VCE Biology Question Thread

[vox nihili]

Yes, if something is water soluble, then it means that it is lipid insoluble. I also do chemistry so I think of it as functional groups. If a molecule has many OH- groups, it only means that is is soluble in water.
Ummm, not quite sure about your other question. I would say no.... but could someone please correct me.
Hope this helps

This works as a rule of thumb, though as lzxnl has pointed out, isn't always correct.

[nubs]

I'd have to disagree with Rishi97. A compound can be both lipid and water soluble.
Like Izxnl has said, solubility is a spectrum
i.e different compounds will show varying levels of hydro/lipophilicity

A compound may have many -OH groups, allowing it to form many hydrogen bonds with water, but if it has a large carbon backbone it could also be very lipid soluble. It's not always one or the other

[ravi2]

Hey guys,
Is serotonin involved in inflammation? Because Nature of Biology says so, and that serotonin causes the dilation of arterioles. But another book (Biol Notes) says that serotonin is used in blood clotting, as it constricts the vessels. This is quite confusing...

[nubs]

It's important to note that serotonin, like all neurotransmitters and hormones, act on many different subtypes of receptors.
Although serotonin binds to its serotonin receptors, there are many different kinds of serotonin receptors, each evoking a different response when activated by serotonin.

Whether the serotonin causes vasodilatation or vasoconstriction depends on the type of receptor serotonin is binding to.

Does that help?

[ravi2]

It's important to note that serotonin, like all neurotransmitters and hormones, act on many different subtypes of receptors.
Although serotonin binds to its serotonin receptors, there are many different kinds of serotonin receptors, each evoking a different response when activated by serotonin.

Whether the serotonin causes vasodilatation or vasoconstriction depends on the type of receptor serotonin is binding to.

Does that help?

yes that explains it well. thank you!
so does that basically mean that all serotonin receptors have the same shape but some have different responses when serotonin binds with it? or are the receptors similar to enzymes according to the "induced fit model" in which they can adjust their shape to bind with the signalling molecule to initiate the response?

[nubs]

Without overcomplicating things, you can go ahead and assume that all the serotonin receptor subtypes have a 'similar' shape.

There is also an 'induced fit' like model, but for receptors. It says that a ligand will bind to a receptor and cause it to change its conformation into an active state.

We aren't really sure if the ligand makes the receptor change its shape, or if the receptor's shape has been changed before the ligand binds. To answer your question though, it doesn't matter if it's one or the other, or if it's somewhere in between. What matters is that different serotonin receptor subtypes are 'linked' or coupled to different types of 'machinery' which elicit different responses.

[MM1]

What commercial exam papers are the hardest/easiest?

[ravi2]

What commercial exam papers are the hardest/easiest?

in my opinion, stav is the hardest. neap and insight are kind of on par, butthey are just behind stav in difficulty imo. And to be honest, I would not say that any company paper is easy haha...
but i guess everyone has their own opinion

[alchemy]

What commercial exam papers are the hardest/easiest?

lisachem is really easy, just sayin'
I haven't tried any others so I might be biased xP

[Jason12]

Is it true that T and B cells are made in bone marrow but then T cells mature in thymus but b cells mature in bone marrow?

[Rishi97]

Is it true that T and B cells are made in bone marrow but then T cells mature in thymus but b cells mature in bone marrow?

Yeppp... remember T stands for thymus 

[ravi2]

I just want to clarify that after an immune response, there will still be some antibodies circulating the system despite most of it being broken down? Or are all antibodies produced by plasma cells at the time of infection broken down and just the memory cells remain? 

[Scooby]

I just want to clarify that after an immune response, there will still be some antibodies circulating the system despite most of it being broken down? Or are all antibodies produced by plasma cells at the time of infection broken down and just the memory cells remain?

Yeah, some antibodies specific to the antigen will remain in circulation after the infection is gone (with the concentration gradually reducing over time)

[Rishi97]

Binary fission in bacteria occurs very quickly with new cells being produced in as little as 20 minutes. Starting with a single bacterial cell and assuming 20 minutes per generation, how many cells would be expected to be present after 3 hours (180 minutes): that is, after 9 binary fission events?

Since when does maths come into biology??? 

What is the best way to approach this? I don't want to spend too much time drawing in each replication

[nhmn0301]

Binary fission in bacteria occurs very quickly with new cells being produced in as little as 20 minutes. Starting with a single bacterial cell and assuming 20 minutes per generation, how many cells would be expected to be present after 3 hours (180 minutes): that is, after 9 binary fission events?

Since when does maths come into biology??? 

What is the best way to approach this? I don't want to spend too much time drawing in each replication

So just realise that after 1 binary fission, you got 2 genetically identical cells. Hence, after 1 more binary fission, you got 4, and then after the next binary fission, you got 8 => this is an exponential growth (can't believe I bring Methods in -,-)
Hence, after 9 binary fission, you got 2^9, which is 512 cells.