1.3 Carbohydrates- Disaccharides and polysaccharides

Question 1

What are disaccharides and how are they formed?

Answer 1

● Two monosaccharides joined together with a glycosidic bond
● Formed by a condensation reaction, releasing a water molecule

all have the formula c12h22 o11 due to Water molecule being rermoved

Question 2

What is the equation for how each of the three disaccharides are formed

Answer 2

Glucose + Glucose—>Maltose + water
Glucose + Fructose—-> Sucrose + water
Glucose + Galactose—-> Lactose + water

Question 3

How do disaccharides form (3)

Answer 3

• Formed via a condensation reaction which releases a water molecule
• Joined together by a glycosidic bond
• Made up of two monosaccharides

Question 4

Describe the test for non reducing sugars

Answer 4

1. Do benedicts test and stays blue/negative
2. heat in a boiling water bath with acid (to hydroloyse into reducing sugars)
3. Neutrlise with alkali
4. heat in a boiling water bath with benedicts solution
5. positive result is either green/yellow/orange/red precipitate

Question 5

What are polysaccharides and how are they formed?

Answer 5

● Many monosaccharides joined together with glycosidic bonds
● Formed by many condensation reactions, releasing many water molecules

Question 6

What is a universal advantage that all polysaccharides have (3)

Answer 6

*They are large and insoluble so they are suitable for storage
*Cannot diffuse out the cell
*Have no osmotic effect

Question 7

Describe the test for reducing sugars

Answer 7

Add benedicts solution to a sample
Heat in a water bath
Positive reuslt is blue- green-red

Question 8

Give examples of polymers

Answer 8

DNA
Proteins
Starch
Glycogen