1. Carbohydrates

Question 1

What is a disaccharide?

Answer 1

Condensation of 2 monosaccharides with a glycosidic bond. (C12H22O11)
Maltose = 2 glucose
Sucrose = glucose + fructose
lactose = glucose + galactose

Question 2

Whats an isomer?

Answer 2

Same chemical formula different structure: .e.g. a-glucose and b-glucose.

Question 3

Whats a monosaccharide?

Answer 3

larger carbohydrates: Glucose, Fructose, Galactose.
C6H12O6
E.g. amino acids

Question 4

Whats the test for Reducing sugars?

Answer 4

Add Benedict’s solution turn heat to 95’C into red precipitate when +.

Question 5

What’s the test for none reducing sugars?

Answer 5

Negative result with Benedict’s so then Boil with an acid and neutralise. heat to 95’C with benedicts. + = red precipitate.

Question 6

Whats the test fro starch?

Answer 6

Iodine. + = blue black from original orange colour.

Question 7

What are the quantitive test using Benedict solution?

Answer 7

Method 1
- Produce dilution series of known concs of glucose solutions.
use colourimeter to measure absorbance of solution after Benedict’s test. Higher absorbance = more sugar present
Plot calibration curve of absorbance.
Method 2
- Filter, dry precipitate. find mass using balance. bigger mass= more sugar present

Question 8

How are polysaccharides formed?

Answer 8

Formed by condensation of many glucose units.

Question 9

Whats the structure and properties of the polysaccharide starch?

Answer 9

Polysacharide
- a-glucose
-condensation reaction
- C1-4, C1-6 glycosidic bonds.
- releases glucose when hydrolysed.
- insoluble, doesnt affect water potential.
- large , cant cross membrane.
- branched/helical, compac t, fit many glucose in small area. - branched , many ends faster hydrolysis to release glucose.

Question 10

Whats the structure and properties of the polysaccharide Cellulose?

Answer 10

Polysaccharide
- plant cell walls made of b-glucose.
- condensation - C1-4 glycosidic bonds
- long straight chain which linked by many hydrogen bonds to form microfibrils to give mechanical strength.

Question 11

Whats the structure and properties of the polysaccharide glycogen?

Answer 11

Polysaccharide
- in liver/muscle cell made a-glucose.
- C 1,4 , C1-6 glycosidic bond.
- colied/compact many storage glucose molecules. - branched, more ends faster hydrolysis , release glucose for use respiratory substrate/energy.
- insoluble, not easily lost, not affect water potential.