Biological Molecules (LIPIDS)

Question 1

Describe the structure of the triglyceride

Answer 1

Made up of one glycerol molecule attached to 3 molecules of fatty acids, via condensation reactions

Question 2

How is the glycerol molecule bonded to the fatty acid chains in triglycerides and phospholipds

Answer 2

By condensation reactions

Question 3

What is the bond between the glycerol and fatty acid acid chain called

Answer 3

An ester bond

Question 4

What is produced when forming a triglyceride

Answer 4

3 molecules of water and 3 ester bonds

Question 5

Describe a glycerol molecule structure

Answer 5

An alcohol of 3 carbons where each carbon is attached to one OH, two H and another C at the bottom

Question 6

Describe fatty acid structure

Answer 6

Fatty acid chains are long hydrocarbon chains with a carboxylic group (-COOH)

Question 7

What letter can be used in a triglyceride structure to represent a hydrocarbon chain

Answer 7

R

Question 8

What is the fatty acid chain made up of

Answer 8

Hydrocarbons

Question 9

Describe what is meant by a saturated fatty acid chain

Answer 9

Thy hydrocarbon chain has only single bonds between carbons

Question 10

Describe what is meant by an unsaturated fatty acid chain

Answer 10

The hydrocarbon chain contains a double bond between carbons and is not saturated by hydrogen

Question 11

Give 2 reasons why triglycerides are used as energy storage molecules

Answer 11

Because the long hydrocarbon fatty acid chains contain lots of chemical energy and are insoluble in water so doesn’t affect water potential of the cell

Question 12

Describe how the structure of a triglyceride makes them insoluble

Answer 12

Triglycerides clump together as insoluble droplets in cells ∵ fatty acid tails = hydrophobic
= tails face inwards = shielding themselves from water with their glycerol heads

Question 13

Fatty acid tails are……

Answer 13

Hydrophobic (repel water)

Question 14

Describe the structure of a phospholipid

Answer 14

Contains one molecule of glycerol attached to 2 fatty acid chains and a phosphate group, via condensation reactions

Question 15

Explain how the structure of phospholipds makes them able to form the bilayer of cell membranes

Answer 15

The phosphate group ‘heads’ are hydrophilic (attracts water) , and the fatty acids are hydrophobic (repel water) , so they form a double layer with the phosphates on the outside and the fatty acids on the inside.
This makes the center of the bilayer hydrophobic, so it acts as a barrier to water-soluble substances

Question 16

Describe the emulsion test for lipids

Answer 16

1) Mix the fat/oil with ethanol
2) shake the boiling tube for about a minute
3) pour the solution into another boiling tube half full of cold water
4) positive test result shows a MILKY white emulsion