VCE Biology Question Thread

[vox nihili]

I don't get it. African populations have the most variations in their mtDNA sure, but why does that suggest the out of africa theory? So you are saying that because african populations have the most variation/mutations that have accumulated in their mtDNA, they have existed for a longer time because as time proceeds, mtDNA mutates at a known rate? I get this part, but could you relate this fact with the other populations in the world? What, do other populations in the world, say Australia, have less mutations accumulated in their mtDNA suggesting they have been around for a less amount of time? But did not we all diverge from Homo Sapiens in Africa? So wouldn't this mean we all initially had the same mtDNA? Not sure...

You've essentially got all of the facts right there.

There is more variation in the mtDNA of African populations because they've had a longer time to diverge. In Europe, for instance, there is les variation because they've had less time to diverge. Simple as that.

[BakedDwarf]

Do cytotoxic T cells only destroy virus-infected cells? Or can they destroy cells infected by any pathogen?

We don't need to know anything about tropisms... Right?

[cosine]

Do cytotoxic T cells only destroy virus-infected cells? Or can they destroy cells infected by any pathogen?

We don't need to know any thing about tropism/s. Right?

Only virally infected cells, or other cells that possess non-self antigens on MHC I markers on their surface, in that case in autoimmune diseases, when self cells are recognised as non-self, organ transplanted cells and also cancerous cells.

Correct about the tropisms.

[grindr]

Simple MC question:
Answer is C.
Why is the structure including tertiary?
I thought some proteins didn't need to have a tertiary structure?

[BakedDwarf]

Simple MC question:
Answer is C.
Why is the structure including tertiary?
I thought some proteins didn't need to have a tertiary structure?

All proteins have a primary, secondary and tertiary structure, but may or may not have a quaternary structure (this is what my textbook says). This is because its tertiary structure is its overall 3D shape that determines its function. Logically, if it didn't have a 3D shape, the protein doesn't have a specific function and so is useless.


In the 2015 STAV exam, an MC question states
In vertebrates the pathway of a nervous impulse is in one direction only because:
A. (obviously wrong answer)
B. the action potential can only jump across the synapse in one direction
C. neurotransmitter receptors are only found on the post-synaptic membranes
D. (obviously wrong answer)

I reasoned that C cannot be the answer (hence circled B) because I thought neurotransmitter receptors are found in both post and pre synaptic membranes. This is because the receptors in the:
- postsynaptic membranes open up the sodium channels
- presynaptic membranes to prevent the release of further neurotransmitters

How is the answer A for the attached question below?

[heids]

In the 2015 STAV exam, an MC question states
In vertebrates the pathway of a nervous impulse is in one direction only because:
A. (obviously wrong answer)
B. the action potential can only jump across the synapse in one direction
C. neurotransmitter receptors are only found on the post-synaptic membranes
D. (obviously wrong answer)

I reasoned that C cannot be the answer (hence circled B) because I thought neurotransmitter receptors are found in both post and pre synaptic membranes. This is because the receptors in the:
- postsynaptic membranes open up the sodium channels
- presynaptic membranes to prevent the release of further neurotransmitters

Can't be B as the impulse can't 'jump', but needs neurotransmitters.  Are you suggesting that neurotransmitters bind to receptors on the presynaptic membrane to prevent release of further neurotransmitters?  I don't know if it's the case or not (my knowledge being fairly limited to the VCE course), but if it does happen you definitely don't have to know it at VCE level.

How is the answer A for the attached question below?

It says that yellow offspring won't be viable - won't survive to maturity due to not enough chloroplasts, so that one quarter is eliminated and thus A.  Make sense?

[grindr]

All proteins have a primary, secondary and tertiary structure, but may or may not have a quaternary structure (this is what my textbook says). This is because its tertiary structure is its overall 3D shape that determines its function. Logically, if it didn't have a 3D shape, the protein doesn't have a specific function and so is useless.


In the 2015 STAV exam, an MC question states
In vertebrates the pathway of a nervous impulse is in one direction only because:
A. (obviously wrong answer)
B. the action potential can only jump across the synapse in one direction
C. neurotransmitter receptors are only found on the post-synaptic membranes
D. (obviously wrong answer)

I reasoned that C cannot be the answer (hence circled B) because I thought neurotransmitter receptors are found in both post and pre synaptic membranes. This is because the receptors in the:
- postsynaptic membranes open up the sodium channels
- presynaptic membranes to prevent the release of further neurotransmitters

How is the answer A for the attached question below?

thanks

[BakedDwarf]

It says that yellow offspring won't be viable - won't survive to maturity due to not enough chloroplasts, so that one quarter is eliminated and thus A.  Make sense?

But the ratio doesn't make sense. It should be 1/3 dark green: 2/3 light green: 0 yellow

Unless i'm interpreting it wrong?

[heids]

But the ratio doesn't make sense. It should be 1/3 dark green: 2/3 light green: 0 yellow

Unless i'm interpreting it wrong?

No, you are, I just blindly thought you didn't get why it wasn't B (since that was what you'd circled) and didn't even read the answer properly... *facepalms*  You're right, they've made a mistake.

[Biology24123]

What is the answer to this?

[heids]

What is the answer to this?

My assumption would be B, because that doesn't suggest that the bacteria enter people (C and D are clearly not right, as they're about fluids containing the bacteria being taken in to the body, so it's down to A or B).  You can touch an animal without anything actually getting inside you (lol it doesn't even say that the animals are sick anyway), whereas when a flea bites you the bacteria might get into your body fluids.

Super poorly worded explanation, but hope you get the gist.

[Biology24123]

My assumption would be B, because that doesn't suggest that the bacteria enter people (C and D are clearly not right, as they're about fluids containing the bacteria being taken in to the body, so it's down to A or B).  You can touch an animal without anything actually getting inside you (lol it doesn't even say that the animals are sick anyway), whereas when a flea bites you the bacteria might get into your body fluids.

Super poorly worded explanation, but hope you get the gist.

I said B as well but the answers say D

[pi]

What is the answer to this?

Do you think people shared needles in the 14th century? It's really a logic question.

[Sine]

I said B as well but the answers say D

It's D because it states rapid transmission, sharing needles is not an efficient way of propagation for the bacterium.

EDIT: Also what pi said XD

[Biology24123]

Do you think people shared needles in the 14th century? It's really a logic question.

What a horrible question.