Edexcel GCE Biology Unit 4 6BI04 June 2013

During the exam to make answers seem clearer and more straightforward.. can we write all our answers in bullet point forms instead of continuous sentences? including the questions with asterisks?

What is a mark scheme definition of trophic level?

During the exam to make answers seem clearer and more straightforward.. can we write all our answers in bullet point forms instead of continuous sentences? including the questions with asterisks?

During the exam to make answers seem clearer and more straightforward.. can we write all our answers in bullet point forms instead of continuous sentences? including the questions with asterisks?

There is nothing saying we cant, but i wouldnt advice it. But forthe * questions if you write in bullet points my teacher says you get no marks

Id suggest at this late stage learn some classic mark scheme answers... and some key words for each typpe of questions..if you like let me know what sorta questions you are struggling on and ill help you get a classic answer for them

thanks for replying,
well generally i get 'suggest why' questions wrong, questions where i have to analyse a table/graph and i also get stuck on things to do with photosynthesis as well as the immune response. i have no idea how to answer things on specific immunity

On the analysing questions, almost always there is a mark for manipulation of figures, so normally that is an easy marking point to pick up, as long as you remember to do it.

There is nothing saying we cant, but i wouldnt advice it. But forthe * questions if you write in bullet points my teacher says you get no marks

Yes you can although it is advisable to write the * questions in continuous prose. In the * questions there are many more marking points than marks available this means that if you get enough of the marking points you don't need the continuous prose.

This is what my teacher told me anyway

I also asked my teacher this and she said that we could as they look more at spelling and the order that it is in. I guess it depends on whether you want to risk it or not.

glucose is fuel? can uplease explain?

thanks for replying,
well generally i get 'suggest why' questions wrong, questions where i have to analyse a table/graph and i also get stuck on things to do with photosynthesis as well as the immune response. i have no idea how to answer things on specific immunity

ok can someone explain what is post transcriptional changes?

and do we need to know southern blotting? I dont see that in specification, but my teacher suggested me to learn it.?

glucose is fuel? can uplease explain?

ok can someone explain what is post transcriptional changes?

and do we need to know southern blotting? I dont see that in specification, but my teacher suggested me to learn it.?

okay in terms of the graph questions:
I always say what happens generally? Like does one factor increase because of another..thus what sort of correlation it is. I look for any anomolies.. i look for any patterns. I always try and briefly suggest what the graph is trying to say, So like if one factor is increasing because of temperature I always say that is because of an increase in kinetic energy and therefore an increase number of collisions. I always do a manipulation. This could be the overall change in the graph. So the change/ original * 100. It also depends what the question is saying like you may be describing an irrelevant part of the graph

For photosynthesis ill try and write down what i always try and include in these questions:
for the light dependant reaction, takes place in the thylakoid membranes of the chloroplasts.and needs light Basically what happens is light is absorbed by phtosystem 2(PSII) and then this splits water into hydrogen and oxygen via photolosis. Oxygen is a waste product. The electrons are excited and their energy level is increased. They are released from PSII and go onto the electron transport chain via the electron carries (this next bit ive never seen come up in a mark scheme but id put it in anyway- There is a higehr concentration of protons in the thylakoid so you get a proton concentration gradient. The protons move down the concentration gradiet via the enzyme ATP synthase which allowes the combination of ADP plus P to get ATP. You also will get NADPH. This is when light is absorbed by PSI and the electrons are transfered with a H proton from the stroma to the NADP to get NADPH.

So essentially when you write an answer on the light dependant reaction make sure you include
-light absorbed by PSII
- light splits water into H+ and o2
-Electrobs ebergy raised because of excitment
- Electrons are released to ETC
-redox reactions occour to synthesize ATP from ADP and P. Whilst this is happening energy of electrons fall
-called phosphorylation
-NADPh is formed when one H+ is added to NADP from the stroma

for light independant reaction
a classic markscheme would want you to contain the folowing

- happens in the stroma
-doesnt need light
-it is the calvin cycle or known as carbon fixing
-cCO2 enters via the stomata of leaf
-combines with the 5 carbon RUBP
-with the help of the enzyme RUBISCO
-Creats an unstable 6 carbon compound which splits into 2, 3 carbon compounds called GP
- Redection reaction occours where by using the energy from ATP it takes the hydrogen from NADPH and adds it to GP to get GALP
- 5/6 molecules of galp used to regenerate RUBP for the reaction
- one is used to make amino acids, carboyhydrates, bucleic acids and lipids

for the suggest why questions:
These involve you to think...sometimes the answer is really obvious so always put down the obvious thing. There is no way of giving advice for these questions excpet think about what you are going to write and it will always link to the syllabus

for the immune response questions
There is lots they could ask you on
Fristly the different types
The fitrst defence a body has s the kertin on the skin forms a physical barrier that protect pathogens form entering
-Skin flora on the skin comepete wiht bacteria to stop them from breeding there
- lysosomes n teras kill bacteria by weaking their cell walls so when they divide they burst and die.
- In the stomach you have hydrcholic acid whihc does not allow bacteria to survive you can only have specially adapted bacteris in the stomach
you have the non specific...
there are 4 types
Inflamation

Theis is when the immune system recognises anitgens and the release histamine
- this causes vasodilation
-this increases the blood flow
-this means lots of immune cells like white blood cells will seep to the site of the infection and then the immune system can start to destroy the pathogen

Lysozome action
This si where lysozomes break down bacteria
- they do this by weakening cell walls
- they only affect bacteria not viruses as viruses dont have a cell wall

Interfernons

these are protiens which are anti viral
-They prevent replication by inhibiting the production of viral proteins
- They dont affect bacteria as bacteria dont make proteins in the same way that viruses do

Phagocytosis

So the phagocyte recognises the antigen on the pathogen
-It engulfs the pathogen and contains it in a pphagocytic vaculoe
A lysosome fuses with the vacuole and enzymes are released to break down the pathogen
- The phagocyte presents this to the other immune cells like the T cell
This can allso be known as the antigen cell presenting immune response

Another type of immunity is the Specific immunity
Firstly you need to know about antibodies
- They are glycoprotiens. They have a 3D Y shape with disulphide bridges between the petides. They have a variable region which are specific to the antigens

So what happens in the specific immune response is that something activates the T cell,. To activate the T cell it has to ve a complementary antigen. And a hagocyte could activate the T cell
- once activated it differentiates into T helper cells-which go and activate the b cells
- Or t killer cells whihc kill the pathogen
- Or T memory cells which speeds up the immune response
The T helper cell goes to activate the B cell
The b cell again is specific and it has to be a complementary antigen
Once the b cell is activated it divides into plasma cells. The plasma cells make antibodies whihc labes the antigen to allow phagocytes to phagocytose them. It can also bind to the toxins produced by the pathogens and prevent the toxins from affecting the humans

That is the 2 types of immune responses

If you are talking about types of immunity there are main ones

Actuve immunity
This can be natural where you become immune after catching the disease
Or articificail where you become immune after reciveing a vaccine which contains a harmfull dose of the antigen...this could be an attenuated virus

Passiv immunty
this can be natural and this happens when a baby gets anitbodies from the mother through the placenta or breast milk
It can be articifical if you are injected with a ton of antibodies

Sorry its really long tried to include a lot..let me know if you need anything else its good revision for me too!
and sorry about any spelling mistakes!

thanks so much for taking time out to help! much appreciated, it all makes sense as well, im guessing its just a matter of properly learning everything for me.
thanks again