AQA BIOL1 Biology Unit 1 Exam - 16th May 2011

Immunity is not that hard. You just need to apply it a lot.

So the main things we need to know are phagocytosis, Cell Mediated Immunity, and Humoral Immunity.

Phagocytosis goes like this.
1) The phagocyte is attracted to the pathogen via chemoattractants and it moves along their conc. gradient towards the pathogen.
2) The phagocyte 1st attatches to the pathogen and then englufs the pathogen and creates a phagosome
3) Vesicles in the phagocyte attatch to the phagosome and secrete lytic enzymes whihc break down the pathogen
4) All soluble products of the breakdown are then absorbed by the Phagocyte.

Cell Mediated immunity goes something like this.
1) A pathogen invades a host and is taken in by a phagocyte.
2) The phagocyte then presents antigens from the pathogen on it's surface.
3) It is then specifically recognised by a Receptor protein on a T Cell
4) This results in induced mitosis and differentiation of the T cell into :
a) T Killer cells=kill the infected cells
b) T helper cell which help in Humorla immunity
c) Memory Cells to prevent recurring infection of the SAME pathogen
d) Stimulates phagocytosis

Humoral Immunity is like this
1)A pathogen invades a host.
2) The antigens of the invading pathogen are then taken up by B cells.
3) They are then presented on their surface
4) T helper cells then help process the antigen and result in induced mitosis
5) PLasma cells are created which secrete antibodies to destroy the pathogen (This is the primary response)
6) Memory cells are made which prevent recurring infection.

In terms of defnitions
Antigen : Any substance which enters a host organism and is specifically recognised as a non self
Antibody: These are immunoglobulins with specifically shaped recognition regions
Vaccination: A substance which contains antigens which stimulates the production of antibodies

Antibodies are specific as they have an exact sequence of amino acids which results in an exact 3D shape which is complementary to only 1 type of antigen

Monoclonal antibodies are essentially clones of 1b cell and so they all have the exact same receptor proteins on their surface and so can only recognise 1 type of antigen

2 Types of immunity
Active and Passive

Active is split into natural and artificial,
Active natural= Becoming immunocompetent to a specific disease by actually suffering it
Active Artificial = Vaccination

Passive is split into natural and artificial:
Passive Natural: Obtaining antibodies from breastmilk as a baby
Passive Artificial: Antiserum

I hope this helps some of you. I think this is all of it and this is most of what I know off the top of my head. If I have missed anything out I'm sure someone will point it out :smile:

Good Luck

Reply 461

Tericon

8

Original post by Sparkly-Star

Does anyone know how to do question 4.c.ii) and 5.a) from the Jan 11 paper? :frown:

Thanks!

and 4ciii and 5.b too, can you do those two?

Just doing that paper now :biggrin:

Reply 462

Sparkly-Star

13

Original post by EffKayy

4cii? you've just gotta know that triglycerides have 3 fatty acids and 1 glycerol

5a! wow aqa are so mean! I wrote sodium chloride but they wanted you to write water or sodium chloride solution?!

Original post by Tericon

and 4ciii and 5.b too, can you do those two?

Just doing that paper now :biggrin:

Oh no I meant 4.c.iii) and 5.b) too :frown:

not the ones I mentioned lol. I know how to do those. :p:

Reply 463

liviaaa

Original post by Tericon

and 4ciii and 5.b too, can you do those two?

Just doing that paper now :biggrin:

It's 9. Look at the diagram above, count how many R groups there are 8, and plus the X bond. 9

--

20cm3 = 1 mol

So

4cm3 = 0.2 mol (divide it by 5)

As there is 4cm3 of NaCl, there must be 16cm3 of water, to make it up ot 20 cm3.

Reply 464

EffKayy

16

Original post by Sparkly-Star

Oh no I meant 4.c.iii) and 5.b) too :frown:

not the ones I mentioned lol. I know how to do those. :p:

For 4Ciii, the question asks, starting with glucose + fructose, so you know that when those two combine there will be one h2o molecule released (makes sucrose).
Then it says R, where a fatty acid is attached to a lipid, we know that when glycerol+3fatty acids attach, condensation occurs, and a h2o molecule is released. So you've just gotta know that when two of those combine, h20 comes out. There are 8 Rs + 1 h2o from glucose + fructose = 9.

