Carbohydrates Flashcards
What is a polymer?
A large, complex molecule composed of long chains of monomers joined together
What is a monomer
A small, basic molecular unit
Give three examples of monomers
- Monosaccharides
- Amino acids
- Nucleotides
All carbohydrates contain what elements?
- Carbon
- Hydrogen
- Oxygen
Give three examples of monosaccharides
- Glucose
- Fructose
- Galactose
What is glucose?
Glucose is a hexose sugar - a monosaccharide with six carbon atoms in each molecule
What are the two types of glucose?
- Alpha glucose
- Beta glucose
What is a condensation reaction?
A condensation reaction is when two molecules join together with the formation of a new chemical bond, and a water molecules released when the bond is formed
How do monosaccharides join together?
Condensation reactions
What bond joins two monosaccharides together?
Glycosidic bonds
What is formed when two monosaccharides join together?
A disaccharide
Give three examples of disaccharides
- Glucose + Glucose = Maltose
- Glucose + Fructose = Sucrose
- Glucose + Galactose = Lactose
How are polymers broken down?
Hydrolysis reactions
What is a hydrolysis reaction?
A hydrolysis reaction breaks the chemical bond between monomers using a water molecule
How do you test for a sugar?
Benedict’s test
Explain the Benedict’s test for a reducing sugar
- Add Benedict’s reagent to a sample and heat it in a water bath that’s been brought to the boil
- If the test is positive it will form a coloured precipitate
- The colour of the precipitate changes from blue-green-yellow-orange-brick red
- The high the conc of reducing sugar the further the colour change will go
Explain the Benedict’s test for a non-reducing sugar
- Add dilute hydrochloric acid to the test solution and heat it in a water bath that’s been brought to the boil
- Neutralise with sodium hydrogencarbonate
- Carry out the Benedict’s test for a reducing sugar, if it’s positive a coloured precipitate will form
What is a polysaccharide?
A polysaccharide is when more than two monosaccharides are joined together by condensation reactions
What is starch?
Starch is a mixture of two polysaccharides of alpha glucose - amylose and amylopectin
What is the structure of amylose?
A long, unbranched chain of alpha glucose. The angles of the glycosidic bonds give it a coiled structure, making it compact so it’s good for storage
What is the structure of amylopectin?
A long, branched chain of alpha glucose. Its de branches allow the enzymes that break it down to get at the glycosidic bonds easier, meaning glucose can be released quickly
Explain the iodine test for starch
Add iodine dissolved in potassium iodide solution to the test sample. If there is starch present, the sample changed from browny-orange to blue-black
What is glycogen?
A long, branched chain of alpha glucose. Similar to amylopectin but it has loads more side branches, meaning stored glucose can be released quickly
What is cellulose?
A long, unbranched chain of beta-glucose
