Year 12s: what will be the first way you research your future options? >>

Serial Dilutions

Q2. A serial dilution is performed in which 1cm3 of a solution containing 8.83 x 10^7 cells is diluted to 10cm3 (to give solution A), then 1cm3 of solution A is diluted to 10cm3 (to give solution B).

Q2.1. What is the overall dilution factor (between the original and final solution)?

1 in 10
1 in 100
1 in 1000
1 in 10000
1 in 100000

I know that the dilution factor is final solution/original solution.

for 1 in 10 would it be 10/1 = 10
and then for 1 in 100 would it be 100/1 = 100

and so on...?

(edited 13 years ago)

Reply 1

I Have No Imagination

Anybody?

Reply 2

charco

Study Forum Helper

Original post by I Have No Imagination

Q2. A serial dilution is performed in which 1cm3 of a solution containing 8.83 x 107 cells is diluted to 10cm3 (to give solution A), then 1cm3 of solution A is diluted to 10cm3 (to give solution B).

Q2.1. What is the overall dilution factor (between the original and final solution)?

1 in 10
1 in 100
1 in 1000
1 in 10000
1 in 100000

I know that the dilution factor is final solution/original solution.

for 1 in 10 would it be 10/1 = 10
and then for 1 in 100 would it be 100/1 = 100

and so on...?

Yes, 1 to 10 dilution followed be another 1 to 10 is the same as one 1 to 100 dilution

Reply 3

I Have No Imagination

Original post by charco

Yes, 1 to 10 dilution followed be another 1 to 10 is the same as one 1 to 100 dilution

Thank you. In relation to the same question how would I work out the concentration of cells per cm3 of solution A?

Reply 4

Calian

Original post by I Have No Imagination

Thank you. In relation to the same question how would I work out the concentration of cells per cm3 of solution A?

If you think about it 1/10 of your solution A is your original solution so theoretically you would have 1/10 of your original concentration which is basically number of cells per cm3.

Reply 5

cttp_ngaf

OLOLOL "SERIAL" DILUTIONS is that where you put too much milk on your cornflakes?!?!?!1

LOLOLOsalowelqel

Reply 6

I Have No Imagination

Original post by Calian

If you think about it 1/10 of your solution A is your original solution so theoretically you would have 1/10 of your original concentration which is basically number of cells per cm3.

Thanks a lot. I completely understand that now.

I have a few more questions that I'm finding rather difficult.

Q3. Three pour and spread dilutions were prepared and 3 plates were set up for each dilution. The resulting counts are shown in Table 1 below.

Table 1. Colony counts per plate of malt extract agar for a viable count of Saccharomyces cerevisiae using the pour plate technique incorporating an inoculum of 1cm3 per plate:

10^-4 10^-5 10^-6
<30 45 >300
<30 48 >300
<30 39 >300

Q3.1. Calculate the mean number of colonies per plate obtained from the 10-5
dilution.

I've got this as 44?

Q3.2. Calculate the mean number of colony forming units (cfu) per cm3 of the original culture.

No idea how to do this?

(edited 13 years ago)