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57 Cards in this Set
- Front
- Back
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Lipoproteins |
droplets of hydrophobic lipids (triacylglycerols and cholesteryl esters) surrounded by phospholipids and cholesterol and proteins embedded within - special forms of micelles |
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Bile |
a mixture of cholesterol, phospholipids, and bile acids |
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Major Bile acid |
cholic acid - resembles soaps and detergents because it contains both hydrophilic and hydrophobic regions |
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Pancreatic Lipase |
partially hydrolyzes the emulsified triacylglycerols, producing mono- and diacylglycerols plus fatty acids and a small amount of glycerol |
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Absorption of small fatty acids and glycerol |
absorbed through the villi that line the small intestine, then carried by the blood to the liver via the hepatic portal vein |
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Absorption of water-insoluble acylglycerols and larger fatty acids |
emulsified again, then absorbed by the cells lining the intestine - to enter the aqueous bloodstream for transport, they are packaged into lipoproteins known as chylomicrons |
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Chylomicrons are absorbed into |
absorbed into the lymphatic system through lacteals and carried to the thoracic duct to dump into bloodstream directly to the liver |
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Lacteals |
small vessels analogous to capillaries, but larger within villi |
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3 sources lipids used in the body's metabolic pathways |
1 - from the digestive tract 2 - from adipose tissue, where excess lipids have been stored 3 - from the liver, where lipids are synthesized |
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Fatty acids released from adipose tissue associate with... |
...albumin - all other lipids are carried by lipoproteins |
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Albumin |
- a protein found in blood plasma that binds up to 10 fatty acid molecules per protein molecule |
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Chylomicrons |
- devoted to transport of lipids from the diet - they carry triacylglycerols through the lymphatic system into the blood and to the liver for processing - these are the lowest-density lipoproteins |
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Very-Low-Density Lipoproteins (VLDLs) |
carry triacylglycerols from the liver (where they are synthesized) to tissues for storage or energy generation |
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Intermediate-Density Lipoproteins (IDLs) |
carry remnants of the VLDLs from peripheral tissues back to the liver for use in synthesis |
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Low-Density Lipoproteins (LDLs) |
transport cholesterol from the liver to peripheral tissues, where it is used in cell membranes or for steroid synthesis |
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High-Density Lipoproteins (HDLs) |
transport cholesterol from dead or dying cells back to the liver, where it is converted to bile acids |
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When do dietary triacylglycerols get hydrolyzed? |
when chylomicrons encounter lipoprotein lipase anchored in capillary walls |
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When energy is in good supply, hydrolyzed dietary triacylglycerols... |
are converted back to triacylglycerols for storage in adipose tissue |
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When cells need energy, hydrolyzed dietary triacylglycerols |
the fatty acid carbon atoms are activated then oxidized as acetyl-CoA |
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Acetyl-CoA serves as the starting material for... |
...lipogenesis, ketogenesis, and the synthesis of cholesterol |
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What happens when stored triacylglycerols are needed as an energy source? |
lipases within fat cells are activated by hormone level variation (low insulin and high glucagon) |
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Stored triacylglycerols are hydrolyzed to... |
...fatty acids -free fatty acids and glycerol - released into the bloodstreams |
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How do these hydrolyzed fatty acids from adipose storage travel to cells? which cells? |
they travel in association with albumins to cells (primarily muscle and liver cells) where they are converted to acetyl-CoA for energy generation |
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Glycerol produced from triacylglycerol hydrolysis is carried to the... where it is converted to... |
liver or kidneys where it is converted to glyceraldehyde 3-phosphate and dihydroxyacetone phosphate (DHAP) |
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What pathway will DHAP enter? |
the glycolysis/gluconeogenesis pathways, linking lipid and carbohydrate paths |
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Acetyl-CoA from fatty acid conversion participate in? |
- triacylglycerol synthesis - ketogenesis - synthesis of sterols and other lipids - citric acid cycle and oxidative phosphorylation |
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After a meal, blood glucose levels? insulin levels? glucagon levels? |
blood glucose levels increase, insulin levels rise, and glucagon levels drop |
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When glucose enters cells, the rate of glycolysis______ and insulin activates... |
the rate of glycolysis increases and insulin activates the synthesis of triacylglycerols for storage |
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The reactants in triacylglycerol synthesis are... |
