Carbohydrates Flashcards
State the elements present in carbohydrates. (F)
- Carbon
- Hydrogen
- Oxygen
State the general formula of carbohydrates. (F)
Cn(H2O)n
Define the term “monosaccharide”. (F)
A single sugar molecule
Define the term “pentose sugar” and give an example. (F)
A monosaccharide composed of 5 carbons i.e. ribose
Define the term “triose sugar” and name an example. (S+C)
A monosaccharide composed of 3 carbons i.e. glyceraldehyde
Describe what is meant by a “furanose ring” and a “pyranose ring”. (S+C)
Furanose ring: a five membered ring with 4 carbon atoms and an oxygen atom
Pyranose ring: a six membered ring with 5 carbon atoms and an oxygen atom
Define the term “isomer”.
Structural variation between molecules with the same atoms.
Describe the difference between alpha- and beta-glucose. (F)
Alpha-glucose has the hydroxyl group on C1 below the carbon ring; beta-glucose has the hydroxyl group on C1 above the carbon ring
List the similarities between alpha-glucose and ribose.
- soluble in water
- composed of C, H and O
- contain -OH groups
List 3 examples of disaccharides and for each state which monosaccharides they are composed of. (F)
- maltose (two alpha-glucose molecules)
- sucrose (alpha-glucose and fructose)
- lactose (beta-glucose and galactose)
State the properties of glucose.
- polar
- water soluble
- sweeter than galactose
State the properties of fructose.
- polar
- water soluble
- sweeter than glucose and galactose
State the properties of galactose.
- polar
- water soluble
- sweet
State the properties of maltose.
- soluble
- less sweet than glucose
State the properties of sucrose.
- sweet
- soluble
State the properties of lactose.
- low solubility
- slow release of energy
Explain why alpha-glucose links together to form starch whereas beta-glucose links together to form cellulose.
Alpha-glucose has both -OH chains on C1 and C4 below the carbon ring, so it forms starch.
Beta-glucose has to rotate to link because the -OH on C1 and C4 are on opposite sides of the carbon ring, so it forms cellulose.
List the two different polysaccharides that make up starch. (F)
- amylose
- amylopectin