Carbohydrates

Question 1

Describe photosynthesis

Answer 1

The process where plants make their own food. Green plants use the energy from the sun to change carbon dioxide and water into glucose and oxygen

Question 2

What is the word and chemical equation for photosynthesis

Answer 2

Carbon dioxide + water = Glucose + oxygen
6CO2 + 6H2O = C6H12O6 +6O2

Question 3

Classification of carbs

Answer 3

1. Monosaccharides
2. Disaccharides
3. Polysaccharides

Question 4

Explain monosaccharides

Answer 4

1 simple sugar unit
C6H12O6
Glucose, galactose, fructose

Question 5

Explain Disaccharides

Answer 5

2 monosaccharides joined together with elimination of water (condensation)
C12H22O11
Maltose, Sucrose, Lactose

Question 6

How are starch units made of glucose arranged

Answer 6

Straight chains - amylose
Branched chains- amylopectin

Question 7

Explain Polysaccharides

Answer 7

3 or more monosaccharides joined together with elimination of water.
(C6H10O5)n
Pectin, cellulose, starch, glycogen, gums
Also known at NSPs

Question 8

Composition of Maltose, Sucrose and Lactose

Answer 8

Maltose = Glucose + Glucose
Lactose = Glucose + Galactose
Sucrose = Glucose + Fructose

Question 9

Sources of monosaccharides

Answer 9

Glucose - Fruit
Galactose - digested milk
Fructose - Honey

Question 10

Sources of polysaccharides

Answer 10

Pectin - Fruit
Cellulose - Pasta
Starch - Bread
Glycogen - Fruit

Question 10

Sources of disaccharides

Answer 10

Maltose - Barley
Sucrose - Table sugar
Lactose - Milk

Question 11

Explain NSPs

Answer 11

Non Starch Polysaccharides
Include dietary fibre/roughage
Can’t be digested and absorbs a lot of water
Aid peristalsis
Bread, pasta, rice
Refined foods have little if any

Question 12

Properties of starch

Answer 12

1. Dextrinization
2. Flavour
3. Solubility
4. Hygroscopic
5. Gelatinisation
6. Hydrolysis

Question 13

Dextrinisation

Answer 13

When dry heat is applied to starch. Molecules broken down into smaller polysaccharides called dextrins. Eg. Toasting bread

Question 14

Explain gelatinisation

Answer 14

When a starch is heated in water the grains swell, burst and absorb liquid and it thickens. As the temp rises the mixture becomes viscous and forms a sol. Gelatinisation occurs between 74-78 C. Eg adding flour to soup

Question 15

Explain hydrolysis

Answer 15

Chemical breakdown of a molecule by adding water to produce smaller molecules. Disaccharides become MS partly due to hydrolysis

Question 16

Properties of NSPs

Answer 16

1 Cellulose - can absorb a lot of water. Can’t be digested, adds bulk. Aids peristalsis
2. Pectin - Polysaccharide in fruit/veg. For setting jam. Can change in ripening of fruit
3. Gel formation - When pectin is heated in presence of acid and sugar, water becomes trapped. Long chains of PS coll ad form a gel. Eg jam

Question 17

Effects of dry heat

Answer 17

1. Food browns (toast)
2. Sugar caramelises (creme brulee)
3. overheating = carbonization
4. Maillard reaction = interaction between sugar and amino acids (sponge cake)

Question 18

Effects of moist heat

Answer 18

1. Cellulose softens (veg)
2. Starch swells, bursts and absorbs liquid (flour)
3. Pectin is extracted by heating fruit is water with sugar and acid
4. Sugar dissolves in warm liquid (caramel slices)

Question 19

Biological functions

Answer 19

1. Heat and energy
2. It spares protein so that is can be used for growth and repair
3. Excess changed to glycogen and stored in liver and muscles as energy reserve or changed to adipose tissue for insulation
4. Cellulose helps peristalsis
5. Cellulose absorbs water and gives feeling of fullness

Question 20

Culinary uses of starch

Answer 20

1. Thickener in soups
2. Hygroscopic - absorbs moisture to increase shelf life
3. Dextrinisation - browning (toast)

Question 21

Culinary uses of sugar

Answer 21

1. Sweetener (desserts)
2. Preservative (jam)
3. Caramelization (creme brulee)
   Fermentation (yeast bread)
4. Gel formation (jam)
5. Decoration (cake)

Question 22

Culinary uses of NSPs

Answer 22

1. Gel formation (jam pectin formas gel with acid and sugar )
2. Cellulose absorbs moisture and gives feeling of fullness
3. Cellulose adds texture (breakfast cereals)

Question 23

Properties of sugar

Answer 23

1. Solubility
2. Assists Aeration
3. Crystallisation
4. Caramelization
5. Maillard reaction
6. Sweetness
7. Hydrolysis
8. Inversion

Question 24

Digestion of carbs

Answer 24

1. Mouth - physically (teeth) salivary amylase (starch - maltose) 2. Stomach physically churned 3. Intestine - pancreatic juice (amylase) intestinal juice - maltase breaks down maltose to glucose

Question 25

Absorption of carbs

Answer 25

Monosaccharides absorbed through villi in small intestine into blood, carried to liver in portal vein. In liver fructose and galactose converted to glucose

Question 26

Assimilation of carbs

Answer 26

Monosaccharides can be oxidised to produce energy. Some changed to glycogen and stored in the liver and muscle as energy reserve. Excess changed to fat and stored in adipose tissue under skin. Vitamin B1, B2 and pyridoxine needed to metabolize carbs