glycerol 3-phosphate and fatty acid acyl groups carried by coenzyme A |
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glycerol 3-phosphate is synthesized from... |
DHAP in a process called glyceroneogenesis |
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When digestion of a meal is finished, blood glucose levels? insulin levels? glucagon levels? |
Blood glucose levels return to normal, insulin levels drop and glucagon levels rise |
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The lower insulin level and higher glucagon level activate... |
triacylglycerol lipase, the enzyme that controls hydrolysis of stored triacylglycerols |
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When glycerol 3-phosphate is in short supply... |
fatty acids and glycerol produced by hydrolysis of stored triacylglycerols are released to the bloodstream for transport to energy-generating cells, otherwise the fatty acids and glycerol are cycled back into new TAGs for storage |
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Oxidation of Fatty Acids: Activation |
- fatty acid must be activated by conversion to fatty acyl-CoA(form that breaks down more easily) - some energy from ATP must be invested |
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Oxidation of Fatty Acids: Transport |
- fatty acyl-CoA must be transported from the cytosol into the mitochondrial matrix - carnitine and fatty acyl-CoA react to form fatty acyl-carnitine ester that moves into the mitochondria by facilitated diffusion - there, another ester formation exchange reaction regenerates the fatty acyl-CoA and carnitine |
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Carnitine undergoes what reaction with fatty acyl-CoA |
an ester formation exchange reaction |
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Fatty acyl-CoA must be oxidized in the...to produce... |
mitochondrial matrix to produce acetyl-CoA plus the reduced coenzymes used in ATP generation |
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The oxidation of fatty acids occurs by |
repeating 4 reactions(spiral pathway), which make up the β-oxidation pathway |
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Each repetition of the 4 reaction in β-oxidation cleaves... |
a 2-carbon acetyl group from the end of a fatty acid acyl group and produces one acetyl-CoA - the acyl group will continue to return to the pathway until each pair of carbon atoms is removed |
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Each acetyl-CoA going through the citric acid cycle will yield... |
1 ATP, 3 NADH, and 1 FADH2 |
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Each acetyl-CoA molecule generates how many ATP from reduced coenzymes? |
11 ATP and if adding 1 from citric acid cycle itself 12 ATP per acetyl-CoA |
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How many ATP molecules are spent in activation of a fatty acid? |
2 ATP |
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Fatty acids yield nearly ______ as much energy per gram as carbohydrates |
three times |
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Carbohydrates yield ___cal/g and fats and oils yield _____cal/g |
Carbs: 4 cal/g Fats and Oils: 9 cal/g |
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The enzymes in the β-oxidation pathway catalyze reactions ________ than the enzymes in the citric acid cycle |
more rapidly |
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Excess acetyl-CoA from β-oxidation is converted by... |
.. .liver mitochondria to 3-hydroxybutyrate and acetoacetate - spontaneously decomposes to acetone - smell on breath and indicates ketogenesis |
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Names of ketone bodies |
3-hydroxybutyrate acetoacetate acetone - all water soluble so they are available to all body tissues |
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Ketogenesis occurs in.... |
4 enzyme-catalyzed steps plus the spontaneous decomposition of acetoacetate |
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How is acetone primarily excreted? |
by exhalation |
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During the early stages of starvation, heart and muscle burn... |
acetoacetate, preserving glucose for the brain |
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Ketone bodies are produced______ than they are ______ in diabetes. Indicated by... |
faster than they are utilized - indicated by acetone on the patient's breath and ketone bodies in urine(ketonuria) and blood(ketonemia) |
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Why does continued ketosis lead to ketoacidosis? |
because ketone bodies are carboxylic acids - the blood buffers are overwhelmed and blood pH drops |
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Symptoms of ketoacidoses |
- dehydration due to increased urine flow, labored breathing (acidic blood is a poor oxygen carrier) and depression - untreated - lead to coma and death |
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Lipogenesis provides a link between |
- carbohydrate, lipid, and protein metabolism - using acetyl-CoA to make fatty acids allows the body to divert the energy of excess carbs and amino acids into storage as triacylglycerols |
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Fatty acid synthesis and catabolism similarities |
- both proceed two carbon atoms at a time - both recursive, spiral pathways |
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Oxidation of fatty acids: occurs - enzymes - intermediates carried by - coenzymes - carbon atoms - |
occurs - in mitochondria enzymes - different from synthesis intermediates carried by - coenzyme A coenzymes - FAD, NAD+ carbon atoms - removed 2 at a time |
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Synthesis of fatty acids: occurs - enzymes - intermediates carried by - coenzymes - carbon atoms - |
occurs - in cytosol enzymes - different from oxidation intermediates carried by - acyl carrier protein coenzymes - NADPH carbon atoms - added 2 at a time |
