Lipids Flashcards
a diverse group of organic compounds that share a common property of insolubility in water
Lipids
What are the functions of lipids? (4)
energy storage and utilization
insulation
structural components of cell membranes
synthesis of other biological compounds
What are the other biological compounds that can be synthesized from lipids?
bile acid
vitamin D
Steroid hormones
eicosanoids
What are some example types of lipids?
“free” fatty acid
triglycerides
phospholipids
cholesteryl ester
What is the simplest of lipids?
fatty acids
what is composed of a straight carbon chain with a carboxyl group (COOH) at one end (alpha end) and a methyl group (CH3) at the other end (omega end)
fatty acids
which of the simple lipids are components of more complex lipids?
fatty acids
Is the Polar head group hydrophobic or hydrophilic?
hydrophilic
Is the nonpolar, hydrocarbon tail hydrophobic or hydrophilic?
hydrophobic
-CH3
methyl or carboxylic?
methyl
-COOH
methyl or carboxylic?
carboxylic
What are the three ways fatty acids can vary and classify by?
Unsaturated/saturated
short/long chain
essential/nonessential
What type of chain is a Fatty acid with less than 6 carbons?
short chain
What type of chain is a Fatty acid with 6-12 carbons?
medium chain
What type of chain is a Fatty acid with 13-24 carbons?
long chain
what determines how fatty acids are digested and metabolized?
chain length
what “saturates” fatty acids?
Hydrogen atoms
Which one is typically solid at room temperature?
Saturated or Unsaturated?
Saturated
Which one is more flexible, thus are more often components of cell membranes?
Saturated or unsaturated?
unsaturated
What fatty acid cannot be made in the body and therefore must be consumed in the diet?
essential fatty acids
What are the two essential fatty acids?
linoleic and a-linolenic
What end is often written as -CH3?
(methyl)
omega end
what end is often written as -COOH?
Carboxylic acid
or
alpha end/delta end
what type of saturated fatty acid is
cis9-18:1 ?
monounsaturated
oleic acid
what type of saturated fatty acid is
18:0 ?
saturated
stearic acid
what type of saturated fatty acid is
cis9,cis12-18:2 ?
polyunsaturated
linoleic acid
What food is an example of monunsaturated fatty acid source
olive oil
What are the three fatty acid naming system?
common names
omega system (w)
Delta (triangle) or alpha (a) system
What system describes:
# of carbons
# of double bonds
# of carbons starting from the omega end, to the first carbon in the first double bond
Omega system
(w)
What system describes:
# of carbons
# of double bonds
# of carbons starting from the delta end, to the first carbon in each of the double bonds.
delta system
(triangle)
What is the common name for
C 18:0
stearic acid
why is stearic acid a saturated fatty acid?
It is “completely saturated” with H atoms
(no double bond)
What is the common name for
C18:1delta 9 ?
oleic acid
Is stearic acid saturated or unsaturated?
saturated
is oleic acid saturated or unsaturated?
(mono)unsaturated
What is the common name for
C18:2delta9,12 ?
linoleic acid
Is linoleic acid saturated or unsaturated?
(poly)unsaturated
Linolenic acid is an omega ? acid
omega 3
what is the common name for
C20:4delta5,8,11,14 ?
arachidonic acid
Is arachidonic acid saturated or unsaturated?
(poly)unsaturated
what is the common name for
C20:5delta5,8,11,14,17 ?
eicosapentaenoic acid
is eicosapentaenoic acid saturated or unsaturated?
(poly)unsaturated
eicosapentaenoic acid is an omega ? acid
omega 3 acid
How can fatty acids be changed in the body to different fatty acids?
