3: Carbohydrates

Question 1

What are carbohydrates?

Answer 1

Molecules that only contain carbon, hydrogen and oxygen

Question 2

What is the general formula of carbohydrates?

Answer 2

Cx(H20)y

Question 3

What are carbohydrates also known as?

Answer 3

Saccharides or sugars

Question 4

What is a single sugar unit called?

Answer 4

Monosaccharide

Question 5

Give 3 examples of monosaccharides

Answer 5

Glucose, fructose and ribose

Question 6

What do two monosaccharides form?

Answer 6

Disaccharide

Question 7

Give 2 examples of disaccharides

Answer 7

Lactose, sucrose

Question 8

What is formed when more than two monosaccharides are linked?

Answer 8

Polysaccharide

Question 9

Give 3 examples of polysaccharides

Answer 9

Glycogen, cellulose and starch

Question 10

What is the chemical formula of glucose?

Answer 10

C6H12O6

Question 11

What is glucose?

Answer 11

Hexose monosaccharide

Question 12

What are the two structural variations of glucose?

Answer 12

Alpha glucose and Beta glucose

Question 13

What is the difference between alpha glucose and beta glucose?

Answer 13

Alpha glucose has the hydroxyl group on carbon 1 below the hydrogen whereas beta glucose has the hydroxyl group on carbon 1 above the hydrogen

Question 14

Why are glucose molecules polar and soluble in water?

Answer 14

Hydrogen bonds that form between hydroxyl groups and water molecules

Question 15

Why is it important that glucose is water soluble?

Answer 15

Glucose can be dissolved in the cytosol of the cell

Question 16

What happens when two alpha glucose molecules are side by side?

Answer 16

Condensation reaction occurs as the two hydroxyl groups interact (react)

Question 17

Why is this called a condensation reaction?

Answer 17

Because a water molecule is formed as one of the reaction products

Question 18

What bond forms between two alpha glucose molecules? Where?

Answer 18

Glycosidic bond. Between carbons 1 and 4 on the glucose molecules. Therefore, is a 1,4-glycosidic bond

Question 19

What is the product of the condensation reaction between two alpha glucose molecules?

Answer 19

Maltose (disaccharide)

Question 20

What is fructose?

Answer 20

A hexose monosaccharide that naturally occurs in fruit

Question 21

What is galactose?

Answer 21

A hexose monosaccharide

Question 22

What is the product of fructose + glucose?

Answer 22

Sucrose (disaccharide)

Question 23

What is the product of galactose + glucose?

Answer 23

Lactose

Question 24

What are pentose monosaccharides?

Answer 24

Sugars that contain five carbon atoms

Question 25

Where is ribose present?

Answer 25

RNA nucleotides

Question 26

Where is deoxyribose present?

Answer 26

DNA nucleotides

Question 27

What is starch?

Answer 27

Many alpha glucose molecules joined by glycosidic bonds

Question 28

What is the function of starch?

Answer 28

Chemical energy store (glucose is stored as starch in plant cells)

Question 29

What is amylose? How is amylose formed?

Answer 29

A polysaccharide in starch. Alpha glucose molecules joined together by only 1-4 glycosidic bonds

Question 30

What is amylopectin? How is amylopectin formed?

Answer 30

A polysaccharide in starch. Alpha glucose molecules joined together by 1-4 glycosidic bonds and 1-6 glycosidic bonds

Question 31

What is glycogen?

Answer 31

Functionally equivalent energy storage molecule to starch in animals and fungi

Question 32

Why is it important that glycogen forms more branches than amylopectin?

Answer 32

It is more compact and less space is needed for it to be stored which is important as animals are mobile (unlike plants)

Question 33

What are the key properties of amylopectin and glycogen?

Answer 33

Insoluble, branched and compact (therefore ideally suited to storage roles)

Question 34

What is glucose stored as in plants?

Answer 34

Starch

Question 35

What is glucose stored as in animals and fungi?

Answer 35

Glycogen

Question 36

How is glucose released for respiration?

Answer 36

Starch or glycogen undergoes hydrolysis reactions (reverse of condensation reactions that form glycosidic bonds)

Question 37

Why can't beta glucose molecules bond together in the same way alpha glucose molecules can?

Answer 37

Hydroxyl groups on carbon 1 and carbon 4 are too far away to react

Question 38

How can beta glucose molecules join together?

Answer 38

Alternate beta glucose molecules are turned upside down

Question 39

What molecule is formed when a polysaccharide is formed from two beta glucose molecules?

Answer 39

Cellulose (straight chain molecule)

Question 40

How do cellulose molecules form microfibrils?

Answer 40

Cellulose molecules make hydrogen bonds with each other

Question 41

How are macrofibrils formed?

Answer 41

Microfibrils join together forming macrofibrils, which combine to produce fibres

Question 42

What are features of the fibres that make up cellulose?

Answer 42

Strong, insoluble, used to make cell walls