1.5 - Lipids Flashcards
What are lipids?
A group of substances that share the following characteristics:
- Contain hydrogen, oxygen and carbon
- Insoluble in water
What are the two main groups of lipids?
- Triglycerides
2. Phospholipids
Give 5 roles of lipids within biology
- Cell membranes
- Source of energy
- Waterproofing
- Insulation
- Protection
Why are lipids an excellent source of energy?
Because they provide more energy per mass than carbohydrates and water
Where are lipids used as waterproofing?
Waxy cuticles in plants to prevent water loss
Animals skin
Why are lipids used as insulators?
Because they are slow conductors of heat
What organs do lipids protect?
Kidneys, liver
What are the components of a triglyceride?
- 3 Fatty acids
- 1 Glycerol molecule
The fatty acids are bonded to the glycerol molecule by an ester bond
How do differences occur within triglyceride molecules?
Through variations in fatty acids.
The glycerol molecule is always the same in triglycerides
How is the structure of triglycerides related to their properties?
- High ratio of energy storing C-H bonds to C atoms
- Lots of energy stored in a small volume
- Large, non-polar molecules, their storage doesnt change water potential within cells
- High ratio of hydrogen to oxygen molecules means they release water when oxidised
What are the components of phospholipids
2 Fatty acids
1 Phosphate molecule
1 Glycerol head
These are joined by ester bonds
What gives phospholipids their unique property when held in water
The hydrophobic fatty acid tail and hydrophillic heads
How does the structure of a phospholipid relate to its properties
- Phospholipids are polar (head and tail) therefore in an aqueous environment they form a bilayer within cell membranes
- The hydrophillic head holds the phospholipid to the surface of the membrane
- Phospholipid structure allows them to form glycolipids by combining with carbohydrates, this is very important in cell recognition
