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74 Cards in this Set
- Front
- Back
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How are all categories of lipids in the body related? |
They are relatively insoluble in water |
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What is the major fat in the human diet? |
Triacylglycerols (triglycerides) |
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What does the structure of triglycerides contain? |
Glycerol backbone, to which 3 fatty acids |
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To what extent & how are triglycerides digested in the mouth and stomach? |
very limited extent - by lingual and gastric lipase by cells at the back of the tongue and in the stomach |
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What hormone is released once triglycerides enter the intestine? |
Cholecystokinin |
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In regards to triglyceride digestion, what 2 things does the hormone, cholecystokinin signal? |
Signals the gallbladder to release bile acids & the pancreas to release digestive enzymes (pancreatic lipase and colipase) to bind and digest triglycerides |
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What are the 2 degradation products of triglyceride digestion (and where are they located)? |
Free fatty acids (FA) 2-monoacylglycerol (2-MG) in the small intestine |
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In addition to triglycerides, what other 3 lipids are present in the food we eat? |
Phospholipids, cholesterol, & cholesterol esters (cholesterol esterified to fatty acids) |
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Where are phospholipids hydrolyzed at and by what? |
In the intestinal lumen and by phospholipase A2 |
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What organ secretes phospholipase A2 that hydrolyzes phospholipids? |
The pancreas |
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Cholesterol esters... what are they hydrolyzed by? what secretes the enzyme? where does this occur? |
cholesterol esterase pancreas intestine |
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After these lipids are digested by their enzymes to form FA, 2-MG, cholesterol, and lysophospholipids... what are they packaged into? |
Micelles combined with bile acids |
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What is the function of the micelle? |
Allows for diffusion of the lipid soluble components of digestion across the cell membrane of the intestine and into the cell |
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In lipid digestion, do bile acids enter the cell with the micelle? |
No - they remain in the intestinal lumen and are reabsorbed and sent back to the liver to be used multiple times in fat digestion |
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In lipid digestion, what occurs after the micelle enters the intestinal cells? |
The intestinal epithelial cells resynthesize triglycerides from the FA and 2-MG |
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In lipid digestion, what would happen if triglycerides entered the blood directly? |
They would coalesce and impede blood flow |
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What is a chylomicron? |
A particle that packages triglycerides, proteins and cholesterol into so that they do not coalesce in aqueous solutions |
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In lipid digestion, what happens to the chylomicrons after they are formed? |
They are secreted into the lymph and end up in circulation where they can distribute dietary lipids to all tissues of the body |
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In lipid digestion, what happens once the newly released, "nascent", chylomicrons are in circulation? |
They interact with another lipoprotein particle - high-density lipoprotein (HDL) |
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In lipid digestion, what does the nascent chylomicron acquire from HDL to convert them into a "mature" chylomicron? |
apolipoprotein CII (apo CII) and apolipoprotein E (apo E) |
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In lipid digestion, what does apoCII on the mature chylomicron activate? |
The enzyme lipoprotein lipase (LPL) |
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In lipid digestion, what does LPL do? |
Digests the triglyceride in the chylomicron, producing FA and glycerol |
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In lipid digestion, where do the fatty acids go and what do they do? |
enter the adjacent organs, either for energy production (muscle) or fat storage (adipocyte) |
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In lipid digestion, where does the glycerol go and what does it do? |
Metabolized in the liver and reused for triglyceride synthesis in the liver |
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In lipid digestion, as the chylomicron loses triglyceride, its density increases and it becomes a... |
chylomicron remnant |
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What happens to this chylomicron remnant? |
apoE is exposed, binds to liver cells that recognize apoE, and taken up by endocytosis. Degraded by lysosomes in the liver and reused |
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Fatty acids are an important fuel source for humans and the major fuel for cardiac/skeletal muscle and the liver during fasting. However the nervous system (brain) can not really use fatty acids directly. How does the nervous system get its energy during fasting? |
the liver converts fatty acids to ketone bodies (acetoacetate and beta-hydroxybutyrate) |
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The fatty acids oxidized as fuels are what type of fatty acids and where are they released? |
long-chain fatty acids released from adipose tissue triacylglycerol stores |
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What hormones control the release of fatty acids from adipose tissue and the regulation of fatty acid metabolism? |
Insulin & glucagon! |
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Fatty acids circulate through the blood bound to what? |
Albumin |
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Between meals, a decreased insulin level and increased glucagon level activate... |
lipolysis |
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How is energy (ATP) derived from oxidation of fatty acids? |
fatty acids are oxidized to acetyl-CoA in the B-oxidation pathway within the mitochondria |
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In B-oxidation, the fatty acyl group is oxidized to yield what products? |
reduced FAD(2H), reduced NADH, and acetyl CoA |
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Subsequent oxidation of NADH and FAD(2H) in the ETC, as well as oxidation of acetyl-CoA to CO2 in the TCA cycle, generates ATP from what process? |
oxidative phosphorylation |
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In the liver, much of the acetyl CoA generated by B-oxidation of fatty acids within the mitochondrial matrix is used for synthesis of... |
