OCR GCSE Biology A J247
Cell Level Systems
Community Level Systems
Genes, Inheritance and Selection
Global Challenges
Organism Level Systems
Scaling Up
Cell Level Systems
Synthesis and breakdown of carbohydrates, proteins and lipids
- 3 things to know
- Paper 1
Overview
How glucose builds starch and glycogen and why they are stored and broken down, amino acids as the monomers of proteins and why about twenty of them give so many proteins, the roles of proteins, lipids built from fatty acids and glycerol and broken down by lipase, why lipids store energy and their other uses, and the Benedict's, biuret and emulsion food tests.
What you need to know
Answer each one before you reveal it.
Why do plants convert glucose into starch for storage?
What happens when a carbohydrate is broken down?
Questions from this subtopic
Each one with the model answer underneath.
- 1
Which simple sugar is the monomer used to build carbohydrates such as starch?
Model answer
Glucose.
- 2
Describe starch in terms of monomers and polymers.
Model answer
Starch is a polymer made from many glucose monomers joined together in long chains.
- 3
Why do plants convert glucose into starch for storage?
Model answer
Starch is insoluble and compact, so it does not draw water into the cell and packs many glucose units into a small space.
- 4
What happens when a carbohydrate is broken down?
Model answer
The bonds between the sugar monomers are broken, releasing individual sugar molecules.
- 5
Which carbohydrate do animals store, and what is it built from?
Model answer
Glycogen, built from many glucose monomers joined together.
- 6
Why must stored starch be broken down before a cell can respire it?
Model answer
The polymer is too large to be respired, so it must first be split into glucose monomers.
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