Ch 11: Lipid and Amino Acid Metabolism Flashcards
MECHANICAL digestion of lipids occurs
primarily in the stomach
CHEMICAL digestion of lipids occurs _____
and is facilitated by _______
small intestine
bile, pancreatic lipase, colipase, and cholesterol esterase
Micelles are formed by
digested lipids for absorption or to be absorbed directly by body
Short-chain fatty acids are
absorbed as micelles and assembled into chylomicrons for release into the lymphatic system
Long-chain fatty acids are
absorbed as miscelles and assembled into chylomicrons for release into the lymphatic system
Hormone-sensitive lipase
lipids are mobilized from adipocytes by this
Lipoprotein lipase
lipids are mobilized from lipoproteins by this
Chylomicrons (lipid transport)
transport mechanism for dietary triacylglycerol molecules and are transported via the lymphatic system
VLDL (lipid transport)
transports newly synthesized triacylglycerol molecules from the liver to peripheral tissues in the bloodstream
IDL (lipid transport)
VLDL remnant in transition between triacylglycerol and cholesterol transport; it picks up cholesterol for use by tissues
LDL (lipid transport)
primarily transports cholesterol for use by tissues
HDL (lipid transport)
involved in the reverse transport of cholesterol
Apoproteins (lipid transport)
control interactions between lipoproteins
Cholesterol may be obtained through
dietary sources or through de nova synthesis of the liver
De nova synthesis
synthesis of complex molecules from simple molecules such as sugar or amino acids
key enzyme in cholesterol biosynthesis is
HMG-CoA reductase
LCAT catalyzes the formation of
cholesteryl esters for transport with HDL
CETP catalyzes the transition of
IDL to LDL by transferring cholesterol esters from HDL
Fatty acids are
carboxylic acids, typically with a single long chain, although they can be branched
Saturated fatty acids have
no double bond character between carbons
Unsaturated fatty acids have
one or more double bonds
Fatty acids are synthesized in the
cytoplasm from acetyl-CoA transported out of the mitochondria
Fatty acid from acetyl-CoA Synthesis includes 5 steps _____
that are repeated 8x to form palmitic acid, the only fatty acid that humans can synthesize
activation bond formation reduction dehydration second reduction
Fatty acid oxidation occurs in the ______ following transport by the _______
mitochondria
carnitine shuttle
Uses cycles of oxidation, hydration, oxidation, and cleavage
B-oxidation
branched and unsaturated fatty acids require
special enzymes
unsaturated fatty acids use ____ and an additional _____ during cleavage
isomerase
reductase
Ketone bodies form (ketogenesis) during
a prolonged starvation state due to excess acetyl-CoA in the liver
Ketolysis regenerates
acetyl-CoA for use as an energy source in peripheral tissues
during prolonged starvation, the brain can derive up to 2/3 of it’s energy from
ketone bodies
protein digestion occurs primarily in the
small intestine
Catabolism of cellular proteins occurs only under
conditions of starvation
Carbon skeletons of amino acids are used for
energy, either through gluconeogenesis or ketone body formation
Amino groups are fed into the ____ for excretion. The fate of the side chain depends on its chemistry
urea cycle
