AQA A-Level Biology: Proteins Quiz

What is the primary structural difference between globular and fibrous proteins?

• Globular proteins are made of amino acids, while fibrous proteins are made of carbohydrates.

• Globular proteins are water-soluble and folded into a compact spherical shape, while fibrous proteins are insoluble and form long fibres.

• Globular proteins have a primary structure, but fibrous proteins do not.

• Globular proteins are more flexible than fibrous proteins.

Which of the following is an example of a conjugated protein, as described in the images?

• Keratin

• Insulin

• Haemoglobin

• Tropoelastin

The solubility of globular proteins in water is due to:

• The presence of a high proportion of hydrophobic R-groups on the outside of the molecule.

• The folding of the protein so that hydrophilic R-groups are on the outside.

• The presence of sulfur-containing amino acids.

• Their long, insoluble, linear structure.

Elastin is a fibrous protein found in elastic fibres. Its function is primarily to provide:

• Structural rigidity and inflexibility.

• The ability to stretch and recoil without breaking.

• Catalytic activity in biochemical reactions.

• A specific binding site for hormones.

Which of the following statements about collagen is correct?

• It is composed of a single polypeptide chain folded into a tertiary structure.

• Its strength is due to a high proportion of sulfur-containing amino acids.

• It is made from three polypeptide chains wound together in a triple helix.

• It is highly soluble in water and transports oxygen.

The unpleasant smell produced when hair is burnt is due to the presence of:

• Disulfide bonds in keratin.

• Cross-links in collagen.

• Iron ions in haemoglobin.

• Hydrophobic R-groups in elastin.

Which type of bond is responsible for the cross-links that stabilise the structure of elastin?

• Hydrogen bonds

• Ionic bonds

• Covalent bonds involving lysine amino acids

• Glycosidic bonds

Insulin is described as a globular protein. This is important for its function because:

• Its long, fibrous structure allows it to be transported in the blood.

• Its insoluble nature prevents it from being broken down in the blood.

• Its water-soluble nature allows for transport in the bloodstream.

• Its flexible structure allows it to expand and contract.

A prosthetic group is:

• A type of amino acid with a special R-group.

• A non-protein component that is part of a conjugated protein.

• The part of a protein that gives it its primary structure.

• A synonym for a polypeptide chain.

What is the role of the iron ion (Fe2+) within the haem group of haemoglobin?

• To provide a structural cross-link.

• To reversibly bind to an oxygen molecule.

• To catalyse the breakdown of hydrogen peroxide.

• To regulate blood glucose concentration.