carbohydrates

Question 1

what is photosynthesis

Answer 1

is the process by which green plants use sunlight to make sugar from carbon dioxide and water

Question 2

how does photosynthesis occur

Answer 2

-plant roots absorb water (H20) from the soil
-leaves take in carbon dioxide (CO2) from the air
-Chlorophyll in leaves absorb energy from the sun

Question 3

what is the end result of photosynthesis

Answer 3

-glucose is formed
-oxygen is released into the air

Question 4

what is the equation for photosynthesis

Answer 4

6CO2 + 6H2O → C6H12O6 + 6O2

Question 5

what is the elemental composition of carbohydrates

Answer 5

carbon, hydrogen, oxygen

Question 6

what are monosaccharides

Answer 6

one sugar molecule. it is the smallest unit of a carbohydrate

Question 7

what is the chemical formula for monosaccharides

Answer 7

C6H12O6

Question 8

give examples and sources of monosaccharides

Answer 8

glucose- fruit
fructose- fruit and honey
galactose- digested milk

Question 9

what are disaccharides

Answer 9

two sugar molecules joined together

Question 10

what is the chemical formula of disaccharides

Answer 10

C12 H22 O11

Question 11

give examples and sources of disaccharides

Answer 11

maltose- barley
sucrose- table sugar
lactose- milk

Question 12

what are polysaccharides

Answer 12

many sugar molecules joined together

Question 13

what is the chemical formula for polysaccharides

Answer 13

(C6H1005)n

Question 14

give examples and sources of polysaccharides

Answer 14

starch- cereals and potatoes
glycogen- meat
cellulose- skins of fruits and vegetables

Question 15

what are the properties of sugars

Answer 15

solubility, sweetness, assist aeration, maillard reaction, caramelisation, crystallisation, hydrolysis and inversion

Question 16

explain solubility as a property of sugar

Answer 16

sugar is a white crystalline compound. it is a soluble in water. a syrup is formed when a large amount of sugar is dissolved in a small amount of water, e.g. canned peaches

Question 17

explain sweetness as a property of sugar

Answer 17

all sugars are sweet and give an appetising flavour to food. some sugars are much sweeter than others. this is measured on a point scale of sweetness, e.g. shortbread

Question 18

explain assists aeration as a property of sugar

Answer 18

Aeration occurs when sugar is whisked with an egg, denatured egg protein unfolds, entraps air bubbles, and creates heat, causing the egg to coagulate and form a permanent foam, e.g. sponges

Question 19

explain maillard reaction as a property of sugar

Answer 19

The maillard reaction is a non-enzymic browning process in food, resulting from the reaction between certain amino acids and sugars under dry heat. it produces an attractive brown colour and an appetising flavour, e.g. roast meat

Question 20

explain caramelisation as a property of sugar

Answer 20

on heating, sugar melts and caramelises. this occurs over ten gradual stages between 104C and 177C. caramelisation normally occurs at 160C, resulting in an attractive brown colour and a sweet taste. if overheated caramel will carbonise or burn, e.g. crème caramel

Question 21

explain crystallisation as a property of sugar

Answer 21

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, e.g. fudged

Question 22

explain hydrolysis as a property of sugar

Answer 22

hydrolysis occurs during digestion. water and enzymes split disaccharides into two monosaccharides into glucose and galactose

Question 23

explain inversion as a property of sugar

Answer 23

occurs when a liquid solution is heated in the presence of an acid or enzyme, causing the sucrose to split into glucose and fructose, e.g. jam-making

Question 24

what are the properties of starch

Answer 24

solubility, flavour, hygroscopy, hydrolysis,

Question 25

explain solubility as a property of starch

Answer 25

starch is a white non-crystalline powder. it is insoluble in cold water

Question 26

explain flavour as a property of starch

Answer 26

starch is not sweet in flavour

Question 27

explain hygroscopy as a property of starch

Answer 27

starch absorbs moisture from the air. this can cause uncovered foods, e.g. biscuits to soften and lose crunch

Question 28

explain dextrinisation as a property of starch

Answer 28

when dry heat is added to starch-based foods, dextrins are formed. this causes a colour change on the surface of the food, resulting in an attractive brown appearance

Question 28

explain gelatinisation as a property of starch

Answer 28

when starch is combined with liquid and heated to 55-70 the grains swell, burst and absorb the liquid around them, increasing the viscosity. as the temperature increases it becomes even more viscous and forms a sol. when the mixture cools, water molecules become trapped resulting in a gel, e.g. roux sauce

Question 29

explain hydrolysis as a property of starch

Answer 29

hydrolysis occurs during digestion. water and enzymes split starch into the disaccharide maltose

Question 30

what are the properties of non-starch polysaccharides

Answer 30

cellulose/dietary fibre, gums, pectin

Question 31

explain cellulose as a property of non starch polysaccharides

Answer 31

cellulose is insoluble in water. it cant be digested by the body, but it absorbs water as it passes through the intestinal tract and helps stimulate peristalsis

Question 32

explain gums as a property of non starch polysaccharides

Answer 32

gums are soluble in water. they can absorb large amounts of water to form a thick gel with a firm texture

Question 33

explain pectin as a property of non starch polysaccharides

Answer 33

present in plants cells and cell walls of fruit and vegetable. its used as a setting agent, as it can absorb water to form a gel. its only present in ripe fruits, if underripe its in the form of protopectin and if its overripe it becomes pectic acid. for pectin to be absorbed it needs heat and acid, e.g. jam-making

Question 34

what are the effects of dry heat on carbohydrates

Answer 34

-maillard reaction, e.g. roast beef -caramelisation, e.g. crème caramel -dextrinisation, e.g. toast

Question 35

what are the effects of moist heat

Answer 35

-syrup formation, e.g. syrup in canned peaches -gelatinisation, e.g. white sauce -cellulose softens, e.g. potatoes -pectin extractions, e.g. jam

Question 36

what are the biological functions of carbohydrates

Answer 36

-supply the body with heat and energy. helps keep the body at 37C -excess carbohydrates intake is converted to glycogen and stored in the liver and muscles as a long-term energy reserve -cellulose/dietary fibre absorbs water as it passes through the intestinal tract and helps stimulate peristalsis. this is beneficial as it speeds up the passage of food and waste, preventing bowel disorders, e.g. constipation