In an industrial bioreactor, yeast is used to ferment glucose under anaerobic conditions to produce biofuel. During this metabolic pathway, a gaseous byproduct is evolved.

Describe a chemical test to identify this gas and state the expected observation.

• Test:
• Result:

Glucose is a simple sugar (monomer) that plants polymerise for storage and structure. Name two naturally occurring polymers produced from glucose monomers, specifying one used for plant storage and one used for plant cell wall structure.

Figure 1 shows the displayed structural formula of serine, a naturally occurring amino acid.

Draw on this

How many functional groups are there in the serine molecule shown in Figure 1?

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• 4

Serine molecules react by condensation polymerisation to form a polypeptide.

Name the other substance produced in this reaction.

Amino acids contain nitrogen, which is not present in glucose.

Which two nitrogen-containing gases from Earth's early atmosphere could have acted as the prebiotic source of nitrogen to form the first amino acids in early organisms?

In living organisms, the sequence of amino acids in proteins is controlled and templated by DNA.

Describe the shape and molecular structure of a DNA molecule.