Carbohydrates

Question 1

formation of carbs in plants (photosynthesis)

Answer 1

roots absorb water from soil
leaves absorb carbon dioxide from air
chlorophyll in leaves convert sunlight into energy
energy from sun reacts with water and CO2 to produce glucose and oxygen

Question 2

chemical formula for photosynthesis

Answer 2

6CO2 + 6H2O + sunlight —) C6H12O6 + 6O2

Question 3

chemical structure

Answer 3

mono
di
poly

Question 4

monosaccharide

Answer 4

simple sugar unit
ring structure
eg glucose, fructose
C6H12O6

Question 5

disaccharide

Answer 5

two simple sugar units joined together with the removal of H2O
sucrose (glucose and fructose)
lactose (glucose and galactose)
C6H22O11

Question 6

polysaccharide

Answer 6

three or more sugar units joined together 
chains may be branched or straight
starch
cellulose
(C6H10O5)n n= number of monos

Question 7

properties of sugar

Answer 7

solubility
crystallisation 
caramelisation 
maillard reaction
hydrolysis 
inversion

Question 8

solubility

Answer 8

sugar is a white crystalline compound, it is soluble in water
solubility increases if water is heated (syrup), when a large amount of sugar is dissolved in a small amount of water

starch a non-crystalline powder, is insoluble in cold water

Question 9

maillard reaction

Answer 9

non enzymic browning of food due to a reaction between certain amino acids and sugars under dry heat
it produces an attractive brown colour and a crust with an appetising flavour
eg shortbread biscuits

Question 10

caramelisation

Answer 10

on heating, sugar melts and caramelises
this occurs over 10 gradual stages, between 104º and 177º
normally occurs at 160º, resulting in an attractive brown colour and a sweet taste
if overheated, caramel will carbonise or burn
eg caramel squares

Question 11

crystallisation

Answer 11

when a liquid has dissolved as much sugar as it can, it is saturated
if more sugar is added, crystals of sugar form in the solution and solidify when cooled
uses- confectionary

Question 12

hydrolysis

Answer 12

the reverse of the condensation reaction
occurs during digestion
water and enzymes split disaccharides into two monosaccharides eg lactose into glucose and galactose

Question 13

inversion of sugar

Answer 13

occurs when a liquid sucrose solution is heated in the presence of an acid or enzyme, causing the sucrose to split into glucose and fructose
this is known as an invert sugar and is sweeter than sucrose
uses- jam making

Question 14

dextrinisation

Answer 14

when starch foods are dry-heated, short chained polysaccharides called dextrins form
on further heating these combine to form pyrodextrins
this causes a colour change on the surface of the food, resulting in an attractive brown colour
eg toast

Question 15

pectin

Answer 15

pectin is naturally present in plant cells and cell walls of fruit/veg
used as a setting agent as it has the ability to absorb water to form a gel
only present in fruits when they are ripe
for pectin to be extracted it needs heat and an acid eg lemon juice
culinary application: jam making

Question 16

biological functions of starch and sugars

Answer 16

cheap sources of heat and energy (starch slow, sugar fast)
excess is converted to fat (adipose tissue under skin)
act as protein sparers
some stored in liver as instant energy resource

Question 17

biological functions of dietary fibre/cellulose

Answer 17

prevent bowel disorders by encouraging peristalsis and speed up waste removal
produces a feeling of fullness, reduces over eating

Question 18

culinary uses of sugar

Answer 18

preservative
sweetener
fermentation

Question 19

culinary uses of starch

Answer 19

thickener
hygroscopic
dextrinisation

Question 20

energy value

Answer 20

1g carbs = 17kJ

Question 21

increasing fibre in the diet

Answer 21

replace processed cereals with wholegrain
eat whole fruits , raw if possible
use wholemeal flour
eat skins of fruit and veg

Question 22

digestion in salivary glands

Answer 22

saliva-salivary amylase- starch-maltose

Question 23

digestion in duodenum/pancreas

Answer 23

pancreatic juice in duodenum-amylase-starch-maltose

Question 24

digestion in small intestine

Answer 24

intestinal juice- maltase- maltose- glucose

Question 25

absorption

Answer 25

monosaccharides are absorbed through the villi of the small intestine into the blood stream
transported to the liver via portal vein
fructose and galactose are converted to glucose

Question 26

utilisation of carbs

Answer 26

in the liver:
glucose is oxidised for heat and energy
glucose is converted into glycogen
excess is converted to fat and stored as adipose tissue

Question 27

gelatinisation of starch

Answer 27

when starch is combined with a liquid and heated to 55-70º, the grains swell, burst and absorb the liquid around them, increasing the viscosity
as the temp increases above 85º, it becomes even more viscous and forms a sol
on cooling, water molecules become trapped, resulting in a gel
culinary application: dry heat - popcorn

Question 28

fermentation

Answer 28

breakdown of organic substances by micro organisms ie bacteria and yeast to produce alcohol, co2 and energy

Question 29

properties of starch

Answer 29

solubility
hygroscopy
gelatinisation
hydrolysis
dextrinisation

Question 30

properties of fibre

Answer 30

dietary fibre function
gums
pectin

Question 31

hygroscopy

Answer 31

starch has the ability to absorb moisture from the air
this can cause uncovered foods to soften and lose crunch
culinary application: keeps cakes moist

Question 32

dietary fibre

Answer 32

insoluble in water
cannot be digested, but absorbs water as it passes through the intestinal tract and helps stimulate peristalsis
this is beneficial to the body as it speeds up the passage of food and waste, preventing bowel disorders

Question 33

gums

Answer 33

soluble in water
have the ability to absorb large amounts of water to form a thick gel with a firm texture
culinary application: ice cream