Term
| Describe the structure of a basic fatty acid |
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Definition
A carboxyl on one end with a chain of carbons.
First carbon from carboxyl is α, second is β, etc. Last is ω. |
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Term
| What distinguishes a saturated fatty acid from an unsaturated fatty acid? |
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Definition
| Unsaturated has a double bond and is therefore less rigid and more liquid at lower temperatures. |
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Term
| How many kilocalories are in 1g fat? How many in 1g carohydrate? |
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Definition
9kcal/g fat
4kcal/g carbohydrate |
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Term
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Definition
A 12-carbon saturated fatty acid
Often found in soaps |
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Term
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Definition
| A 16-carbon saturated fatty acid |
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Term
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Definition
A 18-carbon saturated fatty acid
Found in beef |
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Term
| Describe Linoleic acid and α-Linoleic acid |
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Definition
18 carbon fatty acid unsaturated at 3 points
Precursors to prostaglandins, found in coldwater fish |
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Term
| Describe the basic structure if a triacylglycerol (TAG) |
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Definition
| A 3-carbon glycerol backbone with 3 fatty acid chains |
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Term
| Describe the characteristics of a longer fatty acid chain compared to a short chain |
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Definition
| The longer the chain, the more hydrophobic and more unhealthy |
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Term
| What is the main form of fat found in the diet? |
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Definition
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Term
| What happens to fats in the small intestine? |
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Definition
| Bile salts emulsify them, forming mixed micelles |
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Term
| After intestinal lipases degrade triacylglycerols, how to do they get into the bloodstream? |
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Definition
| They are taken up into mucosa, reconverted to TAGs, incorporated into chylomicrons, and moved through the lymphatic system to blood |
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Term
| How does a chylomicron in the blood enter a cell as fatty acids? |
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Definition
| A lipoprotein lipase on the capillary wall degrades TAGs, allowing the free fatty acids to enter the cell |
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Term
| Describe the structure of a chylomicron |
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Definition
| Shell of phospholipids with triacylglycerols inside. B48, CIII, and CII apolipoproteins in shell. |
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Term
| What does apolipoprotein CII do? |
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Definition
| It activates lipoprotein lipase on capillary walls |
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Term
| What does apolipoprotein B48 do? |
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Definition
| They are important for clearance of the phospholipid shell after the chylomicron is broken down. The protein is recognized by the liver to recycle the scell. |
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Term
| What happens to the glycerol background during TAG breakdown? |
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Definition
| It can be converted to glycerol-3-phosphate to enter glycolysis (using an ATP and NADH) |
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Term
| Why is it important to turn a free fatty acid into Fatty acyl-CoA as soon as it enters a cell? |
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Definition
| Otherwise, it could be deprotonated at the carboxyl, forming a salt that will act as a detergent, causing damage to membranes |
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Term
| What enzyme converts a fatty acid to fatty acyl-CoA? What does it require? |
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Definition
| Fatty acyl-CoA synthetase, requires ATP and CoA-SH |
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Term
| What is the rate limiting step for β-oxidation? |
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Definition
| Transport into the membrane by the carnitine shuttle |
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Term
| What enzyme converts fatty acyl-CoA to fatty acyl carnitine to get into the matrix? |
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Definition
Carnitine acyltransferase I
(Carnitine acyltransferase II transforms it back once in the matrix) |
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Term
| Where does β-oxidation occur? |
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Definition
| Inner mitochondrial matrix |
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Term
| Describe the steps of β-oxidation |
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Definition
1. Dehydrating the fatty acyl-CoA to form a double bond between the α and β carbons
2. Hydrating the double bond to have an OH on the β carbon
3. Dehydrating so the β carbon -OH is now a ketone, forming a di-keto
4. Thiolytic cleavage, releasing Acetyl CoA. The original fatty acyl-CoA is now reduced by 2 carbons |
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Term
| How can β-oxidation be limited? |
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Definition
| If there is no free coenzyme A in the matrix |
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Term
| What is important about the acyl-CoA dehydrogenase in the first step of β-oxidation? |
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Definition
There are different enzymes for different chain lengths, and these can have genetic deficiencies.
