KA1: laboratory techniques for biologists: liquids and solutions

Question 1

describe how to carry out linear dilution

Answer 1

dilutions in a linear series differ by an equal interval e.g. 0.1, 0.2, 0.3

Question 2

describe how to carry out a log dilution

Answer 2

dilutions in a log series differ by a constant proportion e.g. 10^-1, 10^-2, 10^-3

Question 3

how can unknown concentrations be determined using a standard curve

Answer 3

Plotting measured values for known
concentrations

Question 4

describe the use of buffers in maintaining and controlling pH

Answer 4

addition of acid or alkali has very small
effects on the pH of a buffer, allowing the pH
of a reaction mixture to be kept constant

Question 5

what is a colorimeter?

Answer 5

used to quantify concentration and turbidity

Question 6

describe how a colorimeter is used to determine turbidity

Answer 6

-calibration with appropriate blank as a baseline

-use of absorbance to determine concentration of a coloured solution using suitable wavelength filters

-use of percentage transmission to determine turbidity, such as cells in suspension.