Chapter 1: biological molecules

Question 1

Give examples of monomers

Answer 1

• amino acids
• monosaccharides
• nucleotides

Question 2

Monomers join together to form….

Answer 2

polymers

Question 3

A pair of monosaccharides is called…

Answer 3

A disaccharide

Question 4

Monosaccharides can be combined in large numbers to form…

Answer 4

polysaccharide

Question 5

Examples of monosaccharides

Answer 5

• glucose
• galactose
• fructose

Question 6

What is the difference between alpha and beta glucose?

Answer 6

The OH group is on top on beta glucose

Question 7

What is the test for reducing sugars?

Answer 7

• benedicts test

Question 8

How would you use benedict’s reagent to test for reducing sugars?

Answer 8

• add food sample in liquid form to a test tube
• add an equal volume of benedict’s reagent
• heat the mixture in water bath
• if reducing sugar present, solution turns orange/brown

Question 9

How would you test for non-reducing sugars?

Answer 9

• complete normal benedict’s test, if no colour change then add more food sample
• then add equal vol of dilute HCl and heat
• add some sodium hydrogencarbonate solution to neutralise
• add more benedict’s solution and heat
• turn orange brown if non-reducing sugar present

Question 10

Give 3 disaccharide reactions

Answer 10

• glucose + glucose ->maltose
• glucose fructose ->sucrose
• glucose +galactose ->lactose

Question 11

When monosaccharides join, a molecule of water is removed and the reaction is called a ______ reaction. The bond that is formed is called a _____ bond.

Answer 11

1) condensation
2) glycosidic

Question 12

When ___ is added to a disaccharide under suitable conditions, it breaks the ____bond releasing the constituent monosaccharides. This is called _____

Answer 12

a) water
b) glycosidic
c) hydrolysis

Question 13

Test for starch

Answer 13

• add sample to test tube
• add iodine solution
• if starch is present turns blue/black from yellow

Question 14

Describe the structure and functions of starch

Answer 14

Starch is made up of chains of a-glucose monosaccharides linked by glycosidic bonds that are formed by condensation reactions. The chains may be branched or unbranched.
The main role of starch is energy storage and it is well suited to this because..
- it is insoluble and therefore does not affect water potential
- being large and insoluble, it does diffuse in/out
- it is very compact so lots in a small space
- when hydrolysed forms a-glucose which is readily used
-the branched form has many ends which can be acted on by enzymes meaning glucose monomers are released rapidly