GCE AQA BIOL - Carbohydrate Digestion
Unit 3.1 Biology and disease
3.1.2 The digestive system provides an interface with the environment. Digestion involves enzymic hydrolysis producing smaller molecules that can be absorbed and assimilated.
Carbohydrates, proteins and fats are considered macromolecules because they are polymers (long chains of molecules). Each is actually composed of a series of monomers, which are small individual units.
In carbohydrates, monosaccharides are the monomers, forming the basic molecular unit of carbohydrates.
2 monosaccharides can be linked up to form a single disaccharide.
Many monosaccharides can also be joined up to form long chains of carbohydrate polymers known as polysaccharides.
Carbohydrates can thus be divided into three levels of organisation:
We have just discussed the building of carbohydrates from the smallest building blocks of monosaccharides. In GCE AQA Biology, you should also be familiar with the breakdown of carbohydrates from its largest polysaccharides or smaller disaccharides into its constituent monomers. This process of breaking down often requires the presence of specific enzymes.
For example, let’s follow the breakdown of starch (found in many foods like bread 🍞or pasta 🍝) in the human digestive system.
Other disaccharides are also broken down by specific enzymes:
Carbohydrate breakdown - what happens when it goes wrong: Lactose intolerance
GCE AQA Biology includes biochemical tests for the presence of specific carbohydrates:
1. Test for reducing sugars: Benedict’s test
2. Test for non-reducing sugars
3. Test for starch: iodine test
And we're finished with this section!
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Written by Justine | Biology Specialist @ Tuttee
ReferencesToole, G. & Toole, S. 2015. AQA Biology (2nd edition). Oxford University Press
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