What structural properties of the phospholipid bilayer enables it to carry out its function?" 2 marks

Phospholipids have a hydrophobic head and hydrophobic tail, allowing small hydrophobic molecules to pass through the phospholipids. The bilayer contains transport proteins allowing hydrophilic molecules to pass through the plasma membrane.

1. Correct...phospholipid bilayer refers to plasma membrane
2. Phospholipids have hydrophillic heads and hydrophobic tails (you've got it the other way around). You could also add that due to the hydrophillic head and hydrophobic tail, the phospholipid bilayer is impermeable to water-soluble molecules or permeable to lipid-based molecules

[QueenSmarty]

Hey everyone

Do we need to know about the negative feedback loop and the reflex arc response for the exam? It's not on the study design but a practice exam from Engage Education (from the current study design) involves it, so I'm really confused now. Thank you in advance!

[solution]

1. Correct...phospholipid bilayer refers to plasma membrane
2. Phospholipids have hydrophillic heads and hydrophobic tails (you've got it the other way around). You could also add that due to the hydrophillic head and hydrophobic tail, the phospholipid bilayer is impermeable to water-soluble molecules or permeable to lipid-based molecules

Thank you. Would it be necessary to explain how polar molecules can use carrier/channel proteins to pass through the membrane (or is it not necessary, as it is just asking for the "phospholipid bilayer")

[gameboy99]

Thank you. Would it be necessary to explain how polar molecules can use carrier/channel proteins to pass through the membrane (or is it not necessary, as it is just asking for the "phospholipid bilayer")

You could but in my opinion, it is unnecessary. 

[fionayu13]

Hey everyone

Do we need to know about the negative feedback loop and the reflex arc response for the exam? It's not on the study design but a practice exam from Engage Education (from the current study design) involves it, so I'm really confused now. Thank you in advance!

I am pretty sure we do not need to known anything to do with negative feedback loop as homeostasis has been taken off the study design.
If you check the biology faq document uploaded by vcaa http://www.vcaa.vic.edu.au/documents/vce/biology/biology-faqs.doc

one of the paragraph written on it follows:
Question: To what extent does homeostasis need to be covered in Unit 3?
Answer: In Unit 3, coordination and regulation are considered at the cellular, rather than whole organism, level. Hence, references to homeostasis and feedback mechanisms have been deleted from Unit 3. The treatment of homeostasis at a systems level, including feedback mechanisms, involving hormonal control (for example, regulation of blood glucose), water balance and temperature control, is included in Unit 2 Biology.

Hope this helps

[vasuk]

Could I have some help with the hypersensitivity reaction:

Question on practice exam:
There are 2 types of immune responses: innate and adaptive. Is hypersensitivity part of the adaptive or innate immune system?

Answer:
Hypersensitivity is an innate immune response because the response to an antigen is caused by the release of histamines. The release of histamine will be the same in each case.

I understand this, but the sensitising of mast cells comes from the production of specific antibodies against the allergen, so is the sensitising part of the process not included when the question talks about the 'hypersensitivity reaction'?

thank you

[solution]

Could I have some help with the hypersensitivity reaction:

Question on practice exam:
There are 2 types of immune responses: innate and adaptive. Is hypersensitivity part of the adaptive or innate immune system?

Answer:
Hypersensitivity is an innate immune response because the response to an antigen is caused by the release of histamines. The release of histamine will be the same in each case.

I understand this, but the sensitising of mast cells comes from the production of specific antibodies against the allergen, so is the sensitising part of the process not included when the question talks about the 'hypersensitivity reaction'?

thank you

I think your answer is correct, it should be both innate (for release of histamines to cause inflammation) and adaptive (due to the presence of specific antibodies on mast cells surface). Just wondering, what practice exam is this from?

[vasuk]

I think your answer is correct, it should be both innate (for release of histamines to cause inflammation) and adaptive (due to the presence of specific antibodies on mast cells surface). Just wondering, what practice exam is this from?

A TSSM practice exam from 2013. Thank you, I was unsure if I was correct or not!

[QueenSmarty]

I am pretty sure we do not need to known anything to do with negative feedback loop as homeostasis has been taken off the study design.
If you check the biology faq document uploaded by vcaa http://www.vcaa.vic.edu.au/documents/vce/biology/biology-faqs.doc

one of the paragraph written on it follows:
Question: To what extent does homeostasis need to be covered in Unit 3?
Answer: In Unit 3, coordination and regulation are considered at the cellular, rather than whole organism, level. Hence, references to homeostasis and feedback mechanisms have been deleted from Unit 3. The treatment of homeostasis at a systems level, including feedback mechanisms, involving hormonal control (for example, regulation of blood glucose), water balance and temperature control, is included in Unit 2 Biology.

Hope this helps

Thank you!!

[Gogo14]

Some qs im having trouble with.
For question 100, why is the answer not c?
Doesn't P being in the fossil record later imply that P is older than R which correlates to the graph?


For the pig question,
I don't even know whats going on someone please explain

http://imgur.com/YCuhrRa
http://imgur.com/XJgSZhd

[lasagne]

Some qs im having trouble with.
For question 100, why is the answer not c?
Doesn't P being in the fossil record later imply that P is older than R which correlates to the graph?
For the pig question,
I don't even know whats going on someone please explain
http://imgur.com/YCuhrRa
http://imgur.com/XJgSZhd

I already answered the pig question so hereee
2009 MC, Q7    C
Meisham sows must be mated with British males in order to have enough teats to account for all piglets, ie, up to 18; If it were the other way around, there would only be 12 teats between 11-16 piglets. Without a teat, some piglets would die
+ The British already have the smaller sized litters and the Chinese already have the larger sized litters.

2008 MC, Q24   
Since species Q and R diverged from species P, species P is older (as seen on the graph). Therefore P would appear in the fossil record earlier. Species Q and R diverged most likely through allopatric speciation and thats why the answer is D.

[AhNeon]

Alright so for exam 2 2012 question 7a
My answer was:
-Different species could have different alleles in their gene pools
-Different Alleles, being alternative forms of the same gene, would cause variation concerning the same genes.
Now im not sure if this would be awarded any of the 2 marks for the question considering the examination report mentions none of this, but since the report are suggested solutions and not the only ones excepted i want a second opinion
Thanks guys

[solution]

Does "denaturation" mean when a reaction does not occur anymore (reaction rate is = 0) or is it the temperature range past the optimum that the reaction rate starts to fall? I thought it was the former, but apparently it's the latter?

[Angelx001]

Can someone please attach a photo of a "labelled diagram to outline the process of DNA replication" (from 2012 bio exam 2- question 4). Thanks!