Session Three (1.4.3): Proteins and Testing for Proteins
Introduction
Proteins are large molecules containing carbon, hydrogen, oxygen and nitrogen atoms. They are built from small molecules called amino acids. Proteins are used to build structures within cells and organisms, they help fight diseases in the form of antibodies and form enzymes which enable essential chemical reactions to occur in cells.
Reading
Read and make notes on page 36.
Tasks
Add any unfamiliar key words to your key word glossary file and or the Quizlett App.
Summarise the uses of proteins in organisms in the form of a table.
Proteins are tested for using the Biuret test. Watch the video in the links below to find out about the Biuret test.
Write a brief summary of how the Biuret test is carried out.
Link
WATCH - Biuret Test Just in 3 Minutes (YouTube) Links to an external site.
WATCH - Food Tests – GCSE Science Biology Required Practical (YouTube) Links to an external site.
WATCH - Amoeba Sisters: Biomolecules (YouTube) Links to an external site.
Download
READ - Food Types, Deficiencies and Food Tests (PowerPoint) Download READ - Food Types, Deficiencies and Food Tests (PowerPoint)
Tip: you will need to be able to describe and explain these biochemical tests: Iodine test (starch), Benedict’s test (reducing sugars), Biuret test (protein) and Ethanol Emulsion test (fats).
Review
Copy and complete the summary table below listing the names of the different food tests, the biological molecules that are being tested for and what a positive result looks like. The table has been started for you:
| Name of Food Test | Biological Molecule being Tested For | Description of Positive Test Result |
|---|---|---|
| Iodine | Blue/black staining | |
| Benedict's test | ||
| Protein | ||
| Fats |