VCE Biology Question Thread

[cosine]

Energy does not just dissipate, it needs to be used. If the energy released during the electron transport chain is not used in phosphorylation, what will happen to the energy?

I said the energy will be lost as heat energy, as the conversion of energy in the form of ATP is not 100% efficient. Is this correct? Also when it says not used in phosphorylation, this means the attachment of the Pi to the ADP, right ?

Thanks!

[EspoirTron]

Energy does not just dissipate, it needs to be used. If the energy released during the electron transport chain is not used in phosphorylation, what will happen to the energy?

I said the energy will be lost as heat energy, as the conversion of energy in the form of ATP is not 100% efficient. Is this correct? Also when it says not used in phosphorylation, this means the attachment of the Pi to the ADP, right ?

Thanks!

Yes it is dissipated as heat energy and this is used as essentially an internal source of heat for the body. And yes, the conversion is relatively inefficient.

Yeah and you're right in the latter too.

[aejays]

What's a possible reason for why more wheat seeds germinate at higher salt concentrations than spinach seeds?

[kimmytaaa]

Hi guys
I just wanted to know if anyone has done a sac on homeostatic (response) where they either drank coffee. What do I have to know about homeostatic?
thanks

[sushibun]

Do all leukocytes have MHC 2 markers?

[grannysmith]

What's a possible reason for why more wheat seeds germinate at higher salt concentrations than spinach seeds?

Wheat seeds may need less water to germinate as compared to spinach seeds.

Do all leukocytes have MHC 2 markers?

Not all - only the antigen-presenting cells (APCs): macrophages, dendritic cells, B-cells (some). In essence, MHC 2 markers are what display the foreign antigens (in what is known as an antigen-MHC complex) which are then 'presented' to T-cells.

[vanessa14]

Hey guys, has anyone done the SAC on coordination and regulation?
Im so confused...  Something to do with the stimulus?
I still don't fully understand signal transduction and hormones... the text book definitions are so confusing.

[TheAspiringDoc]

Wheat seeds may need less water to germinate as compared to spinach seeds.

This involves osmosis right?

[cosine]

Hey guys, has anyone done the SAC on coordination and regulation?
Im so confused...  Something to do with the stimulus?
I still don't fully understand signal transduction and hormones... the text book definitions are so confusing.

Hey vanessa14

I can give you a quick run down on hormones and signal transduction but I still haven't done the SAC for it yet. Hormones are basically chemical messengers in the body that are secreted/released (meaning specific glands produce them and release them) into the blood stream. Once in the blood stream, each hormone has a specific target cell that it needs to communicate with so that the stimulus can be regulated. This hormone molecule will travel through the bloodstream, passing many cells on its journey until it reaches its specific target tissue of cell. The hormone molecule then binds to its specific receptor, which has a complementary shape to the molecule, so that not any hormone can bind but only that specific one. Now, there can be intercellular receptors (called cytoplasmic receptors) or receptors in the cell membrane (called transmembrane receptors). Now from your studies in AOS1, you should know that the cell membrane is semi-permeable to only certain molecules, this means that lipid-soluble (lipophillic/hydrophobic) hormones can DIRECTLY diffuse through the membrane, so their specific receptors are inside the cell. But we have protein-based hormones, and we know that proteins are hydrophilic, so their chemical nature restricts them from diffusing through the membrane, so how will they communicate to the cell? Well, they bind to a receptor that's om the cell surface, and the message is related from there. So now that the hormone-receptor complex has been formed (a hormone has binded to its receptor), a series of chemical reactions occur where the message being communicated is related among other molecules. You do not need to know the specifics to the signal transduction pathways (beyond VCE levels). The end of the signal transduction pathway basically determines the cells response. The cells response can anything from producing new enzymes that will break down other molecules or even enzymes that bind molecules together! This is the cells response, it RECIEVED the message, it TRANSDUCTED the message, and then it RESPONDED to it. Obviously once the response has been carried out, the original hormone or one of the signalling molecules must be broken down so that the response can be regulated to prevent an over-stimulation!

I hope that helped, good luck with your SAC!

[TheAspiringDoc]

travel through the bloodstream, passing many cells on its journey until it reaches its specific target tissue of cell. 

Very nice explanation cosine, although I think it might be more appropriate to think of the hormones as bouncing off the other non-target cells on its way to its target cell as the hormone does attempt to interact with them but it kinda gets rejected or something when they 'realise' they aren't the right 'fit' for eachother and that the cell isn't the target cell. It's kinda like you've got a big tub of marbles, except one of them is metal - when you drop a magnet into the tub and shake everything around the magnet still touches the glass marbles but it only binds with the iron marble?

[cosine]

Very nice explanation cosine, although I think it might be more appropriate to think of the hormones as bouncing off the other non-target cells on its way to its target cell as the hormone does attempt to interact with them but it kinda gets rejected or something when they 'realise' they aren't the right 'fit' for eachother and that the cell isn't the target cell. It's kinda like you've got a big tub of marbles, except one of them is metal - when you drop a magnet into the tub and shake everything around the magnet still touches the glass marbles but it only binds with the iron marble?

My emphasis on 'complementary to its specific receptor' should have sufficed, but yet again there's many ways to explain it!

[grannysmith]

Very nice explanation cosine, although I think it might be more appropriate to think of the hormones as bouncing off the other non-target cells on its way to its target cell as the hormone does attempt to interact with them but it kinda gets rejected or something when they 'realise' they aren't the right 'fit' for eachother and that the cell isn't the target cell. It's kinda like you've got a big tub of marbles, except one of them is metal - when you drop a magnet into the tub and shake everything around the magnet still touches the glass marbles but it only binds with the iron marble?

Haha that's an interesting way of thinking about it. I don't think hormones actually attempt to interact with cells (unless we want to personify them); rather, they move relative to the fluid in which they are in. They only 'interact' with cells which have the specific receptors to which the hormone can bind. If you think about it, a hormone may not even reach a target cell - the magnet analogy is good, however hormones aren't attracted to their target cells in the same way opposite charges attract. And even if it did reach its target cell, it may not even get close enough to the receptor and so it doesn't get the chance to bind. This is obviously not something you'd be tested on but it's interesting to think about nonetheless

This involves osmosis right?

Yep, it would.

[tiff_tiff]

1) what types of 'materials' are required to make a red blood cell from a stem cell?

is it like haemoglobin, i'm not sure.
i find it weird how a whole bunch of different blood cells types can be made from the myeloid lineage. Always thought it was just random, not sure how it will turn into red blood cells as opposed to white blood cells for example.

2) What is an example of a colony stimulating factor?
I know colony stimulating factors are glycoproteins used to stimulate the production of white blood cells, but I can't find any examples for them!

help please

[StupidProdigy]

How would coffee affect reaction times and what would the role of homeostasis be in caffeine consumption?? Thanks!

[cosine]

Do we need to know anything about plant regulators for the exam?

Also I have a few questions about the nervous system:
1). Do motor neurones directly target cells, or do they target muscles/glands ?
2). Do we need to know what depolarisation is in terms of action potentials?
3). Do we need to know what occurs (the chemical intakes/outputs) when an action potential is travelling through an axon?
4). Do microorganisms have the nervous system?

Cheers guys xD