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Biochem > Fatty Acid Metabolism I > Flashcards

Fatty Acid Metabolism I Flashcards

1
Q

What are the 3 classes of lipids?

A
  • Free fatty acids
  • Triglycerides
  • Cholesterol
  • Cholesterol esters
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2
Q

Describe the characteristics of the “fasting state”

A
  • Glucagon ↑
  • Glycogenolysis ↑
  • Gluconeogenesis ↑
  • Fatty acid oxidation ↑
  • Glycolysis in liver ↓
  • Glycogenesis ↓
  • Fatty acid biosynthesis ↓
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3
Q

Describe the characteristics of the “fed state (after a meal)”

A
  • Insulin ↑
  • Glycolysis ↑
  • Glycogenesis ↑
  • Fatty acid biosynthesis ↑
  • Glycogenolysis ↓
  • Gluconeogenesis ↓
  • Fatty acid oxidation ↓
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4
Q

What gives us the drive to eat?

A
  • Ghrelin
  • Peptide hormone released by the stomach
  • Acts in the hypothalamus of the brain
    Tells the brain to tell your body that you are hungry
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5
Q

What makes triglycerides very hydrophobic?

A
  • The structure
  • Triglycerides = T-shaped
  • All of the non-polar parts are on the ends
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6
Q

What does the body produce in order to emulsify lipids?

A

Bile

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7
Q

Describe bile

A
  • Synthesized in the liver
  • Stored in the gall bladder
  • Amphipathic
  • Acts as a detergent that coats lipids and breaks them into smaller pieces
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8
Q

What is the purpose of pancreatic lipase?

A
  • Enzyme secreted by the pancreas
  • Cleaves triglycerides at the 1 and 3 position
  • The result is 2 fatty acids and a monoacylglycerol (these can be absorbed directly into the cells of the small intestine)
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9
Q

What happens to triglycerides after they are cleaved by pancreatic lipase?

A
  • The 2 fatty acids and monoacylglycerol are absorbed into the cell where they are converted back into triglycerides
  • Cholesterol = converted into cholesterol esters (extremely hydrophobic)
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10
Q

How do the cholesterol esters and triglycerides (which are extremely hydrophobic) make their way out of the cells of the small intestine and into circulation?

A

Chylomicrons

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11
Q

Describe the structure and function of chylomicrons

A
  • Contains inner core filled with triglycerides and cholesterol esters
  • Outside layer = phospholipid monolayer
  • Surface contains multiple proteins
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12
Q

What important protein (the you must remember) is located on the surface of chylomicrons?

A

ApoC-II

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13
Q

Once chylomicrons have been generated, how are the triglycerides hydrolyzed back into fatty acids so that they can be taken up by the cell?

A

Lipoprotein Lipase

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14
Q

Describe the function of lipoprotein lipase

A
  • Enzyme that lines the endothelium of capillaries surrounding adipose and muscle tissue
  • Cleaves triglycerides within chylomicrons into fatty acids and monoacylglycerides
  • The fatty acids and monoacylglycerides can then be taken up by the adipose tissue for storage or the ,muscle tissue for energy
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15
Q

What is the purpose of ApoC-II

A

Activate LPL increasing triglyceride hydrolysis

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16
Q

What happened to chylomicron remnants once the triglycerides from the inner core have been broken down?

A

They are taken up by the liver

17
Q

What happens in individuals that do not have lipoprotein lipase?

A
  • They have excess chylomicrons in their blood stream
  • Symptoms include:
  • Loss of appetite
  • Abdominal pain
  • Nausea
  • Vomiting
18
Q

How are fatty acids stored?

A

Intracellular lipid droplets

19
Q

Describe the structure of lipid droplets?

A
  • Structurally similar to chylomicrons
  • Inner core = triglycerides and cholesterol esters
  • Outer core = phospholipid monolayer
20
Q

Describe what happens to stored lipids in the fasting state

A
  • Lypolyisis is stimulated
  • 3 enzymes are involved in the cleaving of triglycerides
21
Q

What are the 3 enzymes involved in cleaving triglycerides?

A
  1. Adipose triglyceride lipase (ATGL): cleave first fatty acid at the 1 position
  2. Hormone sensitive lipase (HSL): cleaves fatty acid at the 3 position
  3. Monoacylglycerol lipase (MAGL/MGL): generates the last free fatty acid and glycerol
22
Q

How is lypolysis regulated?

A

Glucagon and epinephrin act on receptors in the adipose tissue that activate PKA (protein kinase A)

23
Q

Describe the regulation of lypolysis

A
  • After a meal you want PKA to be turned off
  • If you are fasting you want PKA to be turned on
  • PKA will posphorylate perilipin-1 and ABHD5
24
Q

Describe the function of perilipin-1

A
  • Located on the surface of the lipid droplet
  • PKA = inactive: perilipin-1 binds to ABHD5 and sequesters it
  • PKA = active: perilipin-1 will release ABHD5
  • When ABHD5 = phosphorylated it will release ATGL to the surface of the lipid droplet
25
Q

What other enzyme does PKA phosphorylate?

A
  • HSL
  • Phosphorylation of HSL brings the lipid droplet to the surface
26
Q

What is an example of a disease that is associated with lipolysis disfunction?

A

Mutation resulting in nonfunctional ABHD5

Biochem (27 decks)

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