Desaturation
elongation
what enzyme desaturates fatty acids?
desaturase enzymes
(delta 4,5,6,9)
what bonds does desatuation cause?
c=c double bonds
what is the highest desaturase in the body?
delta 9
What enzyme cause fatty acid elongation?
elongase enzymes
how does elongation happen?
carbons are added in pairs of 2 from the delta end
Myristic Acid (c14) + elongase
palmitic acid (c16)
Palmitic acid (c16) + elongase
stearic acid (c18)
stearic acid (c18) + desaturase
oleic acid (c18:1delta9)
How can we form oleic acid (c18:1delta9) from stearic acid (c18)?
using desaturase delta9
can we form linolenic acid from oleic acid?
No, because we don’t have a delta12 or 15 desaturase
Why is linolenic acid an essential fatty acid?
because we do not have a delta12 or delta15 desaturase
how do we form arachidonic acid (C20:4delta5,8,11,14) from linoleic acid (C18:2delta9,12)?
desaturation at delta6 (C18:3delta6,9,12)
elongate (add 2 carbons (C20:3delta8,11,14))
desaturation at delta5 (c20:4delta5,8,11,14)
What saturated Fatty acid has 4 carbons and what is it’s source?
butyric
butter
What saturated Fatty acid has 6 carbons and what is it’s source?
Caprioc
butter
What saturated Fatty acid has 14 carbons and what is it’s source?
Myristic
coconut and palm
What saturated Fatty acid has 16 carbons and what is it’s source?
palmitic
animal and some fat
What saturated Fatty acid has 18 carbons and what is it’s source?
stearic
animal and some fat
What Unsaturated Fatty Acid has 18 carbons and 1 double bond and what is its source?
Oleic
olive, canola
What Unsaturated Fatty Acid has 18 carbons and 2 double bonds and what is its source?
Linoleic
corn, sunflower
What Unsaturated Fatty Acid has 18 carbons and 3 double bonds and what is its source?
a-linolenic
soybean, canola
What Unsaturated Fatty Acid has 20 carbons and 4 double bonds and what is its source?
arachidonic
eggs, animal fat
What Unsaturated Fatty Acid has 20 carbons and 5 double bonds and what is its source?
eicosapentaenoic (EPA)
seafood
What Unsaturated Fatty Acid has 22 carbons and 6 double bonds and what is its source?
Docosahexaenoic (DHA)
seafood
substituents are on the same side of the bond
cis-
substituents are on opposite sides of the bond
trans-
what bond results in folding and kinking of the fatty acid into a U-like orientation
cis bond
what fats are extended into a linear shape?
trans fats
Does a trans fat act more like a saturated fatty acid or unsaturated fatty acid?
saturated fatty acid
How are trans fats manufactured?
partial hydrogenation
double bonds of cis orientation undergo an electronic rearrangement to the trans form
partial hydrogenation
What source of fat makes up 85% of a typical american diet?
unsaturated fat
What source of fat make up 12% of a typical american diet?
saturated fat
What source of fat make up 3% of a typical american diet?
Trans fat
What source of fat appear to increase the risk of chronic heart disease more than any other macronutrient?
Trans fats
Trans fat consumption increases the risk of what diseases?
heart disease
diabetes
alzheimer’s
certain cancers
what source of fat is “generally no longer regarded as safe”?
trans fat
3 carbon alcohol molecule containing 3 hydroxyl groups (OH)
Glycerol
C3H8O3
a bond formed by the reaction of an alcohol and an acid with the removal of water
ester bond
what represents the main storage form of a fat in the body?
Triacylglycerols
What term has replaced triglyceride?
triacylglycerol
what accounts for nearly 95% of a dietary fat intake?
Triacylglycerols
True or False
Fatty acids attached to glycerol may be different
True
Characterized by a four-ring core structure called the cyclopentanoperhydrohphenanthrene (or steroid) nucleus
Sterol
What is the most common sterol?
cholesterol
What sterol serves as a precursor for other steroids (bile acids, sex hormones, vitamin D, etc)?
