Chapter 17 (Beta oxidation)
Beta oxidation – the 4-step cycle that breaks down fatty acids into acetyl-coA and electrons for
Triacyglycerol – glycerol backbone + 3 fatty acids
Adipocyte – fat storing cell containing a single large droplet of lipid, pushing the mitrochondria,
nucleus, and other organelles up against the edge of the cell
Fatty acid – contains 95% of total TAG energy
Glycerol – carbon backbone of the TAG, contains 5% of the total TAG energy
Adipose tissue – fat-storing tissue
Cellular location of beta oxidation
Beta oxidation occurs in the mitochondrial matrix.
Relationship between beta oxidation, citric acid cycle, and ETC
Beta oxidation breaks down fatty acids into acetyl-coA while simultaneously giving off electrons
The acetyl-coA molecules are oxidized in the CAC to yield ATP, NADH, and
The NADH and FADH2 join the NADH produced in beta oxidation in the ETC for
Properties of fats that make them good energy sources, and difficulties of digestion
related to these same properties
Fat intake (as percentage of energy intake) in most industrialized countries vs.
Role of fats in plants
Overview of fat ingestion, digestion, absorption
In the small intestine, bile salts emulsify fats into mixed micelles so that more surface area is
available to lipases.
These lipases degrade TAGs into glycerols and fatty acids, both of which
are taken up into intestinal cells and reconverted into TAGs.
These TAGs become a part of
chylomicrons (cholesterol + apolipoproteins).
Chylomicrons transport TAGs into the blood.
There, lipases are activated by the apoC-II lipoprotein in the chylomicrons, and they degrade
TAGs (once again) into glycerols and fatty acids.
Fatty acids then enter cells—either adipocytes
or myocytes—and are either oxidized as fuel or reesterfied for storage.
Glycerols are converted
into glycerol-3-phosphate, then dihydroxyacetone-phosphate, and finally glyceraldehyde-3-
phosphate by glycolysis.
Epinephrine/glucagon initiated reaction cascade resulting in fatty acid release
Epinephrine or glucagon binds to an extracellular receptor, a part of a GCPR.
The G protein is
activated and moves to the adenyl cyclase, which is activated and thus converts ATP into cAMP.
cAMP activates protein kinase, which in turn activates triacylglyercol lipase.
This initiates the
breakdown of stored TAGs in adipocytes.
The fatty acids that are released move into the blood
stream, carried by serum albumin, then enter myocytes for beta oxidation.
Carnitine-fatty acid transport into mitochondrial matrix (how, why)
The carnitine shuttle exists in order to separate fatty acids for different purposes.
mitochondrial intermembrane space, activated fatty acids are used for lipid biosynthesis.
mitochondrial matrix, activated fatty acids’ fates are sealed for beta oxidation.
begins with activated fatty acyl-coA being converted to fatty acyl-carnitine by carnitine