Biology AQA AS Unit 1 June 2014

Original post by samee_1

Anyone got any idea of what might come up or won't come up as it was on previous exam papers?

Hey, how are you planning out you're revision and how are you finding the content in unit 1?

Not that long left now, test is the 21 May 2014

COUNTDOWN:

#

105
DAYS

19
HOURS

7
MINUTES

31
SECONDS

Reply 3

Omg, I never thought this thread will start so soon...

Reply 4

Original post by JackTeh96

Omg, I never thought this thread will start so soon...

I know aha :wink:

time is moving so fast :biggrin:

Reply 5

Original post by H.Ibrahim

I know aha :wink:

time is moving so fast :biggrin:

We finished Unit 1 and we are on Unit 2 :wink:

Reply 6

jjjoelle

What topics does everyone find the hardest in unit 1?

Posted from TSR Mobile

Reply 7

king101

3

Hi I was just wondering if anyone could help me understand this chapter on immunity.

It says in the text book; ‘So many different types of lymphocytes there is a high probability that, when a pathogen gets into the body one of these lymphocytes will have a protein on its surface that is complementary to one of the proteins of the pathogens’.

My understanding of this is that; each lymphocyte consists of a specific membrane bound antibody on its cell surface membrane and hence the protein the text book talks about. And it’s the fact that a membrane bound antibody on the cell surface membrane of at least one lymphocytes has a specific antigen binding site that is therefore complementary to the antigen present on the cell surface membrane of the pathogen and hence the protein on the pathogen that the text book talks about.

And it is then the factor this lymphocyte with the correct membrane bound antibody on its cell surface membrane consisting of a specific tertiary structure that makes up its specific antigen binding site that allows it to act upon a complementary antigen found on the cell surface membrane of the pathogens binds to it. This activates the lymphocyte to divide by mitotic division and form clones of it’s self.

But then this is what I don’t get. Lets look at T-cells (cell mediated immunity-immunity involving organisms own body cell).

1- Pathogen is taken up by phagocyte

2- Phagocyte places antigen from pathogen on its own CSM

3-T-helper cells WTF are these??? Are these just T-cells? Specific T-helper cells on their cell surface membrane consist of membrane bound antibodies with a specific antigen binding site that can bind to the antigen present on the cell surface membrane of the phagocyte.

4- This activates other T-cells with the same membrane bound antibodies on their cell surface membrane to divide by mitotic division to form clones.

5- The clones develop into;
a) Memory cells
b) Stimulates B-cells to divide
c) Stimulates Phagocytes to engulf pathogens via phagocytosis
d) Kill infected cells.

The fact it says in the text book ‘The role of receptors on T cells is important. The receptors on each T cell responds to a single antigen. It follows there are a vast number of different types of T-cells each one responding to a different antigen’.

Whenever it refers to the receptors on T-cells –its talking about the membrane bound antibodies specific antigen binding site right? And in this case the T-helper cells right?

Reply 8

king101

3

And then in B-cells the text book says something along the lines of: ‘ When a pathogen enters the blood or tissue fluid there will be one type of B cell that has an membrane bound antibody on its cell surface membrane whose shape fits exactly to that of the antigen present on the pathogens cell surface membrane. This type of B cell divides by mitosis to form a clone of identical B cells all of which produce an antibody that is specific to that antigen’

OKAY…I’m confused…why? Well, look at these stages of my understanding:

1- B-cell takes up antigen from Pathogens cell surface membrane in the blood/tissue fluid

2- B-cell processes antigen and places it on own cell surface membrane

3- T helper cells have specific antigen binding site on their membrane bound antibody specific to the antigen on B-cells surface membrane.

4- Activates this B-cell to there divide by mitosis to form clones

5- Develop into plasma cells=antibodies

6- Develop into memory cells

SO WHERE IS MY CONFUSION? Well…where in that process is the membrane bound antibodies on the B-cells used?? No where in that process is the B-cells membrane bound antibodies binding to any antigen present on pathogens cell surface membrane. What causes them to divide is the T-cells after they have taken the antigen from the pathogen up and places it on their cell surface membrane WHICH then can lead to formation of the antibodies via plasma cells…

Or maybe my thoughts where that because the text book says this: ‘When a pathogen enters the blood or tissue fluid there will be one type of B cell that has an membrane bound antibody on its cell surface membrane whose shape fits exactly to that of the antigen present on the pathogens cell surface membrane. This type of B cell divides by mitosis to form a clone of identical B cells all of which produce an antibody that is specific to that antigen’

It’s referring to it in general terms i.e. it increases the quantity of B-cells with that membrane bound antibody which means any more pathogens with that same antigen theres more B-cells to deal with it and hence produce more antibodies??

anyone can help me out please?

