Carbohydrates

Question 1

Define a polymer.

Answer 1

Polymers are large, complex molecules made of repeating monomers joined by bonds.

Question 2

Define a monomer.

Answer 2

Monomers are small, basic molecular units.

Question 3

Give an example of a polymer and its corresponding monomer.

Answer 3

Carbohydrates are polymers made from monosaccharide monomers.

Proteins are polymers made from amino acid monomers. Nucleic acids are polymers made from nucleotide monomers.

Question 4

Which three elements are present in all carbohydrates?

Answer 4

Carbon (C), Hydrogen (H), Oxygen (O)

Question 5

State the general formula of a carbohydrate

Answer 5

(CH2O)ₙ

Question 6

What are monosaccharides?

Answer 6

Monosaccharides are Single sugar units (monomers).

Question 7

Give three examples of monosaccharides.

Answer 7

Glucose, Fructose, Galactose

Question 8

What is the molecular formula of glucose?

Answer 8

C₆H₁₂O₆

Question 9

What type of sugar is glucose and how many carbon atoms does it have?

Answer 9

Glucose is a hexose sugar (6 carbon atoms).

Question 10

Name and describe the two isomers of glucose.

Answer 10

• α-glucose: The –OH group on carbon-1 is below the ring.
• β-glucose: The –OH group on carbon-1 is above the ring.

Question 11

Describe one function of glucose.

Answer 11

Glucose is a Rapid energy source; is soluble; and easily transported

Question 12

How is a disaccharide formed?

Answer 12

Disaccharide forms from Two monosaccharides joined via a glycosidic bond, formed by a condensation reaction, releasing water

Question 13

Name three disaccharides and their constituent monosaccharides.

Answer 13

• Maltose = α-glucose + α-glucose
• Sucrose = α-glucose + fructose
• Lactose = α-glucose + galactose

Question 14

How are polysaccharides formed?

Answer 14

Polysaccharide form from Many monosaccharides joined by condensation reactions to form polymers.

Question 15

Describe the structure and function of starch.

Answer 15

• Starch is made of α-glucose.
• Amylose: amylose is unbranched, coiled to be compact so its good for storage
• Amylopectin: amylopectin is branched so enzymes access bonds for fast glucose release
• amylopectin is Insoluble so doesn’t affect water potential/osmosis

Question 16

Describe the structure and function of glycogen.

Answer 16

glycogen is
• Similar to amylopectin but more highly branched
• Stored in liver & muscle
• Highly branched for quick energy release
• glycogen is Compact for efficient storage

Question 17

Describe the structure and function of cellulose.

Answer 17

• Made of β-glucose
• cellulose is Long, unbranched chains
• Chains are linked by hydrogen bonds to form microfibrils which give high tensile strength
• cellulose Function is to provide Structural support in cell walls

Question 18

Describe a condensation reaction.

Answer 18

Condensation reaction Joins monomers and forms bond and releases water

Question 19

Describe a hydrolysis reaction.

Answer 19

Hydrolysis reaction Breaks bonds by adding water to split polymers into monomers

Question 20

What is is Biochemical Test for carbohydrates

Answer 20

You test for carbohydrates using Benedict’s Test for Reducing Sugars

Question 21

Describe how to test for reducing sugars.

Answer 21

• Add Benedict’s reagent (blue) to the sample
• Heat in boiling water bath
• Positive result = coloured precipitate formed
• Colour change: from Blue to→ green → yellow → orange → brick red

Question 22

What does a more intense colour in the Benedict’s test indicate?

Answer 22

A more intense colour of the Benedict‘s test indicates A higher sugar concentration and there are Non-Reducing Sugars

Question 23

Describe the test for non-reducing sugars.

Answer 23

• First do Benedict’s test → if negative:
• Add dilute HCl, boil to hydrolyse sugar
• Neutralise with sodium hydrogencarbonate
• Repeat Benedict’s test
• Positive = if coloured precipitate is formed

Question 24

Describe how to test for starch.

Answer 24

• Add iodine in potassium iodide to the sample
• Positive result = solution turns from browny-orange to dark blue-black

Question 25

Which structural diagrams must you memorise for carbohydrates?

Answer 25

• α-glucose and β-glucose • Glycosidic bond formation (condensation) • Polysaccharide branching in amylopectin & glycogen • Cellulose microfibrils (hydrogen bonding)

Question 26

State five biological roles of carbohydrates.

Answer 26

Energy supply – main role, fuels cellular respiration. Energy storage – stored as complex carbohydrates (e.g. starch, glycogen). provides structural support– cellulose in plants and chitin in some organisms. Cellular recognition – glycoproteins aid in cell signalling. Building blocks – ribose and deoxyribose are used in nucleic acids.

Question 27

What is the general formula of monosaccharides, and what range of carbon atoms can they have?

Answer 27

The general formula is (CH₂O)ₙ

Question 28

Name three hexose sugars and two pentose sugars. Answer:

Answer 28

Hexose sugars: Glucose, Fructose, Galactose Pentose sugars: Ribose, Deoxyribose

Question 29

Describe two properties of monosaccharides and where monosaccharides are commonly found?

Answer 29

Monosaccharides are soluble and sweet-tasting and They are found in fruits, vegetables, and grains.

Question 30

Explain two properties of glucose and their relevance.

Answer 30

Soluble – forms hydrogen bonds with water, allowing transport. Bonds store lots of energy, released during respiration.

Question 31

Describe the structure and bonds in starch.

Answer 31

Starch is made of α-glucose joined via 1-4 and 1-6 glycosidic bonds. It has branched and unbranched chains.

Question 32

List 4 properties of starch that make it good for energy storage.

Answer 32

starch: Insoluble – doesn’t affect water potential. Large – can’t diffuse out of cells. Many branches – enzymes access easily. Coiled – compact for storage. Hydrolysis releases α-glucose for respiration.

Question 33

How is glycogen structurally similar and different to starch?

Answer 33

Like starch, glycogen is made of α-glucose via 1-4 and 1-6 bonds, but it is more highly branched.

Question 34

Give four properties of glycogen and their functional benefits.

Answer 34

Insoluble – doesn’t affect osmosis. Compact – efficient storage. Highly branched – rapid enzyme action. Large – can’t diffuse out of cells. Also, hydrolysis releases α-glucose for respiration.

Question 35

Describe the structure of cellulose and how it is formed.

Answer 35

Cellulose is made of β-glucose with 1-4 glycosidic bonds. Every other β-glucose is flipped 180° to allow bond formation, forming long, straight, unbranched chains.

Question 36

List three structural properties of cellulose and their functions.

Answer 36

High tensile strength – due to hydrogen bonding. Provides rigidity – to cell walls. Microfibrils – reinforce structural strength.

Question 37

. How does Benedict’s test indicate concentration of reducing sugar?

Answer 37

Blue = none Green = low Orange = medium Brick-red = high

Question 38

Name two quantitative methods to improve Benedict’s test accuracy.

Answer 38

Use a colorimeter (measures absorbance). Filter and weigh precipitate.