Lipids - Exam 1 Flashcards
what are the building blocks of lipids
fatty acids
what is a lipid, where is it found, what does it do
hydrophobic organic molecule; membranes or bound to plasma proteins; major source of energy for the body and help with compartmentalization, vitamins
definition of hydrophobic
water insoluble
examples of common lipids
fatty acids, triacylglycerol, phospholipid, steroid, glycolipid, prostaglandins, steroid hormones
definition of amphipathic
hydrophilic (polar) head, hydrophobic tails
where does lipid digestion start via what enzyme
in the stomach via lipases
what is emulsification and where does it occur
makes fats more soluble so lipases can work by breaking down into smaller particles ; duodenum
what emulsifies fat droplets and where are they found
bile acids ; synthesized in liver and stored in gall bladder
how does lipid digestion occur
CCK is synthesized when lipids and proteins (food) enters the duodenum, it stimulates bile acid and pancreas enzyme secretion, which then stimulates bicarbonate from the pancreas
significance of bicarbonate and where it’s found
helps neutralize stomach pH; lumen of the SI
mixed micelles are formed post digestion by
FFA + cholesterol + MAG + lipid soluble vitamins + bile acids
what do mixed micelles do
approach brush border of enterocytes and are absorbed into the jejunum
what happens to bile acids post digestion
reabsorbed into the ileum (SI) and recycled multiple times
only long chain FA form micelles because
small and medium chain so small they just diffuse right into the plasma membrane
what is re-esterification and where does it occur
synthesis of more complex lipids (long chain fatty acids); endoplasmic reticulum
chylomicron composition ; where is it found
phospholipids, TAG, fatty acids ; inside enterocyte or blood plasma
what happens to short and medium chain fatty acids
directly released into portal circulation where they bind to albumin
what happens to chylomicrons
released by exocytosis into the lymphatic vessels -> veins -> blood
what is unique about chylomicrons
it is so large it can’t go straight into blood so the route it takes bypasses the liver
main function of chylomicron
send lipids to the rest of the body without involving the liver
types of plasma lipoproteins
chylomicron, LDL, VLDL, HDL
composition of plasma lipoproteins
triacylglycerol, proteins, phospholipids, cholesterol
what is the “good” cholesterol
HDL - 40% protein
what is the “bad” cholesterol
LDL - 50% cholesterol
lipoprotein lipase function
strip TAG of FFA & glycerol at the capillaries.
after stripped, FFA will
go into muscle cells or adipocytes or stay in the blood binding to plasma proteins
after stripped, glycerol will
go to the liver to synthesize glycerol 3 phosphate (gluconeogenesis)
chylomicron remnants will
be absorbed by the liver
relevance of fatty acids
during a fast, bound to albumin in plasma on the way to tissues -> oxidation to create energy
structural components of fatty acids
phospholipids & glycolipids in the plasma membrane
lipid hormone precursor
prostaglandins
lipid energy reserve
TAG in adipose tissue
saturated fatty acid structure
no double bonds
unsaturated fatty acid structure
double bonds (kinks), cis
alpha C
carboxyl group
beta C
3
gamma C
4
omega C
terminal methyl group
essential fatty acids can’t
be synthesized in the body so we must ingest them
example of essential fatty acid and where it’s found
arachidonic acid ; plasma membrane ; alpha linoleic acid
de novo synthesis of fatty acids occurs
cytosol of liver, mammary gland, adipose tissue cells
substrates of de novo synthesis
carbs & proteins from diet that were consumed in excess
1st step of de novo synthesis
Acetyl CoA from mitochondrial matrix broken down to citrate into the cytosol
2nd step of de novo synthesis (rate limiting)
ACoA -> malonyl CoA via ACC
all other fatty acid synthesis uses what enzyme
FAS (fatty acid synthase, or ACP)
when FAS/ACP is used what is generated
palmitate (fully saturated fatty acid)
newly synthesized fatty acids are stored
as 1, 2, or 3 molecules in lipid droplets in adipocytes
small portion stored in liver and released into blood as VLDL
mobilization of fat requires
release from TAG via enzyme stimulated by glucagon or epinephrine
Beta oxidation of fatty acids occurs
in the mitochondria
beta oxidation of fatty acids entails
the removal of 2 C and a transport carrier to get the long chain fatty acylcoa from the cytosol into the mitochondria; can do several times
beta oxidation net gain
1 palmitoyl -> 8 ACoA, 7 NADH, 7 FADH2 -> 129 ATP
how are ketone bodies made
converted from ACoA from fatty acid oxidation by liver (mitochondria)
examples of ketone bodies
acetoacetate, acetone, etc.
ketongenesis occurs when
there’s a fast and fatty acids come from adipose tissue to the liver and it produces a lot of NADH which shifts OAA to malate
why do diabetic patients have a lot of ketone bodies
because they’re hypoglycemic so not using glucose to use energy so will mobilize fat to make energy and ketone bodies form because of that
ketone bodies in peripheral tissues
converted to ACoA -> TCA cycle (used for energy)
when is a liposom made
if not building a lipid bilayer chain
phospholipid synthesis pathway
2 precursors + enzyme -> phosphatidic acid -> diacylglycerol -> phosphatidyl_______
all cells can make phospholipids except
RBC
synthesis of phospholipids occurs
in the sER -> Golgi -> membranous organelles
donation of phosphatidic acid makes
1 option
donation of DAG makes
2 options
glycerophospholipids composed of
phosphatidic acid + alcohol
cardiolipin
inner mitochondrial membrane; maintenance of ETC
PAF
platelet activating factor; activates inflammatory cells, hypersensitivity, anaphylactic rxn
sphingomyelin
myelin in nerve fibers
IP3 & DAG intracellular signaling
1st messenger: hormone, 2nd messenger: IP3 (released into cytosol) & DAG (stay in membrane)
G protein coupled receptors activate enzymes, IP3 can send and retrieve Ca2+
glycosphingolipids
ABO blood group antigens, only difference is one phospholipid off the sugar molecule
prostaglandins
20C, made by arachidonic acid, aspirin blocks it; vasoconstriction, uterine contractions (induce labor)
thromboxanes
20C, made by arachidonic acid, aspirin blocks it; vasoconstriction, platelet aggregation, Ca, smooth muscle contraction
cis =
same side
trans =
opposite side
carnitine translocase
facilitates transport of fatty acid from cytosol -> mitochondrial matrix
how do NSAIDS work
block synthesis of inflammatory mediators
