VCE Biology Question Thread

[whys]

Are you allowed to use pencil for the vcaa biology MC section and pen for SA questions, also when remembering signalling molecules do we also need to know the specific details e.g. action potentials in neurotransmitters

You are required to use pencil for multiple choice and pen for short answer. Multiple choice requires you to shade in bubbles, similar to many other standardised tests, and so should be done in pencil. Short answer is almost always in pen for most exams as well. You need to know specific details to an extent. It is best to know that action potentials stimulate the release of neurotransmitter molecules, as well as how this occurs.

[chiarra]

Hi, I'm really confused about the concept of antigens and b lymphocytes as well as t lymphocytes and I'm struggling with a definition for antigens because they can't initiate an immune response because isn't that immunogens? 

[whys]

Hi, I'm really confused about the concept of antigens and b lymphocytes as well as t lymphocytes and I'm struggling with a definition for antigens because they can't initiate an immune response because isn't that immunogens? 

Hello.

An antigen is a non-self marker that is recognised by T-lymphocytes or antibodies produced by B-lymphocytes and triggers a response from a B or T-cell. Antigens that trigger an immune response are referred to as immunogens, but immunogens are still generally referred to using the umbrella term 'antigen'. Essentially, not all antigens will initiate an immune response, but when we usually refer to antigens in this area of study, we refer specifically to immunogens (but this word is less commonly seen) because it's just easier to refer to everything as an 'antigen'.

B and T lymphocytes are specialised white blood cells that respond to pathogens. B-cells initiate the humoral response and T-cells initiate the cell-mediated response, but they both work together in the immune system.

The T-cells we need to know about are these:
Helper T cells - stimulate B cells to divide and form a clone of plasma cells
Cytotoxic T cells - kill virus-infected cells and cancer cells
Suppressor T cells - suppress further action by the immune system once the pathogen is defeated
Memory T cells - 'remember' the pathogen so it can be responded to more efficiently if it enters the body again

Hope this helped!

[chiarra]

Hello.

An antigen is a non-self marker that is recognised by T-lymphocytes or antibodies produced by B-lymphocytes and triggers a response from a B or T-cell. Antigens that trigger an immune response are referred to as immunogens, but immunogens are still generally referred to using the umbrella term 'antigen'. Essentially, not all antigens will initiate an immune response, but when we usually refer to antigens in this area of study, we refer specifically to immunogens (but this word is less commonly seen) because it's just easier to refer to everything as an 'antigen'.

B and T lymphocytes are specialised white blood cells that respond to pathogens. B-cells initiate the humoral response and T-cells initiate the cell-mediated response, but they both work together in the immune system.

The T-cells we need to know about are these:
Helper T cells - stimulate B cells to divide and form a clone of plasma cells
Cytotoxic T cells - kill virus-infected cells and cancer cells
Suppressor T cells - suppress further action by the immune system once the pathogen is defeated
Memory T cells - 'remember' the pathogen so it can be responded to more efficiently if it enters the body again

Hope this helped!

thankyou so much I don't know why but I'm finding it so hard to make notes for responding to antigens

[Erutepa]

Hi, I'm really confused about the concept of antigens and b lymphocytes as well as t lymphocytes and I'm struggling with a definition for antigens because they can't initiate an immune response because isn't that immunogens? 

Anitgens are a "unique molecule or part of a molecule that initiates an immune response" (as stated by the study design). Immunogens are actually a type of antigen, however knowing the distinction between immunogens and antigens is not neccasary for VCE bio - and its best to use the term 'antigen' rather than immunogen as that is what the study design uses.

b and t lymphocytes are a fairly broad topic so it would be great if you could clarify what you don't understand about them. To give a little overview though, B and T lymphocytes are key parts of the adaptive immune response. Both lymphocytes are produced in the bone marrow; however while B cells remain and mature in the bone marrow, T cells migrate to and mature in the thymus. Once matured, these cells will circulate through the lymphatic system and will generally be in high concentration in the lymph nodes. These mature B and T cells are each complimentary to a specific antigen. There are two main types of T cells: T helper cells and cyctotoxic t cells. Antigen presenting cells ( such as a dendritic cell) can present antigens to these t helper lymphocytes to activate them resulting in proliferation and activation of B cells or cytotoxic t cells. B cells will differentiate and into many plasma B cells which produce antibodies to its specific antigen, and some memory b cells which will remain in the body to confer immunological memory of that antigen allowing for faster subsequent immune responses to that antigen. Once activated proliferation and differentiation occurs, resulting in active cytotoxic t cells and memory t cells (similar in function to memory b cells). These cyctotoxic t cells will patrol the body, where its t cell receptor will bind to its specific complimentary antigen presented in a MHC class II protein receptor of another cell. Upon this binding, the t cell will induce apoptosis within its target cell through release of perforins and granzymes aswell as the FAS ligand (death ligand).

As mentioned, this is a bit of a quick summary and is not the depth you need to know, so if there is anything in there you are unsure about or want a bit more of an explanation of, please feel free to ask.

[tigerclouds]

Regarding cell signalling, my textbook separates plant and animal signalling. With animals, it mentions contact-dependent, autocrine, paracrine and endocrine signalling and with plants, it mentions the hormones like auxin, ethylene etc. Does that mean that the signalling categorised in the animal section does not occur in plants? As in, do plants use autocrine signalling (for example) in delivering auxin to and from cells? I'm just curious as to how the plant hormones are transferred from one cell to another?

