1.3-Lipids

Question 1

1) Describe the structure of a triglyceride

Answer 1

One molecule of glycerol and three molecules of fatty acid

Question 2

1) How is a triglyceride form?

Answer 2

A condensation reaction between glycerol and 3 fatty acids (RCOOH), with the elimination of 3 molecules of water and the formation of 3 ester bonds.

Question 3

Draw a triglyceride – circle the ester bon

Answer 3

0

Question 4

1) Describe the structure and how it relates to the properties of a triglyceride

Answer 4

Non-polar structure (cannot form hydrogen bonds with water molecules)  Not water soluble (so doesn’t affect water potential) and water proof.
High proportion of C-H bonds  Good store of energy

Question 5

1) Describe the structure of a phospholipid

Answer 5

It is made of 1 glycerol molecule, 1 phosphate group and 2 fatty acid chains

Question 6

1) In terms of structure, explain the difference between a phospholipid and a triglyceride

Answer 6

Phospholipids have a phosphate group which replaces 1 of the fatty acids

Question 7

1) Draw a phospholipid and label the hydrophilic and hydrophobic parts

Answer 7

0

Question 8

1) Describe how Phospholipids can arrange themselves to form a cell membrane. Draw and label a diagram to show this.

Answer 8

The plasma membrane is a phospholipid bilayer. With hydrophilic phosphate heads on the outside of the bilayer and hydrophobic fatty acid tails on the inside of the bilayer.

Question 9

Unsaturated

Answer 9

Unsaturated

At least one double bond between carbon atoms in the fatty acid chain
No
The chains are rigid
The chains have bends (kinks) in in them (where the double bonds occur). This means that they can’t line up so closely next to each other
Low
Less dense
Low melting point and boiling point
Less i.m.f. so less energy required to overcome them
Usually liquid

Question 10

Saturated

Answer 10

ONLY single bonds between carbon atoms in the fatty acid chain (no C=C bonds)
Yes
The chains are flexible
The chains are straight, so they can line up closely next to each other
High
More dense
High melting point and boiling point
More of i.m.f – lots of energy needed to overcome them
Usually solid

Question 11

10 Describe the test for lipids

Answer 11

• Crush/grind the food
• Dissolve in ethanol
• Then add water
• If it forms a WHITE EMULSION this means that lipids are present