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Report Thread starter 5 years ago
Okay, well for GCSE Biology Controlled Assessment we are required to do an ISA where we have to formulate a hypothesis based on information given and research a possible method which could be used to test you hypothesis. The situation I've been given is as follows:

Cathy went on a work placement to the Renal Unit in the Royal Victoria Hospital. There she observed how dialysis machines were used to filter the blood of patients who had damaged and diseased kidneys. One of the consultants explained that the process of diffusion allowed waste materials to pass from the patient's blood into the dialysis fluid. There was a long network of fine membranes that seemed to seperate the dialysis fluid from the patient's blood. Cathy asked of this set up was important in allowing diffusion to take place effeciently.

Well, I understand that we're meant to investigate factors affecting the rate of diffusion but I am confused as to what factor specifically? Is it the surface area of the membrane, or the distance, or the surface area to volume ratio? I'm slightly confused as to what the source means also when it says 'long network of fine membranes that seemedto seperate the dialysis fluid from the patient's blood'. Is there not just one membrane? And how is there a long network? Is tubing or such not seperating the blood? Ah, I'm sure I'm overcomplicating this but I'm rather confused and the ISA is in 3 days... Help please? I've been thinking about this all weekend and I can't figure it out!
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Report 5 years ago
I think you're looking into it too much. You'll need to formulate your hypothesis based on the context of the situation. All that's important is that there's a process of diffusion set up to filter the patient's blood for them. A suitable hypothesis to me would be: Dialysis machines containing long networks of fine membranes is important for efficient diffusion of waste products.

As for researching a possible method to test this hypothesis, you'd need a set up an experiment comparing the efficiency of 2 dialysis machines, one with long networks of membranes and the other without. You wouldn't be able to do that in your school, so they'll probably do a smaller but similar experiment to try and replicate the conditions. Then you can say that obviously this won't be the same as in the hospital using a live patient.

Hope this helps.

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