1.1 - 1.5 Carbohydrates and Lipids

Question 1

• OH
• COOH
• NH2
• R

Answer 1

Hydroxyl
Carboxylic/carboxyl acid
Amine/amino
Variable

Question 2

Hydrogen bonds

Answer 2

Attraction between polar molecules
Weak
Can be broken by increasing kinetic energy/temp

Question 3

Covalent bonds

Answer 3

Sharing of electrons

A strong bond that can form stable molecules

Question 4

Ionic bonds

Answer 4

Exchange of electrons resulting in attraction between two oppositely charged ions

Question 5

List the three key bonds from strongest to weakest

Answer 5

Covalent bond
Ionic bond
Hydrogen bond

Question 6

Condensation reaction

Answer 6

Covalent bond formed
Water molecule released
Builds up smaller molecules into large ones

Question 7

Hydrolysis reaction

Answer 7

Covalent bond broken
Water molecule used
Breaks up larger molecules into smaller ones

Question 8

Metabolism

Answer 8

All the chemical processes that take place in living organisms

Question 9

Name the three types of carbohydrates

Answer 9

Simple:
- Monosaccharides
- Disaccharides
Complex:
- Polysaccharides

Question 10

What are the characteristics of a simple carbohydrate?

Answer 10

Small, sweet tasting, soluble

Question 11

What are the characteristics of a polysaccharide?

Answer 11

Large, non-sweet, insoluble

Question 12

List three examples of a monosaccharide

Answer 12

Glucose, fructose, galactose

Question 13

List three examples of a disaccharide

Answer 13

Sucrose, lactose, maltose

Question 14

List three examples of a polysaccharide

Answer 14

Starch, glycogen, cellulose

Question 15

Which two monomers join to form maltose?

Answer 15

Alpha glucose + alpha glucose

Question 16

Which two monomers join to form sucrose?

Answer 16

Alpha glucose + fructose

Question 17

Which two monomers join to form lactose?

Answer 17

Alpha glucose + galactose

Question 18

Describe the structure of starch

Answer 18

Amylose:
- Unbranched
- Alpha glucose monomers
- Alpha 1,4 glycosidic bonds

Amylopectin:
- Branched
- Alpha glucose monomers
- Alpha 1,4 glycosidic bonds and alpha 1,6 glycosidic bonds

Question 19

Explain how the structure of starch aids its function

Answer 19

• Insoluble so does not cause osmosis
• Large so does not diffuse out of cell
• Helical shape is compact so lots in small space
• Branched forms have many ends which can be hydrolysed simultaneously to release glucose rapidly
• Forms alpha glucose when hydrolysed, ideal for transport and use

Question 20

What is the function of starch?

Answer 20

Energy storage in plants

Question 21

Describe the structure of glycogen

Answer 21

• Highly branched
• Alpha glucose monomers
• Alpha 1,4 glycosidic bonds and alpha 1,6 glycosidic bonds

Question 22

Explain how the structure of glycogen aids its function

Answer 22

• Insoluble so does not cause osmosis
• Large so does not diffuse out of cell
• Compact so a lot can be stored in a small space
• More highly branched so can be broken down faster than starch (animals more active and must regulate temp = higher metabolic rate)

Question 23

What is the function of glycogen?

Answer 23

Energy storage in animals and bacteria

Question 24

Describe the structure of cellulose

Answer 24

• Unbranched
• Beta glucose monomers
• Beta 1,4 glycosidic bonds and hydrogen bonds

Question 25

Explain how the structure of cellulose aids its function

Answer 25

• Beta glucose is unbranched so forms long, straight chains that run parallel to each other and are held together by hydrogen bonds
• Chains -> Microfibrils -> Fibres

Question 26

What is the function of cellulose?

Answer 26

Found in cell walls. Provides strength and stops cell bursting when turgid.

Question 27

What are some typical features of lipids?

Answer 27

• Made up of C, H and O
• Insoluble in water
• Soluble in alcohols

Question 28

What are the main roles of lipids?

Answer 28

• Cell membrane made of phospholipids
• Energy source
• Waterproofing (waxes on the cuticles of plants and insects, sebum on animals)
• Insulation (fat tissue containing triglycerides)
• Protection (fat tissue again)

Question 29

Saturated fatty acid

Answer 29

• All carbon-carbon single bonds in hydrocarbon chain
• Forms fats/solid at room temp
• Can pack tight and regular

Question 30

Unsaturated fatty acids

Answer 30

• At least one carbon-carbon double bond in hydrocarbon chain
• Forms oils/solid at room temp
• Carbon-carbon double bonds kink chain so it cannot lie straight and regular

Question 31

Triglyceride

Answer 31

One glycerol joined to three fatty acids by ester bonds

Question 32

Phospholipids

Answer 32

One glycerol joined to two fatty acid (by ester bonds) and one phosphate

Question 33

How do phospholipids react to water?

Answer 33

Phospholipids are amphiphillic - heads are hydrophobic, tails are hydrophilic.
Can form a micelle or a phospholipid bilayer.

Question 34

How do you test for reducing sugars?

Answer 34

1. Add 2cm3 of sample to a test tube
2. Add equal volume Benedict’s reagent
3. Heat in gently boiling water for 5 minutes
   Blue -> Red

Question 35

How do you test for non-reducing sugars?

Answer 35

1. Add 2cm3 of sample to a test tube
2. Add equal volume hydrochloric acid (to hydrolyse)
3. Heat in gently boiling water bath for 2 minutes
4. Slowly add sodium hydrogen carbonate until it stops fizzing (neutralises acid so Benedict’s can work)
5. Test with pH paper to check solution is neutral or alkaline
6. Run test for reducing sugars
   Blue -> Orange/brown

Question 36

How do you test for starch?

Answer 36

1. Add 2cm3 of sample to test tube or two drops of sample to spotting tile
2. Add 2 drops of iodine in potassium iodide
3. Shake/stir
   Orange/brown -> Blue/black

Question 37

How do you test for lipids?

Answer 37

1. Add 2cm3 of sample to a test tube
2. Add 5cm3 ethanol
3. Shake (to dissolve any lipids in sample)
4. Add 5cm3 water and shake gently
   Colourless -> Milky white emulsion