Lipids Flashcards
What are lipids?
Usually known as fats and oils.
Why do lipids differ from carbohydrates?
They are not polymers formed from monomers (repeating units). They are made from a variety of different components.
Name a component found in all lipids.
Hydrocarbons (molecules that contain carbon and hydrogen only).
Name two types of lipids.
Triglycerides and phospholipids.
What is meant by hydrophobic?
Repels water.
How many fatty acids are in one triglyceride?
3
How many molecules are in a triglyceride? How are they bonded?
There are 4: 3 fatty acids and 1 glycerol. They are bonded by ester bonds formed in a condensation reaction.
What makes triglycerides insoluble in water?
Fatty acids have long tails made of hydrocarbons. They hydrocarbons are hydrophobic and repel water. Hence these tails make triglycerides insoluble in water.
What is meant by hydrophilic?
Attracts water
Name two categories of fatty acids.
Saturated and unsaturated.
Describe the structure of a saturated fatty acid.
Fatty acid: RCOOH
R group contains only single C-C bonds
Describe the structure of an unsaturated fatty acid.
Fatty acid: RCOOH
R group contains one/more double C=C bonds
How are triglycerides formed?
A molecule of glycerol and 3 fatty acids are chemically joined by 3 ester bonds in a condensation reaction producing a triglyceride and 3x H2O
What are the lipids found in a cell membrane called?
Phospholipid bilayer
How many molecules are found in a phospholipid?
There are 4: 2 fatty acids, 1 glycerol and 1 phosphate group
Which part of a phospholipid is hydrophobic?
The fatty acid chains
Which part of a phospholipid is hydrophilic?
The phosphate head
What is the difference between triglycerides and phospholipids?
Triglycerides contain 3 fatty acids and phospholipids contain 2 fatty acids. Phospholipids contain a phosphate group and triglycerides don’t.
What are some similarities between phospholipids and triglycerides?
They’re both lipids.
They both contain glycerol.
They both contain hydrophobic features.
What are triglycerides used for?
Used as energy storage molecules
What is a benefit of triglycerides being insoluble?
Water unable to pass through and thus doesn’t take up space that can be used for energy.
How are triglyceride structures related to their properties?
High ratio of energy storing C-H bonds to C-C bonds; excellent energy store.
Low mass to energy ratio; good for storage as lots of energy can be stored in a small volume.
They’re non-polar and insoluble in water; their storage does not affect the water potential of cells.
High ratio of O-H bonds means that triglycerides release water when oxidised; provides water for organisms to live in dry environments.
How are phospholipid structures related to their properties?
Polar in aqueous environment; bilayer can be formed.
Hydrophilic heads; used to hold at the surface of the cell surface membrane.
Structure allows them to form glycolipids with carbohydrates; important on cell surface membrane for cell recognition.
What is the test for lipids?
The emulsion test
How do you test for lipids?
Add sample to grease-free test tube.
Add ethanol and shake.
Milky, white emulsion formed if lipid is present
