VCE Biology Question Thread

[Jason12]

what is the major histocompatability complex and class 1 + 2 markers?

[katiesaliba]

what is the major histocompatability complex and class 1 + 2 markers?

This excerpt from my notes might help -

MHC class I- found on all cells with a nucleus (therefore not red blood cells)
MHC class II- found on professional APCs (antigen presenting cells) like macrophages, dendritic cells and B- and T-lymphocytes.

The major histocompatibility complex itself is a complex of genes that code for MHC (major histocompatibility complex) markers. These markers are unique in every human (excluding identical twins), and are protein molecules which are ultimately located on the surface of cell membranes. They are examples of self molecules.

Foreign antigens as well as self antigens can be displayed on the MHC markers. These can, however, only be peptide antigens. MHC markers can therefore aid in distinguishing between self and non-self.

Cytotoxic T-lymphocytes register MHC I markers
Helper T-lymphocytes register MHC II markers

T-lymphocytes are MHC restricted, where as B-lymphocytes are not.

[walkec]

Got a few questions:

-there's a table in a take home quiz my teacher gave us where we have to say an example of a prion? I know some diseases caused by prions but what is an example of a prion?

-is a virus likely to be responsible for food poisoning? Explain

-is non specific immunity innate or learned? Explain

Thanks 

[Jason12]

what are interferons and interleukins and what do they do?

also what is a bacteriophage?

[katiesaliba]

Got a few questions:

-there's a table in a take home quiz my teacher gave us where we have to say an example of a prion? I know some diseases caused by prions but what is an example of a prion?

-is a virus likely to be responsible for food poisoning? Explain

-is non specific immunity innate or learned? Explain

Thanks 

You're doing a NEAP test 

It means an example of a disease. So, mad cow disease would be an example.

No, food poisoning is usually caused by bacteria. Viruses require a host cell to multiply, where as bacteria can reproduce without one. Bacteria would therefore be abundant on food. (Note that viruses can also be present on food, but food poisoning is most commonly caused by bacteria. The wording of the question is important in this case!)

Non-specific immunity is innate as the same response occurs for any foreign antigen detected. No memory is established.

what are interferons and interleukins and what do they do?

also what is a bacteriophage?

Both are types of cytokines (signalling molecules, used for communication between cells)

Interferon is secreted by viral infected cells to 'alert' surrounding uninfected cells of the pathogen's entry. The surrounding cells will then become more resistant to the virus, therefore reducing their chances of infection. Resistance occurs because interferons trigger the uninfected cells to produce enzymes which will inhibit the virus from synthesising more copies of itself inside the cell.

Interleukins have a variety of roles. For example, interleukin-1 activates T-helper lymphocytes and interleukin-2 stimulates the proliferation of B- and T-lymphocytes.

Bacteriophages are viruses that infect and replicate inside bacteria. They kinda resemble alien spaceships!

[Jason12]

my book says interferons can make enzymes not just cause other cells to make enzymes. is this true?

what is rh incompatibility and is it needed for VCAA exam?

[simpak]

my book says interferons can make enzymes not just cause other cells to make enzymes. is this true?

what is rh incompatibility and is it needed for VCAA exam?

Interferons are just signalling molecules - they can't produce enzymes themselves because they are not cells.  They would trigger production of enzymes in other cells but other than that I can't understand what your book is trying to say.

Rh incompatibility is where people have a mismatch for their rhesus antigens.  So just like there are ABO antigens on blood cells, there are other antigens that can be 'incompatible' between individuals and rhesus antigen is one of those.  Some people express the rhesus antigen (Rh+) and others do not (Rh-).  So when you say you're 'B+' blood type or 'O-' the positive and negative is referring to your Rhesus antigen. I don't think rhesus is on the VCAA curriculum, last I knew.  But someone else confirm?

[Jason12]

To what extent do we need to know about cell-mediated immunity and humoral immunity? Are these part of active, passive or on their own?

[Reus]

To what extent do we need to know about cell-mediated immunity and humoral immunity? Are these part of active, passive or on their own?

Not too sure to what extent we need to know, I'd get my head around it though. They're both natural active.

[alchemy]

Not too sure to what extent we need to know, I'd get my head around it though. They're both natural active.

Not quite right. Cell mediated immunity doesn't involve the production of antibodies. Hence, it's not active. Natural and active are simply classifications for Induced Immunity.

[Reus]

Ah good pickup! Completely misunderstood that.
Would Humoral fall under Natural Active Acquired Immunity?

[Jason12]

what exactly is cell mediated and humoral anyway? Can't find it in the textbook

[Reus]

what exactly is cell mediated and humoral anyway? Can't find it in the textbook

Ive answered this before so I had a skim through...

Well Humoral and Cell-Mediated responses fall under the 3rd line of defence also known as the specific/adaptive immunity.

Humoral:
-B-lymphocytes are the major cells involved.
- Produced in the Bone Marrow (thus the name B-lymphocytes)
-Each B-Cell has its individual antibody/antigen complex
-Production of antibodies
B-Cells differentiate (clonal expansion) into
- B-Plasma cells (effector cells): secrete antibodies
- B-memory cells: remain in the body so when the antigen is encountered again, a response can rapidly be reenacted.

Cell-Mediated:
-Cell mediated response occurs when a pathogen is already in the cell. This level of immunity is carried out by T cells.
-T-Cells made in the Bone Marrow however matured in the Thymus (hence its name  T-Cells)
T-Cells include; Helper T cells (Th), Cytotoxic T cells (Tc) and Suppressor T cells.
-Helper T cells active cytotoxic cells and present antigens to immature B cells.
-Cytotoxic cells detect/recognise cells with infection, are able to destroy these foreign cells with contact
-Lastly Suppressor T cells, literally suppress the immune responses once the antigen has been removed

Antibodies; are proteins that bind and neutralise antigens. Are quite specific (like an enzyme-substrate complex).

[Jason12]

are we required to know the different kinds of blood groups?

[Reus]

are we required to know the different kinds of blood groups?

Blood groups? Or blood types? If so, no.