Ex. Some people have "medium" acyl CoA dehydrogenase deficiency |
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Term
| Would β-oxidation take place in a fed or fasted state? |
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Definition
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Term
| In a fasted state, what happens with the Acetyl-CoA produced in β-oxidation? |
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Definition
1. 2 Acetyl CoA are converted into acetoacetyl-CoA
2. HMG-CoA synthetase forms HMG-CoA by adding an acetyl CoA
3. Removal of Acetyl CoA produces ketone bodies: acetocetate and D-β-hydroxybutane |
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Term
| What would detection of acetone in the breath indicate? |
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Definition
| Very high ketogenesis due to Atkins diet or uncontrolled type 1 diabetes |
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Term
| What is the purpose of ketones |
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Definition
| A way to take Acetyl CoA from the liver to areas of the body it is needed (even the brain can adapt to this) |
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Term
| How can ketone bodies acetocetate and D-β-hydroxybutane be converted back into 2 Acetyl CoA |
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Definition
It's fairly simple, they are converted back to Acetoacetyl-CoA by β-ketoacyl-CoA transferase
Thiolase splits it into 2 Acetyl CoA |
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Term
| What enzyme interchanges ketone bodies acetocetate and D-β-hydroxybutane? |
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Definition
| D-β-hydroxybutyrate dehydrogenase |
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Term
| Where does ketone synthesis occur? |
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Definition
| Mitochondrial matrix of the liver |
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Term
| How does an energy-rich state promote fatty acid synthesis? |
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Definition
| Insulin promotes acetyl-coA carboxylase to turn acetyl-CoA into Malonyl CoA, used to make fatty acids |
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Term
| How does the presence of malonyl CoA inhibit β-oxidation? |
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Definition
| Malonyl CoA inhibits carnitine acyl-transferase in the carnitine shuttle |
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Term
| How would low blood glucose inhibit fatty acid synthesis |
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Definition
| It would deactivate acylCoA carboxylase, leaving Acetyl CoA to be converted to glycose |
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Term
| Describe the structure of malonyl CoA |
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Definition
Acetyl CoA attached to a carboxylic acid derived from bicarbonate
Its C-C bond is important for anabolism |
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Term
| What are three parts in the acetyl CoA carboxylase? |
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Definition
1. Biotin carboxylase
2. Biotin carrier protein
3. Transcarboxylase |
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Term
| How does acetyl-CoA carboxylase convert acetyl-CoA into malonyl CoA? |
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Definition
| A biotin side chain attaches to Acetyl CoA then uses ATP and biocarbonate to add on carbon, forming malonyl CoA |
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Term
| Where is malonyl CoA formed? |
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Definition
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Term
| What are the steps of fatty acid synthesis? |
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Definition
1. Malonyl CoA is activated with primer acetyl group
2. Reduction of keto group to an alcohol
3. Elimination of water to form a double bond
4. Reduction of double bond to form a saturated acyl group (resulting in a final addition of 2 hydrocarbons) |
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Term
| Even though fatty acid synthesis (condensation, reduction, elimination, reduction) is basically reversing β-oxidation (reduction, hydration, reduction, cleavage) why are they NOT considered reversible processes? |
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Definition
| A different set of enzymes is used |
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Term
| What is the final product of fatty acid synthesis? |
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Definition
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Term
| What energy sources are needed for fatty acid synthesis |
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Definition
7 ATP, but more significantly 14 NADPH
7ATP is >1 glucose, 14 NADPH is about 7 glucose |
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Term
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Definition
1. PPP
2. Malate -> pyruvate via malic enzyme |
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Term
| What three carbon sources can transverse the matrix membranes? |
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Definition
| Citrate, malate, pyruvate |
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Term
| How does insulin promote formation of Malonyl-CoA? |
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Definition
| By activating citrate lyase (forming acetyl CoA) and acetyl CoA carboxylase (forming Malate) |
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Term
| How does glucagon promote Malonyl CoA formation? |
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Definition
| Trick question! Why would glucagon promote malonyl CoA and fatty acid synthesis? |
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Term
| How does glucagon/epinephrine inhibit malonyl CoA formation? |
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Definition
| By inhibiting acetyl-CoA carboxylase |
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Term
| What are positive regulators of acetyl-CoA carboxylase? |
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Definition
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Term
| What are negative regulators of acetyl-CoA carboxylase? |
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Definition
| Glucagon, epinephrine, palmitoyl CoA |
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Term
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Definition
| A signaling molecule derived from oxidation of essential fatty acids |
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Term
| What are essential fatty acids? |
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Definition
| ω-6 or ω-3 fatty acids that only plants have the enzymes to make (can also be found in some things, like fish, that eat them) |
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Term
| Why do we need ω-3 fatty acids? |
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Definition
| They are needed for regulatory lipids that mediate inflammation (prostaglandins, leukotrines) |
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Term
| In polyunsaturated fatty acids, where is the double bond found? |
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Definition
| Between carbon 9 and the ω carbon |
