Lipids Flashcards
What are most lipids?
Most lipids are triglycerides
A triglyceride is an ester of fatty acids and glycerol
What does a molecule of fatty acid consist of?
A molecule of fatty acid consists of a hydrocarbon chain and a carboxyl group (-COOH)
None
What combines to form a triglyceride?
A condensation reaction combines glycerol and 3 fatty acids to form a triglyceride and 3 water molecules
What is a simple triglyceride formed from?
A simple triglyceride is formed from 3 same fatty acid molecules
None
What is a mixed triglyceride formed from?
A mixed triglyceride is formed if fatty acids are different
None
What makes the structure of triglycerides useful in living organisms?
The structure of triglycerides makes them useful in living organisms because they are insoluble in water, store chemical energy, are readily hydrolyzed to fatty acids and glycerol, and used in respiration in cells if glucose is in short supply
Roles of lipids
What are lipids?
Lipids are fats + oils
What determines the physical state of lipids?
The physical state depends on melting point
What elements do organic compounds containing lipids consist of?
Organic compounds containing lipids consist of H, C, O
How does the oxygen content in lipids compare to carbohydrates?
The oxygen content is much lower than in carbohydrates
What are the key roles of lipids?
- Structural role in cell membranes
- Energy store
- Waterproofing + reducing water loss
- Insulation (thermal + electric)
- Protection - shock absorber to protect vital organs from physical impact
What are phospholipids?
Triglycerides that contain a phosphate group instead of one of the fatty acids.
The phosphate group dissolves in water, therefore hydrophilic. The hydrocarbon chains of the two fatty acid components do not dissolve in water, therefore hydrophobic.
How can you perform the emulsion test for lipids?
Mix ethanol and test material in equal volumes. Shake to help dissolve any lipids present. Add an equal volume of water and shake again. A milky white emulsion indicates the presence of lipids.
What is stearic acid?
Mammalian adipose tissue, melting point 69.6°C (solid)
Example: Stearic acid is a saturated fatty acid commonly found in animal fats.
Where is oleic acid found?
Found in olive oil, melting point 13.4°C (fluid)
Example: Oleic acid is an unsaturated fatty acid that is liquid at room temperature.
