Unit 1 - Topic 1 - Laboratory Techniques for Biologists - Section B - Liquids and solutions

Question 1

What is linear dilution?

Answer 1

Dilutions in a linear dilution series differ by an equal interval, for example 0·1, 0·2, 0·3 and so on.

Question 2

What is log dilution

Answer 2

Dilutions in a log dilution series differ by a constant proportion, for example 10-1,10-2, 10-3 and so on.

Question 3

How is a standard curve produced and what is it used for?

Answer 3

Plotting measured values for known concentrations to produce a line or curve allows the concentration of an unknown to be determined from the standard curve.

Question 4

What is a buffer and what does it do?

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

Method and uses of a colorimeter

Answer 5

• 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.