biochem lecture 8 pt 1 Flashcards
(197 cards)
1
Q
what is lipid catabolism
A
how lipids are used as an E source
2
Q
major functions of fatty acids
A
formation of cell membranes, role in energy metabolism
3
Q
major component of lipids
A
fatty acids
4
Q
what are fatty acids
A
long chains of hydrocarbons
5
Q
2 types of fatty acids
A
saturated and unsaturated
6
Q
saturated fatty acids
A
C-C bonds are all single bonds
7
Q
unsaturated fatty acids
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one or more double bond (C=C)
8
Q
what are fatty acids
A
hydrocarbon chains; made up excluisvely of Cs and Hs. C-C bonds form backbones, Hs bonded to Cs
9
Q
what does double bond present in unsaturated fat cause
A
causes it to bend or kink
10
Q
what can kinking affect
A
membrane fluidity
11
Q
most abundant dietary lipids
A
triglycerides
12
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where are triglycerides found
A
animal and plant foods
13
Q
what are triglycerides referred to
A
neutral fat/lipid (cuz its uncharged)
14
Q
why are triglycerides neutral fat
A
because they are uncharged
15
Q
what are triglycerides structure
A
glycerol backbone (3 C structure), 3 fatty acids attached to backbone via ester linkages
16
Q
what is an “essential” compound
A
something an organism cannot synthesize on its own; requires it from exogenous source
17
Q
2 essential fatty acids
A
linoleic and linolenic acid
18
Q
can we synthesize linoleic and linolenic acid on our own
A
nope; need them from outside sources
19
Q
where do we primarily get linoleic and linolenic acid
A
from vegetable sources
20
Q
what are adipocytes
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fatty acids/fats that deposit in certain parts of the body/ specific kinda cell
21
Q
what kinda tissue due adipocytes form
A
adipose tissue
22
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functions of adipose tissue
A
protective cushion around body organs, insulating function underneath skin, highly concentrated store of E
23
Q
roles of dietary fats
A
E metabolism, E source, cell membranes
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Q
another function of lipids
A
can be metabolites of lipids; bioactive compounds
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example of bioactive lipid
prostaglandin
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what are prostaglandins important in
regulation of blood pressure, activation of inflammatory responses, smooth muscle contraction
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another important lipid
cholesterol
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functions of cholsterol
regulates membrane fluidity, precursor of synthesis of molecules like bile salts, steroid hormones
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importance of liver in glucose metabolism
major storage site for glycogen. hormones that regulate catabolic and anabolic glycogen pathways are in liver. basically, liver is important for distribution & storage of carbs
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how is liver important for lipid metabolism
important for synthesis of lipoproteins, can synthesize clotting factors, and is where cholesterol biosynthesis occurs.
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what are lipoproteins
proteins w/ lipids, important for transport of cholesterol and fats
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what is precursor for cholesterol biosynthesis
acetyl CoA
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what is cholesterol a precursor of
synthesis of bile salts, steroid hormones like estrogen, progesterone, testosterone
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two main functions of lipids
membrane lipids, energy storage form
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diff types of membrane lipids
phospholipids, glycolipids, archaeobacterial ether lipids
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are membrane lipids polar or nonpolar
polar
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what are two categories of lipids
membrane and storage lipids
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what are phospholipids
major type of membrane lipids we find in cells
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what are what we generally call phospholipids
glycerol phospholipids
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describe structure of glycerol phospholipids
three carbon glycerol backbone; ester bonds attaching fatty acids at first 2 positions, and phosphate group on C3, on which is a polar head group (alcohol, etc.)
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what are sphingolipids
sphingosine backbone; found in membranes, covering of nerve tissue, myelin sheaths, etc.
