lipids |
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- the one class of biological molecules that does not include/form true polymers- generally not big enough to be considered macromolecules- grouped together because they share one important trait: they mix poorly, if at all, with water- thus are hydrophobic |
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the hydrophobic behavior of lipids is based on what? |
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their molecular structure |
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other characteristics of lipids include what? |
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- consist mostly of hydrocarbon regions- varied in form and function- include waxes and certain pigments- also fats, phospholipids and steroids |
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fats |
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- not smaller molecules, large molecules assembled from smaller molecules by dehydration reactions- constructed from two kinds of smaller molecules: glycerol and fatty acids |
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glycerol |
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a 3 carbon alcohol with a hydroxyl group attached to each carbon |
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fatty acids |
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- a fatty acid has a carboxy attached to a carbon skeleton- contain a long carbon skeleton, usually 16 to 18 carbon atoms in length
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the carbon at the end of a fatty acid's carbon skeleton is part of what? |
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a carboxyl group which is the functional group that gives the molecules the name fatty acid |
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the rest of the carbon skeleton is composed of what? |
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hydrocarbon chain |
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what is the reason why fats are hydrophobic? |
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- the relatively non polar C--H bonds in the hydrocarbon chains of fatty acids- fats separate from water because the water molecules hydrogen bond to one another and exclude fats |
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in making fat, how many fatty acid molecules are each joined to glycerol by an ester linkage? |
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- three- a bond b/w a hydroxyl group and a carboxyl group |
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triacylglycerol |
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- resulting fat of a bond b/w a hydroxyl group and a carboxyl group- consist of 3 fatty acids linked to one glycerol molecule |
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what are the similarities and differences in the fatty acids in a fat? |
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- they can be the same - or they can be two or three different kinds |
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saturated and unsaturated fats |
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terms refer to the structure of the hydrocarbon chains in the fatty acids |
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saturated fatty acid |
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- if there are no double bonds between carbon atoms composing in a chain, then as many hydrogen atoms as possible are bonded to the carbon skeleton- and is said to be saturated with hydrogen |
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unsaturated fatty acid |
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- has one or more double bonds- with one fewer hydrogen atom on each double-bonded carbon- nearly all double bonds in naturally occurring fatty acids are cis double bonds, which cause a kink in the hydrocarbon chain wherever they occur |
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most animals fats are saturated or unsaturated? |
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- saturated- the hydrocarbon chains of their fatty acids, the "tails" of the fat molecules, lack double bonds, and their flexibility allows the fat molecules to pack together tightly
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saturated (animal) fats |
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- solid at room temperature- include lard and butter |
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unsaturated (plant and fish) fats |
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- liquid at room temperature- built of one or more unsaturated fatty acids- referred to as oils ( such as olive oil)- the kinks where the cis double bonds are located prevent the molecules from packing together closely enough to solidify at room temperature |
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trans fats |
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- may contribute more than saturated fats atherosclerosis- especially common in baked goods and processed foods |
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unsaturated fatty acids must be supplied in the human body because? |
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- they cannot be synthesized in the body- include omega-3 fatty acids, which are required for normal growth in children and protect against cardiovascular decease in adults |
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what is the major function of fats? |
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- energy storage- the hydrocarbon chains in fat are similar to gasoline molecules and just as rich in energy- the energy is in the bond |
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phospholipids |
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- two fatty acids and a phosphate- the two fatty acids are hydrophobic, the phosphate is hydrophilic- without it cells could not exist- essential for cells because they make up cell membranes - when phospholipids are added to water, they self- assemble into double-layered structures called "bilayers" shielding their hydrophobic portions from water - at the surface of a cell, phospholipids are arranged in a similar bilayer - the phospholipid bilayer form a boundary between the cell and its external environment and allow cells to exist |
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the structure of a phospholipid is based on what? |
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differences in the two fatty acids and in the groups attached to the phosphate group of the head
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