Six original Cambridge-style questions on the elements in biological molecules, the small molecules that large ones are built from, and the link to digestion and plant nutrition.
List the chemical elements found in (a) carbohydrates, (b) fats and (c) proteins.
Complete the table by naming the small molecules from which each large molecule is made.
| Large molecule | Made from |
|---|---|
| cellulose | |
| protein | |
| oil |
A student analysed four pure substances found in a seed. The table shows the elements present in each.
| Substance | Elements present | Small molecules produced when digested |
|---|---|---|
| P | C, H, O | glucose |
| Q | C, H, O, N, S | amino acids |
| R | C, H, O | fatty acids and glycerol |
| S | C, H, O | cannot be digested by humans |
Identify substances P, Q, R and S, giving a reason for each.
Starch, glycogen and cellulose are all made from glucose, yet starch is a food store while cellulose forms strong cell walls. Suggest how molecules made from the same unit can have such different properties.
A plant makes glucose by photosynthesis. Explain why the plant also needs to absorb nitrate ions from the soil in order to grow.
A fat molecule and a protein molecule are each broken down into their small molecules. State how many small molecules a single fat molecule gives, and name them. Then explain why the same question cannot be answered with a single number for a protein.
Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.