Carbohydrates Flashcards
What are the 3 key monosaccharides?
Glucose
Galactose
Fructose
How do you form a disaccharide from two monosaccharides?
A condensation reaction forms a glycosidic bond between the monosaccharides and releases a water molecule.
What are the 3 key disaccharides?
Maltose
Lactose
Sucrose
What is maltose formed from?
Alpha Glucose + Alpha Glucose
What is lactose formed from?
Alpha Glucose + Galactose
What is sucrose formed from?
Alpha Glucose + Fructose
What is the difference between alpha glucose and beta glucose?
The hydroxide on the right side of the monomer is switched with the hydrogen (up not down).
Give the 3 key polysaccharides.
Starch
Glycogen
Cellulose
What is glycogen and starch polymers of?
Alpha Glucose
What is cellulose a polymer of?
Beta Glucose
What is the structure of cellulose?
Long, unbranched chains of beta glucose. Microfibrils are long cellulose chains running parallel to each other with hydrogen bonds as cross-linkages.
What is the function of cellulose structure?
Plant cell rigid because of strong-in-large-numbers hydrogen bonds. Strong microfibrils so doesn’t change shape of cell which will not burst, maintaining pressure. Turgid cell maximises photosynthesis.
What is the structure of starch?
Made of amylose and amylopectin. Amylose is an unbranched, coiled chain. Amylopectin is branched with lots of side branches.
What is the function of starch’s structure?
Coiled amylose is very compact, storing a lot of energy in small space. Amylopectin’s side branches can be rapidly hydrolysed to release a lot of energy. Insoluble so doesn’t affect water potential of cell.
What is the structure of glycogen?
Has 1,4 and 1,6 glycosidic bonds between alpha glucose molecules. Shorter chains, more branches than starch.
What is the function of glycogen’s structure?
Side branches can be easily hydrolysed releasing a lot of energy for respiration (higher metabolic rate than plants). Compact so stores a lot of energy in small amount of space. Insoluble so doesn’t affect water potential and will not diffuse out of cells.
Where is starch found?
In plants ONLY, as small grains.
Where is glycogen found?
In animal cells as small granules.
Where is cellulose found?
In plant cells ONLY.
How do you test for reducing sugars?
Add Benedict’s reagent to food sample. Heat mixture in a heated water bath for some time, a brick-red precipitate will form which is a positive result.
How do you test for non-reducing sugars?
Add Benedict’s reagent to food sample and heat mixture. Solution will remain blue. Boil with hydrochloric acid and then add sodium hydroxide to nuetralise the acid. Add Benedict’s reagent again and a brick-red precipitate should form. This is a positive result.
How do you test for starch?
Add potassium iodide or iodine solution to the food sample. Mixture should turn from orange-brown to a blue-black colour for a positive result.
