Edexcel A2 Biology Unit 5 (6BIO5) - 22/06/2011- OFFICIAL THREAD !

Ah ok, I'll do that then. Do you remember if they asked a lot of synoptic stuff for Unit 4? Our school decided to make us sit both exams in June

And thanks

Ummm not sure about unit 4 (But don't count on me being correct, my memory has become clouded since it's a year since I sat the paper!) But I remember topics from units 1 & 2 being mentioned in unit 5 paper!

Did you revise AS stuff for the exam?

i think just a general appreciation of the AS content should be good... i dont think a thorough revision of AS will be of benefit... it will be more of a waste of time tbh...

you should definitely know the things in the synoptic article that refer directly to the AS content... gene therapy and atherosclerosis and clinical trials are the things that jump to my mind straight away

Does anyone know what the mark scheme answer for the meaning of ''myogenic'' is?

I know it's that the heart contracts by itself without outside stimulation, but often with these definitions they want it worded in a particular way

Well

I'll start with the resting membrane potential

RESTING MEMBRANE POTENTIAL
A neurone that is not conducting an impulse is said to be at rest. However, this is slightly wrong because the neurone is not "actually resting". It is actively maintaining a potential difference across it...(actively meaning by the use of ATP)

so the key points for when the membrane is at rest:

1) there are MORE sodium ions outside neurone than inside
2) there are MORE potassium ions inside neurone than outside
3) there are also negative proteins and chloride ions inside the neurone
4) this causes the inside to be negative with respect to the outside
5) There is a potential difference across the membrane... this is said as "the membrane is polarised"
6) this potential difference is maintained because of the uneven distribution of ions across the membrane... which is maintained by the Na/K pump
7) This, consequently depends on the PERMEABILITY of the membrane to ions
8) At rest, the membrane is permeable to potassium ions and impermeable to sodium ions...
9) The Na/K pump actively pumps out 3 Na ions and brings in 2 K ions against their concentration gradients...
10) Since the membrane is more permeable to K, these can move back out down their concentration gradient through Potassium Ion Channels
11) Some potassium will also be attracted back into the neurone (to balance the charge)... this is said as the K ions move down the electrochemical gradient...
12) Eventually, a dynamic equilibrium is reached between the conc. gradient and electrochemical gradients...

When this equilibrium is reached... the potential difference is -70mV ... and it stays like that because the dynamic equilibrium means no net movement of ions

do you really need to know this much detail for a resting potential, its only like one specification point.... i would have thought it to be more imprtant to remember how an AP is triggered (depolarisation, repolarisation and hyperpolarisation)
also im really worried that my teacher has not taught me everything, i looked in the snab book and there is a whole page on spatial and temproal summation ( i have no idea what this is can someone explain please???? thanks)

thanks

Help Please,

Explain how variation in ventilation and cardiac output enable rapid delivery of tissues and the removal of carbondioxide from them, Including how the heart rate and ventilation rate are controlled and the roles of cardiovascular centre and the ventilation centre

This is on the syllabus and i dont understand it,

Can someone please explain it in depth.

Thanks

do you really need to know this much detail for a resting potential, its only like one specification point.... i would have thought it to be more imprtant to remember how an AP is triggered (depolarisation, repolarisation and hyperpolarisation)
also im really worried that my teacher has not taught me everything, i looked in the snab book and there is a whole page on spatial and temproal summation ( i have no idea what this is can someone explain please???? thanks)

Hi,
in the article they mention epo production leading to more red blood cells and i wanted to make sure I understand how this occurs is it like this:

- epo binds to receptor on red blood celll presur cell membrane in the bone marrow
- activates a second messenger in the cytoplasm of the cell
- which activates a transcription factor through a cascade reaction
- which then binds with the RNA polymerase to the promoter region transcription factors bind to the promoter region of the DNA and if they are activators they allow the RNA polymerase to attach onto the promoter
- which increases transcription and translation
- producing mRNA, then complentary tRNA anticodon bind to codon, peptide bonds form
- leads to signal protein i think better to say leads to production of proteins from active genes ... it is unlikely to be one protein
- which stimulates differentiation of stem cells by causing permanent changes
- so they become specialised - more red blood cells
??

Thank you! just want to make sure i really understand this part!

me too please thanks

Hi,
in the article they mention epo production leading to more red blood cells and i wanted to make sure I understand how this occurs is it like this:

- epo binds to receptor on red blood celll presur cell membrane in the bone marrow
- activates a second messenger in the cytoplasm of the cell
- which activates a transcription factor
- which then binds with the RNA polymerase to the promoter region
- which increases transcription and translation
- producing mRNA, then complentary tRNA anticodon bind to codon, peptide bonds form
- leads to signal protein
- which stimulates differentiation of stem cells
- so they become specialised - more red blood cells
??

Thank you! just want to make sure i really understand this part!

Seems good. Do we need to write the bit in italics? ^

This is what i have in my notes

4. Explain how EPO has an effect on cells
• EPO is a peptide hormone that increases the production of enzymes needed for RBC (erythrocytes) synthesis
• binds to a receptor on the cell-surface membrane
• this complex activates a 2nd messenger in the cell cytoplasm
• which triggers a protein kinase cascade which results in the activation of several proteins
• until the final product enters the nucleus and acts as a transcription factor
• this transcription factor binds to promoter regions of a gene
• revealing the RNA polymerase binding site and allowing RNA polymerase to bind to DNA and start transcription of enzymes needed for RBC synthesis

summation is basically the idea of adding a lot of weak transmissions together to reach the threshold needed to produce an AP

Spatial is when several different synapses arrive, usually from different neurones, each bulb releases neurotransmitter which builds up to reach the threshold amount so an AP can be produced.

temporal is when the several synapses travel alobg the same neurone one after the other each releasing neurontransmitter as it reaches the postsynaptic neurone, the second synapse arrives before the neurotransmitter from the last one al; breaks down so it leads to a build up to reach threshold amount to produce sufficient depolarisation leading to AP.

overall summation is the idea all synapses combine to reach sufficient depolarisation.

Here is my notes for that specification point... hope its useful...



• During exercise, the frequency of muscle contractions increases and thus to provide the ATP requirements for this, the rate of aerobic respiration will need to increase. For this to occur there needs to be a rapid delivery of oxygen to the muscles and rapid removal of carbon dioxide.
• The body responds to these changes of exercise by increasing the cardiac output and the depth and rate of breathing.


Cardiac Output


Ventilation Rate

wow :O you guys are truelly amazing, i could kiss you. you cannot believe how grateful i am for this. thank you so much

Hey this is really amazing!you seems to have to clear answers.
Have you done like this for each point of specificatin?
Could I have a copy of your notes?)