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what lipids are we primarily focusing on
energy storage lipids --> triglycerides
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what else are triglycerides known as
storage lipids or neutral lipids
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describe structure of triglycerides
3 C glycerol backbone; fatty acids attached to all 3 positions on glycerol backbone via esterification
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why do we call triglycerides neutral lipids
because they have 3 fatty acids attached, not 2 fatty acids and polar head group
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what kinda molecules are phospholipids
amphipathic
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why are phospholipids amphipathic
cuz they have both polar and nonpolar parts (polar head group)
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what are neutral lipids
glycerol backbone w/ 3 fatty acids attached
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what is glycerol
a triol
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what is triol
3 carbon alcohol
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describe triglyceride structure
fatty acids linked to glycerol via ester bonds
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are glycerol and fatty acids metabolized in the same ways
nope; different ways
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how do we get triglycerides
we can synthesize them or ingest from diet
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what kinda bonds in triglycerides
ester bond
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what kinda bond is ester bond
covalent bond that joins fatty acids to glycerol backbone
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do glycerol and fatty acids have same or diff pathways
diff pathways
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what processes occur in cytosol
glycolysis, pentose phosphate pathway, fatty acid synthesis
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what happens in mitochondrial matrix
cTCA, ox phos, b-oxidation of fatty acids, ketone body formation
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what is an interplay of both cytosolic and mitochondrial compartments
gluconeogenesis, urea synthesis
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where does synthesis of fats occur
in cytosol
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what 3 ways do cells obtain fatty acid fules
diet, fats stored in cells as lipid droplets, fats synthesized in liver for export to other organs
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where are fats stored in lipid droplets
adipocytes/adipose tissue
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what kinda molecules are fats
hydrophobic nonpolar molecules
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what is needed for fats to be distributed/transported to tissues to undergo breakdown/catabolic processes
need to be transported into chylomicrons
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what are chylomicrons
allow for nonpolar fat molecules to travel thru otherwise polar aqueous environment (blood)
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how are most products of fat metabolism transported in lymph as
as chylomicrons
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what happens when chylomicrons are delivered to the specific tissue
undergo metabolic processing; hydrolytic enzymes will break them down
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what does process of hydrolyzing triglycerides entail
separating fatty acids from glycerol backbone
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where are hydrolytic enzymes found
some in blood, some intracellular
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what 2 pathways are in catabolism of fats
glycerol pathway, fatty acid pathway
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before we talk about pathways, what do we need to address
how dietary lipids are processed
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what happens when we ingest fats from our diet
lipids pass thru stomach, small intestine
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where are bile salts stored
gallbladder
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what happens to bile salts when we eat food w/ lots of fats
bile salts will be released from gallblader thru a duct system, into duodenum/upper portion of small intestine (bile salts, gallbladder--> small intestine)
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what process do bile salts carry out
emulsification
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what is emulsification
separation of triglycerides from each other
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does emulsification break covalent bonds
nope, just separate triglycerides
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what comes after bile salts do emulsification
intestinal lipases
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what are lipases
hydrolytic enzymes; cleaves or separates fatty acids from glycerol backbone
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what do intestinal lipases do
degrade the triglycerides
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what are we left with after intestinal lipases do their jobs
individual fatty acids and glycerol backbone
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what is next step after intestinal lipases
absorption of individual fatty acids and glycerol into intestinal mucosa
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what is important for absorption of individual fatty acids
lipoproteins; specific transport systems involving lipoproteins
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what happens once these individual fatty acids (derived from triglycerides) are absorbed into intestinal mucosal cells
reassembled into triglycerides
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what happens to triglycerides when procesed
degradation and then reassembly
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why is degradation and reassembly necessary
important for enabling fatty acids to be more efficiently absorbed into intestinal mucosa
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what happens to reassembled triglycerides
packaged into a structure called chylomicron
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what are chylomicrons made of
combo of triglycerides, cholesterol, apolipoproteins, other lipids
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what is the goal of chylomicrons
to transport fatty acids in form of triglycerides that are housed within chylomicron to the target organs (where they will be used as energy
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what happens to fatty acids at target organs
will be used as energy
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what is goal of chylomicron
to transport fatty acids (in triglyceride form) to target, where it can be used as energy
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what are chylomicrons
what we store lipids in as they are being transported throughout bloodstream in body
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what are 2 possibilities where we have fatty acid metabolism going on
muscle, adipocytes
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what happens in muscle
major site where b-oxidation of fats takes place
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what happens in adipocytes
adipose tissue is where we store triglycerides; can be processed and go thru beta-oxidation in muscles
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describe where fats are stored and used
we can store them in adipose tissue; if muscle requires E, some triglycerides can be processed, fatty acids oxidized thru b-oxidation in muscles
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then what do chylomicrons do
transport fatty acids to target tissues
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what happens to triglycerides once they reach target tissue
undergo further processing
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what is lipoprotein lipase
does the same thing as intestinal lipase
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what do lipoprotein lipase do to chylomicrons
break htme down to individual fatty acids
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what happens to individual fatty acids broken down by chylomicrons
absorbed into myocytes/adipocytes, where they can be oxidized/stored
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what happens to fatty acids in myocites
undergo oxidation
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what happens to fatty acids in adipocytes
stored in fat droplets
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describe chylomicron structure
phospholipid surface, polar head groups facing outward
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where do polar head groups face in chylomicrons
face outward
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what makes up chylomicrons
major composition is triglycerides
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what part of chylomicrons do triglycerides make up
80% of mass
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what other lipids in chylomicron
phospholipids, etc.
