VCE Biology Question Thread

[swagsxcboi]

Are plant hormones transported by both the xylem and phloem?

ethylene diffuses into the surrounding external environment

[soNasty]

do we need to know the processes associated with the folding and replication of a prion protein?

[vox nihili]

do we need to know the processes associated with the folding and replication of a prion protein?

No

[alchemy]

do we need to know the processes associated with the folding and replication of a prion protein?

As prions are a relatively new discovery, you probably don't need to know about them in detail; knowing what they are should suffice.

[soNasty]

thank you both

[Frozone]

What's the difference between the feedback response mechanism and the stimulus response model?
Is it that the response affects the original stimulus in the feedback mechanism?


And does signal transduction refer to water soluble hormones?

[alchemy]

And does signal transduction refer to water soluble hormones?

Refers to both water soluble and lipid soluble hormones, as they both can undergo signal transduction.

[Frozone]

Could some one please help me with understanding this question. I always get confused with these types of questions.


And also, there is another question(not included in image) that asks what is the role of the myelin sheath:

I said it increases the speed of impulses but the answer is that it releases neurotransmitter  sat synapses. Why is this so?

[Scooby]

What's the difference between the feedback response mechanism and the stimulus response model?
Is it that the response affects the original stimulus in the feedback mechanism?


And does signal transduction refer to water soluble hormones?

A negative feedback system is just a stimulus-response system where the response counteracts the initial stimulus (eg. if the stimulus was elevated blood glucose concentration the response would be a reduction in blood glucose concentration)

Signal transduction occurs for all classes of hormones, and neurotransmitters as well (a lot of people think signal transduction only applies to hormones and forget the neurotransmitters)

[Scooby]

Could some one please help me with understanding this question. I always get confused with these types of questions.


And also, there is another question(not included in image) that asks what is the role of the myelin sheath:

I said it increases the speed of impulses but the answer is that it releases neurotransmitter  sat synapses. Why is this so?

If secretion of TSH by the pituitary gland is reduced, secretion of thyroxine by the thyroid gland will also reduce (since TSH stimulates the thyroid gland to secrete thyroxine). Normally, as thyroxine levels increase, secretion of TRH by the hypothalamus decreases (an example of negative feedback). As thyroxine levels decrease, secretion of TRH by the hypothalamus increases (which normally stimulates increased release of TSH by the pituitary gland and therefore increased release of thyroxine by the thyroid gland). Since, due to the pituitary gland tumour, thyroxine levels are reduced, release of TRH by the hypothalamus will increase (but will not lead to increased thyroxine production by the thyroid gland due to the pituitary gland tumour)

As a result of decreased thyroxine levels the overall metabolic rate of body cells would slow (since thyroxine stimulates an increased metabolic rate, as stated by the question)

The answer is wrong. Myelin increases the speed at which an action potential is propagated along the neural axon. Neurotransmitters are released at the axon terminals

[EFPBH]

"mechanisms monitor conditions inside the body, when change is detected body systems react to restore the balance"

what is it referring to when it mentions mechanisms and body systems?

thanks

[katiesaliba]

Where are neurotransmitters formed?

[nerdmmb]

Where are neurotransmitters formed?

Neurotransmitters are composed of amino acids and thus are classified as proteins.
The Golgi complex of each neurone secretes them and they therefore become readily available in vesicles at the axon terminal (as depicted in many diagrams)

[vox nihili]

Where are neurotransmitters formed?

Synthesised by the ribosomes in the rough ER, transported via the Golgi from which they bud off as vesicles that migrate down to the axon terminals. They then await a calcium flux to get exocytosed.

[Scooby]

Neurotransmitters are composed of amino acids and thus are classified as proteins.
The Golgi complex of each neurone secretes them and they therefore become readily available in vesicles at the axon terminal (as depicted in many diagrams)

Not all of them are composed of amino acids. A lot of them are (either as a single amino acid or a peptide), some of them are derived from amino acids (monoamines). Others aren't amino acid-based at all