VCE Biology Question Thread

[alondouek]

Why do interneurons lack myelin?

They're pretty short already, so increasing the speed of transmission by myelination would be somewhat unnecessary.

[MM1]

Ex-Biology students, when would you suggest is the best time to finish the whole course? [the month] Thanks!

[vox nihili]

Ex-Biology students, when would you suggest is the best time to finish the whole course? [the month] Thanks!

There really isn't. I finished it the week before the exam and I was fine. It sort of balances out really. If you spend more time doing the course, you learn it better in the first place. If you really quickly finish it, you just spend the time you have left over learning the stuff you've yet to learn. How you use your time is far more important.

[EFPBH]

because two-exchanges of many substances can occur between cells, tissue fluid and plasma, the make-up of one fluid can be affected by the make-up of tissue fluid.

what does it mean by this?

thanks

[Rishi97]

because two-exchanges of many substances can occur between cells, tissue fluid and plasma, the make-up of one fluid can be affected by the make-up of tissue fluid.

what does it mean by this?

thanks

I'll have a go:
I like to think of this sentence representing diffusion. Pretend that both the extracellular and intracellular environment is even (talking about amount of substances). Then suddenly, there is an increase in solutes in the extracellular fluid. Thus, some solute will diffuse into the cell and enter the intracellular fluid. Thus, the increase in one fluid also increased the solutes in the other fluid. Like you said, the make-up of one fluid can be affected by the make-up of tissue fluid.
Hope I'm right in saying this.

[magpiesrule]

I'll try to cover as much as I can (in a VCE level obviously)

1. Transcription: when a gene becomes active, it will make a "mobile" copy of its genetic instructions that can transfer to the ribosome, since it cannot leave the nucleus. This genetic copy take form of RNA.
RNA polymerase unzips DNA, this enzyme (RNA polymerase) collects free RNA nucleotides that can complementary pair with the DNA template strand. A three base sequence of DNA is called "triplet", a three base sequence mRNA is called a "codon" and a three base sequence tRNA is an "anticodon", all of these 3 base sequence codes for an amino acid.

2. Translation: this is where the synthesis of protein start to take place, everything is determined by the codon of mRNA. Ribosomes will attach to mRA and start translation. Firstly, each codon on mRNA is translated by the process where tRNA carries a complementary amino acid  (i.e anticodon) to fit the codon of mRNA and make sure we obtain an exact amino acid sequence. Codon and anticodon pair using H-bond, and the polypeptide starts to grow from peptide bond. After this tRNA that carries a specific amino acid finish its mission, it will be released back and again can be used to supply the same type of amino acid over again. Finally, in order for translation to stop, a protein molecule, called release factor will occupy the codon site, create a "stop codon", also the bond between the last amino acid and the last tRNA is broken, release a free polypeptide. the ribosomal subunit ultimately break free the mRNA.
Still confused, try this video which contains more detailed and visual explanation https://www.youtube.com/watch?v=ZNl1z6Lev1E
Hope this helps!

Thanks so much!!! Greatly apprecisted:)

[vox nihili]

because two-exchanges of many substances can occur between cells, tissue fluid and plasma, the make-up of one fluid can be affected by the make-up of tissue fluid.

what does it mean by this?

thanks

This is just a reference to concentration gradients.

[Frozone]

Is there any way if remembering the difference between the role of the axon and the role of the dendrite? As I get them mixed up sometimes.

[MM1]

Is there any way if remembering the difference between the role of the axon and the role of the dendrite? As I get them mixed up sometimes.

Dendrites are branched extensions of the neural cell body that receive impulses, whereas axons transfer the impulse along their length.

Hope that helps?

[gohfish]

Ex-Biology students, when would you suggest is the best time to finish the whole course? [the month] Thanks!

I agree with Mr. T-Rav in that there's no point finishing the course really early if it means you haven't developed a good understanding of the content. Having said that, I think it's important to have a sufficient period of time for revision, even if you've learnt it super well the first time round. I would recommend completing the course before the September holidays. This should give you at least 6 weeks to consolidate your understanding and fine-tune exam technique. If you feel like you can finish it earlier without sacrificing understanding, then go for it!

[Jason12]

what do we need to know about communication by neurotransmitters and neurohormones? I know na+/K stuff is gone but still confused. Also what about reflex arcs?

[katiesaliba]

Is myelin sheath secreted by Schwann cells or is it an extension of the plasma membrane?
Are CNS neurons generally non-myelinated?

ALSO

Are antivenoms a class of antitoxin?

[katie101]

When people inadvertently put their hands in very hot water, they feel the heat before they feel the pain. Both signals are transmitted to the brain by nerves. Do the nerves appear to have the same speed of conduction? Explain.

[katie101]

The chameleon is a kind of lizard that can change both the colour and pattern of its skin very rapidly.

Explain whether hormonal control or nerve control is more likely to be involved.

Suggest how this feature helps control the internal temperature of the animal.

[gohfish]

what do we need to know about communication by neurotransmitters and neurohormones? I know na+/K stuff is gone but still confused. Also what about reflex arcs?

Know about:
Different parts of a neuron (axon, dendrites etc)
Neurotransmitter release and diffusion across a synapse
Specificity of neurotransmitter receptors
Neuro-muscular junctions
Difference between autocrine, paracrine and endocrine neurotransmitters
Just know that neurohormones are released by neurons and enter the bloodstream
Not sure about reflex arcs, but if you remember that they synapse at the spinal cord (rather than the brain) and they produce a quicker response than a normal nervous response, that should be sufficient

This is not an exhaustive list, have a look at the study guide to check what you need to know

Is myelin sheath secreted by Schwann cells or is it an extension of the plasma membrane?
Are CNS neurons generally non-myelinated?

ALSO

Are antivenoms a class of antitoxin?

The myelin sheath is a modified extension of the plasma membrane, so it is technically the Schwann cells themselves that coil around and provide insulation for the axon

CNS neurons are actually mostly myelinated. If you look at a cross section of the brain, the "white" matter you see is myelin

Yes, antivenoms are a sub-class of antitoxins

When people inadvertently put their hands in very hot water, they feel the heat before they feel the pain. Both signals are transmitted to the brain by nerves. Do the nerves appear to have the same speed of conduction? Explain.

The nerves would have different conduction speeds since one response (heat) is generated before the other (pain)

The chameleon is a kind of lizard that can change both the colour and pattern of its skin very rapidly.

Explain whether hormonal control or nerve control is more likely to be involved.

Suggest how this feature helps control the internal temperature of the animal.

Since the change is rapid, it is most likely under nervous control (a faster response system than hormones)