Edexcel A2 Biology SNAB 6BI04 ~ 6BIO5 June 2016

Does anyone have a prediction list for the topics likely to come up relating to the article?

Also, I had a question about the rods and action potentials. I'm sorry about all these questions.

In the green book, it says rods that are exposed to light have their rhodopsin broken down into opsin and retinal. This bleaching means that Na+ channels are closed, but Na+ is still actively pumped out causing the rod cell to enter a state of hyperpolarisation. This hyperpolarisation is a generator potential in the rod which, if large enough to reach the threshold, will allow neurotransmitter substance to enter into the synapse which will stimulate an action potential at the bipolar cell.

The orange book, however, says that the state of hyperpolarisation in the rod cell means no neurotransmitter (glutamate) is released, and this leads to an action potential occuring in the rod cell.

I'm confused about the role of the neurotransmitter. The orange book also says neurotransmitter is released when rods are exposed to darkness, which prevents an action potential occuring.

Does anyone have a prediction list for the topics likely to come up relating to the article?

The orange book is talking about inhibitory neurotransmitters, i.e. glutamate. If glutamate is released into the synapse and binds to the receptors on the post-synaptic membrane then the bipolar neurone cannot depolarise as the neurotransmitter inhibits it from doing so. I ignored what the green books says because the orange book is more accurate in terms on mark scheme answers.

Does anyone know how 'assassin cells' may target the cancerous ones? (scientific article) :/

On exam questions about the spirometer practical it always mentions calibration for volume and calibration for time on the mark schemes, what does that mean? Is it setting the drum to rotate at a fixed speed?

What do we need to know about promoters and transcription factors?

also want to know this

also want to know this

I think it's unlikely we'll need to know much but you calibrate for volume using a calibration syringe (I've seen that as a mark point a few times). Basically it has a set volume of air and you put it in then read the trace (how many vertical squares) so you know what the volume is. To calibrate for time I think you just make the trace run for a minute then see how many horizontal squares it's gone over. Then you can use that to determine the time and volume of an actual breathing trace.

Most questions seem to focus on the trace itself rather than operating the machine though so it should be fine.

suggest how a kill switch might cause a cell to commit suicide....any ideas?