Cholesterol
What is an essential component of cell membranes? (2)
cholesterol
phospholipids
What has been implicated in CVD but is essential for various processes?
cholesterol
What forms can cholesterol exist in?
free form
esterified form
approximately how much of our cholesterol is made from our body?
approx 75%
lipid class that contain phosphate and one more fatty acids
phospholipids
what is less hydrophobic than other lipids, thus are often expressed on the surface of lipid transport particles
phospholipids
what two components of cell membranes comprise of 5% of dietary lipids?
cholesterol and phospholipids
what are the two different core structures a phospholipid can be?
glycerol (glycerophosphatides)
amino alcohol sphingosine (sphingolipids)
What makes up the interior portion of the cell membrane?
Hydrophobic fatty acids tails
What points towards the hydrophilic (watery) environment?
Hydrophilic polar head groups
what is made of a bilayer of phospholipids with proteins and cholesterol dispersed?
cell membranes
Proteins are embedded in the ___.
cell membrane
Why are fats emulsified?
increase the surface area
increase the accessibility of the fat to the digestive enzymes
How does emulification start?
starts in the stomach via muscular contractions
Where does emulsification largely occur at?
in the small intestine via bile acid
Where is lingual lipase produced?
in the salivary glands
What does lingual lipase do?
removes some fatty acids starting in the mouth
after lingual lipase removes some of the fatty acids starting in the mouth, what is sent to the stomach?
Triglycerides, Diglycerides, and fatty acids
Once Triglycerides, Diglycerides, and fatty acids from the mouth get to the stomach, what are they further digested by?
Gastric Lipase
where is gastric lipase produced?
in the stomach
Where are Triglycerides, diglycerides, and fatty acids sent to after the stomach?
small intestine
What is Phase 1 of digestion in the Small intestine?
Emulsification
What emulsifies lipids?
bile
What represents the most significant means of eliminating excess cholesterol?
bile
Where is bile created?
liver
Where is bile stored?
gallbladder
How does cholesterol medications lower blood levels?
by binding bile in the GI tract and enhancing fecal excretion; thus body must use more cholesterol to make bile, decreasing blood levels
What is made in the liver, stored in the gallbladder, and acts in the small intestine?
bile
What does emulsified lipid droplets in the small intestine stimulate the release of?
cholecystokinin (CCK)
Where is bile released into when the gallbladder contracts?
cystic duct, joining the common bile duct
What helps contract the gallbladder and releases pancreatic juice?
cholecystokinin (CCK)
how does bile aid in lipid digestion?
enabling large lipid globules to disperse in the watery environment of the small intestine
What happens to the bile constituents after aiding in lipid digestion?
bile constituents are reabsorbed from the ileum and returned to the liver via the hepatic portal vein
How does the liver reuse the bile constituents after being reabsorbed from the ileum and returned to the liver?
to resynthesize bile to store in the gall bladder
What is Phase 2 of digestion in the Small Intestine?
Enzymatic digestion
Where is pancreatic lipase produced?
in the pancreas
what does pancreatic lipase do in the small intestine?
removes some fatty acids
What is orlistat?
an anti-obesity drug that inhibits pancreatic lipase
What results in enzymatic digestion?
monoglycerides and fatty acids
Phospholipid digested by Phospholipase A2 produces
fatty acid and lysophospholipid
cholesteryl ester digested by bile salt-dependent cholesteryl ester hydrolase produces
fatty acid and cholesterol
Micellar solubilization of lipid digestion products
AKA…
Making the insoluble…soluble
What interact at the brush border of enterocytes?
Micelles
the contents enter the enterocyte primarly via ____ diffusion?
simple diffusion
What happends to the lipids after the contents of micelle are absorbed into the enterocytes?
intracellular re-formation in the endoplasmic reticulum
After re-formation, what are lipids packaged into?
lipoproteins
where do lipoproteins go after reformation in the endoplasmic reticulum?
sent out into the circulation
What happens short- and medium- chain fatty acids once they are absorbed?
bind to albumin and circulated in the blood
What are packaged into micelles and then taken up by the enterocyte? (4)
Long-chain fatty acids
lysophospholipids
cholesterol
monoglycerides
What happens to triglycerides phospholipids and cholesteryl esters in the enterocyte?
they are reformed and then packaged into chylomicrons and circulated in the lymph.
what is the most common short chain fatty acid?
butyrate (C4)
what are directly ingested and formed as a byproduct of fermentation by gut microbiota?
