Title: Jack Sparrow Biochem / Biochemistry / Biochemistry Chapter 11
Tags: #JackSparrow::#B/B::#Biochemistry::#Chapter.11

Q: How are short-chain fatty acids absorbed?
A: Short chain fatty acids can pass through the intestine directly into the blood.

Q: How are long-chain fatty acids absorbed?
A: Long-chain fatty acids are absorbed as micelles and assembled into chylomicrons for release into the lymphatic system.

Q: What is Hormone Sensitive Lipase?
A: HSL is an enzyme that breaks down triacylglycerols into fatty acids and glycerol for use as energy.  HSL responds to low insulin levels, high epinephrine levels, and high cortisol, which all serve the common purpose of increasing blood sugar.

Q: What is meant by mobilization of triacylglycerols?
A: Triacylglycerol can only really be used to generate energy in the liver, but we store them all over our body.  Mobilization refers to the way we transfer triacylglycerol break down products to the liver so they can be Beta Oxidized.

Q: What is lipoprotein lipase?
A: Lipoprotein lipase is necessary for the metabolism of very low density lipoproteins (VLDL's) and chylomicrons.  It's function is to release free fatty acids from triacylglycerols in these lipoproteins.

Q: How are free fatty acids transported through the blood?
A: Albumin, the archetypal carrier protein, carries fatty acids.

Q: What are the different types of Lipoproteins?
A: 1.  Very Low Density Lipoproteins (VLDL)
2.  Intermediate Density Lipoproteins  (IDL)
3.  Low Density Lipoproteins (LDL)
4.  High Density Lipoproteins (HDL)

Q: How are triacylglycerol and cholesterols transported through the blood?
A: Triacylglycerols and cholesterols are transported through protein/lipid complexes called lipoproteins of varying density.

Q: What is a chylomicron?
A: A chylomicron is a highly soluble transporter of dietary lipids to other tissues.  Assembly of chylomicrons occurs in the intestinal lining.

Q: What is a VLDL?
A: A VLDL is a similar structure to a chylomicron; however, these are assembled and produced in liver cells.  The main function of VLDL's is to transport triacylglycerols to other tissues.

Q: What is an IDL?
A: An IDL is a VLDL after it has been emptied of its triacylglycerols.  IDLs are either reabsobred by the liver to make more VLDL's or further processed downstream to become even higher density Lipoproteins.

Q: LDL and HDLs are primarily [cholesterol or triacylglycerol] carriers?
A: cholesterol

Q: Chylomicrons and VLDL are primarily [triacylglycerol or cholesterol] carriers?
A: triacylglycerol

Q: What is a LDL?
A: LDLs are lipoproteins that specialize in carrying cholesterol through the body.

Q: What is an HDL?
A: HDL's are synthesized inthe liver and intestines and released as dense, protein rich particles into the blood.  HDL contains apolipoproteins that help it clean the blood vessels of extra cholesterol.  For this reason, HDL is considered "good" cholesterol.

Q: What is an apolipoprotein?
A: Also referred to as apoporteins, they form the protein component of lipoproteins and play important roles in determining and regulating their function.

Q: What are the main ways we obtain cholesterol?
A: Cholesterol can be obtained through dietary sources or synthesized in the liver.

Q: How are fatty acids named?
A: Fatty acids are written like so
carbons:double bonds omega#
Carbons refer to the number of carbons in the fatty acid.
Double bonds refers to the number of double bonds in the fatty acid.
Omega# is a number that designates how close to the 1 carbon the closest double bond is.
For example, a 20 carbon fatty acid with 5 double bonds, the closest of which is at carbon 3, would be called C20:5 omega3.

Q: What must happen to acetyl-CoA before it can be used in fatty acid synthesis?
A: Excess acetyl-CoA (after a large meal perhaps) must be transferred to the cytoplasm from the matrix using a series of enzymes.

Q: Describe Acetyl-CoA Carboxylase
A: Acetyl-CoA Carboxylase uses biotin, ATP, and CO_2 to form malonyl-CoA from Acetyl-CoA.  This is one of the first steps of fatty acid synthesis.  This enzyme is activated by insulin and citrate.

Q: Describe Fatty Acid Synthase
A: Fatty Acid Synthase (AKA Palmitate Synthase) is a large multienzmye complex that uses NADPH to add 2 carbon fragments to malonyl-CoA.  This happens over and over until the fatty acid is 16 carbons long (Palmitate).

Q: How can one easily understand Beta Oxidation and Fatty Acid synthesis?
A: Understand that they are basically just the exact opposite of one another.

Q: How are triacylglycerols synthesized from fatty acids?
A: Three fatty acids are attached to glycerol in the liver and adipose tissue.

Q: What is beta oxidation?
A: Beta oxidation is the process of breaking down Fatty Acids into acetyl CoA for use in the citric acid cycle.  Just like Fatty Acid Synthesis, it is a cycle of reactions that produces NADH and liberates 2 carbon fragments of the fatty acid at a time.

