Carbohydrates

Question 1

What is a monosaccharide?

Answer 1

The most basic monomer of a carbohydrate.

Question 2

What are structural isomers?

Answer 2

Same molecular formula, different arrangement of atoms in space.

Question 3

Name 3 monosaccharides.

Answer 3

Galactose, Glucose, Fructose

Question 4

What is the difference between alpha glucose and beta glucose?

Answer 4

The OH group is found below the H in alpha glucose.
The OH group is found above the H in beta glucose.

Question 5

What is a disaccharide?

Answer 5

2 monosaccharides held together by a glycosidic bond, formed in a condensation reaction.

Question 6

What is a condensation reaction?

Answer 6

A reaction that joins 2 or more monomers together while eliminating a water molecule.

Question 7

Name 3 disaccharides.

Answer 7

Maltose, Sucrose, Lactose

Question 8

a Glucose + a Glucose

Answer 8

Maltose

Question 9

a Glucose + Fructose

Answer 9

Sucrose

Question 10

a Glucose + Galactose

Answer 10

Lactose

Question 11

What is a hydrolysis reaction?

Answer 11

A reaction that breaks up a polymer, requiring water

Question 12

What are polysaccharides?

Answer 12

Large sugar molecules containing 2+ monomers joined together, formed by the condensation of many monomers.

Question 13

Name 3 polysaccharides.

Answer 13

Starch, Glycogen, Cellulose

Question 14

What is the function of starch?

Answer 14

Energy store in plant cells.

Question 15

What 2 molecules make up starch?

Answer 15

Amylose and amylopectin.

Question 16

Describe the structure of amylose.

Answer 16

Straight molecule with C1-C4 glycosidic bonds.

Question 17

Describe the structure of amylopectin.

Answer 17

Branched molecule made of a glucose with C1-C4 and C1-C6 glycosidic bonds.

Question 18

What property of starch makes it compact for cell storage?

Answer 18

Helical, meaning it can coil tightly for maximum storage in cells.

Question 19

Why can’t starch leave cells?

Answer 19

It’s large.

Question 20

Why won’t starch affect the water potential of cells?

Answer 20

It is insoluble, so there is no osmotic effect.

Question 21

What is the function of glycogen?

Answer 21

Energy store in animal cells.

Question 22

Describe the structure of glycogen.

Answer 22

Branched molecule made of a glucose, with glycosidic bonds at C1-C4 and C1-C6.

Question 23

What are the benefits of glycogen being branched?

Answer 23

It can be rapidly hydrolysed back into a glucose so it can be used in respiration to release energy.

Question 24

Why is glycogen unable to leave the cell?

Answer 24

It is a large polysaccharide.

Question 25

Why won’t glycogen affect the water potential of a cell?

Answer 25

It’s insoluble in water, so there is no osmotic effect.

Question 26

What is the function of cellulose?

Answer 26

To provide strength and structural support to plant cell walls.

Question 27

Describe the structure of cellulose.

Answer 27

Polysaccharide of B glucose held by glycosidic bonds in straight chain. Each B glucose is inverted 180 degrees to the previous one. Straight chains are held close together by hydrogen bonds.

Question 28

Why is cellulose so strong?

Answer 28

The high volume of hydrogen bonds makes cellulose strong.

Question 29

How does cellulose form microfibrils?

Answer 29

Hydrogen bonds form cross links.

Question 30

Describe benedicts test for reducing sugars.

Answer 30

1. Add benedicts to sample
2. Heat in a boiling water bath.
3. Positive result shows colour change from blue to green/yellow/brick red.

Question 31

Describe benedicts test for non reducing sugars.

Answer 31

1. Add a few drops of HCl to hydrolyse the disaccharide into its monosaccharides
2. Heat in a boiling water bath
3. Neutralise with sodium bicarbonate
4. Add Benedict’s reagent and reheat
5. If a non reducing sugar is present, colour changes from blue to green, yellow or red