Food tests — final check

1. explain

Egg white is mostly water, but it contains protein. Cooking oil is almost all fat. Explain which of the two contains nitrogen, and name the smaller molecules that the protein and the fat are built from.

2. compare

Compare how a starch molecule and a fat molecule are built from smaller molecules.

3. describe

Describe how to use Benedict's solution to find out whether a fruit drink contains a reducing sugar. Include the control, the conditions and the results you could see.

4. predict / explain

A sponge cake is made from flour (which contains starch and some protein), eggs (protein and fat), butter (fat) and glucose syrup (a reducing sugar). It contains no vitamin C. Crumbs are ground with water and all five food tests are done, each beside a water control. (a) Predict what you would see in each test. (b) Which test would be negative, and why is "not detected" a better way to report it than "none"?

(a) Iodine

(a) Benedict's

(a) Biuret

(a) Emulsion

(a) DCPIP

(b) Negative test, and why "not detected"

5. describe

Describe how to carry out the ethanol emulsion test on a food, and what a positive result looks like. Give one safety precaution for this test.

6. describe

Describe the structure of a DNA molecule, including the rule for how its bases pair.

7. calculate

A piece of DNA contains 100 bases in total. 18 of them are C. How many of the bases are A?

Number of A bases: ______________ unit ________