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Term
| What enzyme do plants have for making ω fatty acids that mammals lack? |
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Definition
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Term
| What is the name of the pathway by which phospholipid containing arachidonate is turned into prostaglandins? |
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Definition
| The cyclooxygenase pathway |
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Term
| What enzyme converts arachidonate 20:4 to cyclooxgenized prastaglandin precursor PGH2? |
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Definition
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Term
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Definition
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Term
| How does aspirin inhibit COX? |
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Definition
| By acetylating an essential serine residue in the active site (covalent modification) |
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Term
| How do ibuprofen and naproxen inhibit COX? |
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Definition
| By acting as competitive inhibitors |
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Term
| What enzyme converts arachidonate into leukotriene precursors? |
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Definition
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Term
| What drug can affect leukotriene action, and how does it function? |
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Definition
| Singulair, by binding antagonistically to leukotriene surface receptors on cells |
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Term
| What are the building blocks of cholesterol? |
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Definition
| Isoprene, derived from Acetyl CoA |
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Term
| Why is cholesterol necessary for life? |
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Definition
| It is important in membranes, bile, steroid hormones |
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Term
| What is the rate limiting step of cholesterol synthesis? |
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Definition
| The conversion of acetate to mevalonate |
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Term
| List the carbon intermediate steps of cholesterol synthesis |
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Definition
1. Acetate
2. Mevalonate
3. Activated (phosphorylated) isoprene
4. Squalene
5. Cholesterol |
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Term
| What enzyme is the target for stain drugs and the rate limiting step for cholesterol synthesis? |
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Definition
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Term
| Why is cholesterol synthesized more in the fed state? |
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Definition
| Because it is derived from a carbohydrate, acetyl CoA |
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Term
| Why are statin drugs not dangerous? (the body does need some cholesterol to function) |
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Definition
Statins only work in the liver, other tissues can make enough for cholesterol needs
Therefore okay for "de novo" synthesis |
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Term
| What are the energetic costs to form cholesterol? |
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Definition
| Several ATP, but more significantly many expensive NADPH |
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Term
How many acetate molecules would be needed for one cholesterol molecule?
(Not sure if she would ask this) |
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Definition
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Term
| What is the regulatory protein on VLDL? |
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Definition
| ApoB-100, which binds to LDL receptor |
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Term
| How are LDL particules formed? |
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Definition
1. Liver sends out VLDL to carry fat to the body, VLDL picks up proteins along the way to facilitate its metabolism
2. LDL are derived from VLDL that have transported all of their triacylglycerol to peripheral tissues |
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Term
| What is the function of HDL particles? |
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Definition
| To pick up cholesterol in peripheral tissues and return it to the liver ("reverse cholesterol transport") |
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Term
| How are HDL particles formed? |
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Definition
| They are not synthesized, but form once they pick up apoA1 from chylomicrons |
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Term
| List the four lipoproteins in order from most triaglycerols to least |
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Definition
| Chylomicrons, VLDL, lDL, HDL |
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Term
| Which lipoproteins have high levels of cholesterol? |
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Definition
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Term
| What cholesterol is "bad" and what is "good"? |
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Definition
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Term
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Definition
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Term
| Where is ApoB-100 found and what does it do? |
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Definition
| VLDL and LDL, binds to LDL receptor on cell membranes |
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Term
| Where is ApoC-II found and what does it do? |
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Definition
| It is in chylomicrons, VLDL, and HDL and it activates lipoprotein lipase |
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Term
| Where is ApoC-III found and what does it do? |
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Definition
| It is in chylomicrons, VLDL, and HDL and it inhibits lipoprotein lipase |
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Term
| How are lipoproteins cleared from the bloodstream? |
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Definition
| By receptor mediated endocytosis |
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Term
| Is HMG-CoA reductase inhibited or activated by insulin? |
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Definition
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Term
| How does cholesterol regulate HMG-CoA reductase? |
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Definition
| Cholesterol stimulates proteolysis of HMG-CoA reductase (negative feedback) |
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Term
| How much can diet and exercise change serum cholesterol levels? |
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Definition
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Term
| In insulin resistance, what process is oddly promoted? |
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Definition
| Gluconeogenesis (increasing blood glucose and increasing cholesterol) |
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