Carbohydrates and Lipids

Question 1

Small identical or similar molecules which can be joined together to make larger molecules called polymers

Answer 1

Monomer

Question 2

The reaction joining monomer units together with the removal of one water molecule

Answer 2

Condensation reaction

Question 3

The addition of one water molecule to break the bond between two monomers

Answer 3

Hydrolysis reaction

Question 4

Sweet tasting, soluble molecules

Answer 4

Monosacchardes

Question 5

The general fomula of a monosaccharide

Answer 5

C6H1206

Question 6

3 monosaccharide examples:

Answer 6

. Fructose
. Glucose
. Galactose

Question 7

2 monosaccharides joined together through a condensation reaction

Answer 7

Disaccharide

Question 8

Maltose

Answer 8

Glucose + Glucose

Question 9

Galactose

Answer 9

Glucose + Lactose

Question 10

Sucrose

Answer 10

Glucose + Fructose

Question 11

Amylose (starch)

Answer 11

. Long straight chains of alpha glucose that coilt into a helix
. Carbon 1:4 glycosidic bonds
. Compact - good for storage
. Insoluble - doesn’t affect water potential
. Large - does not diffuse

Question 12

Amylopectin (starch)

Answer 12

. Branched chains of alpha glucose
. Carbon 1:4 and 1:6 glycosidic bonds
. LSA - fast hydrolysis by enzymes = quick energy release
. Insoluble - doesn’t affect water potential
. Large - doesn’t diffuse out of cells

Question 13

Glycogen

Answer 13

. Found in liver and muscle cells
. Short branched chains provide LSA so is more easily hydrolysed
. Insoluble - doesn’t affect water potential
. Large - doesn’t diffuse out of cell

Question 14

Cellulose

Answer 14

. Plant cell wall
. Beta glucose in long straight chains
. Every other beta glucose is inverted 180 degrees
. Carbon 1:4 glycosidic bond
. Several chains in layers held together by H bonds formed between OH groups
. Very strong
. The chains make microfibrils which are further wound together to form cellulose fibres - they provide strength and support

Question 15

Test for carbohydrates

Answer 15

Benedict test

Question 16

Benedict test for reducing sugar

Answer 16

. Add equal volumes of sample and Benedict solution
. HEAT
. Brick red precipitate = reducing sugar present

Question 17

Benedict test for non-reducing sugar

Answer 17

. Add Hydorchloric acid to the sample
. HEAT
. Neutralise with sodium hydrogen carbonate
. Can then perform a Benedict test

Question 18

Test for unknown concentrations

Answer 18

. Carry out a Benedict’s test on known concentrations sugar
. Use a colorimeter to measure the colour of each solution and draw a calibration curve
. Find the concentration of the unknown sample using the calibration curve

Question 19

Test for starch/Iodine test

Answer 19

. Add two drops of iodine to the sample

. Blue/black colour = present

Question 20

Test for lipids/emulsion test

Answer 20

. A small amount of sample is placed in 2cm3 of ethanol
. The mixture is shaken so the fat dissolves
. Water is added then the mixture is shaken again
. A white cloudy emulsion = present

Question 21

Lipid solubility

Answer 21

They are insoluble in water but are soluble in organic solvents like ethanol, acetone and other lipids

Question 22

Name five roles of lipids

Answer 22

1. Make up the membrane
2. Source of energy
3. Insulation (heat and electrical)
4. Protection
5. Waterproofing

Question 23

Triglyceride structure

Answer 23

One molecule of glycerol joined to three fatty acids using an ester bond

Question 24

Saturated

Answer 24

All the available bonds are used

Question 25

Unsaturated

Answer 25

Not all available bonds are used

Question 26

What does an unstaturated fatty acid mean?

Answer 26

The fatty acid chain contains a double bond between the carbon atoms. The molecules can bend so it remains liquid at room temperature

Question 27

How does the triglyceride structure relate to their properties?

Answer 27

. They contain a lot of energy due to the high ratio of C-H bonds compared to C-C bonds . Low energy:mass ratio - good as storage . Compact - more can be stored in the same place . Large and insoluble in water - doesn't effect water potential . High ratio of H:O - important source of water in desert animals

Question 28

Phospholipid structure

Answer 28

A phosphate group, a glycerol and two fatty acid tails

Question 29

How does the phospholipid structure relate to its function?

Answer 29

. A hydrophilic head - attracted to water due to the polar nature of the phosphate group . Hydrophobic fatty acid tails - repelled by water due to the non-polar nature of the tails