Lipids Flashcards
What is the primary form of dietary and stored fat?
Triglycerides
What are the main (3) differences between carbohydrates/proteins and lipids?
Lipids are:
-Primarily hydrophobic
-emulsified or packaged for optimal absorption
-packaged in lipoproteins in blood
Explain how lipids are digested and absorbed
-lipids enter duodenum and are emulsified by bile salts
-lipases act on TG to produce free fatty acids
-micelle formation and transportation into jejunal mucosal cells
What is a bile salt?
bile salts are conjugated with glycine or taurine, they are synthesized in the liver. *Cats use only taurine for bile acid conjugation
What are the three sites that secrete lipases?
salivary glands, stomach, and pancreas
How much of TG digestion is lingual and gastric lipases responsible for?
~10%
Why are lingual and gastric lipases inactivated in the duodenum?
Because the pH is too high, the optimal pH is 4 where its around 8 in the duodenum
What form is pancreatic lipases secreted into the duodenum as?
already active
What do lipases yield?
2-monoglyceride and 2 molecules of free fatty acids
What happens once the micelle enters the jejunal mucosal cells?
The digested TG need to be resynthesized to then be excreted in chylomicrons
Describe TG resynthesis
-Acyl-CoA synthetase: (activation step) CoA transferred to free fatty acid
-Acyl transferases: FAA are esterified to glycerol
-Two pathways for esterification to form TG: monoglyceride acylation pathway (primary) and phosphatidic acid pathway
Which tissues utilize the phosphatidic acid pathway to make small amounts of TG?
liver, adipose, lactating mammary tissue, and aerobic muscle
Why do TG have to enter the lymphatic circulation instead of portal?
Because they are packaged into chylomicrons and they are too big to enter portal blood, so they enter lymphatic and then systemic.
What are the two outcomes of the phosphatidic acid pathway
triglycerides and phospholipids (phosphatidylinositol or phosphatidylcholine)
What are the 5 main biologic functions of phospholipids?
-Components of membranes and lipoproteins
-Constituents of intracellular signal transduction molecules and eicosanoid synthesis
-coagulation
-functional elements of bile
-lung surfactant
What is a plasmalogen
phospholipids that contain a fatty alkyl group attached to carbon one of glycerol via an ether bond
What is the role of platelet activating factor?
-Mediator of inflammatory responses, platelet aggregation
What are the roles of cardiolipids?
-Inner mitochondrial membrane to aid in electron transport chain
-Involved in apoptosis
What is the role of dipalmitoylphosphatidylcholine?
-DPPC is an important component of pulmonary surfactant, it decrease surface tension of alveolar membranes, thus helping to keep alveoli open
What stimulates DPPC at birth?
epinephrine and cortisol
What is the disease caused by the lack of surfactant in premature neonates?
Infant respiratory distress syndrome (IRDS)
What is the main role of phosphatidylcholines?
It is a major cell membrane component
How do phospholipases work?
They are hydrolases that act on ester bonds of phospholipids
Where does phospholipase A2 work?
cleaves fatty acid at carbon 2
