Carbohydrates And Lipids

Question 1

What are monomers

Answer 1

Small identical similar molecule which are condensed together to make large molecules called polymers

Question 2

What are polymers

Answer 2

Larger molecules made from 3+ small identical similar molecules by condensation reaction

Question 3

What is a condensation reaction?

Answer 3

Removal of a water molecule to form a bond between 2 monomers forming a chemical bond

Question 4

What is hydrolysis reaction?

Answer 4

Addition of a water molecule to break a bond between two monomer

Question 5

structure of alpha glucose

Answer 5

Question 6

Difference between structure of alpha glucose and beta glucose

Answer 6

ABBA
Hydroxyl group below carbon in Alpha glucose
Hydroxyl group above carbon and beta glucose

Question 7

Glucose plus glucose
Enzyme

Answer 7

Maltose
Maltase

Question 8

Glucose plus galactose
Enzyme

Answer 8

Lactose
Lactase

Question 9

Glucose plus fructose
Enzyme

Answer 9

Sucrose
Sucrase

Question 10

What is the name of the bond between these monomers

Answer 10

Glycolytic bond

Question 11

Three polysaccharide

Answer 11

Starch
Glycogen
Cellulose

Question 12

Use of glycogen and starch

Answer 12

Storage in humans and plants

Question 13

Structure of starch (plants)

Answer 13

Two molecules= amylose and amylopectin
Both alpha glucose
Amylose = has 1-4 glycosidic bonds , helical shape so compact
, insoluble in water so doesn’t effect water potential, large so doesn’t diffuse out of cell
Amylopectin =1-4 and 1-6 glycosidic bonds. Large surface area for rapid hydrolysis by enzymes to realise glucose by respiration

Question 14

Structure of glycogen

Answer 14

Alpha glucose
Similar to starch but shorter chains , more highly branched, larger surface area
Insoluble in water so doesn’t effect water potential
More shorter chains so more rapid hydrolysis into glucose as faster than in plants

Question 15

Use of cellulose

Answer 15

Structural molecule in plant cells

Question 16

Structure of cellulose

Answer 16

Long straight branched chains of beta glucose joined by many weak hydrogen bonds which provide strength and rigidity.
Only 1-4 glycosidic bonds
Forms microfibrils
Every other beta glucose molecule flipped 180°

Question 17

Benedict test for reducing sugars

Answer 17

1. Add equal volumes of Benedict solution.
2. Heat to 95°C
3. Colour change from blue to brick red precipitate in presence of reducing sugar

Question 18

Type of non-reducing sugar

Answer 18

Sucrose

Question 19

Test for non-reducing sugar

Answer 19

1. Do reducing sugar test and get negative result
2. Heat with acid (HCl) to hydrolyse glycosidic bonds to 95°C
   3 . Neutralise with alkali- sodium hydrogen carbonate
3. Add equal volumes of Benedict solution
4. Heat again to 95°C
5. Blue to brick red ppt

Question 20

Iodine test for starch

Answer 20

1. Add potassium iodide solution.
2. Turns/Black, if presence of starch

Question 21

What does semiquantitative mean?

Answer 21

We have some idea of sugar quantity present by the range of colours but doesn’t tell the concentration of sugar in the solution

Question 22

What equipment do you use to test unknown concentration of reducing sugar?

Answer 22

Colorimeter

Question 23

What does a colorimeter measure?

Answer 23

The intensity of light transmitted through sample

Question 24

Method to determine concentration of unknown solution (6)

Answer 24

1. Make up several known concentrations of name sugar.
2. Carry out biochemical test on each sample
3. Take readings of absorbance using a colorimeter
4. Plot a graph called a calibration curve
   X axis = concentration of name sugar
   Y axis = absorbance
5. Draw a line of best fit
6. Read unknown sample absorbance and use line of best fit to determine concentration

Question 25

How to standardise this method (4)

Answer 25

1. Sample should always be shaken before testing. 2. Zero the colorimeter before you 3. Use same absorbent filter throughout 4. Use same volume for each reading

Question 26

Two types of lipids

Answer 26

Phospholipids= form cell membrane of cell Triglycerides = found in food

Question 27

Uses of lipids

Answer 27

Conduct heat slowly so good thermal and electrical insulators for your neurons Stored around delicate organs to protect them

Question 28

Structure of triglyceride

Answer 28

One glycerol and three fatty acid joined by Ester bond by condensation reaction

Question 29

What is a unsaturated fatty acid?

Answer 29

Double bonds between carbon atoms within the hydrocarbon chain

Question 30

Emulsion test

Answer 30

Add ethanol and shake Add water and shake If presence of lipid then white cloudy emulsion

Question 31

Structure of phospholipid

Answer 31

One glycerol, two fatty acids and phosphate group

Question 32

Features of phospholipids

Answer 32

Phosphate group is hydrophilic as it’s polar Fatty acids are nonpolar so are hydrophobic Forms a bilayer

Question 33

Compare and contrast the structure and properties of triglycerides and phospholipids

Answer 33

Both contain ester bonds (between glycerol and fatty acid);  Both contain glycerol;  Fatty acids on both may be saturated or unsaturated;  Both are insoluble in water;  Both contain C, H and O whereas phospholipids also contain P;  Triglyceride has three fatty acids whereas phospholipid has two fatty acids plus phosphate group;  Triglycerides are hydrophobic/non-polar and phospholipids have hydrophilic and hydrophobic region;  .  Phospholipids form bilayer in water whereas triglycerides don’t;  (or monolayer on surface)

Question 34

Why do phospholipids form a bilayer, but triglycerides do not

Answer 34

Phospholipid has two hydrophobic fatty acid tails and a hydrophilic phosphate head Triglycerides have three hydrophobic fatty acid tails only. The hydrophilic phosphate group on phospholipids attracts water to either side of the bilayer.

Question 35

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

Answer 35

2. Filter and dry precipitate. Find the mass.