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 R group

Answer 9

Thy hydrocarbon chain has only single bonds between carbons

Question 10

Describe what is meant by an unsaturated R group

Answer 10

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

Question 11

What does a kink in a fatty acid diagram show

Answer 11

That its unsaturated ( has a double bond between the carbons)

Question 12

Give 2 reasons why triglycerides are used as energy storage molecules

Answer 12

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 13

Describe how the structure of a triglyceride makes them insoluble

Answer 13

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

Question 14

Fatty acid tails are……

Answer 14

Hydrophobic (repel water)

Question 15

Describe the structure of a phospholipid

Answer 15

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

Question 16

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

Answer 16

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 17

Describe the emulsion test for lipids

Answer 17

1) Mix the fat/oil with ethanol ( if solid food sample, dissolve in 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