Fatty acid metabolism Flashcards
what are the sources of lipids and fatty acids
diet
adipose storage
synthesis in tissue
what are the fates of lipids and fatty acids
energy substrates
precursors (acrachodinate acid)
structural elements(phospholipids)
signaling molecules(
what are bile salts and what do they do
emulsify dietary fats(lipids) in the small intestine and form mixed micelles
what do lipases do
degrade triaclyglycerols in to fatty acid
what do fatty acids get put back together in?
chylomicrons
what is a chylomicron?
it is an apolipoprotein that travels through the lymphatic system and blood stream to tissues that need them
carry triglycerides and fatty acids
made in enterocyte ER
what are apolipoproteins
lipid binding proteins
combine with lipids to form lipoproteins
diverse functions
what are the two ways that fatty acids are transported?
carried by serum albumin(free fatty acids)
and in lipoproteins (chylomicron)
what are the four types of lipoproteins
chylomicrons
very low density lipoprotein (VLDL)
low density lipoprotein (LDL)
high density lipoprotein (HDL)
where are the VLDLs produces?
liver
VLDL takes the fatty acid and cholesterol to the blood stream to target tissues. What are they called once they deliver the fatty acids or cholesterol?
LDL and go back to liver
also can deliver cholesterol to Macs
What is the exogenous pathway?
fats from our diet are packaged into chylomicrons and is sent to the liver for processing into VLDL
what is the endogenous pathway?
fats from the liver are put into VLDL and sent to target tissues (muscle, adipose, adrenal gland, gonads)
what do high density lipoproteins do?
take the excess cholesterol from the macs and the body back to the liver
what is the receptor on the LDL particle necessary for endocytosis?
apoB-100
When an LDL is internalized and broken down what can it be made into?
AAs, FAs and cholesterol
What is the triacylglycerol cycle?
under conditions of starvation or intense exercise fatty acids from adipose tissue and released into blood.
75% of released FAs are cycled back liver where they are make into triglycerides and transported via lipoproteins t target tissues
fatty acid mobilization process
glucagon released from pancreas stimulates Gprotein receptor to activate adenylyl cylcase
- this activates PKA(protein kinase A)
- this phosphorylates perilipin
- this causes it to dissociate and release CGI
- CGI activates Adipose tryglyceride lipase (ATGL)
- ATGL breaks down lipids into monoacylglycerol and diacylglycerol
- PKA also phosphorylates hormone sensitive lipase
- HSP breaks down the diacylglycerol into monoacylglycerols
- Monoglyceride lipase removes the glycerol so the fatty acids can be released
how are triglycerides broken down?
via lipases
broken down into glycerol and fatty acids
fatty acids form fatty acyl CoAs
glycerol is made into glyceraldehyde 3-phosphate
how do the fatty acyl CoA get into the matrix of mitochondria?
via carnitine through an antiporter
**the CoA does NOT get transferred with the fatty acyl
what are the three stages of fatty acid oxidation?
- beta oxidation
- citric acid cycle
- Oxidative phosphorylation
* *remember this happens in the matrix of mitochondria
how much ATP is produced by 1 16 carbon (palmiate) fatty acid?
108
per 1 oxidation step in beta oxidation what are the products?
1 Acetyl CoA (goes to CAC) 1 NADH ( goes to ETC) 1 FADH2 (goes to ETC)
what enzyme feeds directly into the ETC?
acyl-CoA dehydrogenase, produces FADH2
what are the two fates of acetyl CoA made in the liver?
- goes into CAC for production of glucose through gluconeogenesis
- can go form ketone bodies
what are the three ketone bodies to know? why are they important?
- Acetoacetate, Acetone(cannot be converted back into acetylCoA), beta-hydroxybutyrate
- allow for recycling of CoA and also serve as energy for fuel for heart, muscle, kidney, and brain
how do dietary proteins and carbs get turned into fatty acids and eventually triacylglycerols?
- the acetyl CoA is carboxylated into malonyl CoA
- acetyl CoA and malonyl CoA combine to start a acyl chain
- fatty acid synthase adds malonyl CoA carbons to create palmitate
- modified in ER (sterols, phospholipids)
the citrate shuttle
transports acetyl CoA that is produced in the matrix into the cytoplasmic space where lipid synthesis occurs
what does malic enzyme do and what does it produce?
takes malate to pyruvate
produces NADPH
What enzyme carboxylates acetyl CoA into Malonyl-CoA
Acetyl-CoA carboxylase (ACC)
biotin is required(vit. B7)
What are the two types of fatty acid synthase?
- type I vertebrates and fungi (only makes plamitate) 16 carbon saturated fatty acids
- type II in bacteria and plants
Acyl carrier protein
fatty acid synthase(FAS) prosthetic group
holds malonyl group to FAS
needs pantothenic acid (vit. B5)
lipid synthesis steps
malonyl added to acetyl via condensation step NADPH reduces dehydration reduction again by NADPH **adds two carbons at a time
what essential fatty acid is produced by fatty acid synthase II
alpha linolenate
what is the longest carbon chain that we can create as humans?
18 carbons
how does Acetyl-CoA Carboxylase activity regulate fatty acid synthesis and breakdown
insulin activates ACC(phosphate dephosphoryates)
glucagon deactivates ACC(phosporylated by PKA)
**high levels of malonyl CoA deactivate fatty acid beta oxidation at the carnitine acyl transferase I enzyme
fatty acid addition make phospholipids and triglycerides
what is the process?
- glucose and glycerol and 2 acyl chains form phosphatidic acid
- head groups and FAs are added to phosphatidic acid to make phospholipids
- phosphatase can remove phosphate group and allow addition of another fatty acid to make a triglyceride
- this occurs at the ER of the cell
what does excess acetate lead to?
the formation of cholesterol, which is the basis for many sterols
T/F cholesterol is involved in lipoprotein and hormone formation?
True, it is a necessary component of lipoprotein walls and for hormones
what are foam cells?
macrophages that have taken up too many cholesterol molecules and build up in the arteries and form atherosclerosis.
*hence HDL is very important in removing the cholesterol from the macrophages
