Lipids Flashcards
When the liver has enough ATP, what does it do with the build-up of acetyl CoA?
it forms polymers of acetyl-CoA (fatty acids)
Are ketone bodies produced in a fed state or in a fasting state?
fasting
Name two key functions of thromboxanes.
coagulation, vasoconstriction
Bile acids (cholic acid and chenodeoxycholic acid) are synthesized in the liver from?
cholesterol
How many carbons are in linoleic acid? How many double bonds?
18:2
T/F: VLDL delivers hepatic triglycerides to peripheral tissues.
T
Where in the cell does beta-oxidation occur?
mitochondrial matrix
What is the biological significance of cardiolipin?
It serves as an insulator and stabilizes the activity of protein complexes important to the electron transport chain
Which enzyme converts arachidonic acid to leukotrienes?
lipoxygenase
What type of bond is formed between each fatty acid and the glycerol molecule in a triglyceride?
ester bonds
Where does the first double bond in linolenic acid occur?
third carbon from the methyl terminus
Type IIa hypercholesterolemia has increased levels of ___
LDL
Generally, when fatty acids are oxidized inside the mitochondria, how many carbons are removed per reaction?
two carbons
Lipoprotein functions: Which cells secrete chylomicrons?
intestinal epithelial cells
ApoE is located on all lipoproteins except ___.
LDL
Before leaving the liver, bile acids are conjugated in amide linkage to ___.
glycine (glycocholic acid) or taurine (taurochenodeoxycholic acid)
In fatty acid synthesis, which Kreb intermediate is translocated form the mitochondria to the cytosol to produce acetyl-CoA?
citrate
citrate is cleaved by citrate lyase to produce cytosolic acetyl-CoA and OAA
Does secretin get activated by low or high pH of intestinal contents?
low pH (chyme entering the intestine is acidic)
How many double bonds are in palmitic acid?
16:0
25-hydroxycholecalciferol is transported to the ___ of the kidneys where it can be hydroxylated by one of two enzymes to different forms of vitamin D.
proximal tubules
Where is lipoprotein lipase synthesized? What would a deficiency cause?
adipocytes and muscle cells
familial lipoprotein lipase deficiency (type I hyperlipoproteinemia) results in extremely high chylomicronemia
Name three cofactors required for the hydroxylation of vitamin D by 25-hydroxylase.
NADPH, O2, MG2+
Which shunt is the major supplier of NADPH for fatty acid synthesis?
hexose monophosphate shunt (pentose phosphate pathway)
Does insulin phosphorylate or dephosphorylate hormone sensitive lipase?
hormone sensitive lipase is dephosphorylated and becomes inactive
Is arachidonic acid a saturated or unsaturated fatty acid?
unsaturated (20:4)
Are triglycerides readily absorbed in the duodenum?
no
Does insulin activate or deactivate HMG-CoA reductase?
activate
List the six steps of cholesterol synthesis starting from acetyl-CoA.
acetyl-CoA to mevalonic acid to isoprene to squalene to lanosterol to cholesterol
HDL is screted from which two places?
liver, intestine
Where in the cell does steroid synthesis occur?
cytoplasm
apoA-1 and apoA-II are proteins located on?
HDL
Is stearic acid an unsaturated or saturated fatty acid?
saturated (found in many foods including red meat and peanuts)
Fatty acids are synthesized in the ___ of the cell.
cytosol
HDL - What is the major molecule it transports?
reverse cholesterol transport (from tissues to liver)
Fatty acid synthesis occurs in the ___ and beta oxidation occurs in the ___.
cytoplasm
mitochondria
Fatty acid entry into cytosol is via the ___.
citrate shuttle
What is the pathophysiology of type IIa hypercholesterolemia?
decreased number of LDL receptors
Name the five main functions of prostaglandins.
inflammation, pain, fever, tissue repair, clotting
What is the role of PIP2?
hormonal signal transmission via activated phospholipase C formation of inositol-3-P (IP3) and diacylglycerol (DAG), followed by mobilization of Ca2+ and activation of protein kinase C
What are two situations where ketone bodies are found in urine?
prolonged starvation, diabetic ketoacidosis
T/F: short and medium chain length FAs require micelles for absorption by the intestinal mucosa
F
Type III dysbetalipoproteinemia has altered apolipoprotein ___, and increased ___ and ___.
E, IDL, VLDL
Corticosteroids (cortisol) inhibit which enzyme involved in prostaglandin synthesis?
phospholipase A2
Do trans fats ever occur naturally in nature, or are they always synthesized?
trans fats do occur naturally
Cholesterol synthesis: 2/3 of plasma cholesterol is esterified by ___.
lecithin-cholesterol acyltransferase (LCAT)
What is the main function of apolipoprotein E?
mediates remnant (extra) uptake
Thromboxane A2 is made from ___ and thromboxane A3 is made from ___.
TXA2 from arachidonic acid (AA) and TXA3 from eicosapentaenoic acid (EPA).
What is the main function of apolipoprotein B-48?
mediates chylomicron secretion
Name the five steps of fatty acid synthesis.
carboxylation, condensation, reduction, dehydration, reduction
Lipoprotein lipase is involved in the storage of triacylglycerol. Name the enzyme that initiates mobilization of stored fat and removes a fatty acid from carbon 1 or 3 of the triacylglycerol.
hormone sensitive lipase
Chylomicrons are released by exocytosis from intestinal mucosa and enter the blood via which vein located near the heart?
left subclavian vein
Apolipoprotein B-100 binds to ___ receptors.
