carbohydrates⭐️ Flashcards
what is maltose?
a disaccharide formed by a condensation reaction of two glucose molecules. reducing sugar
what is sucrose?
a disaccharide formed by a condensation reaction of a glucose molecule and a fructose molecule. non reducing sugar
what is lactose?
a disaccharide formed by a condensation reaction of a glucose molecule and a galactose molecule. reducing sugar
how is a disaccharide formed?
by a condensation reaction between two monosaccharides with the formation of a glycosidic bond
what are three examples of monosaccharides?
glucose, galactose, fructose
what is a disaccharide?
two monosaccharides joined together by a condensation reaction
what is a polysaccharide?
two or more monosaccharides joined together by a condensation reaction
how is glycogen formed?
the condensation of alpha glucose
how is starch formed?
the condensation of alpha glucose
how is cellulose formed?
condensation of beta glucose
how do you test for reducing sugars?
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
what is a disadvantage of benedicts reagent?
subjective so could be difference in opinion
what is a more accurate method to test for reducing sugar?
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
how do you test for non reducing sugar?
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
what is the chemical test for starch?
add iodine, orange to blue black colour change
what is a carbohydrate constructed of?
carbon, hydrogen and oxygen. the carbon acts as a backbone to which other molecules attach
describe how alpha glucose molecules are linked to form starch
many alpha molecules are linked together by 1,4 glycosidic bonds to form polysaccharide starch
describe how beta glucose molecules are linked together to form the polymer cellulose
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
name two isomers of glucose
alpha and beta
name 3 monosaccharides
glucose, fructose, galactose
what are the advantages of using a colorimeter to measure the concentration of a reducing sugar
standardized method, not subjective, produces quantitative data
what are the disadvantages of using the benedicts test to measure the concentration of a reducing sugar
subjective
Describe the structure of monosaccharides
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
Explain how monosaccharides are linked together to form disaccharides
Disaccharide formed from two monsaccharides linked by a condensation reaction. Water is removed to form a glycosidic bond
Describe the test for starch
Add iodine solution to sample of food
Positive result for starch: blue/black
What bond forms between two monosaccharides?
Glucose
What’s sucrose made of?
Glucose and fructose molecule
What is lactose made of?
Glucose and galactose molecule
