VCE Biology Question Thread

[grannysmith]

do we still have to know the differences between the individual plant hormones for the current study design?

Yep

[shivaji]

oh. because this is what is says on the VCAA  biology FAQs:

"The distinction between different types of growth regulators (auxins, cytokinins, gibberellins, abscisic acid and ethylene) are not required, although teachers may use one or more of them to illustrate a particular signal transduction pathway. "

^not sure if legit

[anat0my]

Are hormones always produced and secreted by endocrine cells into extracellular fluid?

Edit: Also, when describing the process of transmitting an action potential to subsequet neurons, is it necessary to mention the involvement of calcium ions? If so, would it suffice to say that "calcium ions move towards the synaptic knob"?

About the extracellular fluid, i'm assuming that since all hormones need to bind to a receptor to initiate a cellular response, they do need to be secreted into the extracellular fluid. But then this poses the question about internal receptors...

[anat0my]

Do we have to know about feedback responses (e.g. negative feedback), or information including thyroxin and thyroid systems?

Also to what degree do we need to know about nerves and nerve impulses?

You must know about feedback responses. They usually have questions asking you to define what it is and to draw a stimulus/response model based on info provided to you, or you have to give an example that you studied. I don't think you need to know about the thyroid systems but it would be good to know as an example.

You also have to know about the nerves, their basic structure, function and the ionic changes that occur when an action potential is fired. Refer to the study design to know exactly what is required.

[dankfrank420]

About the extracellular fluid, i'm assuming that since all hormones need to bind to a receptor to initiate a cellular response, they do need to be secreted into the extracellular fluid. But then this poses the question about internal receptors...

Wouldn't they just diffuse into the cell and bind to a receptor there?

[anat0my]

Wouldn't they just diffuse into the cell and bind to a receptor there?

Possibly. However, do all products such a proteins synthesised by the Golgi need to be secreted into the extracellular fluid, can't they just be secreted within the cell?

[anat0my]

Is anyone else still in the arduous process of note-making? -.-

[millie96]

Just to confirm about MHC markers

Are MHC2 markers located on WBCs which have engulfed the pathogen and thus display the foreign antigen?
So if the immune system identifies WBCs with MHC2 markers it will launch an attack?
•

[RazzMeTazz]

Is anyone else still in the arduous process of note-making? -.-

yep, just fixing up my photosynthesis and enzyme notes
:p

So tedious!

[RazzMeTazz]

How does enzymes having a more flexible structure (instead of being rigidly folded) mean that they have lower optimal temperatures?

For example, the enzymes of psychrophiles are said to be able to operate at very low temperatures and this is thought to be due to the loss of of some bonds keeping enzyme rigidly folded.

[grannysmith]

Possibly. However, do all products such a proteins synthesised by the Golgi need to be secreted into the extracellular fluid, can't they just be secreted within the cell?

Proteins required for the cell itself are synthesised by free ribosomes; ribosomes on rough endoplasmic reticulum synthesise proteins destined for exocytosis.
Edit: ribosomes are NOT membrane-bound organelles, but they can be attached to the rough endoplasmic reticulum. Just to clear any confusion.

[anat0my]

Proteins required for the cell itself are synthesised by free ribosomes; membrane-bound ribosomes on rough endoplasmic reticulum synthesise proteins destined for exocytosis.

Can it then be assumed that proteins synthesised by free ribosomes are not complex? Since the rough E.R does all the modifications and make a protein into its 3-dimensional shape? hmm...

[grannysmith]

Just to confirm about MHC markers

Are MHC2 markers located on WBCs which have engulfed the pathogen and thus display the foreign antigen?
So if the immune system identifies WBCs with MHC2 markers it will launch an attack?
•

MHC II markers are found on antigen presenting cells (APCs) such as macrophages, dendritic cells and B cells(?), which display foreign antigens (after engulfing it) to be recognised by helper T cells.

Helper T cells with specific receptors bind with the antigen-MHC II complex (of the APC), which "activates" the helper T cell, allowing to release chemicals (cytokines) which stimulate specific B cells to undergo clonal expansion and cytotoxic T cells to recognise foreign antigens displayed on MHC I markers of infected cells, cancer cells etc.

[anat0my]

How does enzymes having a more flexible structure (instead of being rigidly folded) mean that they have lower optimal temperatures?

For example, the enzymes of psychrophiles are said to be able to operate at very low temperatures and this is thought to be due to the loss of of some bonds keeping enzyme rigidly folded.

Taq Polymerase which is used in PCR has an optimal temp. of 72 degrees. Enzymes vary in their optimal temperature ranges. Not sure though.

[grannysmith]

Can it then be assumed that proteins synthesised by free ribosomes are not complex? Since the rough E.R does all the modifications and make a protein into its 3-dimensional shape? hmm...

I'm pretty sure they'd still be complex (have a tertiary structure). But apparently these proteins lack disulfide bridges due to the nature of cytosol, and remain only in cytosol. This is definitely straying away from the study design haha