[Erutepa]

Regarding cell signalling, my textbook separates plant and animal signalling. With animals, it mentions contact-dependent, autocrine, paracrine and endocrine signalling and with plants, it mentions the hormones like auxin, ethylene etc. Does that mean that the signalling categorised in the animal section does not occur in plants? As in, do plants use autocrine signalling (for example) in delivering auxin to and from cells? I'm just curious as to how the plant hormones are transferred from one cell to another?

contact dependent, autocrine, paracrine and even endocrine can be used to describe types of signalling found in plants, but especially for this course, these terms are pretty much just used in reference to signalling in animal cells. As such, I wouldn't worry about it too much, but if you are comfortable with the definitions of each type of signalling you should be able to apply it to plants if VCAA throw it at you, although I don't think that its likely as I can't seem to find any previous questions asking about this.

[WhatisaMeMe]

Regarding cell signalling, my textbook separates plant and animal signalling. With animals, it mentions contact-dependent, autocrine, paracrine and endocrine signalling and with plants, it mentions the hormones like auxin, ethylene etc. Does that mean that the signalling categorised in the animal section does not occur in plants? As in, do plants use autocrine signalling (for example) in delivering auxin to and from cells? I'm just curious as to how the plant hormones are transferred from one cell to another?

Hi
Of course paracrine/autocrine signalling occurs in plants and animals. However, there are some differences. For example, in endocrine signalling of hormones in animals, it travels via the blood stream to target cells. However, in plants, they don't have this blood stream. So how do plants transmit hormones/growth factors around plant then? Well the answer varies depending on the hormone. For example, cytokinins travel in xylem, absicic acid in both xylem and phloem, and gibberelins autocrine signalling and ethylene diffuses into the atmosphere to target cells of other plants.

[Moonblossom]

Hi, I have some questions about signal transduction. I get that there is a difference in this stage depending on the type of receptor the signal had originally bound to but I can't really get the hang of the flow of events that occurs when the signal binds to an extracellular receptor.

I also don't really get the active potential and resting potential of neurotransmitters (neurohormones?). What does it mean for the cell if it has active potential?

Thanks!

[GodNifty]

Hi, I have some questions about signal transduction. I get that there is a difference in this stage depending on the type of receptor the signal had originally bound to but I can't really get the hang of the flow of events that occurs when the signal binds to an extracellular receptor.

I also don't really get the active potential and resting potential of neurotransmitters (neurohormones?). What does it mean for the cell if it has active potential?

Thanks!

Molecules binding to extracellular receptor causes a shape change in said receptor, which stimulates the release of intracellular second messengers.

Do you mean action potential? Don't think it's necessary for biology but it's pretty much an electrical impulse that travels in one direction from axon hillock to axon terminals - just know that neurotransmitters are released from the axon terminal, travels down the synaptic cleft and binds to receptors on another neuron's dendrite

[Erutepa]

Hi, I have some questions about signal transduction. I get that there is a difference in this stage depending on the type of receptor the signal had originally bound to but I can't really get the hang of the flow of events that occurs when the signal binds to an extracellular receptor.

I also don't really get the active potential and resting potential of neurotransmitters (neurohormones?). What does it mean for the cell if it has active potential?

Thanks!

GodNifty was exactly write about action potentials - this level of neurotransmitter release used to be in the course, but is no longer. The important thing to know is that neurotransmitters are a type of signalling molecule that acts between neurons.

Extracellular signalling molecule (these will be hydrophilic) will bind to a surface receptor, causing a conformational change. This will (as GodNifty said) will result in the activation of secondary messger molecule. Its important to note that the binding of one signaling molecule will activate many secondary messenger molecules, amplifying the signal. In a way signal cascade (like in apoptosis) these secondary messenger molecules might activate different secondary messengers before eventually activating an effector molecule. This effector can then act as a transcription factor modifying gene expression, or might lead to a more immediate cellular response (I.e. Opening a ion channel). For the VCE course we mainly consider these extracellular binding signaling molecules as producing a more immident cellular response.
Hopefully this helps!

[makram]

- What must we know in regard to 'vaccination programs' in the study design?

- Do we need to know type I-IV hypersensitivity, or only type I?

- How exactly does multiple sclerosis work?

[GodNifty]

- What must we know in regard to 'vaccination programs' in the study design?

- Do we need to know type I-IV hypersensitivity, or only type I?

- How exactly does multiple sclerosis work?

- How it maintains herd immunity. You should get an idea of booster injections and why it's needed as well.

- Think you just need to know multiple sclerosis, allergic reactions and HIV. You don't need to categorise it into type I-IV hypersensitivity.

- Myelin sheath on axon are damaged by cytotoxic T cells due to a mistake in identification of self-cells.

[Moonblossom]

Molecules binding to extracellular receptor causes a shape change in said receptor, which stimulates the release of intracellular second messengers.

Do you mean action potential? Don't think it's necessary for biology but it's pretty much an electrical impulse that travels in one direction from axon hillock to axon terminals - just know that neurotransmitters are released from the axon terminal, travels down the synaptic cleft and binds to receptors on another neuron's dendrite

Thank you for that! Yeah, sorry I meant to action not active. Sorry, I have another question about neurons. Are they electrical impulses or chemical signals? I'm sorry, I cannot get the hang of them

[ErnieTheBirdi]

Hey everyone! I was just wondering whether anyone knew whether or not we were required to memorize the different hormones for animals and plants? For example, glucocorticoids and mineralocorticoids are in the adrenal cortex and then the hormone class or each, target, function, etc. Same goes with plants? Thanks in advance everyone!