Carbohydrates

Question 1

Give the properties of monosaccarhides

Answer 1

Hydrophilic - Soluble in water because they have a large number of hydroxyl groups, which can form hydrogen bonds with water molecules

Question 1

What is a monosaccharide?

Answer 1

Monomers from which larger carbohydrates are formed

Question 1

Give examples of monosaccarhides

Answer 1

Glucose, fructose and galactose

Question 2

Describe the difference between alpha and beta glucose

Answer 2

The position of the hydroxyl group on each carbon 1 differs, in alpha glucose its below carbon 1 and beta glucose is above carbon 1

Question 3

How do disaccharides form?

Answer 3

When two monosacharides chemically bond together in a condensation reaction releasing water from a hydrogen from one monosacharide and a hydroxyl from the other.

Question 4

How is maltose formed?

Answer 4

Two alpha glucose monosacharides chemically bonding together in a condensation reaction.

Question 5

What is a glycosidic bond?

Answer 5

The bond that is formed when two monosacharides bond during a condensation reaction is a glycosidic bond

Question 6

What happens when you add water to a disachharide?

Answer 6

It reforms back into a monosachharide by breaking the glycosidic bond in a hydrolysis reaction.

Question 7

How is sucrose formed?

Answer 7

Glucose and fructose

Question 8

How is lactose formed?

Answer 8

Glucose and galactose

Question 9

Describe the differences between glycogen and starch.

Answer 9

• Glycogen is found in animals whereas starch is found in plants.
• Glycogen has many more branched ends than starch

Question 10

Give the structure of glycogen and describe how this relates to its function.

Answer 10

• Compact so a lot can be stored in a small space.
  -Insoluble so does not draw water in by osmosis and does not effect water potential
  -More higher branched than starch meaning it has more ends that can be acted simultaneously on by enzymes so it is more rapidly broken down into glucose monomers which are used in respiration and this is important because animals have a higher metabolic rate and therefore a higher rate of respiration than plants.
  Large so it cannot diffuse out of cells.

Question 11

Name the polysachharides made by polymers of alpha glucose

Answer 11

Amylose, amylopectin and glycogen

Question 12

How is cellulose formed?

Answer 12

Monomers of beta glucose where every second beta glucose is flipped.

Question 13

Give a key feature of cellulose

Answer 13

This is an unbranched polysacharride

Question 14

Describe the structure of cellulose and how this relates to its function

Answer 14

Forms long, straight unbranched chains, which are parallel allowing hydrogen bonds to form , which also form crosslinks, and because a large number of hydrogen bonds are made this makes cellulose very strong. These cellulose molecules grouped together are called microfibril.

Question 15

What is it called when cellulose molecules join together? And how does this relate to its function?

Answer 15

Microfibrils, then these will join together to make larger macrofibrils, then these join together to form cellulose fibres. This provides yet more strength to cellulose.

Question 16

How does the strength of the cellulose allow the cell wall to carry out its functions?

Answer 16

Cellulose is very strong meaning that when water moves through osmosis into the permeable membrane of the cell wall, outwards pressure from the contents of the cell is resisted by the inwards pressure of the cell wall due to its strength, preventing the plant cell from bursting. This means the plant cell is turgid.

Question 17

Why is glucose extremely soluble in water?

Answer 17

Because it has a large number of hydroxyl groups, and these hydroxyl groups are polar due to the small negative charge on the oxygen atoms and the small positive charge on the hydrogen atoms. This means these hydroxyl groups can form hydrogen bonds with water molecules, making glucose hyrdrophilic.

Question 18

What two molecules make up starch?

Answer 18

Amylose and amylopectin

Question 19

How is amylose formed?

Answer 19

Polymer of alpha glucose molecules forming glysosidic bonds in a condensation reaction removing one water molecule for each bond.
This then twists into a complex helix ( helping starch become a very compact molecule) with hydrogen bonds forming between glucose molecules along the chain.

Question 20

How is starch converted back into glucose?

Answer 20

Water is used to break the glysosidic bonds in a hyrdolysis reaction

Question 21

Give a key difference between amylose and amylopectin

Answer 21

Amylose is an unbranched polysaccahride whereas amylopectin is a branched polysaccarhide

Question 22

How does the structure of starch relate to its function?

Answer 22

• Insoluble meaning the water potential is not affected so water is not drawn into cells by osmosis
• Helix shape meaning it is very compact so alot can be stored in a small space
  -When hydrolysed it forms alpha glucose which is easily transported and readily used in respiration
  -Branched form has many ends so enzymes can act simultaneously on each branch meaning glucose monomers are released very rapidly
  -Large so it does not diffuse out of cells.

Question 23

Give examples of disaccharides

Answer 23

Sucrose lactose and maltose

Question 24

Give examples of polysaccharides

Answer 24

Glycogen, starch, cellulose

Question 25

Describe all differences between glycogen and cellulose

Answer 25

Cellulose is made up of b glucose monomers whereas glycogen is made up of a glucose molecules
Cellulose molecules are straight chains whereas glycogen is branched
Cellulose has straight chain and glycogen is coiled
Glycogen has 1-4 and 1-6 glysosidic bonds whereas cellulose has only 1-4