Short and medium chain fatty acids
True or false
short and medium chain fatty acid digestion is different from long chain fatty acids
false
What are not re-formed into triacylglycerols in the enterocyte, but pass through the enterocyte directly into the portal blood, where they bind to albumin and are transported directly to the liver
short and medium chain fatty acids
what chain of fatty acids have had supported research suggesting protective effects against obesity and diabetes?
short chain fatty acids
molecule containing lipids and proteins that allow transport of lipids through the blood
lipoprotein
What lipoprotein transport dietary and other fatty acids from the liver to the body with the help of lipoprotein lipase?
Very Low Density Lipoprotein
What makes VLDL?
liver
VLDL with the loss of fatty acids makes?
Intermediate-density lipoproteins (IDL)
What lipoprotein continue to deliver dietary and other fatty acids to the body and is in between VLDL and LDL?
Intermediate-density lipoproteins (IDL)
Intermediate-density lipoproteins (IDL) with the loss of fatty acids makes?
Low-Density Lipoproteins (LDL)
what lipoprotein deliver cholesterol to the body (especially liver, adipose, and muscle cells).
Low-Density Lipoproteins (LDL)
What lipoprotein pick up excess cholesterol from nonhepatic cells and deliver it to the liver
(reverse cholesterol transport)?
High-density lipoprotein (HDL)
What 2 organs make High-density lipoprotein (HDL)?
liver and small intestine
What lipoprotein delivers dietary triglycerides to the body via lipoprotein lipase?
chylomicrons
What organ makes chylomicrons?
small intestine
Protein portion of a lipoprotein
Apoprotein
What does apoproteins affect in lipoproteins?
structure and function
what are apoproteins typically abbreviated as?
apo
What composes major lipoproteins (4)
Phospholipid
cholesteryl ester
cholesterol
triglyceride
What apoprotein do chylomicrons contain?
apoB48 (stabilizes the chylomicron in aqueous environment)
apoCII (activates lipoprotein lipase)
apoE (allows uptake into the liver via LDL receptor)
what apoproteins does a Nascent chylomicron contain?
B-48
What apoproteins does a mature chylomicron contain?
Apo B-48 Apo CII and E from HDL (in the blood)
“forward” lipid transport
chylomicrons deliver FA to tissues.
What is in the endothelial lining of capilaries in extra hepatic tissues, stimulated by insulin (in adipose tissue), activated by Apo II, and Hydrolyzes TAGs to FA’s and glycerol?
Lipoprotein lipase
What apoprotein does a chylomicron remnant have that allows uptake into the liver via the LDL-R or LRP
Apo-E
(e-ticket)
Inside the capillary, When activated by Apo C-II, what results from LPL hydrolyzing TAGS in the chylomicron?
Fatty Acid Uptake
When chylomicrons deliver fatty acids to tissues, what stays in the blood to be taken up by the liver?
glycerol
Enzyme that hydrolyzes triacylglycerols into 2 FA and one monoacylglycerol, and requires ApoC-II?
Lipoprotein Lipase
Lipoprotein Lipase, AKA..
Clearing factor
where is lipoprotein lipase expressed the most at?
Heart, adipose, skeletal muscle, and mammary glands
What is a consequence of LPL deficiency?
more fat in blood leading to increased risk of atherosclerosis
How does fatty acids help energy needs?
when energy is needed, Fatty acids can be released from TAGs via lipolysis to be metabolized in B-oxidation.
What lipoprotein transports endogenous triacylglycerols from the liver to other tissues (muscle, heart, adipose tissue)?
