Carbahydrates Flashcards
(17 cards)
What are the isomers of the monosaccharide?
a- glucose: hydroxyl group is below the ring plane.
B-glucose: hydroxyl group is above the ring plane.
What are reducing sugars?
A sugar that can transfer electrons to reduce another chemical.
What is the test for reducing sugars?
The Benedict’s test: add equal volume of Benedict’s reagent to the sample, then heat gently until an insoluble precipitate is formed. A brick-red precipitate indicates that reducing sugars are present.
Green = low concentration, orange = medium, red = high.
What are disaccharides and examples?
Two a-glucose monosaccharides joined together by glycosidic bonds between carbon 1-4 in a condensation reaction.
Draw the formation of maltose.
glucose + glucose = maltose.
Draw the formation of sucrose.
glucose + fructose = sucrose.
Draw the formation of lactose.
glucose + galactose = lactose.
What is the test for non-reducing sugars?
Heat with Benedict’s. If negative (stays blue), hydrolyse substance with HCl and neutralise with NaOH. Then heat with Benedict’s.
Brick red precipitate indicates non-reducing sugar.
What are polysaccharides?
Large macromolecules formed from monosaccharides. They are insoluble in water, making them suitable for storage. When hydrolysed, they break down into disaccharides and monosaccharides.
What is starch?
Polysaccharide, in the form of grains, major energy source, made up of 1-4, 1-6 a-glucose monosaccharides linked together by glycosidic bonds in a condensation reaction.
How is starch’s structure related to its function?
Insoluble, so it doesn’t affect water potential and no osmosis; doesn’t diffuse out of cells. Compact, so lots can be stored in a small space. Hydrolysed, it forms a-glucose which is easily transported and ready for use in respiration.
What is the test for starch?
Add iodine, turns blue/black.
What is glycogen?
Storage polysaccharide in animals, made of 1-4 and 1-6 a-glucose. Stored as small granules mainly in muscle and liver.
How is glycogen adapted to its function?
Insoluble, doesn’t affect water potential of the cell and doesn’t diffuse out of cells. Compact, lots can be stored in a small space. Branched (more than starch) so more hydrolysable free ends that can be acted on simultaneously by enzymes.
What is cellulose?
Made from 1-4, b-glucose. Forms straight unbranched chains with every other b-glucose inverted 180 degrees.
What is cellulose’s function?
Provides rigidity to plant cells, prevents cells from bursting as water enters by osmosis by exerting inward pressure.
How is cellulose adapted to its function?
Made of B-glucose, forms long straight unbranched chains which are cross-linked by hydrogen bonds, adding collective strength.
