VCE Biology Question Thread

[TwinNerd]

Hey everyone

I keep getting confused with antibodies, antigens and MHC markers. Can someone please distinguish them for me? I have not done immune system before so any help would be greatly appreciated. <3

Antigens: they are group of compounds, typically proteins which provoke/trigger an immune response, including the production of antibodies.
Antibodies: protein molecules designed to attach to only one specific type of antigen.
MHC Markers: In order to to distinguish non-self from self molecules, MHC markers are located on the surface of cell membranes.
Class 1 MHC Markers: located on the surface of all human cells with a nucleus (except RBCs). Infected cells display MHC class 1 markers.
Class 2 MHC Markers: located on antigen-presenting WBCs

[biy]

Thanks everyone! <3

Once APC's (antigen presenting cells) engulf and digest the antigens, they present them on their surface. Do we need to know what this process is called, and the name of the receptor/structure that actually holds them on the cell membrane?

Once the antigen fragments are presented, what happens now?

Thank you

[vox nihili]

Thanks everyone! <3

Once APC's (antigen presenting cells) engulf and digest the antigens, they present them on their surface. Do we need to know what this process is called, and the name of the receptor/structure that actually holds them on the cell membrane?

Once the antigen fragments are presented, what happens now?

Thank you

You don't need to know the name of the process or how it works, but you do need to know the name of the structure that holds them on the surface (that's an MHC!).

T-cells can bind to the antigen in complex with the MHC. This binding event activates them

[sschneider]

hey what is the function of the lymph nodes in the lymphatic system?

[Ha_Nguyen]

Got this right but could someone explain? Thanks

[CarterGray12]

Got this right but could someone explain? Thanks

So, a gamete is sperm or an egg. Only one copy of the gene is in an egg or a sperm. Option A shows two alleles of the same gene and hence cant be a gamete, option B is wrong because it shows genotype, and option D is wrong because it shows a phenotype. This leaves option c as correct. Hope that makes sense

[biy]

So i have my bio sac next week and i really need to clarify some things (beware, some might not be able to take this amount of questions):

1). What is the main difference between the first line of defence and the second line of defence? Is it just that first line are physical (outer) barriers such as mucus, intact skin, cilia etc? If this is so, what are some examples of second line of defence?

2). What happens during the second defence? And when is this response initiated?

3). Is the third line of defence specific to a particular type of pathogen? If so how?

4). Whats the difference between a lymphocyte and leukocyte?

5). Are these all the white blood cells we need to know for VCE: neutrophils, basophils, eosnophils, dendritic cells, NK cells, T cells, B cells, macrophages/monocytes

6). How do i know which of the above cells are lymphocytes or leucocytes?

7). Which of the cells are Antigen presenting cells?

. Do we need to know about the two different classes of MHC markers? If so, I know MHC class 1 is found in all nucleated cells, but why? and what do MHC class 1 do? I know that MHC class 2 markers are found on Antigen presenting cells, but what is their role exactly, is it only to engulf pathogens and present their fragments on their MHC class 2 markers?

9). when the above happens where the pathogen is engulfed, and the fragments are showed on the surface, what happens now? Why is this done?

Thank you <3

[sunshine98]

3). Is the third line of defence specific to a particular type of pathogen? If so how? Yes. Third line of defence falls under specific immunity. This is because the antibodies (on B lymphocytes) have a specific shape to fit the antigen. Also in cell-mediated immunity the T-cells have specific receptors.

4). Whats the difference between a lymphocyte and leukocyte? leukocyte= WBC. Lymphocytes = B cells , T cells and NKC

5). Are these all the white blood cells we need to know for VCE: neutrophils, basophils, eosnophils, dendritic cells, NK cells, T cells, B cells, macrophages/monocytes I think so. Well at least that's how many WBC I know about, maybe someone else can clarify

6). How do i know which of the above cells are lymphocytes or leucocytes? Refer to previous answer about leukocytes and lymphocytes

7). Which of the cells are Antigen presenting cells? APC is usually dendritic cells, macrophages and B lymphocytes

. Do we need to know about the two different classes of MHC markers? If so, I know MHC class 1 is found in all nucleated cells, but why? and what do MHC class 1 do? I know that MHC class 2 markers are found on Antigen presenting cells, but what is their role exactly, is it only to engulf pathogens and present their fragments on their MHC class 2 markers?
Because MHC I markers are found on all cells of the organism , they serve as a means of distinguishing between self and non-self. MHC II markers are found on APC and as u said present the antigen

