Carbohydrates 1A

Question 1

What are monomers?

Answer 1

Small, basic molecular units from which polymers are made

Question 2

What are polymers?

Answer 2

large, complex units composed of long chains of monomers joined together

Question 3

Examples of monomers are

Answer 3

monosaccharides, amino acids and nucleotides

Question 4

What elements are carbohydrates made of

Answer 4

carbon, hydrogen and oxygen

Question 5

what monomers are carbohydrates made of

Answer 5

monosaccharides eg glucose, fructose and galactose

Question 6

What type of sugar is glucose

Answer 6

hexose

Question 7

what are the two isomers of glucose

Answer 7

alpha glucose and beta glucose

Question 8

what is an isomer

Answer 8

a molecule with the same molecular formula but different atomic arrangement

Question 9

Alpha glucose arrangement

Answer 9

H atom on top, OH atom on bottom

Question 10

Beta glucose arrangement

Answer 10

H atom on bottom, OH on top

Question 11

what is a condensation reaction

Answer 11

When two molecules join together with the formation of a new chemical bond and a water molecule is released when the bond is formed

Question 12

What are monosaccharides joined by

Answer 12

condensation reactions

Question 13

What bond forms between two monosaccharides as a water molecule is released

Answer 13

glycosidic bond

Question 14

what is formed when two monosaccharides join together

Answer 14

a disaccharide

Question 15

How is the disaccharide maltose formed

Answer 15

when two alpha glucose molecules are joined together by a glycosidic bond via a condensation reaction

Question 16

How is the disaccharide sucrose formed

Answer 16

formed from a condensation reaction between a glucose molecule and a fructose molecule

Question 17

How is the disaccharide lactose formed

Answer 17

formed from a condensation reaction between a glucose molecule and a galactose molecule

Question 18

What is a hydrolysis reaction

Answer 18

A hydrolysis reaction breaks the chemical bond between monomers using a water molecule

Question 19

Example of a hydrolysis reaction

Answer 19

Polymers broken down into monomers maltose broken down into two alpha glucose molecules

Question 20

What is the test for reducing sugars

Answer 20

Benedicts Test:
Add Benedics reagent to a sample and heat in a water bath that has been brought to the boil
If the test is positive then a coloured precipitate will form
Compare the amount of reducing sugar by filtering the solution and weighing the precipitate

Question 21

What is the test for non reducing sugars

Answer 21

These first need breaking down into monosaccharides you do this by adding dilute hydrochloric acid to the sample and carefully heating it in a water bath that has been brought to the boil, then neutralise it with sodium hydrocarbonate. Then carry out the benedicts test, if it’s positive then a coloured precipitate will form

Question 22

What are polysaccharides

Answer 22

More than two monosaccharides joined together by condensation reactions eg lots of alpha glucose joined together by glycosidic bonds to form amylose

Question 23

Structure and function of starch

Answer 23

Plants store excess glucose as starch
Starch is a mixture of amylose - long unbranched chain of a- glucose coiled structure compact, good for storage
amylopectin - long branched chain of a- glucose. Its side branches allow the enzymes to get to the glycosidic bonds more easily which allows the glucose to be released more quickly
insouble in water so does not affect water potential so water cannot enter cell by osmosis and cause it to swell

Question 24

What is the test for starch

Answer 24

Iodine in potassium iodide solution. If starch is present then the sample will change from browny orange to blue/black

Question 25

Structure and function of glycogen

Answer 25

Animals store excess starch as glycogen. Structure is similar to amylopectin except it has loads more side branches meaning glucose can be released more quickly. Very compact - good for storage

Question 26

Structure and function of cellulose

Answer 26

Long unbranched chains of beta glucose
Cellulose chains linked together by hydrogen bonds to form microfibrils which provide structural0
support