VCE Biology Question Thread

[cosine]

question -> in vce, are we allowed to use dot points to explain short answer questions in the sciences, specifically bio,chem , or psych?
i'd assume so, but i've heard conflicting info, and don't want to be penalised unnecessarily! thank you.

Yes you are, actually on the exam the assessors like it more when you do this because it makes their marking scheme easier to follow. It also helps yourself in structuring your answer in order.

[HasibA]

Yes you are, actually on the exam the assessors like it more when you do this because it makes their marking scheme easier to follow. It also helps yourself in structuring your answer in order.

thanks cosine!

[blacksanta62]

"When B-cells are maturing in the bone marrow, a particular part of the genetic material undergoes change and only a few of each kind of B-cells are made. In this way millions of different B-cells are made with different immunoglobulins on their surface. These are able to identify the millions of different antigens with which a person may come into contact with"

Can someone explain how the above works? So by producing only a few kind of B-cells variation increases? Really confused.

Thank you

[sweetcheeks]

"When B-cells are maturing in the bone marrow, a particular part of the genetic material undergoes change and only a few of each kind of B-cells are made. In this way millions of different B-cells are made with different immunoglobulins on their surface. These are able to identify the millions of different antigens with which a person may come into contact with"

Can someone explain how the above works? So by producing only a few kind of B-cells variation increases? Really confused.

Thank you

Each antibody (protein) is specific to an antigen. When an antigen is detected in the body, the immune system must make the correct antibody. Genes in B cells are rearranged to manufacture different types of antibodies (specific to each kind of B cell), as rearranging genes can change the code for proteins. When the correct antibody is produced, the antigen binds to the b-cell which causes it (along with some other triggers) to rapidly divide and differentiate into B plasma cells and also B memory cells. By producing only a small amount of B cells with a specific antibody, many different kinds can be produced to quickly identify the antigen and carry out a response.

Anyone who is more knowledgeable of this, please correct me if I have said anything wrong.

[blacksanta62]

Each antibody (protein) is specific to an antigen. When an antigen is detected in the body, the immune system must make the correct antibody. Genes in B cells are rearranged to manufacture different types of antibodies (specific to each kind of B cell), as rearranging genes can change the code for proteins. When the correct antibody is produced, the antigen binds to the b-cell which causes it (along with some other triggers) to rapidly divide and differentiate into B plasma cells and also B memory cells. By producing only a small amount of B cells with a specific antibody, many different kinds can be produced to quickly identify the antigen and carry out a response.

Anyone who is more knowledgeable of this, please correct me if I have said anything wrong.

I understand a majority of what you said but could you clarify this for me please: If a large amount of B cells were to be produced would this be a negative(not through clonal expansion, just through rearranging and trying to get the correct 'combo')? Are a small and select amount produced to ensure that energy isn't wasted on B-cells without the correct antibodies?

Thank you

[sweetcheeks]

I understand a majority of what you said but could you clarify this for me please: If a large amount of B cells were to be produced would this be a negative(not through clonal expansion, just through rearranging and trying to get the correct 'combo')? Are a small and select amount produced to ensure that energy isn't wasted on B-cells without the correct antibodies?

Thank you

It would waste time, energy and supplies (amino acids etc.), things which the body generally cannot afford to lose. The body can only produce a certain amount of b-cells in a given time, it would rather manufacture different antibodies in fewer amounts to increase the chance and/or rate at which a match is made. The immune system wants to remove the antigen from the body as quickly as possible, if time was wasted on producing large amounts of a specific antibody that doesn't match, the infection will have spread a lot more.

[vox nihili]

I understand a majority of what you said but could you clarify this for me please: If a large amount of B cells were to be produced would this be a negative(not through clonal expansion, just through rearranging and trying to get the correct 'combo')? Are a small and select amount produced to ensure that energy isn't wasted on B-cells without the correct antibodies?

