Chapter 11: Lipid and Amino Acid Metabolism Flashcards
Dietary fat consists mainly of ________________, with the remainder comprised of what 4 types?
triacylglycerols;
1. cholesterol
2. cholesteryl esters
3. phospholipids
4. free fatty acids
Emulsification of lipids occurs in the ________________.
duodenum
What aids emulsification?
Bile
What happens after emulsification?
Intestinal cells absorb fats
At the end of the ileum, ________ ________ are actively reabsorbed and recycled.
bile salts
Digested lipids are absorbed into the mucosa and re-esterified to form triacylglycerols and cholesteryl esters and packaged, along with certain apoproteins, fat-soluble vitamins, and other lipids into ________________. These leave the intestine via ____________, the vessels of the lymphatic system, and re-enter the bloodstream via the ____________ ________.
chylomicrons; lacteals; thoracic duct
Although human adipose tissue does not respond directly to glucagon, a fall in insulin levels activates a ____________-____________ ____________ that hydrolyzes triacylglycerols, yielding what 2 things?
hormone-sensitive lipase; fatty acids and glycerol
While free fatty acids are transported through the blood in association with ____________, a carrier protein, triacylglycerol and cholesterol are transported in the blood as ____________.
albumin; lipoproteins
Chylomicrons are highly soluble in both ____________ fluid and ________ and function in the transport of dietary triacylglycerols, cholesterol, and cholesteryl esters to other tissues.
lymphatic, blood
________ metabolism is similar to that of chylomicrons; however, it is produced and assembled in liver cells. Its primary function is the transport of ____________ to other tissues.
VLDL - very low density lipoprotein; triacylglycerols
Once triacylglycerol is removed from VLDL, the resulting particle is referred to as either a VLDL remnent or ________. Some of this is reabsorbed by the ________, and some is further processed in the blood stream.
intermediate-density lipoprotein (IDL); liver
ALthough LDL and HDL are primarily cholesterol particles, the majority of the cholesterol measured in blood is associated with ________
LDL
The normal role of LDL is to do what?
Deliver cholesterol to tissues for biosynthesis
____ is synthesized in the liver and intestines and released as dense, protein-rich particles into the blood.
HDL
HDL is used for what?
Cleaning up excess cholesterol from blood vessels for excretion
Apolipoproteins, aka, apoproteins form what?
THe protein component of lipoproteins (they combine with the lipid)
Most cells derive cholesterol from LDL or HDL, but some is synthesized de novo in the ________ and is driven by ________-________ and ________.
liver; acetyl-CoA, ATP
The ____________ shuttle carries mitochondrial acetyl-CoA into the ____________, where cholesterol synthesis occurs.
citrate; cytoplasm
____________ promotes cholesterol synthesis.
insulin
________ ________ are long-chain carboxylic acids. The carboxyl carbon is carbon 1, and carbon 2 is referred to as the ____-________.
fatty acid; alpha-carbon
When describing a fatty acid, the total number of ________ is given along with the number of ____________ ____________, written how?
carbons; double bonds
carbons:double bonds
____________ fatty acids have no double bonds while ____________ fatty acids have one or more double bonds.
saturated; unsaturated
Humans can synthesize only a few of ____________ fatty acids; the rest come from essential fatty acids found in the diet that are transported as chylomicrons as triacylglycerols from the intestine.
unsaturated
What are the 2 important essential fatty acids? What are they used for?
- alpha-linolenic acid
- linoleic acid
Used for maintaining cell membrane fluidity
Fatty acid biosynthesis occurs in the ________ and its products are subsequently transported to adipose tissue for storage.
liver
Both of the major enzymes of fatty acid synthesis, ________-____ ____________ and ________ ________ ____________ are also stimulated by ________.
acetyl-CoA carboxylase, fatty acid synthase; insulin
____________ ________ is the primary end product of fatty acid synthesis.
palmitic acid
____________-________ is the product of the pyruvate dehydrogenase complex, and it couples with ____________ to form citrate at the beginning of TCA.
acetyl-CoA; oxaloacetate
____________ ________________ is the rate-liming enzyme of TCA; as the cell becomes energetically satisfied, it slows TCA, which causes ____________ acccumulation.
isocitrate dehydrogenase; citrate
In the cytosol, ________ ________ splits citrate back into ____________-________ and ____________.
citrate lyase; acetyl-CoA and oxaloacetate
________-________ ____________ requires biotin and ATP to function, and adds ____ to acetyl-CoA to form ____________-________.
acetyl-CoA carboxylase; CO2, malonyl-CoA
Fatty acid synthase is more appropriately called ____________ ____________ because palmitate is the only fatty acid that humans can synthesize de novo.
palmitate synthase
____________, the storage form of fatty acids, are formed by attaching ________ fatty acids (as fatty acyl-CoA) to ____________.
triacylglycerols; three, glycerol
Triacylglycerol formation from fatty acids and glycerol 3-phosphate occurs primarily in the ________.
liver
What is the reverse of fatty acid syntehsis?
beta-oxidation
When fatty acids are metabolized, they first become activated by attachment to ____, which is catalyzed by ________-________-________ ____________.
CoA; fatty-acyl-CoA synthetase
Short-chain fatty acids get into the mitochondria how? How about long-chain fatty acids? What enzyme is used to oxidize?
Simple diffusion (then oxidized); long-chain are transported via carnitine shuttle with carnitine acyltransferase I as the oxidizing enzyme
Fatty acids with an ____ number of carbon atoms undergo beta-oxidatino in the same manner, except in the final cycle, these fatty acids yield one acetyl-CoA and one ____________-CoA (from the 5-carbon remaining fragment). This CoA is converted to methylmalonyl-CoA by ____________-________ ________________.
odd; propionyl-CoA; propionyl-CoA carboxylase
Methylmalonyl-CoA is then converted into ____________-________ by what enzyme?
succinyl-COA; methylmanlonyl-CoA mutase
____________-____ is a TCA intermediate and can be converted into ________ to enter the gluconeogenic pathway in the cytosol.
succinyl-CoA; malate
Amino acids are classified by their ability to turn into specific metabolic intermediates: ____________ amino acids can be converted into glucose through ________________; ____________ amino acids can be converted into acetyl-CoA and ketone bodies.
glucogenic, gluconeogenesis; ketogenic
