Chapter 13 - Lipids

• storage of energy

• insulation from environment

• water repellant

• buoyancy control in marine animals

• membrane structure

• cofactors for enzymes

• signaling molecules

• pigments

• antioxidants

9 common functions of lipids

they are reduced compounds, so they have lots of available energy and they are hydrophobic, so they are good at packing

why are lipids good for storage of energy

they have low thermal conductivity, high heat capacity (can absorb heat), and mechanical protection by absorbing shocks

how are lipids able to provide insulation from the environment

vitamin K (blood clot formation) and coenzyme Q (ATP synthesis in the mitochondria)

2 cofactors for enzymes that are lipids

paracrine hormones (act locally), steroid hormones (act body-wide), growth hormones, and vitamins A and D (hormone precursors)

4 signaling molecules that are lipids

vitamin E

which vitamin is a lipid and antioxidant

structure and function

what are lipids classified based on

lipids that do not contain fatty acids vs lipids that do contain fatty acids (complex lipids)

how are lipids classified based on structure

storage lipids vs membrane lipids

how are complex lipids classified based on function

draw ester vs ether

carboxylic acids with hydrocarbon chains containing between 4 to 36 carbons

what are fatty acids (composition wise)

most have an even number of carbons and are unbranched

2 characteristics of most natural fatty acids

saturated have no double bonds, monounsaturated have 1 double bond, and polyunsaturated have more than 1 double bond

saturated vs monounsaturated vs polyunsaturated fatty acids

essential nutrients (humans need them but cannot synthesize them)

what are omega-3 fatty acids considered

ALA, DHA, and EPA

3 examples of omega-3 fatty acids

solubility decreases

how does solubility change as fatty acid length increases

melting point decreases

how does melting point change as fatty acid length decreases

melting point decreases

how does melting point of fatty change when double bonds increases

cis-configuration which kinks the chain

what configuration are the double bonds in natural unsaturated fatty acid commonly in

saturated fatty acids pack in a fairly orderly way while unsaturated cis fatty acids pack less orderly due to the kink

saturated vs unsaturated cis fatty acid packing

unsaturated cis fatty acids because it takes less thermal energy to disrupt their disordered packing

do saturated fatty acids or unsaturated cis fatty acids have lower melting point

formed by partial hydrogenation of unsaturated fatty acids and change from liquid to solid form

how are trans fatty acids formed

trans fatty acids can pack more regularly and have higher melting points

trans fatty acid packing and melting point compared to cis fatty acids

cardiovascular disease

what does the consumption of trans fatty acids increase risk of

triacylglycerols

what form are majority of fatty acids in biological systems found in

liquids ones are called oils and solid ones are called fats

what is a liquid vs solid triacylglycerol called

triacylglycerols

what is the primary storage form of lipids

triacylglycerols are less soluble in water due to the lack of charged carboxylate group

solubility of triacylglycerols compared to fatty acids

triacyclglycerols are less dense than water (float in water)

density of triacylglycerols compared to water

fatty acids carry more energy per carbon because they are more reduced and they carry less water per gram because they are nonpolar

advantage of fats over polysaccharides

• glucose and glycogen are for short-term energy needs, quick delivery

• fats are for long-term energy needs, good storage, slow delivery

energy needs fatty acids vs polysaccharides provide

esters of long-chain saturated and unsaturated fatty acids with long-chain alcohols

what are waxes (composition)

they are insoluble and have high melting points

characteristics of waxes

• storage of metabolic fuel in plankton

• protection and pliability for hair and skin in vertebrates

• waterproofing of feathers in birds

• protection from evaporation in tropical plants and ivy

• used by people in lotions, ointments, and polishes

5 functions of waxes

• modifying a different backbone

• changing the fatty acids

• modifying the head groups

how can structural lipids in membranes be diversified

the properties of head groups

what determines the surface properties of membranes

different organisms and different tissues

what is composed of different membrane lipid head group compositions

glycerophospholipids

primary constituents of cell membranes

two fatty acids form ester linkages with the first and second hydroxyl groups of L-glycerol-3-phosphate

how is glycerophospholipid formed

at physiological pH

when is head group of glycerophospholipid charged

glycerol with highly polar phosphate group, saturates fatty acid, unsaturated fatty acid connected to C2, and head group alcohol

general structure of glycerophospholipids

phosphatidyl-”name of head-group alcohol”

how is type of glycerophospholipid named

phosphatidic acid

what is the parent compound glycerophospholipid

phosphatidylcholine

glycerophospholipid found in eukaryotic cell membranes

vinyl ether analog of phosphatidylethanolamine → vertebrate heart tissue, some protozoa and anaerobic bacteria

what is plasmalogen and where is it found

aliphatic ether analog of phosphatidylcholine

what is platelets-activating factor