Carbohydrates 1A Flashcards
What are monomers?
Small, basic molecular units from which polymers are made
What are polymers?
large, complex units composed of long chains of monomers joined together
Examples of monomers are
monosaccharides, amino acids and nucleotides
What elements are carbohydrates made of
carbon, hydrogen and oxygen
what monomers are carbohydrates made of
monosaccharides eg glucose, fructose and galactose
What type of sugar is glucose
hexose
what are the two isomers of glucose
alpha glucose and beta glucose
what is an isomer
a molecule with the same molecular formula but different atomic arrangement
Alpha glucose arrangement
H atom on top, OH atom on bottom
Beta glucose arrangement
H atom on bottom, OH on top
what is a condensation reaction
When two molecules join together with the formation of a new chemical bond and a water molecule is released when the bond is formed
What are monosaccharides joined by
condensation reactions
What bond forms between two monosaccharides as a water molecule is released
glycosidic bond
what is formed when two monosaccharides join together
a disaccharide
How is the disaccharide maltose formed
when two alpha glucose molecules are joined together by a glycosidic bond via a condensation reaction
How is the disaccharide sucrose formed
formed from a condensation reaction between a glucose molecule and a fructose molecule
How is the disaccharide lactose formed
formed from a condensation reaction between a glucose molecule and a galactose molecule
What is a hydrolysis reaction
A hydrolysis reaction breaks the chemical bond between monomers using a water molecule
Example of a hydrolysis reaction
Polymers broken down into monomers maltose broken down into two alpha glucose molecules
What is the test for reducing sugars
Benedicts Test:
Add Benedics reagent to a sample and heat in a water bath that has been brought to the boil
If the test is positive then a coloured precipitate will form
Compare the amount of reducing sugar by filtering the solution and weighing the precipitate
What is the test for non reducing sugars
These first need breaking down into monosaccharides you do this by adding dilute hydrochloric acid to the sample and carefully heating it in a water bath that has been brought to the boil, then neutralise it with sodium hydrocarbonate. Then carry out the benedicts test, if it’s positive then a coloured precipitate will form
What are polysaccharides
More than two monosaccharides joined together by condensation reactions eg lots of alpha glucose joined together by glycosidic bonds to form amylose
Structure and function of starch
Plants store excess glucose as starch
Starch is a mixture of amylose - long unbranched chain of a- glucose coiled structure compact, good for storage
amylopectin - long branched chain of a- glucose. Its side branches allow the enzymes to get to the glycosidic bonds more easily which allows the glucose to be released more quickly
insouble in water so does not affect water potential so water cannot enter cell by osmosis and cause it to swell
What is the test for starch
Iodine in potassium iodide solution. If starch is present then the sample will change from browny orange to blue/black
