Lesson 7 - Carbohydrates

Question 1

Elements in carbohydrates:

Answer 1

Carbon, Oxygen, Hydrogen

Question 2

Meaning of ‘carbohydrates’:

Answer 2

Hydrated carbon

Question 3

General formula of carbohydrates:

Answer 3

Cx(H2O)y

Question 4

Monomer of carbohydrates:

Answer 4

Monosaccharide

Question 5

Examples of monosaccharides:

Answer 5

• Glucose
• Fructose
• Ribose

Question 6

Two monosaccharides bonded together:

Answer 6

Disaccharide

Question 7

Examples of disaccharides:

Answer 7

• Lactose
• Sucrose

Question 8

Polymer of carbohydrates:

Answer 8

Polysaccharides

Question 9

Examples of polysaccharides:

Answer 9

• Cellulose
• Starch
• Glycogen

Question 10

Other words for carbohydrates:

Answer 10

• Saccharides
• Sugars

Question 11

Chemical formula of glucose:

Answer 11

C6H12O6

Question 12

As Glucose is conformed of 6 carbons, it is called a …

Answer 12

hexose monosaccharide (hexose sugar)

Question 13

Different types of glucose:

Answer 13

α-glucose
β-glucose

Question 14

Difference between α-glucose and β-glucose?

Answer 14

Hydroxyl group on carbon 1 are in opposite positions.

Question 15

Properties of glucose?

Answer 15

Soluble in water and polar

Question 16

How are glucose molecules soluble in water and polar?

Answer 16

They have hydrogen bonds that form between hydroxyl groups and water.

Question 17

Why is the solubility of glucose important?

Answer 17

Glucose is dissolved in the cytosol of the cell.

Question 18

How condensation reactions occur between glucose?

Answer 18

When two alpha-glucose molecules are side by side, the two hydroxyl groups interact. When this happens bonds are broken and new bonds form in different places producing new molecules.

Question 19

Condensation reaction in glucose?

Answer 19

Two hydrogen atoms and an oxygen atom are removed from glucose monomers and join to form a water molecule. A bond forms between carbons 1 and 4 on the glucose molecules, which are now joined.

This bond is called a glycosidic bond and is formed between 2 glucose molecules. This is a condensation reaction, as water is formed as one of the products of the reaction.

Question 20

1,4 Glycosidic bond:

Answer 20

Carbon 1 of one glucose molecule is joined to carbon 4 of the other glucose molecule.

Question 21

New molecule formed in condensation of glucose?

Answer 21

Maltose

Question 22

Hexose monosaccharides:

Answer 22

• Glucose
• Fructose
• Galactose

Question 23

Fructose

Answer 23

Naturally occurs in fruits, often in a combination with glucose to form disaccharide sucrose (cane sugar or just sugar)

Question 24

Can sugar

Answer 24

Disaccharide sucrose
- Fructose + Glucose

Question 25

Disaccharide lactose:

Answer 25

Galactose + Glucose

Commonly found in milk and milk products

Question 26

Order of sweetness of Glucose, Fructose, and Galactose

Answer 26

1. Fructose
2. Glucose
3. Galactose

Question 27

Sugars that contain 5 carbon atoms:

Answer 27

Pentose monosaccharides

Question 28

Ribose and deoxyribose:

Answer 28

Two pentose monosaccharides

Question 29

Ribose present:

Answer 29

RNA nucleotides

Question 30

Deoxyribose present:

Answer 30

DNA nucleotides

Question 31

Starch made up of:

Answer 31

Alpha glucose molecules joined by glycosidic bonds to form two slightly different polysaccharides collectively known as Starch.

Question 32

How is starch a chemical store:

Answer 32

Glucose made by photosynthesis in plant cells is stored as starch.

Question 33

What is amylose?

Answer 33

One of the polysaccharides in starch

Question 34

Structure of amylose?

Answer 34

Formed by alpha glucose molecules joined together by only 1,4 glycosidic bonds. Angle of the bond means that the long chain of glucose twists into a helix structure. The helix structure is stabilised by hydrogen bonding within the molecule. This makes the polysaccharide more compact, much less soluble, than the glucose molecules used to make it.

Question 35

Amylopectin:

Answer 35

Another starch polysaccharide.
Formed from 1,4 polycosidic bonds in glucose and bonds between carbon 1 and 6 atoms in glucose.

Question 36

Results of carbon 1 and 6 bonds in amylopectin:

Answer 36

Amylopectin has a branched structure. with 1,6 branching points occurring approximately 1 in every 25 glucose subunits.

Question 37

Functionally equivalent energy store to starch (plants) to animals and fungi is …

Answer 37

glycogen

Question 38

Structure of glycogen:

Answer 38

Has more branches than amylopectin, so is more compact and less space is needed for storage.

Question 39

Why is glycogen’s compact structure important?

Answer 39

Animals (unlike plants) are mobile.
- Branching makes it extremely compact, ideal for storage.
- There are lots of ends glucose can be added and removed from. This speeds up process of storing or releasing glucose molecules required by the cell.

Question 40

Key properties of amylopectin and glycogen:

Answer 40

• Compact
• Branched
• Insoluble

Question 41

How is glucose released from starch/glycogen for respiration?

Answer 41

Hydrolysis reactions.
- Requires addition of water molecules
- Enzymes catalyse reaction
- Reverse condensation reactions that form glycosidic bonds.

Question 42

Beta glucose reactions:

Answer 42

Beta glucose molecules are unable to join together in the same way as alpha molecules. Carbon 1,4 are too far away.

Alternate beta molecules are turned upside down.

Unable to coil or form branches, so a straight chain molecule is formed called cellulose.

Question 43

Cellulose:

Answer 43

Form hydrogen bonds with each other to form microfibrils.
Microfibrils join together to form macrofibrils.
Macrofibrils join together to form fibres.
Fibres are strong and insoluble. They join together to form the cell wall.

Question 44

Importance of cellulose:

Answer 44

Important for diet. Hard to break down into monomers so forms to ‘fibres’ and ‘roughage’ important for a healthy digestive system.