Lipids

Question 1

What is the primary form of dietary and stored fat?

Answer 1

Triglycerides

Question 2

What are the main (3) differences between carbohydrates/proteins and lipids?

Answer 2

Lipids are:
-Primarily hydrophobic
-emulsified or packaged for optimal absorption
-packaged in lipoproteins in blood

Question 3

Explain how lipids are digested and absorbed

Answer 3

-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

Question 4

What is a bile salt?

Answer 4

bile salts are conjugated with glycine or taurine, they are synthesized in the liver. *Cats use only taurine for bile acid conjugation

Question 5

What are the three sites that secrete lipases?

Answer 5

salivary glands, stomach, and pancreas

Question 6

How much of TG digestion is lingual and gastric lipases responsible for?

Answer 6

~10%

Question 7

Why are lingual and gastric lipases inactivated in the duodenum?

Answer 7

Because the pH is too high, the optimal pH is 4 where its around 8 in the duodenum

Question 8

What form is pancreatic lipases secreted into the duodenum as?

Answer 8

already active

Question 9

What do lipases yield?

Answer 9

2-monoglyceride and 2 molecules of free fatty acids

Question 10

What happens once the micelle enters the jejunal mucosal cells?

Answer 10

The digested TG need to be resynthesized to then be excreted in chylomicrons

Question 11

Describe TG resynthesis

Answer 11

-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

Question 12

Which tissues utilize the phosphatidic acid pathway to make small amounts of TG?

Answer 12

liver, adipose, lactating mammary tissue, and aerobic muscle

Question 13

Why do TG have to enter the lymphatic circulation instead of portal?

Answer 13

Because they are packaged into chylomicrons and they are too big to enter portal blood, so they enter lymphatic and then systemic.

Question 14

What are the two outcomes of the phosphatidic acid pathway

Answer 14

triglycerides and phospholipids (phosphatidylinositol or phosphatidylcholine)

Question 15

What are the 5 main biologic functions of phospholipids?

Answer 15

-Components of membranes and lipoproteins
-Constituents of intracellular signal transduction molecules and eicosanoid synthesis
-coagulation
-functional elements of bile
-lung surfactant

Question 16

What is a plasmalogen

Answer 16

phospholipids that contain a fatty alkyl group attached to carbon one of glycerol via an ether bond

Question 17

What is the role of platelet activating factor?

Answer 17

-Mediator of inflammatory responses, platelet aggregation

Question 18

What are the roles of cardiolipids?

Answer 18

-Inner mitochondrial membrane to aid in electron transport chain
-Involved in apoptosis

Question 19

What is the role of dipalmitoylphosphatidylcholine?

Answer 19

-DPPC is an important component of pulmonary surfactant, it decrease surface tension of alveolar membranes, thus helping to keep alveoli open

Question 20

What stimulates DPPC at birth?

Answer 20

epinephrine and cortisol

Question 21

What is the disease caused by the lack of surfactant in premature neonates?

Answer 21

Infant respiratory distress syndrome (IRDS)

Question 22

What is the main role of phosphatidylcholines?

Answer 22

It is a major cell membrane component

Question 23

How do phospholipases work?

Answer 23

They are hydrolases that act on ester bonds of phospholipids

Question 24

Where does phospholipase A2 work?

Answer 24

cleaves fatty acid at carbon 2

Question 25

What are the roles of PLA1 and where does it work?

Answer 25

Cleaves fatty acids at carbon 1, it is involved as a digestive enzyme and involved in membrane phospholipids turnover. It’s also involved in platelet aggregation and smooth muscle contraction

Question 26

What are the three main functions of phospholipase D

Answer 26

-Endo/exocytosis
-Cytoskeletal reorganization
-Cell migration during development, wound healing and immune responses

Question 27

What can be reacylated via acyl CoA in the presence of acyltransferases as a form of phospholipid degradation/recycling?

Answer 27

lysolecithin (lysophosphatidylcholine)

Question 28

How does phospholipase C affect signal transduction?

Answer 28

It cleaves the phospholipid to make diacylglycerol (DAG) and inositoltriphosphate (IP3)

Question 29

Where can we find high amounts of sphingolipids? specifically sphyingomyelin?

Answer 29

Brain tissue

Question 30

What is structurally distinct about sphingolipids?

Answer 30

no glycerol

Question 31

What two things is sphingosine synthesized from?

Answer 31

palmitoyl CoA and serine

Question 32

What is a glycosphingolipids? (glycolipids)

Answer 32

Sugar is linked to ceramide instead of phosphocholine or phosphoethanolamine

Question 33

What is the difference between cerebrosides and gangliosides?

Answer 33

cerebrosides are glycoproteins with only one sugar, while gangliosides have oligosaccharides attached

Question 34

Name 5 biological functions of glycolipids

Answer 34

-Present in outer cell membrane, interact with extracellular environment
-Provide antigenic chemical markers for cells ( blood type antigens)
-cell to cell communication
-provide structure to cell membranes
-important in nervous tissue

Question 35

What degrades glycolipids for turnover or otherwise

Answer 35

lysosomal hydrolases

Question 36

What causes lysosomal storage diseases?

Answer 36

accumulation of lipid intermediates in lysosomes due to lysosomal hydrolase deficiencies