Quiz 7 Flashcards
What things make fatty acids good for energy substrates and storage?
They are highly reduced, inert, they pack tightly together, hydrophobic (so they do not affect they osmolarity of the cell)
Do chylomicrons transport triglycerides or free fatty acids? What about albumin?
Chylomicrons transport triglycerides.
Albumin transports free fatty acids.
What occurs when a chylomicrons reaches its target location? What enzyme is involved?
ApoC-II (on the chylomicron) activates lipoprotein lipase. Lipoprotein lipase breaks down the chylomicrons and converts the triacylglycerols to FA and glycerol which can then be taken up by the tissue
Where are chylomicrons synthesized?
In the ER of Enterocytes (absorptive small intestine cells)
What are apolipoproteins?
They are proteins that bind to lipids to form lipoproteins. They serve diverse functions such as activating enzymes and receptors.
Is a chylomicron a lipoprotein or an apolipoprotein?
Lipoprotein. Apolipoproteins are just associated with lipoproteins
What are the four classes of lipoproteins? What are their relative sizes?
Chylomicrons (extra large)
VLDLs (large)
LDL (Medium)
HDL (small)
Which lipoproteins contain the most protein? (In descending order)
1) HDL
2) LDL
3) VLDL
4) Chylomicron
Which lipoproteins contain the most triglycerides in descending order?
1) chylomicron
2) VLDL
3) LDL
4) HDL
Are lipoproteins composed of a mono layer or a bilayer?
Monolayer of phospholipids
Which lipoprotein contains the most cholesterol (in descending order)?
1) LDL
2) HDL
3) VLDL
4) Chylomicron
What happens to the chylomicron after it has dumped off its lipids in the target tissue?
The chylomicron remnants go back to the liver. This is where the endogenous pathway begins
The liver produces what lipoprotein to deliver fatty acids to the tissues? What happens after? (Two things)
VLDL.
After VLDL dumps off its fatty acids to the tissue, it becomes LDL. The LDL can either go back to the liver to recycle back to VLDL orrrr it can dump off their excess cholesterol to macrophages in the vasculature.
What does HDL do?
HDL takes up the cholesterol obtained in the macrophages (foam cells) and delivers the cholesterol back to the liver.
Explain how lipoproteins are internalized by target tissue cells. (5 steps)
1) LDL receptor binds to apoB-100 on lipoprotein
2) LDL is internalized in endosome
3) LDL receptors segregate from vehicle and recycled to surface
4) endosome fuses with lysosome
5) enzymes in lysosome break down LDL into aa, FA, and cholesterol
Where is perilipin located? What is its function?
It is located on the surface of lipid droplets in adipose cells. Perilipin functions to stabilize the lipid droplet.
What does perilipin do once it is phosphorylated by PKA?
It will activate CGI (compatible gene indicator)
What does CGI do once it is activated?
Comparative gene indicator will go on to phosphorylate ATGL (adipose triglyceride lipase)
What does ATGL do once activated?
It will break up triacylglycerols into diacylglycerides and monoacylglycerides.
What two things does PKA do in an adipose cell?
Phosphorylates perilipin
Phosphorylates hormone sensitive lipase (HSL)
What does HSL (hormone sensitive lipase) do once phosphorylated?
HSL will break diacylglycerides down to monoacylglycerides
What is the role of MGL (monoglyceride lipase)?
MGL removes glycerol from monoacylglycerides to form free fatty acids. The free fatty acids can then be taken up in the blood.
Once fatty acids are released into the blood, they are transported by ___ and taken up into cells via ____
1) serum albumin
2) fatty acid transporters
How is glycerol catabolized? What is it turned into? What is produced in the process?
It will be converted into Glyceraldehyde-3- phosphate to enter glycolysis. In this process, you use 1 ATP and create one NADH
What will the fatty acids form?
Fatty acyl coAs
Where is carnitine acyltransferase I and II located?
I is located in the outer mitochondrial membrane
II is located in the inner mitochondrial membrane
How is a fatty acyl coA molecule transported into the matrix of a mitochondria?
The fatty acyl coA is attached to a carnitine molecule via carnitine acyltransferase I. The carnitine+fatty acid is transported into the intermembrane space. Then it goes through a carnitine transporter where carnitine goes into the intermembrane space while carnitine+fatty acid goes into the matrix. The carnitine is removed from the complex via carnitine acyltransferase II
In fatty acid oxidation… Which carbon gets oxidized?
The beta carbon
What are the products per oxidation step?
1 acetyl coA
1 NADH
1 FADH2
What is special about the first step of B oxidation?
The enzyme is acyl-coA dehydrogenase which feeds directly into the electron transport chain
What enzymes of B oxidation are directly correlated with the electron transport chain?