Reply 465

Tericon

8

Original post by Sparkly-Star

Oh no I meant 4.c.iii) and 5.b) too :frown:

not the ones I mentioned lol. I know how to do those. :p:

Whilst we wait for help, can you please explain 3d ii to me? Looked at MS but still confuses me :P Thanks :smile:

Reply 466

Rikku Kisaragi

I HOPE THERE IS NOTHING ON CHOLERA/ SODIUM POTASSIUM PUMP!!! I will actually get 0 on an applied Cholera question :L oh, I hope there are not as many mathsy questions...I always mess up somewhere :/
I hope there is lots on immunity though :smile:

Reply 467

Rikku Kisaragi

The January 2011 paper was actually awful :frown:

Reply 468

Sparkly-Star

13

Original post by liviaaa

It's 9. Look at the diagram above, count how many R groups there are 8, and plus the X bond. 9

--

20cm3 = 1 mol

So

4cm3 = 0.2 mol (divide it by 5)

As there is 4cm3 of NaCl, there must be 16cm3 of water, to make it up ot 20 cm3.

You're awesome! :biggrin:

Reply 469

Abby :)

8

Aaaaah since alot of you are thinking immunity will come up tomorrow, im gonna go revise that section in detail again now. Then i think i'll do the final practice paper that i havnt done yet....

Reply 470

Abby :)

8

Ooooh can someone please explain how you convert UM measurements into MM? i really dont get that atall. xD I always get it wrong. :/

Reply 471

Sparkly-Star

13

Original post by Tericon

Whilst we wait for help, can you please explain 3d ii to me? Looked at MS but still confuses me :P Thanks :smile:

This one is quite simple. :smile:

You know that the equation is:

Cardiac output = stroke volume x heart rate

They told us that the guy's heart rate became lower but the cardiac output is still the same. This means that his stroke volume must've gone up to still get the same cardiac output, so this means more blood is pumped out of the heart per heartbeat. And the reason it pumps more blood could be due to an increase in the strength of the heart muscle. :smile:

Reply 472

Spongebobu

6

Original post by Abby :)

Ooooh can someone please explain how you convert UM measurements into MM? i really dont get that atall. xD I always get it wrong. :/

essentially, 1mm=1x10^3 um and 1mm=1x10^6 nm

So you would measure it in mm and then do either x10^3 or x10^6 of it depending if it asks for um or nm
and divide by the magnification.
Simples :biggrin:

Reply 473

BeejTheone

Why are controls used in experiments??

Reply 474

Abby :)

8

Original post by reaperguy

essentially, 1mm=1x10^3 um and 1mm=1x10^6 nm

So you would measure it in mm and then do either x10^3 or x10^6 of it depending if it asks for um or nm
and divide by the magnification.
Simples :biggrin:

Thank you so much! <3 You just explained it better then the textbook hahaha.

Reply 475

Spongebobu

6

Original post by BeejTheone

Why are controls used in experiments??

To prove that the effect is due to the addition of something e.g. a chemical e.g. in an enzyme experiment the control is almost always boiled enzyme to show that the change is always due to the enzyme and nothing else.

In terms of a control group you would always use a placebo and keep everything else the same

You must make sure you say both those things to get both the marks

Reply 476

Tericon

8

Original post by Sparkly-Star

This one is quite simple. :smile:

You know that the equation is:

Cardiac output = stroke volume x heart rate

They told us that the guy's heart rate became lower but the cardiac output is still the same. This means that his stroke volume must've gone up to still get the same cardiac output, so this means more blood is pumped out of the heart per heartbeat. And the reason it pumps more blood could be due to an increase in the strength of the heart muscle. :smile:

Thank you, makes perfect sense now :smile:

Reply 477

A_clizzy

Original post by liviaaa

It's 9. Look at the diagram above, count how many R groups there are 8, and plus the X bond. 9

--

20cm3 = 1 mol

So

4cm3 = 0.2 mol (divide it by 5)

As there is 4cm3 of NaCl, there must be 16cm3 of water, to make it up ot 20 cm3.

Cheers, that mol stuff was really confusing me

Reply 478

BeejTheone

Original post by reaperguy

To prove that the effect is due to the addition of something e.g. a chemical e.g. in an enzyme experiment the control is almost always boiled enzyme to show that the change is always due to the enzyme and nothing else.

In terms of a control group you would always use a placebo and keep everything else the same

You must make sure you say both those things to get both the marks