VCE Biology Question Thread

[StupidProdigy]

Cheers grannysmith, appreciate it.

You know when the cell's response has been achieved, how does the response come to a stop? Is it that intracellular enzymes break down one of the signalling molecules of signal transduction, and how exactly does this affect the duration of the response?

It comes to a stop by switching the signal off via negative feedback or by breaking down a molecule in the signalling pathway

[Dkontro]

Question I came across in a practise exam

What advantage does an animal cell gain by converting pyruvate to lactic acid. Explain

Thanks

[grannysmith]

Question I came across in a practise exam

What advantage does an animal cell gain by converting pyruvate to lactic acid. Explain

Thanks

The conversion requires the oxidation of NADH to NAD+. In turn, the process frees up the number of NAD+ available to be used in glycolysis, so that this latter process can continue (not indefinitely, however). Recall that glycolysis produces a net of 2 ATP and 2 NADH per glucose (edit: also 2 pyruvate).

[Jay.C]

Hey guys I've got a few questions,

1. Why is there mitochondria in the axon terminal?
2. Why is a nervous signal fast?
3. What is the structure and function of acetylcholine?   

Thanks!
 

[grannysmith]

Hey guys I've got a few questions,

1. Why is there mitochondria in the axon terminal?
2. Why is a nervous signal fast?

Thanks!

1. The exocytosis of neurotransmitters into the synaptic cleft from the pre-synaptic membrane (which is the axon terminal) requires the expenditure of energy, being a form of active transport. Hence, mitochondria would be required as this is the site of aerobic respiration, which produces the energy in the form of ATP.

2. It's fast because it's electrical (and chemical)! The action potentials generated are electrical in nature, however remember the neurotransmitters involved are chemical.

Edit: you need not know it's structure or function - just know that it's an important neurotransmitter.

[Jay.C]

1. The exocytosis of neurotransmitters into the synaptic cleft from the pre-synaptic membrane (which is the axon terminal) requires the expenditure of energy, being a form of active transport. Hence, mitochondria would be required as this is the site of aerobic respiration, which produces the energy in the form of ATP.

2. It's fast because it's electrical (and chemical)! The action potentials generated are electrical in nature, however remember the neurotransmitters involved are chemical.

Thanks! Also what is the structure and function of acetylcholine?

[TheAspiringDoc]

Thanks! Also what is the structure and function of acetylcholine?

Structure - no idea
Function - Acetylcholine is a neurotransmitter produced by particular neurons called cholinergic neurons. Acetylcholine is the neurotransmitter responsible for skeletal muscle movement in the PNS and when it is fired/transmitted within cardiac tissue it slows down heart rate. I looked it up and it also said it's works as a neuromodulator in the CNS and works alongside other cholinergic neurons to form a neurotransmitter system.
Hopefully someone can add on though cos I'm not quite sure..? vzzzz

[vaish_vj]

heyy,
i recently did my detecting and responding SAC. in it we had to test planarian's response to touch and light. in one of the tests we had to place a black film canister and place it on the top of the cylinder and test the movement of the planaria. in the second test we placed the film canister on the top again and then inverted the cylinder. for both experiments the planaria moved up and down from the dark area to the clear area. also for the inverted cylinder the planaria moved to the darkside quicker. on the intro of the prac the sheet told us that planaria like the dark.

my question is why do the planaria like the dark? 
i investigate the question but i haven't been able to get an exact answer. can someone please help? thankyouu   

[Jay.C]

heyy,
i recently did my detecting and responding SAC. in it we had to test planarian's response to touch and light. in one of the tests we had to place a black film canister and place it on the top of the cylinder and test the movement of the planaria. in the second test we placed the film canister on the top again and then inverted the cylinder. for both experiments the planaria moved up and down from the dark area to the clear area. also for the inverted cylinder the planaria moved to the darkside quicker. on the intro of the prac the sheet told us that planaria like the dark.

my question is why do the planaria like the dark? 
i investigate the question but i haven't been able to get an exact answer. can someone please help? thankyouu   

The planaria are attracted to the dark because in there natural habitat the dark allows for them to hide from their predators.

[Sine]

On Friday I have got my SAC on Signalling molecules and Homeostasis. I was told that we would be first doing something with coffee, energy drinks and Coca Cola. Does anyone know what the practical consists of and what I should expect?

[warya]

My guess is that groups of you will drink the same amount of each drink and later assess the response your body has given to it (as they all contain caffiene which is a stimulant). Maybe you guys will run or something and see if you are faster after drinking, I think the main point though is that you are exposing your body to a stimulus and, as a consequence, your body will respond in some sort of way.

I had a SAC on this where we exposed bacteria to different antibiotics (change in external environment) and assessed whether or not they grew (response)

[cosine]

Few questions about hormone signalling:

1). When does signal transduction actually occur in both lipid soluble and water soluble hormones? Is it right after the reception of the hormone of water soluble, or is it right after the second messenger is activated?

2). What happens to the signalling molecule after the response has been carried out?

3). Hormones are secreted via the bloodstream, explain why the hormones do not bind to receptors to every cell they come across

4). What are the things called that produce/secrete hormones?

Thanks guys!

[sunshine98]

Few questions about hormone signalling:

1). When does signal transduction actually occur in both lipid soluble and water soluble hormones? Is it right after the reception of the hormone of water soluble, or is it right after the second messenger is activated?

2). What happens to the signalling molecule after the response has been carried out?

3). Hormones are secreted via the bloodstream, explain why the hormones do not bind to receptors to every cell they come across

4). What are the things called that produce/secrete hormones?

Thanks guys!

1)Signal transduction is the cascade of events that occur after a hormone binds to the receptor( including the reception of the hormone and the activation of the second messenger)
Not entirely sure about 2 and 3.
4) Glands(can be endocrine glands or exocrine glands)
Hope this is helpful 

[grannysmith]

2). What happens to the signalling molecule after the response has been carried out?

3). Hormones are secreted via the bloodstream, explain why the hormones do not bind to receptors to every cell they come across

2. It's either broken down or recycled.

3. Not all cells have the specific receptors to which a particular hormone can (only) bind to.

[cosine]

1)Signal transduction is the cascade of events that occur after a hormone binds to the receptor( including the reception of the hormone and the activation of the second messenger)
Not entirely sure about 2 and 3.
4) Glands(can be endocrine glands or exocrine glands)
Hope this is helpful 

Thanks guys!

Are you sure this part is part of signal transduction? Isn't this called reception?