Lipids Flashcards
what are special about lipids
Lipids do not fit the polymer model like the other macromolecules
why are lipids grouped together
because they are hydrophobic
what is it about their structure and bonds that make them hydrophobic?
lipids consist mainly of hydrocarbons, with few O2-containing functional groups so they are soluble in nonpolar solvents
what are two non polar solvents
ether and chloroform
what are lipids used for
energy storage, structural components of membranes and hormones
what are four types of lipids
-triglycerides
-fatty acids
-steroids
-phospholipids
what are characteristics of triglycerides
-water insoluble
ex: lard, suet, olive oil, butter
what are characteristics of fatty acids
-water insoluble
ex: linoleic, linolenic (omega)
what are characteristics of steroids
-membrane component, hormones
ex: estrogen, vitamin D, cholesterol
what are characteristics of phospholipids
-amphipathic (membrane component)
ex: lecithin
what is energy storage
this is the main function of fats
in the seeds and fruits of plants and in animals (1g fat = 9kcal and 1g carbs = 4kcal)
what is insulation against the cold, cushion for mechanical injury and buoyancy
adipose cells cushion vital organs, such as the kindneys, and the layer of fat underneath the skin insulates the body
what is the main component of seed composition
starch and then protein
what is the purpose of neutral fats
-energy storage
-insulation against the cold
-cushion for mechanical injury
-buoyancy
what is a triglyceride
a fat composed of 2 kinds of smaller molecules, 3 fatty acids and 1 glycerol
what is a fatty acid
lipid molecule composed of often
long hydrocarbon tail (usually 16 or 18 C) with a carboxyl group
(-COOH) at one end where glycerol joins to
what is glycerol
a 3-carbon alcohol containing 3 hydroxyl (-OH) groups
what are ester linkages
3 fatty acids are joined to 1 glycerol molecule through bonds called ester linkages
how are triglycerides formed
formed following three dehydration reaction:
-hydroxyl group from glycerol
-removal of water
-carboxyl group from a fatty acid
how many different fatty acids are found in lipids
30
what are saturated fatty acids
contain the maximum # of H atoms bonded to the C skeleton (NO double bonds)
how are saturated fatty acids found at room temp
solid (ex: butter)
-straight and structured formation
what are monounsaturated fatty acids
contains one double bond
how are monounsaturated fatty acids found at room temp
liquid (oils) at room temp. and are found in fish and plants (ex: olive oil)
-fatty acid chain is bent
what are polyunsaturated fatty acids
contains more than one double
bond
how are polyunsaturated fatty acids found at room temp
also liquid (oils) at room temp. and are nutritionally the best type of lipid (ex: linseed oil)
-also bent
what are CIS unsaturated fatty acids
a cis fatty acid has both H atoms located on the same side of
the double bond (this gives the chain a pronounced bend)
where are are CIS unsaturated fatty acids found
found in nature, in foods such as olive oil
what are TRANS unsaturated fatty acids
a trans fatty acid has the H atoms attached on diagonally opp sides of the double carbon bond
what is the form of TRANS unsaturated fatty acids
more rigid and straighter, just like
saturated fatty acids making them easier to stack
where are TRANS unsaturated fatty acids produced
the majority of trans fatty acids are produced during the processing of foods are not recognized by our bodies as well and tend to accumulate in our systems instead of being broken down
what does hydrogenation create
trans fats
what are hydrogenated fats
those in which H atoms have been
added to unsaturated fatty acid chains during the process of
hydrogenation
what is the purpose of hydrogenation
this results in making a fat more SOLID at room temp, but the process does NOT saturate all the double bonds thereby
leaving many unsaturated fatty acids, it converts many cis to trans
how is most margarine created
because most margarine is the result of hydrogenation, it has more trans fatty acids than butter (which naturally contains low levels of trans fats)
how are triglycerides digested
in order for fats to be digested,
they must first be emulsified
(mixed) with the surrounding
aqueous solution in the digestive
tract using bile salts made by liver
what happens to emulsified fats
hydrolyzed into fatty acids and monoglycerides to be absorbed into the mucosal cells lining the inner wall of the small intestine
what happens to emulsified fats after they are absorbed
these are then reassembled and
packaged into lipoproteins (water-
soluble lipid-carrying particles) called chylomicrons
how do chylomicrons work
chylomicrons enter the blood to deliver fats to the cells of the body (vessel the digestive uses to transport fats out of the digestive system)
what sytem are chylomicrons transported by
since cholesterol and fats are insoluble in blood, they can only be transported in the circulatory system when encapsulated in these lipoproteins
what are lipoproteins
spherical molecules with:
- a hydrophobic interior
- a hydrophilic exterior composed in part by water-
soluble proteins (play a role in determining to
which type of cell to deliver the cholesterol) and phospholipid
what happens when you injest more protein or carbs than required
these are transported to the liver and converted to fats which are packaged in lipoproteins called Very-Low Density Lipoproteins (VLDL)
what are VLDLs
VLDLs carry triglycerides produced by the liver to
the body’s cells
describe the density of lipoproteins
the density of lipoproteins increases as
the lipids are released to body cells leaving behind
mainly the protein components
chylomricron packaging
look at diagram
what are HDLs
high density lipoproteins which have few lipids within the lipoprotein
what are steroids
characterized by a C skeleton of 4 interconnected hydrocarbon rings with various functional groups attached
(ex: cholesterol, hormones, vitamins, bile salts)
what is the structure of steroids
3 of the rings contain 6 carbon atoms and 4th ring contains 5 (side chain determines function)
what are anabolic steroids
a group of hormones very close in structure to
testosterone that promote muscle growth but causes enlarged prostate and shrinkage of testicle
how is cholestrol transported
cholesterol is transported in the blood by lipoproteins, LDL and HDL.