Reply 9

Original post by king101

And then in B-cells the text book says something along the lines of: ‘ When a pathogen enters the blood or tissue fluid there will be one type of B cell that has an membrane bound antibody on its cell surface membrane whose shape fits exactly to that of the antigen present on the pathogens cell surface membrane. This type of B cell divides by mitosis to form a clone of identical B cells all of which produce an antibody that is specific to that antigen’

OKAY…I’m confused…why? Well, look at these stages of my understanding:

1- B-cell takes up antigen from Pathogens cell surface membrane in the blood/tissue fluid

2- B-cell processes antigen and places it on own cell surface membrane

3- T helper cells have specific antigen binding site on their membrane bound antibody specific to the antigen on B-cells surface membrane.

4- Activates this B-cell to there divide by mitosis to form clones

5- Develop into plasma cells=antibodies

6- Develop into memory cells

SO WHERE IS MY CONFUSION? Well…where in that process is the membrane bound antibodies on the B-cells used?? No where in that process is the B-cells membrane bound antibodies binding to any antigen present on pathogens cell surface membrane. What causes them to divide is the T-cells after they have taken the antigen from the pathogen up and places it on their cell surface membrane WHICH then can lead to formation of the antibodies via plasma cells…

Or maybe my thoughts where that because the text book says this: ‘When a pathogen enters the blood or tissue fluid there will be one type of B cell that has an membrane bound antibody on its cell surface membrane whose shape fits exactly to that of the antigen present on the pathogens cell surface membrane. This type of B cell divides by mitosis to form a clone of identical B cells all of which produce an antibody that is specific to that antigen’

It’s referring to it in general terms i.e. it increases the quantity of B-cells with that membrane bound antibody which means any more pathogens with that same antigen theres more B-cells to deal with it and hence produce more antibodies??

anyone can help me out please?

Original post by king101

And then in B-cells the text book says something along the lines of: ‘ When a pathogen enters the blood or tissue fluid there will be one type of B cell that has an membrane bound antibody on its cell surface membrane whose shape fits exactly to that of the antigen present on the pathogens cell surface membrane. This type of B cell divides by mitosis to form a clone of identical B cells all of which produce an antibody that is specific to that antigen’

OKAY…I’m confused…why? Well, look at these stages of my understanding:

1- B-cell takes up antigen from Pathogens cell surface membrane in the blood/tissue fluid

2- B-cell processes antigen and places it on own cell surface membrane

3- T helper cells have specific antigen binding site on their membrane bound antibody specific to the antigen on B-cells surface membrane.

4- Activates this B-cell to there divide by mitosis to form clones

5- Develop into plasma cells=antibodies

6- Develop into memory cells

SO WHERE IS MY CONFUSION? Well…where in that process is the membrane bound antibodies on the B-cells used?? No where in that process is the B-cells membrane bound antibodies binding to any antigen present on pathogens cell surface membrane. What causes them to divide is the T-cells after they have taken the antigen from the pathogen up and places it on their cell surface membrane WHICH then can lead to formation of the antibodies via plasma cells…

Or maybe my thoughts where that because the text book says this: ‘When a pathogen enters the blood or tissue fluid there will be one type of B cell that has an membrane bound antibody on its cell surface membrane whose shape fits exactly to that of the antigen present on the pathogens cell surface membrane. This type of B cell divides by mitosis to form a clone of identical B cells all of which produce an antibody that is specific to that antigen’

It’s referring to it in general terms i.e. it increases the quantity of B-cells with that membrane bound antibody which means any more pathogens with that same antigen theres more B-cells to deal with it and hence produce more antibodies??

anyone can help me out please?

Okay you are slightly confused but let me share some light into this.

You should break this down into smaller chunks.

Phagocytes perform phagocytosis right.

1. Phagocyte's are chemically attracted to pathogens, then they bind with it.
2. They engulf the pathogen and create a vesicle around the pathogen.
3. This then binds with Lysosome organelle, which releases Lysosomal/Lytic enzymes.
4. This breaks down the pathogen and presents it's antigen on it's surface, hence the name 'Antigen-presenting cell'.

This is where the B and T Lymphocytes come in.

T cell:

1. The phagocyte finds the right T-cell complementary to the antigen on it's surface.
2. Once the right T-cell has been found, it binds with the antigen on the phagocyte, hence the name 'Cell-mediated immunity'.
3. The T-Cell has been found and now divides via mitosis.
4. The T-Cell has different jobs:

A. T-Killer cell, where it breaks the membranes of infected host cells, which cause the organelle along with the pathogens to leak, hence cause it's death.
B. Divide into T-memory cells, to stimulate the immune system at secondary response (when same pathogen with same antigen infects you again)
C. Activate B Cells.

Now we reach B lymphocytes, finally wooow.