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where is phospholipids on chylomicron
form exterior layer
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what is present on surface of chylomicron
apolipoproteins
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function of apolipoproteins
trigger activation of some lipases
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example of apolipoproteins activating lipases
lipoprotein lipases being triggered one chylomicron reaches destination
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what are main functions of apolipoproteins
binding to specific cell surfaces, and activating lipases
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what happens to triglycerides once they've been reassembled in target tissues
if in muscle tissue (where we're gonna oxidize fatty acids and glycerol to generate ATP E), two separate pathways
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what does glycerol undergo
converted to GAP I(in short multi step pathway), GAP converted to acetyl CoA, acetyl CoA goes to krebs cycle
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what happens to the GAP
fed into glycolysis, converted into acetyl CoA
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what happens to acetyl CoA
into TCA cycle, carbons get completely oxidized
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what convergence do we see w/ glycerol
convergence of glycerol pathway thru formation of GAP in glycolysis pathway
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what pathway for fatty acids
beta-oxidization pathway
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what do we get after fatty acids go thru b-oxidation
two carbon acetate fragments (from fatty acids, long chain hydrocarbons)
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what happens to those 2 carbon acetate fragments
joined w/ coenzyme A to generate acetyl CoA
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what happens to acetyl CoA
enter TCA cycle, carbons undergo complete oxidation
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where does term B-oxidation come from
from the fact that we generate two carbon fragments; indicates where cleavage rxns are gonna cocur
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what can be genrated from oxidation of fats
substantial amount of reducing power
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what can we get from acetyl CoA
lot of PE, lot of NADH and FADH2
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why can we get a lot of NADH, FADH2
because each of those acetyl CoA units can enter TCA cycle and generate a lot of NADH, FADH2
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what happens when triglycerides get degraded
individual fatty acids have been separated from glycerol backbone
128
what happens to individual fatty acids
beta-oxidation pathway
129
what happens to glycerol
glycerol pathway
130
how many steps in glycerol pathway
3 steps
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what happens in glycerol pathway
glycerol is converted to glyceraldehyde-3-phosphate (GAP)
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what is first step of glycerol pathway
glycerol --> glycerol-3-phosphate
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what enzyme for step 1 of glycerol pathway
glycerol kinase
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what is second step of glycerol pathway
glycerol-3-phosphate --> dihydroxyacetone phosphate (DHAP)
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what enzyme for second step
glycerol-3-phosphate dehydrogenase
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what does glycerol-3-phosphate do
generates some reducing power
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what is DHAP
glycolysis intermediate; metabolically a dead end
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can DHAP undergo further processing
nope
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what do we need to do to DHAP
convert it to GAP
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what is step 3 of glycerol pathway
dihydroxyacetone phosphate (DHAP) --> glyceraldehyde-3-phosphate (GAP)
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what enzyme in step 3 of glycerol pathway
triose phosphate isomerase
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is there an energy investment? where
yes, step 1
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why does it not matter that we used ATP
cuz we will harvest E thru substrate level phosphorylation in glycolysis, and more from reducing power in TCA cycle
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what do lipases do
hydrolyze triglycerides; get fatty acids and glycerol
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what happens to fatty acids
form acetyl CoA (thru beta oxidation), go into TCA
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what happens to glycerol
glycerol pathway
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sum yp glycerol pathway
glycerol is phosphorylated to glycerol-3-phosphate. glycerol-3-phosphate is oxidized to DHAP. DHAP is isomerized to GAP
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what happens to GAP
enters glycolysis
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what is end product of glycerol pathway and what happens to it
glyceraldehyde-3-phosphate; goes into glycolysis
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what happens to GAP after glcyolysis
converted to pyruvic acid
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what happens to pyruvic acid at end of glycolysis
converted to acetyl CoA
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where does acetyl CoA go
TCA
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what is end product of beta oxidation of fatty acids
acetyl CoA
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what happens to acetyl CoA
goes into TCA cycle
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what is generated in steps where fatty acids converted to acetyl CoA
little bit of reducing power
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another word for beta oxidation of fatty acids
fatty acid breakdown (catabolism)
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what 3 steps are required for fatty acid breakdown
mobilization, activation & transport, breakdown or beta oxidation
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what is first overall step in beta oxidation
mobilization. triglycerols degraded into fatty acids and glycerol, subsequently released from adipose tissue into E-requiring tissues.
