Carbohydrates, polysaccharides and food tests Flashcards
Biological compounds
What elements do carbohydrates contain?
Carbon, Hydrogen and Oxygen
What are monosaccharides?
Small organic molecules that are the building blocks to larger carbohydrates.
What reaction joins two monosaccharides together to form a disaccharide?
Condensation reaction.
What is an isomer?
Molecules with the same molecular formular but different structure.
What is Glucose’s two isomers?
Alpha- Glucose and Beta-Glucose.
Which carbons in Alpha-Glucose and Beta-Glucose is the glycosidic bond between?
Alpha-Glucose= Carbon 1
Beta-Glucose= Carbon 4
What is the bond called that uses Alpha and Beta glucose to form Maltose?
Glycosidic bond.
What happens in a Glycosidic bond?
The oxygens are bonded and water is removed (condensation reaction).
Define Hydrolysis.
Water used to break up larger molecules.
List the functions of Monosaccharides.
- A source of energy in respiration.
- Building blocks for larger molecules.
- Constituents of nucelotides.
Describe the test for the presence of sugars.
The solution being tested should have an equal volume to Benedicts Reagent and should be warmed to at least 70°C.
If a reducing sugar is present the solution will change colour from green to a brick red precipitate.
Why is the test for the presence of sugars qualitative?
Because it does not tell you the concentration of reducing sugars.
Give some examples of Polysaccharides.
Starch, Amylose, Amylopectin and Glycogen (Alpha-Glucose).
Cellulose and Chitin (Beta-Glucose).
Why is glucose converted into starch (plants) and glycogen (animals)?
It is the main source of energy and needs to be stored. It is soluble in water so it would increase the concentration of cell contents and draw in water by osmosis.
Why are starch and glycogen more suitable storage products for glucose?
- They are insoluble.
- They can’t diffuse out of cells.
- They are compact molecules and can be stored in small spaces.
- They carry lots of energy in their C-H and C-C bonds.
Describe the test for the presence of starch.
When iodine interacts with starch there is colour change from orange-brown to blue- black. This is also a qualitative test.
Describe the test for fats and oils.
The sample needs to be tested with absolute ethanol to dissolve lipids present. Then shake with equal parts water. The lipids will come out of the solution because they are insoluble in water. The sample will result in a white cloudy emulsion.
Describe the tests for proteins.
A few drops of biuret reagent to the solution. If protein is present the positive biuret test turns from blue to purple. It is a qualitative test.
What monomer makes up starch?
Alpha- Glucose.
What monomer makes up Glycogen?
Alpha-Glucose.
What monomer makes up cellulose?
Beta-Glucose.
What monomer makes up chitin?
Beta-Glucose and amino acids.