1. The B-Cell finds the antigen in the blood, hence the name 'Humoral immunity' due to it being in the fluid.
2. The antigen is presented on it's surface, so it can be activated via the T-Helper cell.
3. T-Helper Cell activates the B-cell with the pathogen's antigen.
4. When activated, the B-cell divides via mitosis into plasma cell and has different roles:

A. Create memory cells which again help the body upon secondary infection.
B. Create's antibodies which can do a numerous of things:

(I) Stick together the pathogens to aid phagocytes.
(II) Prevent pathogens to enter host cells.
(III) Counteract toxins produced by the pathogens.

I guess this is really the fundemental's of it. This is all from memory (test tomorrow!) so there might be one or two facts missing, but yeah, learn this and you should be fine!

Reply 10

Original post by H.Ibrahim

Okay you are slightly confused but let me share some light into this.

You should break this down into smaller chunks.

Phagocytes perform phagocytosis right.

1. Phagocyte's are chemically attracted to pathogens, then they bind with it.
2. They engulf the pathogen and create a vesicle around the pathogen.
3. This then binds with Lysosome organelle, which releases Lysosomal/Lytic enzymes.
4. This breaks down the pathogen and presents it's antigen on it's surface, hence the name 'Antigen-presenting cell'.

This is where the B and T Lymphocytes come in.

T cell:

1. The phagocyte finds the right T-cell complementary to the antigen on it's surface.
2. Once the right T-cell has been found, it binds with the antigen on the phagocyte, hence the name 'Cell-mediated immunity'.
3. The T-Cell has been found and now divides via mitosis.
4. The T-Cell has different jobs:

A. T-Killer cell, where it breaks the membranes of infected host cells, which cause the organelle along with the pathogens to leak, hence cause it's death.
B. Divide into T-memory cells, to stimulate the immune system at secondary response (when same pathogen with same antigen infects you again)
C. Activate B Cells.

Now we reach B lymphocytes, finally wooow.

1. The B-Cell finds the antigen in the blood, hence the name 'Humoral immunity' due to it being in the fluid.
2. The antigen is presented on it's surface, so it can be activated via the T-Helper cell.
3. T-Helper Cell activates the B-cell with the pathogen's antigen.
4. When activated, the B-cell divides via mitosis into plasma cell and has different roles:

A. Create memory cells which again help the body upon secondary infection.
B. Create's antibodies which can do a numerous of things:

(I) Stick together the pathogens to aid phagocytes.
(II) Prevent pathogens to enter host cells.
(III) Counteract toxins produced by the pathogens.

I guess this is really the fundemental's of it. This is all from memory (test tomorrow!) so there might be one or two facts missing, but yeah, learn this and you should be fine!

It is an impressive account of the immunity process. Just wanna add that when T cells undergo mitosis, it specialises into four different types (you mentioned three), the other one is T-helper cell, which stimulates B cells to divide. HIV/AIDS works by kill T-helper cells, so there is no effective B cells to tackle them.

Another thing is that B cells divide into Plasma Cells and Memory cells. Plasma cells are for the production of antibodies.

Reply 11

Original post by JackTeh96

It is an impressive account of the immunity process. Just wanna add that when T cells undergo mitosis, it specialises into four different types (you mentioned three), the other one is T-helper cell, which stimulates B cells to divide. HIV/AIDS works by kill T-helper cells, so there is no effective B cells to tackle them.

Another thing is that B cells divide into Plasma Cells and Memory cells. Plasma cells are for the production of antibodies.

Yeah aha, I typed it up in a rush didn't really check it :biggrin:

I should have expanded on "Activate B cells" you're right. It does indeed do this via the T-helper cell.

I think I did well on today's mock, anyone else done a unit 1 mock yet?

Reply 12

Original post by H.Ibrahim

Yeah aha, I typed it up in a rush didn't really check it :biggrin:

I should have expanded on "Activate B cells" you're right. It does indeed do this via the T-helper cell.

I think I did well on today's mock, anyone else done a unit 1 mock yet?

We finished Unit 1 mock three weeks ago. Could have be better.

Reply 13

Original post by JackTeh96

We finished Unit 1 mock three weeks ago. Could have be better.

Don't worry, you'll only improve from your mistakes. look at it as a positive thing, so next time you do a paper, bring in techniques/info on answering questions from your last paper.

Reply 14

king101

3

Original post by H.Ibrahim

Yeah aha, I typed it up in a rush didn't really check it :biggrin:

I should have expanded on "Activate B cells" you're right. It does indeed do this via the T-helper cell.

I think I did well on today's mock, anyone else done a unit 1 mock yet?

Thanks mate!

Reply 15

Original post by king101

Thanks mate!

It's alright man, that's what TSR bro's are for :wink:

Reply 16

Swifty1322

What topics were on the June 2013 paper?

Reply 17