AQA A Level Mini Biological Molecules

The monomers of proteins are

• nucleotides

• amino acids

• monosaccharides

• fatty acids

Answer explanation

The monomers of proteins are amino acids, which link together to form polypeptides. Nucleotides are for nucleic acids, monosaccharides are for carbohydrates, and fatty acids are for lipids.

Starch, cellulose an glycogen belong to the class of

• proteins

• lipids

• sugars

• Polysachharides

Answer explanation

Starch, cellulose, and glycogen are all types of carbohydrates known as polysaccharides. They are long chains of sugar molecules, distinguishing them from proteins, lipids, and simple sugars.

A carbon compound that contains two functional groups: amino and carboxyl

• amino acid

• enzyme

• carbohydrate

• nucleic acid

Answer explanation

An amino acid is a carbon compound that contains both an amino group (-NH2) and a carboxyl group (-COOH). This distinguishes it from enzymes, carbohydrates, and nucleic acids, which do not have both functional groups.

Three fatty acids bonded to glycerol

• glycogen

• polypeptide

• protein

• triglyceride

Answer explanation

Three fatty acids bonded to glycerol form a triglyceride, which is a type of fat. Glycogen, polypeptides, and proteins are different types of biomolecules and do not consist of this specific structure.

A large molecule made up of many similar or identical subunits.

• lipids

• polymer

• monomer

• monosaccharide

Answer explanation

A polymer is a large molecule composed of many similar or identical subunits called monomers. This definition directly matches the question, making 'polymer' the correct answer.

Which of the following tests for starch?

• Iodine

• Benedicts

• Biuret

Answer explanation

Iodine is the test that specifically detects starch. When iodine is added to a starch solution, it turns blue-black, indicating the presence of starch. The other options, Benedict's and Biuret, test for sugars and proteins, respectively.

Which of the following tests for protein?

• Iodine

• Benedicts

• Biuret

Answer explanation

The Biuret test specifically detects proteins by forming a complex with peptide bonds, resulting in a color change. Iodine tests for starch, while Benedict's test is for reducing sugars, making Biuret the correct choice for protein detection.

Which of the following tests for glucose?

• Iodine

• Benedicts

• Biuret

Answer explanation

Benedict's test is specifically used to detect reducing sugars, including glucose. Iodine tests for starch, while Biuret tests for proteins, making Benedict's the correct choice for glucose detection.

Which test requires heat?

• Benedicts

• Biuret

• Iodine

Answer explanation

The Benedict's test requires heat to detect reducing sugars. When heated with a sugar solution, it changes color, indicating the presence of glucose or other reducing sugars, unlike the Biuret and Iodine tests which do not require heat.

What is the colour change if you add Iodine (Brown colour) to the food contains protein?

• Red Brick

• No changes (Negative Results)

• Black

• Navy Blue

Answer explanation

Iodine is used to test for starch, not protein. When added to protein-containing food, there is no reaction, resulting in no color change, which confirms a negative result.