Chapter 29 Flashcards
what are triacylglycerols?
storage form of fatty acids
reservoir of potential energy
primary fuel storage in humans
what are membrane lipids?
phospholipids and sphingolipids
inner converting membrane compartments
What is Cholesterol?
membrane component and precursor to steroid hormones
increases/controls membrane fluidity
what is the central portion of triacylglycerol metabolism?
liver
what happens to triacyclglycerols after they become free fatty acids?
they are released into the bloodstream and head to the liver
what are the two fates of triacylglycerol?
glycerol
free fatty acids
How is Triacylglycerol synthesized?
Triacylglycerol synthase is bound to the endoplasmic reticulum, synthesizes triacylglycerol from phosphatide and acyl CoA
how are cholesterol and triacylglycerols transported into the blood?
in the form of lipoprotein particles
what do lipoprotein particles consist of?
they consist of a protein(s) component and various lipids, depending on the type of particle
what do the protein(s) of lipoprotein particles do?
they serve to solubilize the lipids and to direct the particles to specific targets
how are lipoprotein particles classified?
according to density
the greater the proportion of lipid, the less dense the particle
what is Low-density lipoprotein (LDL)?
the major carrier of cholesterol in the blood
bad cholesterol
distributes through body
causes plaque build up
what is high-density lipoprotein (HDL)?
carries cholesterol released into the blood back to the liver (reverse cholesterol transport)
good cholesterol
scavenge cholesterol from body for liver
what do Apo-lipoproteins do?
target the lipoprotein particles to different organs
what cells have LDL/HDL receptors?
receptor-mediated endocytosis cells
why is the liver so important to lipid synthesis?
it is the central portion of the triacylglycerol metabolism
it is the center part for leaving and receiving of cholesterol
major site of cholesterol biosynthesis
what is the process of cholesterol formation from receptor-mediated endocytosis?
LDL binds to LDL receptor on a cell
it is internalized
Lysosomal Hydrolysis separates amino acids and cholesteryl oleate
cholesterol is formed
why is cholesterol vital to the body?
it maintains proper fluidity of animal cell membranes and is the precursor of steroid hormones such as progesterone, testosterone, estradiol, and cortisol
how is cholesterol synthesis regulated?
by controlling the amount and activity of HMG CoA reductase
what is HMG CoA reductase?
the enzyme that catalyzes the synthesis of mevalonate
regulated allosterically
what is the committed step of cholesterol synthesis?
Actyl CoA + acetoacetyl CoA
when is HMG CoA reductase active?
during dephosphorylation
how is HMG CoA Reductase regulated?
Gene expression - rate of mRNA synthesis
Rate of translation of the mRNA
degradation of the HMG CoA Reductase protein (control destruction of HMG)
Phosphorylation of HMG CoA Reductase decreases activity (controls phosphorylation of HMG)
what can cholesterol become?
Glucocorticoids
Mineralocorticoids
Androgens → Estrogens
how is vitamin D derived from cholesterol?
cholesterol is catalyzed by the energy of sunlight
why is vitamin D important?
it plays a key role in the regulation of calcium and phosphate metabolism
what is the active form of vitamin D?
calcitriol
how is calcitriol formed?
from cholesterol in a pathway that involves ultraviolet light-induced cleavage of one of the rings of the steroid nucleus
what is rickets?
deficiency of vitamin D that results in inadequate calcification of cartilage and bone
what can vitamin D deficiency cause?
rickets
osteomalacia
what is osteomalacia?
a condition characterized by soft weak bones
