2: Carbohydrates Flashcards
What are ‘monosaccharides’?
sugars that consist of a single sub-unit (monomer)
Which atoms do monosccharides contain? What is the ratio between these atoms?
- carbon, hydrogen, and oxygen
- 1:2:1
Give an two exampls of monosaccharides. How many, and of what sort, of atoms are in your two examples?
ribose - C5 H10 O5
glucose - C6 H12 O6
Draw a ribose molecule (technically a D-ribose). (p20)
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What sort of ribose and glucose do living organisms use? What is the other sort called? What is the difference between them?
- liv org use: right handed versions or glucose/ribose
- other called: left handed version…
- difference: ?
Draw an a-D-glucose molecule. Draw a b-D-glucose molecule. (p20)
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How are pairs of monosaccharides linked together? What do they form?
- condensation reactions
- disaccharides
Give 3 common examples of monosaccharides.
- glucose
- galactose
- fructose
Give 3 common examples of disaccharides.
- maltose
- lactose
- sucrose
How can disaccharides be recognised?
by their double ring structure
What would a condensation reaction involving 2 glucose molecules form?
maltose + H2O
What would a condensation reaction involving a glucose molecule and a galactose molecule form?
lactose + H2O
What would a condensation reaction involving a glucose molecule and a fructose molecule form?
sucrose + H2O
Give 3 common examples of polysaccharides. What are all these molecules composed of?
- cellulose
- glycogen
- starch
- all made up from glucose
What is used to help describe the structure of polysaccharides?
a numbering system for the carbon atoms in glucose molecules
Draw an a-D-glucose molecule with the right numbers by the carbon atoms (numbers from the numbering system). (p20)
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What is the basic linkage between glucose subunits in polysaccharides called? Between which carbon atoms do most form? What, therefore, is this bond called?
- glycosidic bond
- forms between C1 of one glucose molecule, and C4 of the next
- called “1,4 glycosidic bond”
Most glycosidic bonds form between C1 of one glucose molecule, and C4 of the next. Where else can they form? What, therefore, is this bond called?
- between C1 of one glucose molecule, and C6 of the next
- 1,6 glycosidic bond
Describe cellulose.
1) unbranched polymer of B-D-glucose
2) orientation of glucose units alternates (up-down-up…)
- which makes the polymer straight, rather than curved
- and means groups of cellulose molecules can be arranged in parallel with hydrogen bonds forming cross links
3) these structures (parallel cellulose molecules with hydrogen bonds forming cross links) are called cellulose microfibrils
4) they have enourmous tensile strength and are the basis of plant cell walls
Draw a cellulose molecule. (p20)
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Describe starch.
1) polymer of a-D-glucose
2) all of glucose units in same orientation = helical shape
3) two forms of starch:
- amylose: 1,4 linkages = unbranched
- amylopectin: some 1,6 linkages = branched
4) starch used by plants to store glucose in an insoluble form (that does not cause osmotic problems)
5) branched molecule = possible to load/unload glucose more rapidly as there are more points on starch molecules to which glucose can be added/detached
Draw a branched starch molecule. (p20)
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Describe glycogen.
1) branched polymer of a-D-glucose (similar to amylopectin)
2) more 1,6 linkages than amylopectin = more branched
3) glycogen used by mammals to store glucose in liver and muscle cells
4) glyocen = insoluble, so large amounts can be stored (if glycogen was soluble it would cause water to enter cells by osmosis and there would be a danger of them bursting)