Only answered a few ,hopefully others can answer the rest.
Hope this helps 

[grannysmith]

So i have my bio sac next week and i really need to clarify some things (beware, some might not be able to take this amount of questions):

1). What is the main difference between the first line of defence and the second line of defence? Is it just that first line are physical (outer) barriers such as mucus, intact skin, cilia etc? If this is so, what are some examples of second line of defence?
Yep, you just need to know that the first line of defence involves barriers that prevent entry into the internal environment of the body. The second line of defence is non-specific as well however it largely deals with things in bodily fluids, tissues etc. (i.e. the internal environment). These include complement proteins, neutrophils, macrophages, and other phagocytes.

2). What happens during the second defence? And when is this response initiated?
It basically comes into play when pathogens penetrate the first line of defence.

3). Is the third line of defence specific to a particular type of pathogen? If so how?
Yes, because it involves lymphocytes which are antigen-specific. For example, a particular B cell (let's call it Beta the B cell) can only identify and bind to antigen X -  not antigen Y or Z, but only X. There will be another B cell specific to antigen Y, another different one specific to antigen Z and so forth.

4). Whats the difference between a lymphocyte and leukocyte?
Lymphocytes are a type of leukocyte; it's essentially a hyponym of the latter. That is, a leukocyte describes a wide range of white blood cells such as monocytes, lymphocytes, neutrophils eosinophils and basophils.

5). Are these all the white blood cells we need to know for VCE: neutrophils, basophils, eosnophils, dendritic cells, NK cells, T cells, B cells, macrophages/monocytes
Yep, although you don't need to know about basophils/eosinophils.

6). How do i know which of the above cells are lymphocytes or leucocytes?
As I mentioned above, there are 5 classes of leukocytes; the only lymphocytes are B and T cells (and also the Naturale Killer cells)

7). Which of the cells are Antigen presenting cells?
B cells, macrophages, dendritic cells

. Do we need to know about the two different classes of MHC markers? If so, I know MHC class 1 is found in all nucleated cells, but why? and what do MHC class 1 do? I know that MHC class 2 markers are found on Antigen presenting cells, but what is their role exactly, is it only to engulf pathogens and present their fragments on their MHC class 2 markers?
The primary role of MHC markers is to present foreign antigens to the appropriate immune cells. Therefore it's reasonable to expect that all nucleated cells would have them. APCs present antigens to T helper cells, because this is only the type of MHC marker a T helper cell can bind to (i.e. MHC II).

9). when the above happens where the pathogen is engulfed, and the fragments are showed on the surface, what happens now? Why is this done?
The antigen fragment is presented so that an appropriate T cell can bind to it using its T-cell receptors, thus allowing the activation of the cell-mediated and/or humoral response, in order to eliminate the pathogen/antigen from the body.

Thank you <3

[StupidProdigy]

What actually happens after antibodies have gone to the infection site (for the humoral response) and agglutinated/activated complement proteins. Do t cells then come along to the agglutinated antigen? Thankyou

[grannysmith]

What actually happens after antibodies have gone to the infection site (for the humoral response) and agglutinated/activated complement proteins. Do t cells then come along to the agglutinated antigen? Thankyou

They're swallowed up by phagocytes

[biy]

Thanks heaps grannysmith and sunshine!

So what  exactly is the role of antibodies? I know foreign antigens trigger the production of them by B plasma cells, but what exactly do antibodies do, how, why and when?

Thank you <3

[kimmytaaa]

has anyone done their sac on ebola yet?

[biy]

Thanks heaps grannysmith and sunshine!

So what  exactly is the role of antibodies? I know foreign antigens trigger the production of them by B plasma cells, but what exactly do antibodies do, how, why and when?

Thank you <3

Bump

[biy]

I have a question about MHC markers

What's the MAIN difference between class 1 and class 2 MHC markers? Is it only that class 1 are on the surface of every nucleates cell, whereas class 2 are only on APCs?

If so, how does the body distinguish between self or non self cells? Does the MHC marker bind to antigens or is the MHC marker the actual thing that signifies self?