Biological molecules - Lipids Flashcards
What is the role of lipids in living organisms?
- Energy store - as triglycerides are insoluble in water they can be stored without affecting their water potential of the cell.
- Insulation - for example adipose tissue is a storage location of lipids in whales acting as heat insulating.
- Energy source - can be broken down in respiration to release energy and generate ATP.
- Protection - humans have fat around delicate organs.
Name 3 types of lipids.
Triglyceride, Phospholipid and Cholesterol.
Describe the structure of a triglyceride molecule (or draw it)
Triglyceride are formed when one glycerol and three fatty acids bond together.
Describe the difference between a saturated and unsaturated fatty acid.
Saturated fatty acids means there is no double bond between the carbons of a fatty acid whereas an unsaturated fatty acid contains at least one double bonded carbon.
Name the bond that forms between glycerol and a fatty acid.
A ester bond (-COO) is formed when a glycerol and a fatty acid bond together. When a condensation reaction happens between the -COOH group of the fatty acid and the -OH group of the glycerol.
How can a bond between a glycerol and a fatty acid be broken?
A hydrolysis reaction can break the ester bonds that are formed.
Describe the structure of a phospholipid molecule (or draw it).
A glyceride molecule consists of a glycerol molecule, two fatty acids and a phosphate group.
What does the term hydrophobic mean?
Hydrophobic means the molecule will repel away from water.
What does the term hydrophilic mean?
Hydrophilic means the molecule will be attracted towards water.
Describe how you can test for lipids.
The emulsion test is used to test for the presence of lipids. Mixing a sample with ethanol. filtering it out and pouring it into water. A cloudy white emulsion indicates the presence of a lipid.
What is the behaviour of a phospholipid in water?
When surrounded by by water, the phosphate group will be attracted to water whereas the fatty acid will be repelled away from it. The phosphate head is hydrophilic and the tail is hydrophobic.
What is a phospholipid bilayer?
The phospholipids form a bilayer, with two rows of phospholipids, tails pointing outwards and tails pointing inwards. Excellent at forming membranes around cells.
Describe the structure of a fatty acid. (or draw it).
Have a carboxyl group (-COOH) attached to a hydrocarbon tail, which can range from 2 to 20 carbons long.
Describe the structure of a glycerol (or draw it).
Contains three carbon atoms and three -OH groups.
