Lipid Metabolism Flashcards
Purpose of Fatty Acid Metabolism
Fatty acid synthesis (lipogenesis) takes place in liver and adipose cells where excess acetyl CoA that builds up when glucose levels are high.
(ANABOLISM)
Fatty acid oxidation is responsible for providing energy to cells when glucose levels are low.
(CATABOLISM)
B-Oxidation Reactions of Fatty Acids
3 steps to break down fatty acids to make energy
- Fatty acid must be activated: bond to coenzyme A 2. Fatty acid must be transported into mitochondria 3. Fatty acid repeatedly oxidized produces Acetyl
CoA, FADH2, & NADH
Digestion of Lipids
Lingual and gastric lipases initiate lipid digestion by hydrolyzing ingested fat to free fatty acids and glycerol
Most lipid digestion occurs in small intestine
Pancreatic enzymes digest the lipids: • lipase
• cholesterol ester hydrolase
Digestion of Lipids
Final products of fat digestion are hydrophobic and therefore the process of absorption is complex
Breakdown of Triglycerides
Broken down by Lipases
Degradation of Phospholipids
Phospholipase A removes 1 fatty acid from carbon 2
lysophospholipase
2
leaving a lysophospholipid
What is glycolysis? What does glucose get converted into during glycolysis?
Why do you need complicated TCA cycle to oxidize acetate?
TCA cycle is a complicated way to oxidize acetate units to CO2. True
or False
Describe the first entry step to TCA cycle.
What are the most important take home points about TCA cycle?
What are fatty acids primarily stored as?
Efficient way to cleave C-C bonds as normal methods do not work to ALSO generate carbon dioxide for the body AND energy
Energy comes from the release of NADH/FADH and ATP
Oxidation forms carbon dioxide
Regeneration forms oxaloacetate
Both acetyl CoA and oxaloacetate are generated from pyruvate, condense to form citric acid
What is the role of catabolism of fatty acids? What is the role of fatty acid anabolism?
Fatty acids are stored as triglycerides and can be stored/released depending on glucose levels
Fatty acid oxidation occurs when glucose levels are low (catabolism)
Fatty acid synthesis (lipogenesis) occurs when glucose levels are high, takes place in the liver and adipose cells where excess acetyl coA that builds up
What are the primary enzymes involved in digestion of lipids?
Lingual/gastric lipase helps to initiate lipid digestion by hydrolyzing ingested fat to free fatty acids/glycerol
Most lipid digestion occurs in the small intestine
Pancreatic enzymes: lipase, cholesterol ester hydrolase
How are the three primary group of lipids digested?
Triglycerides
Require lingual, gastric, pancreatic lipase
Yields a monoglyceride and two FA
Cholesterol ester
Cholesterol ester hydrolase
Yields a cholesterol and a FA
Phospholipid
Uses phospholipase A2
Yields lysolecthin and FA
Explain the role of bile.
Bile is works to emulsify dietary fats
Bile covers the fat as it has hydrophobic sides facing the fat and a hydrophilic side that covers the rest of the body
Step wise explain the absorption of lipids in the intestine.
Final products of fat digestion are hydrophobic SO fat is covered with bile to form micelles
These micelles move to the epithelial cells of the small intestine (enterocytes)
Inside, these are re-esterfied into their original lipids and packaged into chylomicrons
Chylomicrons are very large transporters so they move through the lymphatic capillaries
Go to the thoracic duct and into the blood stream
What is the primary role of CCK and secretin in controlling lipid digestion?
CCK is produced in the presence of lipids and partially digested proteins
Causes the stomach to slow gastric motility, signals the release of bile, and the pancreas to release lipase
Secretin is released in response to low pH
Causes the contents of the gastric system to neutralize by signaling the pancreas and liver to release bicarbonate
What happens to fat anabolism and catabolism when glucagon or insulin is high?
Explain the role of insulin in triggering fat storage during fed state? What does the enzyme lipoprotein lipase do?
Explain the role of glucagon in fasting state. What is adipocyte lipase?
What is the difference between the role of lipoprotein lipase and
adipocyte lipase?
What is ketogenesis?
Describe how acetyl CoA is in the crossroads of the different metabolism pathways.
