1. Lipids: Fats & Oils

2. Concentrated energy molecules
Lipids
Concentrated energy molecules

3. Lipids Examples fats oils waxes hormones sex hormones
testosterone (male)
estrogen (female)

4. What are the functions of lipids?
STRUCTURAL: biological membranes (phospholipids, steroids, glycolipids), cushioning (fat deposits round the kidneys)
ELECTRICAL INSULATION: myelin sheath round axons
THERMAL INSULATION: subcutaneous fat deposits.
WATER PROOFING: waxes and oils
ENERGY STORE AND SUBSTRATE: very condensed form of energy (37 kJ g-1) used by animals and seeds.
HORMONES: steroids
VITAMINS: precursor to Vit D
BUOYANCY: oil droplets in plankton

5. Fatty acids: carboxylic acid + long hydrocarbon chainOH
CH3
Carboxylic acid
Hydrocarbon chain
A saturated fatty acid
An unsaturated fatty acid C O OH
CH3
© 2007 Paul Billiet ODWS

6. Condensation in triglycerides
fatty acids + glycerol (1, 2 or 3 = mono , di or triglycerides) C O OH
CH3
HO – CH2
HO - CH2
HO - CH C O OH
CH3
Condensation reactions
© 2007 Paul Billiet ODWS

8. Two fatty acids joining glycerol = A diglyceride
CH3
O - CH3
HO - CH3
O - CH
+ 2H20
© 2007 Paul Billiet ODWS

9. Molecular Structure of Fat
not a chain (polymer) = just a “big fat molecule”

10. A TRIGLYCERIDE: C H O
Glycerol
Fatty acid
Can be drawn as:
Ester bond

11. Unsaturated fatty acids
no double bonds
one or more double bonds
abundant in fats
abundant in oils
more reduced
less reduced
more energy
less energy
high melting point
low melting point
© 2007 Paul Billiet ODWS

12. Saturated fats Most animal fats Limit the amount in your diet
solid at room temperature
Limit the amount in your diet
contributes to heart disease
deposits in arteries

13. Unsaturated fats Plant, vegetable & fish fats
liquid at room temperature
the fat molecules don’t stack tightly together
Better choice in your diet

14. Saturated vs. unsaturated

15. Other lipids in biology
Cholesterol
good molecule in cell membranes
make hormones from it
including sex hormones
but too much cholesterol in blood may lead to heart disease

16. Other lipids in biology
Cell membranes are made out of lipids
phospholipids
heads are on the outside touching water
“like” water
tails are on inside away from water
“scared” of water
forms a barrier between the cell & the outside

17. Other lipids Steroids: multiple ring structures (e.g. cholesterol)
Functions: cell membrane structure, digestion (help to emulsify fats), hormones (testosterone etc), vitamins (e.g. Vitamin D), poisons
Waxes: long chain alcohol + fatty acids
Water proof coating to leaves, fur feathers, insect exoskeletons.
Used by bees to construct their honey combs.
© 2007 Paul Billiet ODWS

18. Compare the use of carbohydrates and lipids in energy storage.
Stored as…?
Starch in plants and glycogen in animals
Triglycerides or fat in animals and oils in plants
Long/short term storage?
Short time storage
Long time storage
Ease of digestion/ release of energy?
Easily broken down to release energy quickly.
More complex and so slower to brake down.
Energy per gram?
17 kJ per gram
38 kJ per gram
Solubility in water?
(and consequence)
Soluble in warm water and insoluble in cold water
Insoluble in water
Use of oxygen in metabolism?
May be used for anaerobic respiration temporarily in muscle cells. In this case lactic acid will be produced.
Only for aerobic respiration