Biology Calculationis this correct?
 This topic has 5 replies, 3 voices, and was last updated 9 years, 10 months ago by Kezzer.

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November 28, 2010 at 4:49 pm #14199KezzerParticipant
Hey just wondering if anyone can tell me whether I have done this calculation right or not.
A baby hamster kidney (BHK) cell has a surface area of 3,400 micrometres². Assume that the endocyte clathrincoated pits account for 2% of this area and that the surface area of a single coated pit is the same of that of a 100nm diameter clathrin coated vesicle that will be formed from it. If the cell surface has 100,000 transferrin receptors, around 70% are localised within coated pits: work out how many coated pits there are.
Ive got:
3,400 * 2% = 68 micrometers(squared)
every pit has a 100 nanometer diameter. area of a circle 2*pi*r(squared)
100nanometers=0.1micrometer
r=radius 2r=d
r=0.05micrometers
2*pi*0.05(squared)=0.0157micromters(squared)
68/0.0157=4329.014is this correct or would I do pir2 rather than 2*pir2 which would give me an answer of 8658? Or do I need to work out the surface area of a sphere? 4*pi*r2?
Please help, thanks 🙂 
November 29, 2010 at 1:43 am #102508pielover1234Participant
i would say so 😀

November 29, 2010 at 6:15 am #102514JackBeanParticipant
1) the vesicle is 3D, not 2D 😉
2) why do you calculate two surfaces and divide them?
3) I think you should calaculate the number of the receptors on pits and from that calculate the number of pits. But I think there is missing some info…

November 30, 2010 at 5:16 pm #102549KezzerParticipant
so I need to calculate the surface area of a sphere then, 4*pir(squared)?
I have done the division at the end because they only account for 2% of the total suface area which is 68micrometers squared. The next question is to then calculate how many transferrin receptors there are in each coated pit, but I just can’t get my head round how to do that.

December 2, 2010 at 10:19 pm #102609KezzerParticipant
Hey, for the number of transferrin receptors in each coated pit I’ve got:
100 000 receptors, 70% localised within the coated pits so:
100 000 x 70% = 70 000 receptors in the coated pits.
There are 70 000 receptors and 2165 coated pits so:
70 000/2165 = 32 transferrin receptors in each coated pit.Does think look right to anyone? Not very confident when it comes to maths lol
Thanks
K 
December 2, 2010 at 10:21 pm #102610KezzerParticipant
I realised for the first question on coated pits I did need to do 4×3.14×0.05(squared) so got 2165 for how many coated pits there are 🙂


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