KETONE BODIES - acetoacetate and beta-hydroxybutyrate |
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Is B-oxidation aerobic or anaerobic? |
aerobic - dependent on oxygen! |
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Do fatty acids serve as significant fuel for the brain? |
NO |
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Are fatty acids used by adipocytes? |
NO - their purpose is to store triglycerides to provide fuel for other tissues. |
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If tissues do NOT use fatty acids, or only use them to a limited extent... what do they use for energy? |
Ketone bodies |
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Ketone bodies - B-hydroxybutyrate and acetoacetate are eventually converted into acetyl CoA which then goes through... |
Oxidation in the TCA cycle! |
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Does the liver use ketone bodies? |
No - just produces them |
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What tissues use fatty acids preferentially in fasting conditions? |
Skeletal muscle, heart, liver |
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What tissues use ketone bodies to a greater extent during fasting? |
brain, kidney cells, cells of intestinal mucosa, adipocytes, fetal |
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Almost all tissues and cell types, with the exception of which two.... are able to use ketone bodies for fuel? |
liver and RBCs |
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Where is the primary site for fatty acid synthesis in humans? |
The liver (can occur to a lesser extent in adipose tissue) |
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Dietary ______ serves as a major fuel source of carbon... |
glucose |
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During Fatty Acid Synthesis... Glucose is converted through glycolysis to ______, which enters the mitochondrion and forms ______ and _____, which condense to form ____. |
pyruvate acetyl CoA and oxaloacetate (OAA) citrate |
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During fatty acid synthesis, citrate is transported to the cytosol, where it eventually partakes in reactions that occur on what complex? |
Fatty acid synthase complex |
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During fatty acid synthesis, the fatty acid chain grows via a series of reactions and once the chain is ___ carbons in length, it is released as a ________. |
16; palmitate |
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Fatty acids are used to synthesize what? |
Triacylglycerol's, glycerophospholipids and sphingolipids |
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In the liver, what are triacylglycerol's produced by? |
Fatty acyl CoA and glycerol 3-P |
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Are triglycerides stored in the liver? |
No - they are packaged with apolipoproteins and other lipids in very-low-density lipoprotein (VLDL) and secreted into the blood |
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What are glycerophospholipids synthesized from? |
fatty acyl coA and glycerol 3-P (same as triacylglycerols) |
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What are glycerophospholipids major components of? |
the cell membrane also... blood lipoproteins, bile and lung surfactant |
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What are sphingolipids synthesized from? |
sphingosine - formed from serine rather than glycerol |
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What do sphingolipids function in? |
serve in intracellular communication and antigenic determinants of ABO blood groups Also prevalent in cell membranes and myelin sheaths |
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What does cholesterol do? |
Regulates/stabilizes membrane fluidity |
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Cholesterol is a precursor to what substances? |
bile salts, steroid hormones, and Vit D |
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How is cholesterol transported in the blood? |
In lipoproteins (insoluble in water) |
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Cholesterol can be obtained from the diet, but it can also be synthesized in the body, especially in cells of which 2 organs? |
Liver and intestine |
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Cholesterol, along with triglycerides, is packaged into ______ in the intestine and ______ in the liver. |
Chylomicrons in the intestine VLDL in the liver |
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What kind of cholesterol is considered "bad"? |
LDL |
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What kind of cholesterol is considered "good" |
HDL |
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Why is HDL cholesterol considered "good"? |
HDL is involved in the process of removing cholesterol from tissues, such as thelining cells of vessels, and returning it to the liver (where endocytosis andlysosomal digestion occur) Thisis a process known as reversecholesterol transport |
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What is ethanol? |
a dietary fuel that is metabolized to acetate, in the liver, with the generation of reduced NADH |
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After ethanol is metabolized to acetate, what is acetate activated to in order to generate energy for most tissues of the body? |
acetyl CoA |
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What family of enzymes catalyzes the first step of alcohol oxidation? |
ADL alcohol dehydrogenase |
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The ALD enzymes oxidize ethanol to ________ in the cytosol of the ______. |
Acetaldehyde; hepatocyte |
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In the metabolism of ethanol, acetaldehyde is further oxidized in a second step, which occurs by which family of enzymes? |
ALDH acetaldehyde dehydrogenase family |
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In the process of ethanol metabolism, during the second step, the enzymes in the ALDH family convert acetaldehyde to _____ in the _______ of the liver cell. |
Acetate; mitochondria |
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~10-20% of ingested ethanol is oxidized through what process by what enzymes, where? |
a microsomal ethanol-oxidizing system (MEOS), consisting of cytochrome P450 enzymes in the ER |
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In acute alcohol ingestion, what occurs in regards to NADH? |
an increased accumulation of NADH (increased ratio of NADH/NAD+... a disequilibrium b/t the reduced and oxidized forms |
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What are some chronic effects of ethanol ingestion? |
hepatic steatosis (fatty liver) hepatitis cirrhosis toxic acetaldehyde in blood and formation of reactive oxygen species |
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What 3 controlling elements determine whether a fuel is metabolized of stored? |
hormones, concentration of available fuels, and energy needs of the body |
