Biological Molecules

Question 1

What is a monomer? Give some examples

Answer 1

Monomers are small, basic molecular units e.g. monosaccharides, amino acids, nucleotides

Question 2

What is a polymer? Give some examples

Answer 2

Polymers are large, complex molecules maid up of long chains of monomers joined together e.g. carbohydrates, proteins, nucleic acids

Question 3

How to monosaccharides join together and break apart?

Answer 3

condensation reaction - join together

hydrolysis reaction - break apart

Question 4

What type of bond is formed between two monosaccharides?

Answer 4

glycosidic bond

Question 5

what is a monomer? Give some examples

Answer 5

a monomer is a small, basic molecular unite e.g. monosaccharides, amino acids, nucleotides

Question 6

what is a polymer? Give some examples

Answer 6

polymers are large, complex molecules made up of long chains of monomers joined together e.g. carbohydrates, proteins, nucleic acids

Question 7

Describe glucose

Answer 7

1. glucose is a hexose sugar (monosaccharide with 6 carbon atoms)
2. 2 types → alpha (α) glucose and beta (β) glucose - they are isomers

Question 8

what reaction forms and breaks monosaccharides?

Answer 8

condensation - forms

hydrolysis - breaks down

Question 9

how do you test for sugars (reducing and non-reducing)

Answer 9

Reducing sugars:
1. Add Benedict’s reagent (which is blue) to a sample and heat it in water bath for 5 minutes
2. If the test is positive there should be a colour change
colour change:
blue → green → yellow → orange → brick red
3. the higher the concentration of reducing sugar, the further the colour change goes
Non-reducing sugars:
1. Add dilute hydrochloric acid to negative sample and heat in water bath for 5 minutes then neutralise with sodium hydrogen-carbonate
2. Then you just carry out the Benedict’s test
3. If positive, there will be a colour change

Question 10

what is a polysaccharide?

Answer 10

polysaccharide is formed when more than two monosaccharides are joined together by a condensation reaction

Question 11

what is starch?

Answer 11

1. starch is a mixture of two polysaccharides of alpha glucose (amylose and amylopectin):
2. amylose (1,4 glycosidic bonds) - long, unbranched chain of α-glucose. coiled structure - makes it compact meaning extremely good for storage
3. amylopectin (1,4 and 1,6 glycosidic bonds) - long, branched chain of α-glucose. side branches allow for enzymes to break glycosidic bonds easily meaning glucose can be release quickly
   starch is insoluble in water and doesn’t affect water potential - good for storage

Question 12

how do you test for starch?

Answer 12

1. add iodine dissolved in potassium iodide solution to test sample
2. if the re is starch present, sample changes forms browny-orange to a blue-black colour

Question 13

describe glycogen

Answer 13

1. polysaccharides formed of α-glucose
2. similar to amylopectin but has a lot more side branches meaning stored glucose can be removed quickly
3. very compact molecule so good for storage

Question 14

describe cellulose

Answer 14

1. cellulose is mad of long, unbranched chains of β-glucose
2. when β-glucose bond, they form straight cellulose chains
3. linked together by hydrogen bonds to form strong fibres called microfibrils - provides structural support
   (multiple microfibrils form fibres)

Question 14

describe cellulose

Answer 14

1. cellulose is mad of long, unbranched chains of β-glucose
2. when β-glucose bond, they form straight cellulose chains
3. linked together by hydrogen bonds to form strong fibres called microfibrils - provides structural support
   (multiple microfibrils form fibres)