Lipids Flashcards
(11 cards)
Which elements do lipids contain?
Lipids contain carbon, hydrogen, and oxygen.
What are two groups of lipids?
Triglycerides, and phospholipids.
What is the importance of triglycerides?
Triglycerides act mainly as energy stores in plants and animals.
How are triglycerides formed?
Triglycerides are formed by the condensation of one molecule of glycerol and three fatty acid molecules joined together by an ester bond.
What is meant by saturated fatty acids?
Saturated fatty acids contain no C=C double carbon bonds, they only contain single bonds in the hydrocarbon chain.
What is meant by unsaturated fatty acids?
Unsaturated fatty acids contain at least one C=C double carbon bond, allowing the molecule to bend. These are also liquid at room temperature as unsaturated fats can’t be tightly packed together.
How are phospholipids formed?
Phospholipids are formed by the condensation of one molecule of glycerol, two fatty acid molecules, and one phosphate group joined together by an ester bond.
How does the structure of triglycerides relate to its function?
Triglycerides are insoluble: they don’t affect water potential which could cause water to move in or out of the cells by osmosis, resulting in the cells swelling, bursting, or shrinking.
The high ratio of energy-storing carbon hydrogen bonds to carbon atoms in triglycerides makes them good sources of energy.
The low mass to energy ratio of triglycerides makes them a good storage molecule as a lot of energy can be stored in a small volume.
A high ratio of hydrogen to oxygen atoms in triglycerides releases water when oxidised, which provides an important source of water, especially for organisms living in dry environments.
What is the importance of phospholipids?
Phospholipids make up the bilayer of cell membranes which controls what enters or leaves a cell/organelle.
How does the structure of phospholipids relate to its function?
Phospholipids are polar molecules (hydrophobic tails and hydrophilic heads) form a bilayer in an aqueous environment as in cell membranes.
The phospholipid structure allows them to form glycolipids by combining with carbohydrates within the cell-surface membrane. Glycolipids are important in cell recognition.
What is the process of the emulsion test for lipids?
1) Dissolve 2cm^3 of sample dissolved in 5cm^3 of ethanol.
2) Shake the test tube.
3) Add distilled water and shake gently.
A positive result is when a white emulsion forms due to the lipid precipitating. You can repeat the experiment with water as a control, as the final solution should remain clear.
