VCE Biology Question Thread

[howlingwisdom]

Why is it that hormonal responses are generally more longer lasting than ones from the nervous system?

[thushan]

What is the name of the actual molecule that binds to a protein receptor on the membrane OR receptor in the cytosol to ultimately trigger the production of insulin?
This question has been in my head for a long time.

Glucose.

Why is it that hormonal responses are generally more longer lasting than ones from the nervous system?

The hormone remains in the blood for a significant period of time, whereas a neurotransmitter is either removed or broken down immediately after it is released and it acts.

[Blurple]

Hey our next SAC for Biology is on Responding to chemical signals. I'll be going to GTAC on the 5th of may which is about a week and a half away. Can anyone tell me the main things to know for this SAC? And things I should mostly be paying attention to at GTAC?

Thankss

[alchemy]

Name the plant hormone responsible for plant abscission. (VCAA 2011 E1, SB, Q3)
The answer is Ethylene. What???! I thought it was abscissic acid.

[MM1]

Name the plant hormone responsible for plant abscission. (VCAA 2011 E1, SB, Q3)
The answer is Ethylene. What???! I thought it was abscissic acid.

Ethylene increases the rate of cellular respiration which causes ripening. Once ripe, the fruit with fall and that's what abscission essentially refers to.
Abscisic acid also causes abscission, as well as seed dormancy and it inhibits germination. So ethylene would be the 'more correct' answer here, I guess. But I get where you're coming from.

[Rishi97]

Name the plant hormone responsible for plant abscission. (VCAA 2011 E1, SB, Q3)
The answer is Ethylene. What???! I thought it was abscissic acid.

The answers say that both ethylene and abscissic acid are accepted

[katiesaliba]

For an action potential to reach its threshold mark, roughly how much excitatory neurotransmitter is needed? Surely >50% of all received neurotransmitters? Sorry if this question is too ambiguous!

[vox nihili]

For an action potential to reach its threshold mark, roughly how much excitatory neurotransmitter is needed? Surely >50% of all received neurotransmitters? Sorry if this question is too ambiguous!

It depends on the particular cell. Wild variation between the various neurones.

[alchemy]

If an excitatory neuron and an inhibitory neuron meet at different dendrites of the same single post synaptic neuron:
A) the inhibitory neuron would have more of a chance of causing the action potential to occur
B) the excitatory neuron would have more of a chance of causing the action potential to occur
C) both neurons have the same chance of causing the action potential to occur

I found this question quite 'tricky' on my SAC as I thought that excitatory and inhibitory neurons cancel each other out when they meet at different dendrites of the same target nerve cell. However, since this option wasn't specified, I wasn't sure what was the correct answer.

[vox nihili]

If an excitatory neuron and an inhibitory neuron meet at different dendrites of the same single post synaptic neuron:
A) the inhibitory neuron would have more of a chance of causing the action potential to occur
B) the excitatory neuron would have more of a chance of causing the action potential to occur
C) both neurons have the same chance of causing the action potential to occur

I found this question quite 'tricky' on my SAC as I thought that excitatory and inhibitory neurons cancel each other out when they meet at different dendrites of the same target nerve cell. However, since this option wasn't specified, I wasn't sure what was the correct answer.

B, because only excitatory neurones cause action potentials to occur.

[alchemy]

B, because only excitatory neurones cause action potentials to occur.

YES! I thought so, and luckily put that down
Feeling happy 

[slothpomba]

Why is it that hormonal responses are generally more longer lasting than ones from the nervous system?

Two chief factors:

(1) Hormones persist longer. Neurotransmitters don't tend to stay around very long.

(2) The kind of mechanisms that hormones use to cause change tend to be more permanent or longer lasting. Hormones are sometimes involved in changes to genetic material (switching genes off or on) and how genes are read. Neurotransmitters are a little like flicking a light off and on, its immediate but it doesn't last. Hormones are a bit closer to painting your walls pink, it takes awhile and the changes by their very nature are more permanent.

For an action potential to reach its threshold mark, roughly how much excitatory neurotransmitter is needed? Surely >50% of all received neurotransmitters? Sorry if this question is too ambiguous!

Depends on the nature of the neuron. It probably depends on stuff beyond VCE like the number of ion channels present, what kind of receptors are present, things like EPSP/IPSP and any long term changes that the neuron has. Muscle cells are generally activated at at lower thresholds of neurotransmitters for reasons beyond VCE compared to other cells for instance.

If an excitatory neuron and an inhibitory neuron meet at different dendrites of the same single post synaptic neuron:
A) the inhibitory neuron would have more of a chance of causing the action potential to occur
B) the excitatory neuron would have more of a chance of causing the action potential to occur
C) both neurons have the same chance of causing the action potential to occur

I found this question quite 'tricky' on my SAC as I thought that excitatory and inhibitory neurons cancel each other out when they meet at different dendrites of the same target nerve cell. However, since this option wasn't specified, I wasn't sure what was the correct answer.

Quite simple really. Excitatory neurons increase the probability of an action potential occurring compared to 'normal', inhibitory neurons reduce the probability of an action potential occurring compared to 'normal'.

[Rishi97]

Explain the role of auxin (IAA) in the following plant growth processes:
a) Apical dominance
b) Stem growth
c) Secondary growth

Thanks

[katiesaliba]

To clarify, sodium-potassium pumps work to maintain the resting phase in neurons, right? So the pumps would also work during the relative refractory period after hyperpolarisation? 

[golden]

So the pumps would also work during the relative refractory period after hyperpolarisation? 

You are correct! Sodium potassium pumps still work during refractory periods.