Biological Molecules (CIE IGCSE Biology: Co-ordinated Sciences (Double Award))

Three statements about proteins are given below. 

1. Different sequences of amino acids give different shapes to protein molecules.
2. Amylase is made from a sequence of amino acids joined together forming a non-specific 3D shape. 
3. When mixed with Biuret solution, there is a colour change from blue to purple. 

Which of the statements above are true?

The table below lists three large molecules found in living organisms. 

Which row correctly describes the smaller molecules these substances are made from?

	glycogen	cellulose	oils
A	glucose	glucose	glycerol
B	glycerol	starch	fatty acids
C	glycerol	glucose	glucose
D	glucose	starch	glycerol

Four statements about large biological molecules are given below:

1. Proteins are made from a number of different amino acids.
2. Both glycogen and starch are made from simple sugar base units.
3. Fats are made from glycerol and fatty acids.
4. Oils are made from glycerol only. 

Which of the four statements above is/are false?

A student carried out two food tests on solution F to determine what food groups it contains.

 

 

What food molecules does solution F contain?

A student mixes a food reagent with solution X in a test tube. 

They observe a positive test result when a cloudy emulsion forms. 

	food reagent	food molecule present in solution X
A	ethanol	glycogen
B	Biuret	lipids (fats and oils)
C	Benedict’s solution	glycogen
D	ethanol	lipids (fats and oils)

Which row of the table below identifies the reagent used and molecule present in Solution X?

Which row of the table below correctly describes the role of cellulose, proteins and water in living organisms? 

	cellulose	proteins	water
A	solvent	enzymes & antibodies	for chemical reactions
B	strengthens cell walls	to make fats & oils	solvent
C	strengthens cell walls	enzymes & antibodies	solvent
D	solvent	enzymes & antibodies	strengthens cell walls

The image below shows two molecules before and after chemical digestion by enzymes in the alimentary canal. 

Which letter(s) identify the product(s) of complete starch digestion?

A group of students tested four different foods using some common food tests.

Their results are shown in the table below.

	Benedict’s test	Biuret test	Iodine test	DCPIP test
A	brick-red	purple	brown	colourless
B	brick-red	blue	brown	colourless
C	blue	blue	black	blue
D	brick-red	blue	black	colourless

Which food contains reducing sugar and Vitamin C but not protein or starch?

The table below shows the elements and basic units used by cells to make large biological molecules. 

	basic units	elements	large molecule
A	amino acid	carbon, hydrogen, oxygen, nitrogen	protein
B	glycerol	carbon, hydrogen, oxygen, nitrogen	fats
C	glycerol	carbon, hydrogen, nitrogen	fats
D	amino acid	carbon, hydrogen, oxygen	carbohydrate

Which row of the table is correct?

Four foods were tested for the following food molecules:

• reducing sugar using Benedict’s reagent
• protein using Biuret solution
• fat using ethanol
• Vitamin C using DCPIP

	colour of food test result
	brick-red/orange	purple/lilac	colourless	milky-white
A	✔	✘	✔	✘
B	✔	✘	✘	✔
C	✘	✔	✔	✘
D	✘	✘	✔	✔

Which food contains sugar and Vitamin C?