3. 1. 2 Carbohydrates Flashcards
What are monosaccharides?
Monosaccharides are the monomers from which larger carbohydrates are made.
Give 3 examples of monosaccharides.
Glucose, galactose and fructose are common monosaccharides.
What does a condensation reaction between two monosaccharides form?
A condensation reaction between two monosaccharides forms a glycosidic bond.
How are disaccharides formed?
Disaccharides are formed by the condensation of two monosaccharides.
Give 3 examples of disaccharides.
Maltose, sucrose and lactose.
How is maltose formed?
Maltose is a disaccharide formed by condensation of two glucose molecules
How is sucrose formed?
Sucrose is a disaccharide formed by condensation of a glucose molecule and a fructose molecule.
How is lactose formed?
Lactose is a disaccharide formed by condensation of a glucose molecule and a galactose molecule.
What is an isomer?
Molecules with the same chemical formula but have different structures.
What are the two isomers of Glucose?
a(alpha)-glucose and b(beta)-glucose.
How are polysaccharides formed?
Polysaccharides are formed by the condensation of many glucose monosaccharides resulting in the formation of glycosidic bonds.
What is formed by the condensation of a(alpha)-glucose?
Glycogen and starch.
What is formed by the condensation of b(beta)-glucose?
Cellulose
What is the function of glycogen?
A reserve source of energy for the body.
What is the function of starch?
Key energy store in plants.
What is the function of cellulose?
Provide strength and rigidity to the plant cell wall.
What are carbohydrates made up of?
Made up of carbon, hydrogen and oxygen.
Describe the test for reducing sugars.
1) Add 2cm^3 of food sample (in liquid form) to a test tube.
2) Then add 2cm^3 of Benedict’s Reagent.
3) Heat mixture in gentle boiling water bath for 5mins
Describe the results of the reducing sugars test.
None-blue
Very low-green
Low-yellow
Medium-brown
High-red
Describe the test for non-reducing sugars.
1) Carry out Benedict’s test: negative result so no reducing sugars.
2) Hydrolyse the unknown to split the sugar into monosaccharides:
- Add HCl
- Heat in water bath
- Neutralise using hydrogen carbonate
3) Repeat Benedict’s test
Describe the results for the non-reducing sugars test.
If it goes brick red this time, there is non-reducing sugars present
Describe the iodine test for starch.
1) Dissolve iodine in potassium iodide
2) Add iodine solution directly to food sample
Describe the results for the iodine test for starch.
A dark blue-black colour indicates presence of starch.
What does quantitative mean?
Relating to, measuring, or measured by the quantity of something rather than its quality.
