Having trouble with questions...

[Dante]

4. What is the concentration in µg ml-1 of a solution of glycine of 23 g litre-1? (2 marks)
(Mol. wt of glycine = 75.07)


Any help on the formula I need to start off with would be great

5. The following colony counts on nutrient agar plates were obtained from dilutions of an overnight culture of the bacterium Pseudomonas aeruginosa:

10-5 = >1000
10-6 = 622
10-7 = 74
10-8 = 14

Choose an appropriate colony count to determine how many colony-forming units (cfu) were present in 1 ml of the original culture (assuming that 100 l of the diluted culture was spread onto each agar plate)? (4 marks)


So lost with this question, I must have missed something in lectures, so just any help would be so appreciated.

6. 50 mg of the amino acid isoleucine (molecular weight of 131.2) has been dissolved in 50 ml water to produce a stock solution. What is the molarity of the stock solution? The assay mixture requires a final concentration of 200 µM isoleucine in 10 ml buffer. What volume of stock solution needs to be made up to 10 ml? (4 marks)

7. The optical density OD (or absorbance) at 600 nm of an overnight culture of the bacterium Vibrio fischeri is 0.4. What volume of this suspension do you need to make up to 100 ml with fresh medium to give an OD of 0.1 at 600 nm? (2 marks)

10. From a bottle of molten nutrient agar you need to pour 20 agar plates each containing 50 g ml-1 ampicillin. Each plate will contain ~ 25ml of nutrient agar, and you have a stock ampicillin antibiotic solution of 200 mg ml-1. What volume of ampicillin stock solution do you need to add to the bottle of molten agar before pouring the plates? (4 marks)

Did 8 and 9 fine, but these other three just lost me.

Cheers