where is cholestrol found
- a common component of animal cell membranes
- precursor from which most other steroids are
synthesized (hormones and vitamins d and e) - important as a fluidity buffer in cell membranes
how to tell if it’s good or bad cholestrol
cholesterol is always the same molecule buy when
measuring good/bad cholesterol they are actually
analyzing the quantity of LDLs and HDLs in your blood
what is BAD cholestrol
diets high in trans fats impede uptake of LDLs by cells (they can cause malformation of plasma membranes) causing LDLs to continue to circulate in the blood
what is the consequence of bad cholestrol
the greater the amount of LDLs circulating in the blood the greater the risk that they will adhere to the walls of blood vessels causing plaques that can block arteries (atherosclerosis)
what is GOOD cholestrol
good cholesterol is the amount of HDLs circulating in the blood
how id the amount of cholestrol in blood reduced
HDLs pick up excess cholesterol from body cells and blood vessels and take it to the liver to be processed, reducing the amount of cholesterol in the blood
how to ensure goood cholestrol
diets rich in omega-3 and 6 fatty acids and exercising have been associated with increased levels of HDLs or good cholesterol
what do diets high in saturated and trans fats cause
- Increased LDL levels
- Decreased HDL levels
- Increased triglyceride levels
what is the formula for total blood cholestrol
Total blood cholesterol = HDL + LDL
**The higher the ratio of LDL/HDL the greater the
risk for cardiovascular disease.
what are essential fatty acids
Omega-3 and -6 fatty acids are essential fatty acids (i.e. your body does not produce them)
where is omega located
‘omega’ is the last carbon in the carbon skeleton
–omega-3 indicates the last double bond is 3 carbons away from the last carbon; omega-6, 6 carbons away
what are the cosequences of dietary trans fats
-raise the level of LDLs
-reduce HDLs
-raise levels of triglycerides in the blood.
what is the consquence of eating partially hydrogenated oils
people who ate partially hydrogenated oils, which are high in trans fats, had nearly twice the risk of heart attacks compared with those who did not consume hydrogenated oils.
what are phospholipids
- structurally related to neutral fats, except they contain only 2 fatty acid molecules
- a phosphate group, OPO32-, replaces the third fatty acid
- additional small molecules usually charged or polar and containing nitrogen (choline) can be linked to the phosphate group to create a variety of phospholipids.
why are phospholipids amphipathic
- non-polar hydrophobic tails (fatty acids)
- polar hydrophilic head (glycerol, phosphate and organic base)
what is the phospholipid bilayer
since they are amphipathic, they are the major constituents of a cell’s membranes – both external and internal, which are composed of phospholipid bilayers
what are the two types of phospholipid bilayer
-phosphoglycerides
-sphingolipids
what are phosphoglycerides
phosphoglycerides contain glycerol, fatty acids,
phosphate, and an alcohol (ex: choline)
what are sphingolipids
sphingolipids contain sphingosine (a long chain amino alcohol) instead of glycerol
where do sphingolipids occur
sphingolipids occur in high concentrations in the brain, nerves, lungs, and spleen tissue (found in the protective layer of axon)
what are tay-sachs
caused by an accumulation of sphingolipids in the nerve cells of the brain
(normally produced by the cell for recognition and cell-cell signaling)
why do tay-sachs occur
the accumulation occurs since the cell cannot correctly produce the enzyme that breaks them down (autosomal recessive allele coding for this enzyme)
