Biological molecules - monosaccharides, disaccharides and polysaccharides Flashcards
Define monomer
The smaller units from which larger molecules are made
Define polymer
Molecules made from a large number of monomers joined together
Define hexose sugar
Six carbons
Define disaccharide
Formed when a pair of monosaccharides combine together
What is a condensation reaction?
Molecules joining together by condensation (releases water)
What is a glycosidic bond?
A chemical bond formed as the result of condensation between two monosaccharides
What is a hydrolysis reaction?
When water is added to a disaccharide under suitable conditions breaks the glycosidic bond releasing the constituent monosaccharides
What is a reducing sugar?
A sugar that can donate electrons to (or reduce) another chemical
What is a non-reducing sugar?
Disaccharides that do not change the colour of the chemical when they are heated with it
What are the monomers present in the disaccharide maltose?
Alpha glucose monomers
What are the monomers present in the disaccharide lactose?
Alpha glucose and galactose
What are the monomers present in the disaccharide sucrose?
Alpha glucose and fructose
Describe how a disaccharide is made
A pair of monosaccharides can combine together to form a disaccharide via a condensation reaction
A glycosidic bond is formed between the pair of monosaccharides
Water is released
What type of chain do 1,4 glycosidic bonds form?
Linear chain
What type of chain do 1,6 glycosidic bonds form?
Branched chain
Describe the structure of starch
- made of alpha glucose
- mixture of amylose and amylopectin
– amylase has C1 - C4 glycosidic bonds so is unbranched - amylopectin has C1 - C4 and C1 - C6 glycosidic bond so is branched
What is the function of starch?
Energy store in plant cells
How does the structure of starch relate to its function?
- helical compact for storage cell
- large polysaccharide molecule, can’t leave cell
- insoluble in water, water potential of cell not affected i.e. no osmotic effect
Describe the structure of glycogen
- glycogen is very similar in structure to starch, but has shorter chains and is more highly branched
- it is insoluble
- it is compact
What is the function of glycogen?
It is a major carbohydrate storage product of animals
How does the structure of glycogen relate to the function?
- highly more branched than starch - has more ends that can be acted simultaneously by enzymes
- it is therefore rapidly hydrolyse to form glucose monomers, which have a higher metabolic rate and respiratory system
- being insoluble - does not diffuse out of cells
- compact - a lot of it can be stored in a small space
Describe the structure of cellulose
- made of beta glucose - beta glucose is flipped 180 so that unbranched chains form
- form long, straight, unbranched chains
- parallel strands from microfibrils
- hydrogen bonds link parallel strands together
What is the function of cellulose?
Provides strength and structural support to plant cell walls
How does the structure of cellulose link to its function?
- cellulose provides support and rigidity because of straight parallel chains of beta glucose - strengthened by hydrogen bonds
- also group to form fibres also adding to the overall strength