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what is mobilization step
lipases degrade triglycerides into 2 main components: glycerol backbone, fatty acids. if in adipocytes, glycerol & fatty acids are gonna be released and transferred to tissues that need E (like muscle and liver)
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what happens after mobilization step, after fatty acids are absorbed into tissues that require E
need to undergo an activation step, and transportation into mitochondria
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what happens once fatty acids are in mitochondrial matrix
undergo step 3, beta oxidation
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where does beta oxidation occur
mitochondrial matrix
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what is beta oxidation
breakdown of fatty acids
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what regulates mobilization of triglycerides
insulin and glucagon
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where else were insulin and glucagon
carbon metabolism
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what are both epinephrine and glucagon
GPCRs
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what do epinephrine and glucagon do
activate adenylyl cyclase
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what does adenylyl cyclase do
converts ATP to cAMP
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what does cAMP do
activates PKA
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what does PKA activate
triacylglycerol lipase
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what does triacylgycerol lipase do
responsible for hydrolysis/release of fatty acids from glycerol backbone of triglycerides
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what happens once fatty acids released from glycerol backbone
gonna be exported from adipocyte to tissues who need E
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what do we have in adipocytes
lipid droplets or concentrations of tryglycerides
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what do triglyceride metabolism and glycogen breakdown/synthesis have in common
same hormones
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what happens in low blood glucose conditions
we will release of glucagon
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what does glucagon do
activates pathway in previous slide (cAMP --> PKA)
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what does PKA do
activates hormone sensitive lipase
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what does PKA do in adipocytes
phosphorylates a protein called perilipin
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where is perilipin
situated on the surface of lipid droplets
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basically what happens when glucagon activates PKA
2 things: PKA phosphorylates and activates hormone sensitive lipase, and will phosphorylate perilipin protein on surface of lipid droplet
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what does phosphorylating perilipin do
increases accessibility of those triglycerides to hormone sensitive lipase; makes triglycerides more accessible to hormone sensitive lipase
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what does hormone sensitive lipase do
hydrolysis of ester bonds that release fatty acids from glycerol backbone
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what happens after lipases breakdown tryglicerides
we get transport of fatty acids in bloodstream
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how are fatty acids being transported thru blood
serum proteins that can bind to fatty acids; specific lipid binding proteins that can cover and transport hydrophobic lipids
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why doesn't this transport involve chylomicrons
cuz chylomicrons are in processing of dietary lipids, not mobilization
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what do serum proteins do
glom onto fatty acids, transport them
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where are fatty acids going
to myocyte; to be fully utilized by b-oxidation
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example of serum protein
albumin
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what do serum proteins do
bind to fatty acids, important for their transport thru bloodstream
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basically sum up mobilizatoin
mobilize triglycerides from fat stores in adipose tissue, transport fatty acids where they can be taken up into myocytes into muscle cells for beta oxidation
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what do hormone sensitive lipases do
cleave these ester linkages
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what are gonna be products of hormone sensitive lipases
individual fatty acids, glycerol backbone
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why are they called hormone sensitive lipases
because pathways are activated by these hormones
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what effect do insulin and glucagon have on these lipases
opposing effects
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what does insulin do to hormone sensitive lipase
inactivates lipase
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what does glucagon do to hormone sensitive lipase
activates it
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sum up overall effects of these lipases in presence of hormones
inhibitory in presence of insulin, stimulatory in presence of glucagon
