Lipids Flashcards
What are lipids?
Biomolecules that contain fatty acids or a steroid nucleus, soluble in organic solvents but not in water.
From what word is ‘lipid’ derived, and what does it mean?
From the Greek word ‘lipos’, meaning ‘fat’.
What are the types of lipids that contain fatty acids?
Waxes, fats and oils (triacylglycerols), glycerophospholipids, and prostaglandins.
What type of lipids do not contain fatty acids?
Steroids.
What are fatty acids?
Long-chain carboxylic acids, usually with 12-18 carbon atoms, insoluble in water, and either saturated or unsaturated.
What is the difference between saturated and unsaturated fatty acids?
Saturated have only single C-C bonds; unsaturated have one or more double C=C bonds.
What are the properties of saturated fatty acids?
Closely packed, strong chain attractions, high melting points, solid at room temperature.
What are the properties of unsaturated fatty acids?
Contain cis double bonds, have kinks in chains, loosely packed, low melting points, liquid at room temperature.
Which fatty acid has the highest melting point: stearic, oleic, or linoleic acid?
Stearic acid (saturated) with a melting point of 69°C.
How do double bonds affect the melting point of fatty acids?
More double bonds = lower melting point due to decreased molecular packing.
What are waxes made of?
Esters of saturated fatty acids and long-chain alcohols.
What is the biological function of waxes in plants?
They act as coatings to prevent water loss from leaves.
What are fats and oils also called?
Triacylglycerols.
What are triacylglycerols made from?
Esters of glycerol and three fatty acids.
How are triacylglycerols formed?
By esterification: hydroxyl groups of glycerol react with carboxyl groups of fatty acids.
What type of bonds form between glycerol and fatty acids in triacylglycerols?
Ester bonds.
What are the fatty acids present in the sample triacylglycerol from the learning check?
Stearic acid, Oleic acid, and Myristic acid.
What is the physical state of fats at room temperature?
Solid.
What is the physical state of oils at room temperature?
Liquid.
Where are fats most commonly found?
In meats, whole milk, butter, and cheese.
Where are oils commonly found?
In plants like olive and safflower.
Why do oils remain liquid at room temperature?
They have more unsaturated fats with cis double bonds that cause kinks, preventing tight packing.
What type of reactions do triacylglycerols undergo?
Similar to alkenes and esters-hydrogenation, hydrolysis, and saponification.
What happens in hydrogenation of oils?
Double bonds in unsaturated fats react with H2 (with a Ni or Pt catalyst), converting them to single bonds and forming solids like margarine.
What is produced by complete hydrogenation of glyceryl trioleate?
Glyceryltristearate.
What is Olestra?
A fat substitute made of sucrose and fatty acid chains that is not broken down in the digestive system.
What are cis and trans fatty acids?
Cis: bulky groups on the same side of C=C. Trans: bulky groups on opposite sides of C=C.
Why are trans fats a health concern?
They raise LDL and lower HDL cholesterol.
What is hydrolysis of triacylglycerols?
The splitting of triacylglycerols into glycerol and 3 fatty acids using acid, base, or enzymes.
What is saponification?
Reaction of fat with strong base to form glycerol and salts of fatty acids (soap); KOH makes softer soap.
What are glycerophospholipids made of?
Glycerol, two fatty acids, phosphate, and an amino alcohol.
What is the role of glycerophospholipids in cells?
They are the most abundant lipids in cell membranes.
What are the polar and nonpolar parts of a glycerophospholipid?
Nonpolar: two fatty acid chains. Polar: phosphate group and amino alcohol.
Name three common amino alcohols in glycerophospholipids.
Choline, ethanolamine, and serine.
What are lecithin and cephalin?
Types of glycerophospholipids found in brain, nerve tissue, egg yolk, wheat germ, and yeast.
Identify: Glyceryl trioleate
B. Triacylglycerol
Identify: Cephalin
D. Glycerophospholipid
Identify: Choline
C. Amino alcohol
Identify: Palmitic acid
A. Fatty acid
