VCE Biology Question Thread

[alchemy]

Do all pathogens that enter an organism cause disease?
No. If a pathogen that is capable of causing a particular disease enters an organism but does not cause damage to the host cells of that organism then, in that case, the micro-organism concerned is not acting as a pathogen.

This answer confuses me. Aren't pathogens defined as disease-causing organisms? Therefore, for a micro-organism to be a pathogen is must cause disease, must it not?

Indeed, pathogens are disease causing organisms. However, not always do they cause disease as they are dealt with by the relevant cells of the immune system before they're able to cause disease.

[Reus]

This thought just came to mind in todays class, as antibodies are specific to antigens. Lets say an antigen has two different shapes (complementary proteins/epitopes), one able to bind to the antigen site, one not able. Would that still have an affinity to that antibody? Excluding the other shape? Or is there a more complicated process? An antibody with two distinct pairs of antigen sites haha?

Thanks!

[EFPBH]

do we need to know about the sympathetic nervous system and the parasympathetic nervous system under the autonomic nervous system?.....if so to what degree?

thx

[melons]

Do all pathogens that enter an organism cause disease?
No. If a pathogen that is capable of causing a particular disease enters an organism but does not cause damage to the host cells of that organism then, in that case, the micro-organism concerned is not acting as a pathogen.

This answer confuses me. Aren't pathogens defined as disease-causing organisms? Therefore, for a micro-organism to be a pathogen is must cause disease, must it not?

Some bacteria is part of our natural flora but if found in a different part of your body it can cause disease, meaning it's pathogenic in that case. Therefore, a micro-organism can be pathogenic in some in some instances but not in others.

[vox nihili]

Some bacteria is part of our natural flora but if found in a different part of your body it can cause disease, meaning it's pathogenic in that case. Therefore, a micro-organism can be pathogenic in some in some instances but not in others.

Good answer. These are called opportunistic infections. When the immune system is healthy and working properly, the commensals are kept in a good balance. When it's not, they can invade.

[alchemy]

How are T-cells involved in humoral immunity? I thought they were only involved in cell-mediated immunity...

[Reus]

How are T-cells involved in humoral immunity? I thought they were only involved in cell-mediated immunity...

So did I?

[vox nihili]

How are T-cells involved in humoral immunity? I thought they were only involved in cell-mediated immunity...

They interact with B-cells by binding to them and secreting cytokines that modulate their behaviour. T-cells are not a part of humoral immunity, BUT they do play a role in humoral immunity.

[Chang Feng]

What are the differences between basophils and mast cells, are they interchangeably used in inflammation, allergies

[Reus]

What are the differences between basophils and mast cells, are they interchangeably used in inflammation, allergies

Relatively carry out similar functions; however differ in origins, sizes, shapes of nucleus, and their locations in the body. Are responsible for similar allergic reactions, and they both are made in the bone marrow, however, they are derived from different progenitors. As basophils mature in the bone marrow then travel throughout the blood stream, whereas mast cells leave the bone marrow in an immature state, and mature in body tissues.

In the case of inflammation, my thought is that they are interchangeable as both produce histamines. Not too sure about that one though!
(might want to check up on that)

[Jason12]

Are we required or to what extent do we need to know about

- specific viruses like HIV, influenza or just that they are a type of virus?
 Also what about protists, fungi, parasites?
- antibiotics and their effect on bacteria

[Frozone]

Why is the helper t lymphocytes activated in cell mediated immunity whilst b lymphocytes are activated in the Humoral immunity?

My guess is that it is because Humoral immunity involves the production if antibodies. Antibodies are produced by B cells, therefore the antigen must activate B lymphocytes. Whilst a cell mediated immunity involves the attack of of pathogens. Cytotoxic T cells are responsible for the destruction of viral cells. Therefore helper T lymphocytes must be activated to create cytotoxic T cells.

[nhmn0301]

Why is the helper t lymphocytes activated in cell mediated immunity whilst b lymphocytes are activated in the Humoral immunity?

Different immunity have different functions, cell-mediated immunity can activate humoral immunity in a sense that helper T-cell releases interleukin-2 (a type of cytokines) which activate B-cells. MOST b-cell will become inactive without the notification of helper T-cell. However, some B-cell can activate itself and trigger humoral immunity as well. The reason why we need humoral response is because only B-cell can produce antibody, whilst T-cell cannot. Hence, if the Same pathogen invade your body again, the B-memory cell from the humoral response can help your body to overcome the  infection at a much faster rate.

[Scooby]

Relatively carry out similar functions; however differ in origins, sizes, shapes of nucleus, and their locations in the body. Are responsible for similar allergic reactions, and they both are made in the bone marrow, however, they are derived from different progenitors. As basophils mature in the bone marrow then travel throughout the blood stream, whereas mast cells leave the bone marrow in an immature state, and mature in body tissues.

In the case of inflammation, my thought is that they are interchangeable as both produce histamines. Not too sure about that one though!
(might want to check up on that)

If you're discussing inflammatory or allergic reactions, refer to mast cells, not basophils. Basophils are very unlikely to come up in the exam

[Scooby]

Are we required or to what extent do we need to know about

- specific viruses like HIV, influenza or just that they are a type of virus?
 Also what about protists, fungi, parasites?
- antibiotics and their effect on bacteria

You don't need to know any specific viruses. You do need to know a bit about fungi and the definition of a parasite, but protists are unlikely to come up. You should know that antibiotics are used mainly to treat bacterial infections, and maybe that they can work in a variety of different ways (eg. some target protein synthesis; others, like penicillin, target bacterial cell wall synthesis)