Students should be able to apply their knowledge of these features in…

The idea

Application questions give you an unfamiliar cell, as an electron micrograph, a table of organelle counts or a short description, and expect you to link a named feature to the job that cell does, in that order. The moves are always the same. Many mitochondria means more ATP released in aerobic respiration, for active transport or for movement. Many ribosomes, or extensive rough endoplasmic reticulum, means rapid synthesis of protein, often for export. A large Golgi apparatus with many vesicles means modification, packaging and secretion of proteins and lipids. Many lysosomes means hydrolysis of engulfed pathogens. Microvilli, or a folded membrane, mean a large surface area for absorption; many carrier proteins mean rapid active transport, co-transport or facilitated diffusion, while channel proteins allow facilitated diffusion; many chloroplasts mean more light absorbed.

What earns the marks

• Naming the feature seen in the cell rather than restating the data given.
• Saying there are many of the organelle, or that the membrane is folded, where number or surface area is the adaptation.
• The process the feature carries out, such as mitochondria releasing ATP in aerobic respiration.
• Linking that process to the overall function of the cell, such as the co-transport of glucose into the cell from the lumen.
• A second, genuinely different adaptation where the question asks for more than one.

Common mistakes and how to put them right

• Listing the organelles visible in a figure without linking any of them to the function of the cell.

• Omitting 'many', since it is the number rather than the presence of an organelle that is being credited.

• Writing that mitochondria 'give energy' rather than release ATP in aerobic respiration.

• Giving two versions of the same adaptation, such as microvilli and folded membrane, when two different features are required.

• Conflating channel proteins, which only perform facilitated diffusion, with carrier proteins that can also perform active transport and co-transport.

Exam tips

• Count the marks and give that many separate feature-and-function pairs; three marks means three distinct adaptations.
• Where transport proteins are involved, say which kind of transport they carry out, since channel, carrier and co-transport proteins function differently.
• Answer 'describe and explain' in two halves for every point: what the feature is, then why it helps.