Acyl-coA dehydrogenase
B hydroxylacyl-coA dehydrogenase
Since B oxidation involves breaking the carbon chain into two carbon segments, what happens to odd numbered carbon fatty acids?
Odd carbon and unsaturated fatty acids must undergo extra steps
How can fatty acids be converted to glucose?
Broken down into acetyl coA, enter citric acid cycle, oxaloacetate can be converted to glucose via Gluconeogenesis
What can happen to acetyl coA if Gluconeogenesis is saturated?
It can form ketone bodies
What are the three ketone bodies?
Acetoacetate
B-hydroxybuterate
Acetone
What are some things that ketone bodies can do?
Release enzyme coA
Can be ulitilezed as a fuel source
What are some things that can cause an excess of acetyl coA
Excess dietary carbohydrates and proteins
What is insulin’s role in the formation of fatty acids?
It promotes the formation of acetyl-coA from carbohydrates and proteins
It promotes the formation of fatty acids from acetyl coA
What are the five stages of fatty acid synthesis?
1) transport acetyl coA to cytoplasm
2) carboxylate on of acetyl coA into malonyl coA
3) fatty acid synthase combines acetyl coA and malonyl coA to start a chain
4) fatty acid synthase adds malonyl coA carbons to create palmitate
5) fatty acids modified in ER
where are the three locations in which fatty acid synthesis takes place?
Cytoplasm
Mitochondria
ER
Acetyl coA is produced in the ____ but lipid synthesis occurs in the ____
1) matrix
2) cytoplasm
How is acetyl coA transported into the cytoplasm from the matrix?
Acetyl coA is attached to citrate and goes through the citrate transporter
Once citrate + acetyl coA is in. The cytosol, how is it converted back. To. Acetyl coA?
Citrate lyase
How is oxaloacetate replenished. In the. Matrix???
The citrate shuttle. The malate a-ketogluterate transporter brings malate in orrrr the pyruvate transporter brings pyruvate in.
What is the role of acetyl-coA carboxylate?
It carboxylates acetyl-coA to form malonyl-coA (which is necessary for acyl chain initiation and synthesis
There are two types of fatty acid synthase. Which type do vertebrates and fungi have? What about bacteria and plants?
Vertebrates and fungi = FAS I
Bacteria and plants = FAS II
What type of fatty acids are produced by fatty acid synthase I?
Only saturated 16 carbon FA. PALMITATE
What is the rate determining step in lipid synthesis?
Conversation of acetyl coA to form malonyl coA by ACC
What is the role of acyl carrier protein in lipid synthesis? What is a critical component of this protein?
It is a FAS prosthetic group. It shuttles malonyl-coA to Fatty acid synthase to help build the FA chains
Needs pantothenic acid (vitamin B5)
Explain the steps of fatty acid synthasis
1) acetyl-coA is carboxylated by ACC to form malonyl coA
2) Malonyl coA + acetyl coA +FAS = condensation reaction and CO2 is released
3) With the use of NADPH the B carbon is reduced (the carbon from acetyl coA)
4) B carbon is dehydrated
5) B carbon is reduced (with NADPH)
Every new two carbons that are added to the FA chain are from malonyl coA or acetyl coA?
Malonyl coA
The omega carbon comes from acetyl coA or malonyl coA?
Acetyl coA
What are the two sources of NADPH that are required for FA synthesis?
Pentose phosphate pathway and the malic enzyme (converts malate to pyruvate)
What are two essential fatty acids that are produced from plants?
A linoleic acid and linoleic acid
Is acetyl coA Carboxylase active in its phosphorylated or dephosphorylated form? What is insulin’s effect on ACC?
ACC is active in its dephosphorylated form
Insulin dephosphorylates ACC to activate it
What is glucagon’ effect on fatty acid synthesis?
It inhibits it by deactivating ACC (phosphorylating Acetyl coA Carboxylase)
the presence of Malonyl coA has what affect one Fatty acid B oxidation? How does this work?
It will inhibit fatty acid B oxidation
It does this by inhibiting the action of carnitine acyl-transferase. This prevents fatty acids from entering the mitochondria for B oxidation
How is it that ACC regulates both fatty acid synthesis and fatty acid oxidation?
When ACC is active, it converts acetyl-coA to Malonyl-coA. the presence of malonyl coA isn’t just necessary for fatty acid synthesis, it inhibits fatty acid B oxidation by Inhibiton of carnitine acyl-transferase
What is necessary to form phosphatidic acid?
Glucose and glycerol
What is phosphatidic acid and what is it used for?
Phosphatidic acid is like a triglyceride except one of the 3 backbone carbons has a phosphate group instead.
Phosphatidic acid is thus a precursor to “a whole slew” of molecules such as triacylglycerols, phospholipids, and diacylglycerides