Chapter 1- Lipids Flashcards
Lipids
Hydrophobic, non-polar molecules (water-hating) bc of hydrocarbon chains
Store energy, provide insulation, cell membranes, synthesis of hormones
Triacylglycerol (triglyceride/fats)
is a lipid molecule found in cells called adipocytes. Contain a glycerol backbone and three fatty acids.
Produced by dehydration reactions.
Glycerol
organic alcohol molecule that has 3 carbons and 3 hydroxyl groups
Fatty acid
long hydrocarbon tail attached to a carboxylic acid.
Fats when dehydrated / fats when hydrolyzed
Dehydration/condensation: hydroxyl group of glycerol molecule react with carboxyl acid of fatty acids to produce ester linkage and loss of water.
Hydrolysis: addition of water to fat’s ester bond will break the fatty acid off the glycerol backbone.
Saturated fatty acid
has no double bonds and results in pack tightly (solid at room temperature!)
ex: butter
Unsaturated fatty acid
have double bonds bc they do not have full hydrogen saturation
Monounsaturated fatty acid
has one double bond
Polyunsaturated
two or more double bonds
Cis-unsaturated fatty acids
create twists in the fatty acid chain bc the hydrogens with the double bond remain on same side.
These twists make it difficult to pack together tightly = liquid at room temperature
ex: olive oil
Trans- unsaturated fatty acids
hydrogens go on the opposite side of the double bond = tightly packing fatty acids .
Industrial hydrogenation
give cheaper oils the desirable room-stable properties of cis-trans fatty acids
Phospholipids
lipid molecules that have a glycerol backbone, one phosphate group, and two fatty acid tails. Ex. of a amphipathic molecule. Phosphate group is polar (hydrophilic) and fatty acids are nonpolar (hydrophobic).
Bc they are amphipathic, they spontaneously assemble into a bilayer in aqueous environment; Cell membranes form through this way
Amphipathic molecules
contain hydrophobic and hydrophilic parts
Glycolipid
looks like phospholipid but contains carbohydrate molecule instead of phosphate group.
Cholesterol
class of lipids containing four hydrocarbon rings and is amphipathic. This allows it to interact with the cell membrane (phospholipid layer) increasing/decreasing the fluidity.
Liver makes cholesterol.
Cholesterol is starting material for vitamin D and precursor to bile acids.
Factors that affect fluidity of cell membrane:
Temperature, cholesterol, and degree of unsaturation in phospholipid fatty acid tail.
- Temperature decreases, phospholipids are packed tight fluidity decreases / temperature increases, fluidity increases
- Cholesterol at low temp, increases space between phospholipids increasing fluidity / chol. at high temp, pulls phospholipids together fluidity decreases
- If fatty acids saturated results in tighter phospholipids , fluidity decreases / If fatty acids unsaturated results in bends leaving space, fluidity increases
Bile acids
aid in fat absorption
Most common steroid precursor
Cholesterol
Steriods
fused structures composed of six-membered rings (cyclohexanes) & a five membered ring (cyclopentane)
Ex: cholesterol, testosterone, estrogen
Lipoproteins
contain a coat of phospholipids, cholesterol, and proteins. Also have a lipid core containing cholesterol and triglycerides allowing to travel through aqueous environment
Low-density lipoproteins (LDLs)
“bad” cholesterol;
low density of proteins; considered unhealthy bc they deposit cholesterol in peripheral tissues like the heart and major blood vessels.
Lead to atherosclerotic blockages and heart diseases.
High density lipoproteins (HDLs)
“good” cholesterol
high density of proteins; good because they take cholesterol away from peripheral tissues and deliver to the liver.
Can be used to make bile acids in the liver
Waxes
long fatty acids connected to monohydroxy alcohols by ester linkages.
Hydrophobic coating that prevents water absorption
Monohydroxy alchohols
molecules that contain one hydroxyl group.
Carotenoids
function as pigments provide color to plants and animals. long fatty acid carbon chains that have conjugated double bonds and 6-membered rings at each end.
