Carbohydrates And Lipids

Question 1

What are monomers?

Answer 1

Small identical similar molecules that join together via condensation reaction to make a larger molecule called polymers

Question 2

What are polymers?

Answer 2

Large molecules made of 3+ small identical similar monomers by condensation reaction

Question 3

What is a condensation reaction ?

Answer 3

Removal of a H2O molecule to form a named bond between named monomers

Question 4

What is a hydrolysis reaction?

Answer 4

The removal of H2O molecule to break a bond between 2 named monomers

Question 5

Glucose and glucose

Answer 5

Maltose catalysed my maltase enzyme

Question 6

Glucose and galactose

Answer 6

Lactose catalysed by lactase

Question 7

Glucose and fructose

Answer 7

Sucrose catalysed by sucrase

Question 8

Name the 3 polysaccharides and what they are used for

Answer 8

Glycogen= storage molecule in animals
Starch = storage molecule in plants
Cellulose = structural molecule in plants

Question 9

Alpha glucose structure

Answer 9

Question 10

Difference in beta and alpha glucose

Answer 10

Remember ABBA ( alpha glucose hydroxyl group below beta glucose hydroxyl group above)
They are isomers of each other

Question 11

Structure and properties of starch

Answer 11

Polymer of alpha glucose
Amylose, which is helical so compact
Amylopectin which is branched so provides a large surface area for rapid hydrolysis to release glucose for respiration
1-6 and 1-4 glycocydic bonds
Insoluble in water so doesn’t effect water potential
Large molecule so doesn’t diffuse out of cell

Question 12

Structure and properties in glycogen

Answer 12

Polymer of Glucose so acts as a respiratory substrate
Highly branched so provides a large surface area for rapid hydrolysis into glucose
Insoluble in water so doesn’t effect water potential
Helical so compact

Question 13

Structure and properties of cellulose

Answer 13

Polymer of Long straight unbranded chains of beta glucose joined by many weak hydrogen bonds which provide strength and stability/rigidity
Forms microfrils
Every other beta molecule flipped 180 degrees
Only has 1-4 glucosidic bonds only

Question 14

What is the only non reducing sugar?

Answer 14

Sucrose

Question 15

Test for non reducing sugar

Answer 15

1. Do bendicts test for a negative result and then only ….
2. Heat/ boil with acid (HCl) to hydrolyse glucosidic bonds
3. Neutralise with an alkali eg sodium hydrogen carbonate
4. Add benedicts reagent
5. Heat to 95 degrees again
6. Blue to brick red if presence of reducing sugar

Question 16

Why is Benedicts test unreliable?

Answer 16

It’s a semi quantitative test which means we don’t know the concentration so not accurate but only the range of colours so we would have to use a colorimeter

Question 17

Standardising the colorimeter

Answer 17

Zero the colorimeter
Samples should be shaken
Use the same volume for each reading
Use the same filter throughout

Question 18

How to determine the concentration of a unknown solution?

Answer 18

1. Make up several known concentrations of solutions of sugar
2. Carry out correct biochemical test on each sample
3. Take readings of absorbance on colorimeter
4. Plot a graph for concentration of sugar on x axis amd absorbance of y axis
5. Draw a line of best fir
6. Read unknown samples absorbance and use line of best fit to find corresponding concentration

Question 19

Test for starch

Answer 19

Add potassium iodide solution
Blue/ Black if presence of starch

Question 20

What are the 2 types of lipids and their uses?

Answer 20

Phospholipids= form the cell membrane of cells
Tryglerides = found commonly in foods
Other functions
Protect delicate organs
Conducts heat slowly so good electrical and thermal insulators

Question 21

Describe how a phospholipid is formed ?

Answer 21

1 glycerol
2 fatty acids
1 phosphate group
2 ester bonds by condensation reaction

Question 22

Describe how a Trygleride is formed?

Answer 22

3 condensation reaction between one molecule of glycerol and 3 fatty acids loosing 3 water molecules forming 3 ester bonds

Question 23

What is an unsaturated fatty acid?

Answer 23

Double carbon bond between carbons within hydrocarbon chain

Question 24

Compare and contrast the structure and properties of triglycerides and phospholipids

Answer 24

Both have ester bonds between fatty acid and glycerol
Both contain glycerol
Both contain C,H,O atoms whereas phospholipids contain P atoms
Both are insoluble in water
Fatty acids may be unsaturated or saturated
Triglycerides has 3 fatty acids whereas phospholipids have 2 fatty acids and 1 phosphate group
Triglycerides are hydrophobic whereas phospholipids are hydrophobic and hydrophilic
Phospholipids form a bilayer whereas Triglycerides don’t

Question 25

Emulsion test

Answer 25

Crush sample to release lipid Add ethanol mix Add water mix Forms white cloudy emulsion

Question 26

Buiret test

Answer 26

Add buirets reagent Purple / lilac if presence of protein

Question 27

Describe the alternative ways to measure the concentration of a reducing sugar

Answer 27

Filter and dry ppt Weigh to Find the mass

Question 28

Test for reducing sugar

Answer 28

Benedicts test 1. Add benedicts reagent to sample in equal volumes 2. Heat to 95 degrees 3. Blue to brick red if presence of reducing sugar

Question 29

Why do phospholipids form a biyaler ?

Answer 29

Phosphate head is polar so is hydrophilic so face outwards and attracts water Fatty acids are hydrophobic so repel water and face inwards forming a bilayer