LDL
HMG-CoA reductase catalyzes the rate-limiting step in cholesterol synthesis and inhibits the formation of?
mevalonic acid from HMG-CoA
Type IIb combined hyperlipidemia has increased levels of ___ and ___.
LDL, VLDL
Cholecalciferol is formed in the skin when UV light acts upon ___.
7-dehydrocholesterol
LDL is taken up by target cells via what process?
receptor-mediated endocytosis
Does EPI turn on or off the cAMP cascade leading to triacylglycerol degradation?
turned on (FA synthesis turned off)
VLDL - What is the major molecule it transports?
delivers hepatic TG to tissues
Which enzyme releases free fatty acids from triglycerides?
lipase
LDL delivers hepatic cholesterol to ___.
peripheral tissues
Type IV hypertriglyceridemia is caused by hepatic overproduction of ___.
VLDL
Name the three products of the beta-oxidation of a fatty acid.
FADH2, NADH, acetyl-CoA
What two factors influence the melting temperature of a fatty acid?
increasing chain length increasing melting temp
addition of double bounds decreases the melting temp
What is the predominant fatty acid in olive oil? How many double bonds are in this fatty acid?
oleic acid
18:1 (omega-9)
If removal of the chylomicron remnant is defective, what condition results? Which apo protein is defective?
familial type II hyperlipoproteinemia (aka dysbealipoproteinemia)
apoE
Which enzyme converts arachidonic acid into prostaglandins?
cyclooxygenase
The simplest glycerophospholipid is ___.
phosphatidic acid
Which lipoproteins contain apoC-II?
chylomicrons, VLDL, HDL
What is the rate-limiting step of cholesterol synthesis?
HMG-CoA reductase
The side chains of bile salts contain which two amino acids?
glycine, taurine
Fatty acids are degraded in the ___ of the cell.
mitochondria
Which organ makes ketone bodies but cannot use them?
liver
T/F: type V mixed hypertriglyceridemia has only increased VLDL.
F
increased VLDL and chylomicrons
In fatty acid synthesis, acetyl-CoA via carboxylation forms ___.
malonyl-CoA
Apolipoprotein C-II is a cofactor for which enzyme?
lipoprotein lipase
How does a drug that lowers bile acids lower cholesterol?
when bile is removed, replacement bile must be synthesized from cholesterol, which lowers cholesterol
Which phospholipid does not have a glycerol backbone and is abundant in neurons?
sphingomyelin
HDL mediates transport of cholesterol from where to where?
periphery to liver (reverse cholesterol transport)
Chylomicrons deliver dietary ___ to ___ and dietary ___ to ___.
triglycerides to peripheral tissues
cholesterol to liver
Is the tail of a phospholipid hydrophilic or hydrophobic?
hydrophobic
Cholecalciferol is hydroxylated in the liver to ___ by the enzyme ___.
25-hydroxycholecalciferol
25-hydroxylase
Vitamin D is hydroxylated first in the ___ and then in the ___.
liver
kidney
Fatty acid entry into mitochondria is via ___, which is inhibited by ___.
carnitine shuttle
cytoplasmic malonyl-CoA
Of the 15-30g of bile salts secreted per day, ___ grams are lost in feces.
0.5
Is the head of a phospholipid hydrophobic or hydrophilic?
hydrophilic
Arrange the following in order of size (largest to smallest): LDL, IDL, HDL, VLDL, Chylomicron
Chylomicron, VLDL, IDL, LDL, HDL
Apolipoprotein A-I activates ___.
activates LCAT
In which part of the small intestine does the process of emulsification of dietary lipids begin?
duodenum
LDL - What is the major molecule it transports?
delivers hepatic cholesterol to tissues
Would high levels of malonyl-CoA increase or decrease the levels of acylcarnitine transferase I?
decrease
malonyl-CoA inhibits acylcarnitine transferase I
Name the enzyme found in the mucosa of the jejunum and lower duodenum that causes gallbladder contractions in response to dietary lipids?
CCK - cholecystokinin
Is oleic acid a mono- or polyunsaturated fatty acid?
mono
Describe the composition of a triglyceride.
triglycerides are formed from a single molecule of glycerol, combined with three fatty acids on each of the OH groups
Define the term amphipathic.
contains both hydrophobic and hydrophilic regions (ex: phospholipid)
The enzyme 1-alpha-hydroxylase is activated by ___ to form the main biologically active vitamin D.
PTH
Congenital abetalipoproteinemia occurs when triacylglycerols accumulate in the intestinal mucosa. Name the apo protein that is deficient.
Apo B-48
Fatty acids are made by a multienzyme complex called ___.
fatty acid synthase
In fatty acid synthesis, what is the enzyme that catalyzes the reaction of acetyl-CoA to malonyl-CoA?
acetyl-CoA carboxylase (biotin enzyme)
Where is VLDL secreted from?
liver
How many carbons are linolenic acid? How many double bonds?
18:3
Excess lipids in the feces is termed ___.
steatorrhea
What is the active carrier of choline?
CDP-choline
Where does the digestion of lipids begin?
stomach
Ketone bodies are metabolized by the brain to two molecules of ___.
acetyl-CoA
Where is the cell acetyl-CoA generated?
cytosol
The hormonally active form of vitamin D is also known as ___.
calcitriol
Chylomicron - where is it secreted and what two main dietary substances does it transport?
delivers dietary TG to peripheral tissue and dietary cholesterol to liver
secreted by intestinal epithelium
Name the four major families of eicosanoids.
leukotrienes (LTA), thromboxanes (TXA), prostacyclins (PGI), prostaglandins (PGE)
