1.2 Carbohydrates

Question 1

What elements do carbohydrates consist of?

Answer 1

Carbon, hydrogen, oxygen

Question 2

What are monosaccharides?

Answer 2

Simple sugars eg glucose, fructose, ribose

Question 3

What 3 properties do monosaccharides all have?

Answer 3

1. Soluble in water
2. Sweet tasting
3. Form crystals

Question 4

What is the general formula of monosaccharides?

Answer 4

n = any number from 3 to 7

Question 5

What is alpha glucose?

Answer 5

Alpha glucose is a monosaccharide that is easily transported (water soluble) and readily used in respiration.

Question 6

Draw an alpha glucose

Answer 6

(Start at carbon 1 and move in a clockwise direction)

Question 7

What is beta glucose?

Answer 7

A monosaccharide that is found in cellulose

Question 8

Draw a beta glucose

Answer 8

Question 9

Remember ABBA for where the OH group is in glucose diagrams

Answer 9

AB= alpha below
BA = beta above

Question 10

What is an isomer?

Answer 10

The same formula but a different arrangement of atoms in the molecule and different properties

Question 11

What is a disaccharide?

Answer 11

When two monosaccharides sugars join together

Question 12

What reaction forms disaccharides?

Answer 12

Condensation

Question 13

What bond is formed in disaccharides?

Answer 13

Glycosidic bond

Question 14

What is the chemical formula for disaccharides?

Answer 14

has one less oxygen and two less hydrogen because it’s been removed for water

Question 15

What monosaccharides are maltose formed from?

Answer 15

Two alpha glucose

Question 16

What monosaccharides are sucrose formed from?

Answer 16

Glucose and fructose

Question 17

What monosaccharides are lactose formed from?

Answer 17

Glucose and galactose

Question 18

What does “1-4 glycosidic bond” and “I-6 glycosidic bond” mean

Answer 18

1-4 = bond forms between carbon 1 and carbon 4
1-6 = bond forms between carbon bond and carbon 6

Question 19

What are polysaccharides?

Answer 19

Polymers formed by combining many monosaccharide molecules together by glycosidic bonds formed during condensation reactions

Question 20

What are the 3 polysaccharides?

Answer 20

1. Starch -
2. Glycogen
3. Cellulose

Question 21

What are the two polymers starch is made up of?

Answer 21

• amylose
• amylopectin

Question 22

What are the main characteristics of starch and how does it relate to its function?

Answer 22

1. Coiled SO compact - molecule can be stored in a small space
2. Large polysaccharide - 2 alpha glucose
3. Insoluble - does not affect the water potential of the cell, so water does not move into the cell by osmosis
4. Glycosidic bonds can be hydrolysed to form alpha glucose monomers which can be easily transported and used in respiration

Question 23

What are the glycosidic bonds for amylose and amylopectin?

Answer 23

• Amylose (alpha glucose) monomers are joined by only 1,4 glycosidic bonds
• Amylopectin is a branched polymer with the 1,4 glycosidic bonds between the alpha glucose and 1,6 glycosidic bonds forming between C1 and C6 of the adjacent alpha glucose

Question 24

Where is glycogen found?

Answer 24

Animals and bacteria

Question 25

Is glycogen branched or unbranched?

Answer 25

Highly branched due to the 1,6 glycosidic bonds

Question 26

What monomers does glycogen consist of and what bonds?

Answer 26

Formed between **alpha glucose** monomers Has both 1,4 and 1,6 glycosidic bonds

Question 27

What is the function of glycogen being insoluble?

Answer 27

Does not affect the water potential of the cell, so water does not move into cell by osmosis

Question 28

Glycogen is a ……. molecule so can be stored in a ….. space

Answer 28

Glycogen is a **compact** molecule so can be stored in a **small** space

Question 29

What is the benefit of glycogen being highly branched?

Answer 29

Has many ends meaning the glycosidic bonds can be rapidly hydrolysed by enzymes to form alpha glucose monomers which can be easily transported and used in respiration. Animals are more active than plants and have a higher metabolic and respiration rate than plants *(more glucose is required for respiration to synthesise ATP)*

Question 30

Is cellulose branched or unbranched?

Answer 30

Cellulose is a straight, unbranched, structural polysaccharide *(which forms plant cell walls)*

Question 31

What monomers and bonds is cellulose made up from?

Answer 31

Beta glucose monomers Held together by 1,4 glycosidic bonds

Question 32

What is alternate glycosidic bonding?

Answer 32

Each beta glucose monomer is rotated 180 degrees relative to the next

Question 33

How are microfibrils formed and what do they do?

Answer 33

Many straight chains of beta glucose form parallel to each other and are linked through hydrogen bonds between the many -OH groups, forming bundles called microfibrils. They are very strong and support the cell wall and prevent it from bursting when a plant cell becomes turgid.

Question 34

Explain why cellulose cannot be digested by mammals

Answer 34

Mammals don’t possess the enzyme cellul**a**se which is required to hydrolyse the glycosidic bonds in cellulose (forms fibre in the human diet)