Thank you

The critical thing is that there are lots of different B-cells, but only a few of each type. When one type is needed, its numbers will expand greatly

[avocadoxxxxx]

Hi I'm finding it difficult to picture exactly where all the immune cells are in the body. As in, which immune cells circulate the bloodstream and which circulate the lymph? And also, which immune cells are located in the lymph nodes (I know that B and T memory cells are, anything else?) Could someone give me a brief summary?

Thanks!

[cosine]

Hi I'm finding it difficult to picture exactly where all the immune cells are in the body. As in, which immune cells circulate the bloodstream and which circulate the lymph? And also, which immune cells are located in the lymph nodes (I know that B and T memory cells are, anything else?) Could someone give me a brief summary?

Thanks!

In the lymph nodes there lies B cells and T cells. These cells sit there and await for the right stimulus. For example, the B cells in the lymph nodes could be naive ones and wait for a pathogen with complimentary antigen on its surface that complements the antibody on that naive B cell. Circulating in the lymph is the white blood cells, including lymphocytes (B or T cells). In the blood stream, there is all types of immune cells, like neutrophils, monocytes (macrophages) and dendritic cells. Some cells enter the lymph nodes but are not permanent. For example, you may see APCs in the lymph nodes that are presenting antigens to the various types of T or B cells to activate them, however when they find their match, the APCs leave the lymph nodes.

[avocadoxxxxx]

In the lymph nodes there lies B cells and T cells. These cells sit there and await for the right stimulus. For example, the B cells in the lymph nodes could be naive ones and wait for a pathogen with complimentary antigen on its surface that complements the antibody on that naive B cell. Circulating in the lymph is the white blood cells, including lymphocytes (B or T cells). In the blood stream, there is all types of immune cells, like neutrophils, monocytes (macrophages) and dendritic cells. Some cells enter the lymph nodes but are not permanent. For example, you may see APCs in the lymph nodes that are presenting antigens to the various types of T or B cells to activate them, however when they find their match, the APCs leave the lymph nodes.

Thank-you so much

[thefrog]

In the lymph nodes there lies B cells and T cells. These cells sit there and await for the right stimulus. For example, the B cells in the lymph nodes could be naive ones and wait for a pathogen with complimentary antigen on its surface that complements the antibody on that naive B cell. Circulating in the lymph is the white blood cells, including lymphocytes (B or T cells). In the blood stream, there is all types of immune cells, like neutrophils, monocytes (macrophages) and dendritic cells. Some cells enter the lymph nodes but are not permanent. For example, you may see APCs in the lymph nodes that are presenting antigens to the various types of T or B cells to activate them, however when they find their match, the APCs leave the lymph nodes.

Wait, so are there T and B cells in the blood as well?

[vox nihili]

Wait, so are there T and B cells in the blood as well?

yes

[QueenSmarty]

Hey, can someone please help me with this question from the Nelson Biology textbook? "Give three examples of ‘non-self’ that may be detected by an organism. Why is this ability to detect ‘self’ and ‘non-self’ significant".

Would the examples of 'non-self' just be bacteria, fungi and viruses? And the ability to detect 'self' and 'non-self' is significant as it allows the body to detect antigens that may cause harm. Would that be right?

[vox nihili]

Hey, can someone please help me with this question from the Nelson Biology textbook? "Give three examples of ‘non-self’ that may be detected by an organism. Why is this ability to detect ‘self’ and ‘non-self’ significant".

Would the examples of 'non-self' just be bacteria, fungi and viruses? And the ability to detect 'self' and 'non-self' is significant as it allows the body to detect antigens that may cause harm. Would that be right?

That seems like a reasonable answer to me!

[chickennugget]

For T cells to be activated, they must bind to an antigen on a MHC marker. There are two types of markers, class I and class II. Class II are on macrophages and B cells (antigen presenting cells). Class I are on any cell with a nucleus. When a virus infects a cell, the cell may present epitopes on its class I MHC markers. Do T cells only bind to class II markers on antigen presenting cells to be activated? Or can they bind to class I markers on any cell to be activated? Sorry if this question is confusing.