Carbohydrates

Question 1

What are the uses of carbohydrates?

Answer 1

• Source of energy (releases glucose when hydrolysed)
• Store of glucose
• Structural units

Question 2

What are monosaccharides?

Answer 2

Monosaccharides are the monomers from which larger carbohydrates are made

Question 3

Name 3 monosaccharides

Answer 3

• Glucose
• Galactose
• Fructose

Question 4

What bond do two monosaccharides form?

Answer 4

A 1 - 4 glycosidic bond

Question 5

How are disaccharides formed?

Answer 5

Disaccharides are formed by the condensation of two monosaccharides

Question 6

How is maltose (a disaccharide) formed?

Answer 6

Maltose is formed by the condensation of two glucose molecules

Glucose + glucose → maltose + water

Question 7

How is sucrose (a disaccharide) formed?

Answer 7

Sucrose is formed by the condensation of a glucose molecule and a fructose molecule

Glucose + fructose → sucrose + water

Question 8

How is lactose (a disaccharide) formed?

Answer 8

Lactose is formed by the condensation of a glucose molecule and a galactose molecule

Glucose + galactose → lactose + water

Question 9

What is an isomer?

Answer 9

Molecules with the same molecular formula but with the atoms connected in a different way

Question 10

What are the two isomers of the monosaccharide glucose?

Answer 10

• α-glucose
• β-glucose

Question 11

What is the difference between α-glucose and β-glucose?

Answer 11

α-glucose has its OH group linked below the ring and β-glucose has its OH group above the ring (on carbon 1)

Question 12

How are polysaccharides formed?

Answer 12

Polysaccharides are formed by the condensation of many monosaccharides

Question 13

Name 3 polysaccharides

Answer 13

• Glycogen
• Starch
• Cellulose

Question 14

How is glycogen and starch formed?

Answer 14

Glycogen and starch are formed by the condensation of α-glucose

Question 15

How is cellulose formed?

Answer 15

Cellulose is formed by the condensation of β-glucose

Question 16

Where is starch found and what is its function?

Answer 16

• Found in plant cells (e.g in chloroplasts)
• It is an insoluble store of glucose

Question 17

Where is cellulose found and what is its function?

Answer 17

• Found in cell walls of plant cells
• Provides structural strength

Question 18

Where is glycogen found and what is its function?

Answer 18

• Found in animals cells (e.g liver and muscle cells)
• Store of glucose

Question 19

What are the two types of starch?

Answer 19

• Amylose
• Amylopectin

Question 20

Structures & features of amylose

Answer 20

coiled / compact
- allowing for a lot of glucose to be stored in a small space

insoluble
- does not dissolve in water + does not affect water potential of the cell

large
- cannot diffuse out of cells

hydrolysis releases α-glucose
- released to be used in respiration

Question 21

Structures & features of amylopectin

Answer 21

coiled
- compact allowing for a lot of glucose to be stored in a small space

many side branches
- larger SA for enzymes to hydrolyse the glycosidic bonds

insoluble
- does not dissolve in water + does not affect water potential of the cell

large
- cannot diffuse out of cells

hydrolysis releases α-glucose
- released to be used in respiration

Question 22

Structures & features of glycogen

Answer 22

compact - allows for a lot of glucose to be stored in a small space

highly branched (more than amylopectin) - larger SA for enzymes to hydrolyse the glycosidic bonds

insoluble - does not dissolve in water + does not affect water potential of the cell

large - cannot diffuse out of cells

hydrolysis releases α-glucose - released to be used in respiration

Question 23

Structures & features of cellulose

Answer 23

chains run parallel to each other held by H bonds - provides collective strength

chains form microfibrils - provide collective strength and rigidity

overall strength - allows cells to develop turgor pressure, making them turgid; this helps plant cells maintain their shape