Biological molecules - carbohydrates

Question 1

Name the main Monosaccharides

Answer 1

• glucose
• fructose
• galactose

Question 2

Name the main Disaccharides

Answer 2

• maltose
• sucrose
• lactose

Question 3

Describe the test for reducing sugars

Answer 3

1) add Benedict’s reagent to food sample
2) place test tube in boiling water bath
3) observe colour change
for a positive result, blue -> green/yellow/orange/brick-red

Question 4

Describe what is meant by a condensation reaction

Answer 4

• Chemical reaction joining two monomers together to form a polymer - resulting in a molecule of water being removed + H20

Question 5

Describe what is meant by a hydrolysis reaction

Answer 5

Chemical reaction using a molecule of water to break the chemical bond between two monomers

Question 6

What bond is formed when two monosaccharides join together

Answer 6

Glycosidic bond

Question 7

Which of the disacccharides are reducing and which are non-reducing

Answer 7

• sucrose is NON- reducing
• maltose and lactose are reducing

Question 8

Which two monosaccharides join to make maltose

Answer 8

glucose + glucose –> maltose

Question 9

Which two monosaccharides join to make sucrose

Answer 9

glucose + fructose –> sucrose

Question 10

Which two monosaccharides join to make lactose

Answer 10

glucose + galactose –> lactose

Question 11

Describe the test for non-reducing sugars

Answer 11

• test for sucrose
  1) test sample as normal using Benedict’s reagent - resulting in no change
  2) with a fresh sample, heat with acid
  3) neutralise with alkali
  4) heat with Benedict’s reagent which will now give a positive result

Question 12

What is a polysaccharide?

Answer 12

• Polymer made up of a chain of monosaccharides joined by glycosidic bonds.

Question 13

Name the main polysaccharides

Answer 13

• starch
• glycogen
• cellulose

Question 14

Describe the test for starch

Answer 14

1) add iodine to food sample
2) for a positive result, orange -> blue/black

Question 15

What is starch used for?

Answer 15

Mainly used for energy storage in plants

Question 16

What are the two polysaccharides that make up starch

Answer 16

• amylose
• amylopectin

Question 17

Test for lipids

Answer 17

Emulsion Test
1) add ethanol to food sample
2) shake gently
3) for a positive result, a cloudy white layer will form at the top

Question 18

Test for proteins

Answer 18

1) add biuret reagent to food sample
2) for a positive result, blue –> purple

Question 19

Test for starch

Answer 19

1) add iodine to food sample
2) for a positive result, orange –> blue/black

Question 20

What does hydrolysis of lipids produce

Answer 20

• fatty acids
• monoglycerides

Question 21

What does hydrolysis of proteins make

Answer 21

• amino acids

Question 22

What does hydrolysis of carbohydrates make

Answer 22

• monosaccharides
• disaccharides

Question 23

State the chemical formula of glucose

Answer 23

C6H12O6

Question 24

What is glucose used for

Answer 24

• energy store in humans
• makes ATP during cellular respiration

Question 25

Describe structure of cellulose

Answer 25

• long chain of beta-glucose
• chains are held together by hydrogen bonds to form microfibrils (strong fibres)

Question 26

What type of polymer and bond is made from the joining of monosaccharides

Answer 26

A polysaccharide - glycosidic bond

Question 27

What type of polymer and bond is made from the joining of amino acids

Answer 27

A polypeptide - peptide bond

Question 28

What type of polymer and bond is made from the joining of nucleotides

Answer 28

A polynucleotide - phosphodiester bond

Question 29

Which biological molecules are required to make proteins

Answer 29

• amino acids
• ( nucleic acids)

Question 30

What are the 2 types of polysaccharides formed from alpha glucose

Answer 30

• starch
• glycogen