BIOSYNTHESIS OF LIPIDS Flashcards
___________ are nonpolar or weakly polar molecules that are very soluble in organic solvents like hexane (C6H14) and carbon tetrachloride (CCl4), and insoluble in a polar medium like water.
lipids
___________ are the major fuel store in the body.
Triacylglycerols
___________ is a rare genetic disease that causes weakness or numbness of the hands and feet (peripheral neuropathy). Due to a genetic abnormality, people with ARD disease lack the enzyme in peroxisomes that break down phytanic acid, a type of fat found in certain foods.
Refsum disease
____________ IS THE MAJOR PRECURSOR FOR FATTY ACID SYNTHESIS
GLUCOSE
provides the carbon for fatty acid synthesis (via acetyl
CoA) as well as the reducing equivalents (NADPH) required for this process.
Glucose
______________ is defined as the synthesis of fatty acids from nonlipid precursors. It is the conversion of fatty acids and glycerol into fats, or a metabolic process through which acetyl-CoA is converted to triglyceride for storage in fat.
Lipogenesis
The saturated ________, is synthesized first, and all other fatty acids are made by its modification.
C16 acid, palmitic acid
Synthesis of fatty acids from acetyl CoA requires the activated intermediate, ___________, which is made by carboxylation of acetyl
CoA by acetyl-CoA carboxylase.
malonyl CoA
______________ catalyzes the rate-limiting step in fatty acid synthesis.
dAcetyl-CoA carboxylase
dAcetyl-CoA carboxylase exists in an inactive, protomeric state and, when activated, as linear polymers. The enzyme is activated by ____________.
citrate or isocitrate.
_________ is a protein constituent of the
multienzyme complex.
It transports the growing fatty acid chain between enzyme domains of fatty acid synthase (FAS) during biosynthesis.
acyl carrier protein (ACP)
The acyl product is b-ketoacyl-ACP. This intermediate is reduced to B-hydroxyacyl-ACP using ___________ as electron donor.
It is the reduced form of NADP+; used in anabolic reactions, such as lipid and nucleic acid synthesis, which require NADPH as a reducing agent.
nicotinamide adenine dinucleotide phosphate (NADPH)
The growing fatty acid proceeds through six more reaction cycles to produce palmitoyl-ACP, which then is
acted on by a thioesterase to produce ____________.
free palmitic acid
The ________________ and __________ are both free, so that another cycle of fatty acid
synthesis can begin.
a. sulfhydryl groups of ACP
b. synthase
The released product is
converted to ___________, preparing it for modification or incorporation into complex lipids.
palmitoyl CoA
The principal products are
______________ and ____________, which are absorbed by the epithelial cells that line the small intestine.
a. 2-monoacylglycerols
b. free fatty acids
____________ is a triacylglycerol-rich plasma lipoprotein.
Also known as ultra low-density lipoproteins, are lipoprotein particles that consist of triglycerides, phospholipids, cholesterol, and proteins. They transport dietary lipids from the intestines to other locations in the body.
chylomicrons
Fatty acids are synthesized in this tissue from excess carbohydrate and amino
acids.
liver
__________________ cholesterol is produced in the liver and released into the bloodstream to supply body tissues with a type of fat (triglycerides).
A second triacylglycerol rich lipoprotein.
very low density lipoprotein (VLDL)
The triacylglycerols in chylomicrons and VLDL are hydrolyzed by ____________________, located on the surface of capillary endothelial cells in tissues such as adipose tissue and skeletal muscle.
lipoprotein lipase
The apoprotein ________, which is found in chylomicrons and VLDL, activates the process by binding the lipoproteins to the enzyme.
ApoC-Il
The products of lipoprotein lipase action are ____________ and ________.
a. free fatty acids
b. glycerol
The triacylglycerols stored in adipose tissue are mobilized for use as fuel in the fasted state. This process is initiated by ______________, which is located within adipocytes.
hormone-sensitive lipase
This enzyme is activated when it is phosphorylated
by _______________________.
Conversely, ________ inhibits the activity of this
enzyme by inducing its dephosphorylation
a. cAMP-dependent protein kinase A
b. insulin
___________ is a lipid droplet coating protein known to regulate lipid metabolism in adipocytes by serving as a physical barrier as well as a recruitment site for lipases to the lipid droplet.
Perilipin
__________ is an enzyme that synthesizes glycerol 3-phosphate from glycerol and ATP.
glycerol kinase
During prolonged fasting, when much of the body’s energy is derived from stored fat, the __________ produced by the hydrolysis of triacylglycerol in adipose
tissue is an important substrate for gluconeogenesis in the liver.
glycerol