Q: Can branched or unsaturated fatty acids be oxidized normally?
A: No!  These fatty acids require special enzymes. These enzymes are isomerases and reductases, and their purpose is to unsaturate and unbranch these fatty acids so that they can be beta-oxidized like normal.

Q: Beta oxidation occurs in the [mitochondria or cytoplasm?]
A: mitochondria

Q: Fatty acid synthesis occurs in the [mitochondria or cytoplasm?]
A: cytoplasm

Q: What are three main steps of fatty acid catabolism?
A: 1.  Activation
2.  Fatty Acid Entry into Mitochondria
3.  Beta Oxidation

Q: What does it mean to say a fatty acid is activated?
A: In order to start the process of fatty acid catabolism, the fatty acid in question must first be activated by fatty-acyl-CoA Synthetase.  This enzyme attaches a CoA to the fatty acid.

Q: How do activated fatty acids enter the mitochondria?
A: Short-chain and medium chain (2 to 12 carbons) diffuse freely into the mitochondria.
Long chain (14-20 carbons) fatty acids require transport via a carnitine shuttle.  This transferring step is slow, and actually serves as the rate limiting step of beta oxidation.

Q: How is the beta oxidation of odd numbered fatty acids different?
A: It is actually the same up until the final cycle.  For even numbered fatty acids, the final cleavage of the 4 carbon molecule will result in two acetyl-CoAs.
However, for odd numbered fatty acids, the final cleavage of the 5 carbon molecule will result in an acetyl-CoA and a propionyl-CoA.
This Propionyl-CoA Undergoes a series of reactions to form succinyl-CoA, which can then enter the citric acid cycle.

Q: What are ketone bodies?
A: Ketone bodies are essentially transportable forms of acetyl-CoA that the liver produces to feed other tissues during prolonged periods of starvation.

Q: What are the three main ketone bodies?
A: 1.  Acetoacetate
2.  3-hydroxybutyrate
3.  Acetone (doesn't really get metabolized, more of a byproduct.)

Q: What is Ketogenesis?
A: Ketogenesis is the process of creating ketone bodies from excess acetyl-CoA in the liver.
HMG-CoA Synthase converts Acetyl-CoA into HMG-CoA.
Then, HMG-CoA Lyase converts HMG-CoA into Acetoacetate, one metabolic ketone body.
Acetoacetate can be sent to tissues in need or reduced to 3-Hydroxybutyrate, which is the other metabolic ketone body.
Acetone is a byproduct of this reaction.  This ketone is not metabolically active.

Q: Ketogenesis occurs in the [mitochondria or cytoplasm] of liver cells.
A: mitochondria

Q: What is Ketolysis?
A: Ketolysis is the breaking down of ketone bodies for energy.
3-Hydroxybutyrate is picked up by the mitochondria of the needy tissue and oxidized to acetoacetate, releasing NADH.
Acetoacetate (the picked up versions and the newly oxidized versions) are activated by succinyl-CoA Acetoacetyl-CoA transferase (commonly called thiophorase) to make Acetoacetyl-CoA, which can be cleaved into two molecules of Acetyl CoA.
Ingeniously, the liver does not have thiophorase, meaning it can never burn the ketone bodies it produces.  This helps the liver serve its purpose as an energy supplier to the rest of the body.

Q: Describe the progress of ketogenesis in the body.
A: For the first few days of starvation, ketogenesis occurs slowly and the muscles will metabolize basically all of them before any other tissue has a chance to.
After about a week of fasting, ketone concentration in the blood is high enough for them to reach the brain.  The brain happily metabolizes these ketones, considering it probably hasn't gotten much food from anywhere else.

Q: Generally speaking, protein metabolism is [pursued or avoided?]
A: avoided
Extra: Makes sense.  Proteins are super important, probably not that good idea to burn them for fuel.

Q: What is proteolysis?
A: Proteolysis is the breakdown of proteins.  This begins in the stomach with pepsin and continues in the small intestine.

Q: What is transamination and deamination?
A: Transamination is when the amino group of an amino acid is transferred to a different molecule.  This is usually done to create a carbon skeleton from an amino acid that can be metabolized.
Deamination is similar, but instead of transferring the amino group, it is just removed.

Q: What are glucogenic amino acids?
A: Glucogenic amino acids (every single one except leucine and lysine) are amino acids that can be converted into intermediates that feed into gluconeogenesis.

Q: What are Ketogenic Amino Acids?
A: Ketogenic amino acids (every single one except leucine and lysine) are amino acids that can be converted into ketone bodies.

Q: How is the ammonia released by protein metabolism excreted by the body?
A: Through the Urea Cycle.  The Urea Cycle occurs in the liver and is the body's main method of removing excess nitrogen from the body.

Q: What is the Urea functional group?
A: The urea functional group is a carbon double bonded to an oxygen, single bonded to two nitrogens.