VLDL
What lipoprotein contain the following apoproteins:
B-100 to allow uptake into the liver
ApoCII activates lipoprotein lipase
apoE allows uptake into the liver
VLDL
What lipoprotein is formed in the liver and inhibited by insulin?
VLDL
In VLDL metabolism, what is hydrolyzed by LPL When Apo C and E are transferred from HDL?
Fatty acids from TAGS are hydrolyzed by LPL
What is VLDL transformed into when TAGs are removed?
It becomes a smaller IDL.
What pathways does heart disease medication target?
endogenous liver pathway
When there is increased [LDL] in the cell, what are the three responses a cell has to reduced cholesterol?
- Increased cholesterol storage
- decreased cholesterol synthesis
- decreased receptor synthesis
Cell surface receptor that recognizes apoB100 on LDL particles as well as apoE in chylomicrons and IDL
LDL receptor
Where are LDL receptors located?
found on all tissues, highest in liver
What is an example of LDL deficiencies in humans?
Familial Hypercholesterolemia
What condition includes a collection of disorders characterized by excessive cholesterol
-most common forms are loss of LDL receptor or ApoB
-accelerated rates of CVD
Familial Hypercholesterolemia
What would happen if there were low LDL receptors?
cholesterol stays in the circulation
What is synthesized in liver (and some in the SI)
has more apoproteins and less lipids (so has higher density)
Reverse cholesterol Transport
HDL
what transport process removes unesterified cholesterol from cells and other lipoproteins and return it to the liver
Reverse Cholesterol Transport
What protein picks up cholesterol in reverse cholesterol transport?
ATP-binding cassette protein 1
ABC1
what protein activates LCAT in reverse cholesterol transport?
apolipoprotein A-1
Apo A1
What sterifies the HDL in reverse cholesterol transport?
lecithin: cholesterol acyltransferase
LCAT
What organ in what metabolism?:
-synthesis of bile salts
-synthesis of lipoproteins from endogenous lipids
-synthesis of new lipds from non-lipid precursors
-catabolizes 70% of LDL from circulation
-catabolizes chylomicron remnants and repackages their lipids into HDL and VLDL
Liver in lipid metabolism
Which cholesterol is considered “bad”
LDL
Which cholesterol is considered “good”
HDL
What are similarities between LDL and HDL
the cholesterol is the same
they both carry proteins
What are the differences between LDL and HDL
the proteins they are holding?
What value is considered High for LDL
> 160 mg/dL
What value is considered High for total cholesterol?
at or above 240 mg/dL
What value is considered low for HDL
at or below 40 mg/dL
what value is considered high for HDL
at or above 60 mg/dL
When lipids are transported to the various tissues, what is their ultimate fate dependant on?
the energy needs of the body
How are energy needs determined for lipid transportation?
by the feeding state
are phospholipids hydrophobic or hydrophilic?
hydrophilic
What enzyme digests phospholipid?
Phospholipase A2
What enzyme digests cholesteryl ester?
cholesteryl ester hydrolase
are the three differences between short chain and long chain fatty acids?
- long chains go into chylomicrons to be shipped to liver. short chain binds to albumin and go into blood.
- short chain fatty acids does not have to use transport system to get into the mitochondria where as the long chain
What do chylomicrons carry?
dietary triglycerides
Where are chylomicrons made?
in the small intestine
What apoproteins do chylomicrons have?
B48- structural
CII - activates lipoprotein lipase
E- key to fit LDL- receptors
What is the function of chylomicrons?
deliver dietary triglycerides to non liver tissues
Where are VLDLs made?
liver
What apoproteins do VLDLs have?
CII
E
B100- structural, also key to a receptor
What do VLDL’s carry?
Triglycerides that our body has made
What is the function of HDL?
to deliver cholesteryl back to the liver (reverse cholesterol transport)W
What enzyme helps HDL pick up free cholesteryl?
ABC1
