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a-level biology > carbohydrates⭐️ > Flashcards

carbohydrates⭐️ Flashcards

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1
Q

what is maltose?

A

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

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2
Q

what is sucrose?

A

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

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3
Q

what is lactose?

A

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

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4
Q

how is a disaccharide formed?

A

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

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5
Q

what are three examples of monosaccharides?

A

glucose, galactose, fructose

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6
Q

what is a disaccharide?

A

two monosaccharides joined together by a condensation reaction

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7
Q

what is a polysaccharide?

A

two or more monosaccharides joined together by a condensation reaction

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8
Q

how is glycogen formed?

A

the condensation of alpha glucose

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9
Q

how is starch formed?

A

the condensation of alpha glucose

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10
Q

how is cellulose formed?

A

condensation of beta glucose

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11
Q

how do you test for reducing sugars?

A

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

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12
Q

what is a disadvantage of benedicts reagent?

A

subjective so could be difference in opinion

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13
Q

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

A

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

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14
Q

how do you test for non reducing sugar?

A

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

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15
Q

what is the chemical test for starch?

A

add iodine, orange to blue black colour change

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16
Q

what is a carbohydrate constructed of?

A

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

17
Q

describe how alpha glucose molecules are linked to form starch

A

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

18
Q

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

A

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

19
Q

name two isomers of glucose

A

alpha and beta

20
Q

name 3 monosaccharides

A

glucose, fructose, galactose

21
Q

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

A

standardized method, not subjective, produces quantitative data

22
Q

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

A

subjective

23
Q

Describe the structure of monosaccharides

A

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

24
Q

Explain how monosaccharides are linked together to form disaccharides

A

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

25
Q

Describe the test for starch

A

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

26
Q

What bond forms between two monosaccharides?

A

Glucose

27
Q

What’s sucrose made of?

A

Glucose and fructose molecule

28
Q

What is lactose made of?

A

Glucose and galactose molecule

a-level biology (25 decks)

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