carbohydrates⭐️

Question 1

what is maltose?

Answer 1

a disaccharide formed by a condensation reaction of two glucose molecules. reducing sugar

Question 2

what is sucrose?

Answer 2

a disaccharide formed by a condensation reaction of a glucose molecule and a fructose molecule. non reducing sugar

Question 3

what is lactose?

Answer 3

a disaccharide formed by a condensation reaction of a glucose molecule and a galactose molecule. reducing sugar

Question 4

how is a disaccharide formed?

Answer 4

by a condensation reaction between two monosaccharides with the formation of a glycosidic bond

Question 5

what are three examples of monosaccharides?

Answer 5

glucose, galactose, fructose

Question 6

what is a disaccharide?

Answer 6

two monosaccharides joined together by a condensation reaction

Question 7

what is a polysaccharide?

Answer 7

two or more monosaccharides joined together by a condensation reaction

Question 8

how is glycogen formed?

Answer 8

the condensation of alpha glucose

Question 9

how is starch formed?

Answer 9

the condensation of alpha glucose

Question 10

how is cellulose formed?

Answer 10

condensation of beta glucose

Question 11

how do you test for reducing sugars?

Answer 11

method 1) add equal volumes of sample and benedicts reagent (blue), heat gently for 5 mins, colour change or green to red with increasing conc of reducing sugar

Question 12

what is a disadvantage of benedicts reagent?

Answer 12

subjective so could be difference in opinion

Question 13

what is a more accurate method to test for reducing sugar?

Answer 13

use a colourimeter to measure how much light passes through the sample, this is quantitative and is a standardised method. could also filter and dry the ppt, weigh its mass. the higher the mass, the more reducing sugar it contains

Question 14

how do you test for non reducing sugar?

Answer 14

complete test for reducing sugar. to a new sample, add HCl and boil for 5 minutes, this hydrolyses the glycosidic bond producing a reducing sugar. add sodium hydrogen carbonate to neutralise sample. add benedicts and heat. colour change from green to red for increasing conc of non reducing sugar

Question 15

what is the chemical test for starch?

Answer 15

add iodine, orange to blue black colour change

Question 16

what is a carbohydrate constructed of?

Answer 16

carbon, hydrogen and oxygen. the carbon acts as a backbone to which other molecules attach

Question 17

describe how alpha glucose molecules are linked to form starch

Answer 17

many alpha molecules are linked together by 1,4 glycosidic bonds to form polysaccharide starch

Question 18

describe how beta glucose molecules are linked together to form the polymer cellulose

Answer 18

beta glucose links together to form glycosidic bonds in a long unbranched chain. each adjacent beta glucose is rotated by 180 degrees. these straight chains form hydrogen bonds with parallel straight chains. groups of cellulose molecules form to make microfibrils. parallel groups of microfibrils form fibres of cellulose

Question 19

name two isomers of glucose

Answer 19

alpha and beta

Question 20

name 3 monosaccharides

Answer 20

glucose, fructose, galactose

Question 21

what are the advantages of using a colorimeter to measure the concentration of a reducing sugar

Answer 21

standardized method, not subjective, produces quantitative data

Question 22

what are the disadvantages of using the benedicts test to measure the concentration of a reducing sugar

Answer 22

subjective

Question 23

Describe the structure of monosaccharides

Answer 23

A monsaccharide is a sugar with the general formula CH2O(n) where n is any number between 3 and 7. The atoms can be arranged in many ways to form isomers

Question 24

Explain how monosaccharides are linked together to form disaccharides

Answer 24

Disaccharide formed from two monsaccharides linked by a condensation reaction. Water is removed to form a glycosidic bond

Question 25

Describe the test for starch

Answer 25

Add iodine solution to sample of food
Positive result for starch: blue/black

Question 26

What bond forms between two monosaccharides?

Answer 26

Glucose

Question 27

What’s sucrose made of?

Answer 27

Glucose and fructose molecule

Question 28

What is lactose made of?

Answer 28

Glucose and galactose molecule