Lecture 22: Lipids and FA Metabolism

Question 1

Role of fatty acids

Answer 1

High energy fuel source that can be oxidized into energy. Stored as triacylglycerols (TAGs). Also building blocks for phospho/glycolipids, hydrophobic protein mods (covalent targeting for membranes), and hormone/intracellular messengers

Question 2

Fatty acid nomenclature

Answer 2

Carboxyl carbon = C1
Then alpha, beta, gamma
Omega = last carbon in chain

Question 3

FA numerical formula

Answer 3

C’s : # dbl bonds (dbl bond locations, C-term.) e.g. 18:2 (9,12)

Question 4

Common saturated FAs

Answer 4

Myristic, palmitic, stearic acid (14/16/18:0)

Question 5

Common unsaturated FAs

Answer 5

Palmitoleic, oleic, linoleic, linolenic, arachidonic acid

Question 6

TAG roles

Answer 6

FA storage in adipocytes for other tissues and in muscle for self. TAGs sourced from G3P (glycolysis), so GLUT4 dominates in fat/muscle (insulin activated)

Question 7

Hormonal regulation of TAG metabolism

Answer 7

Glucagon, epi -> breakdown
Insulin -> synthesis, -| breakdown

Question 8

Obesity

Answer 8

Overly full fat stores; rupture of fat cells leads to a chronic inflammatory state. Excess lipid overflow is due to abnormal TAG accumulation and is associated with insulin resistance

Question 9

Key enzyme in lipolysis (TAG breakdown)

Answer 9

HSL; hormone sensitive lipase

Question 10

Pyrophosphatase function in FA oxidation

Answer 10

Activation of FA oxidation occurs with attaching FA to CoA to create acyl CoA. Pyrophosphatase on PPi pulls this activity toward products

Question 11

Control of FA oxidation

Answer 11

Long chain FA-CoA is always synthesized in the cytosol, requiring transport by CPT shuttle into the mitochondria for oxidation. Not true for medium/short chain (synth in mitochondria)

Question 12

Diabetic ketoacidosis

Answer 12

Very high ketone bodies from unrestrained lipolysis despite high blood glucose. Life threatening.

Question 13

Regulation of CPT-1

Answer 13

Malonyl-CoA inhibits CPT-1; produced by ACC for FA synthesis

Question 14

Regulation of Acetyl-CoA Carboxylase (ACC)

Answer 14

PKA and AMP-activated protein kinase (AMPK) phosphorylate and inhibit ACC; thus low energy inhibs FA synthesis and uninhibs FA oxidation

Question 15

Medium Chain Acyl-CoA DH Deficiency

Answer 15

One of most common inherited metabolic errors; diagnosed with med. chain dicarboxylic acids, carnitine ester, glycine in urine.
Impaired beta-oxid. leads to more glucose use and inhibited gluconeogenesis -> hypoglycemia

Question 16

Ketone bodies

Answer 16

Alternate fuel for cells in prolonged fasting with low glucose

Question 17

Advantages of ketone bodies for fuel

Answer 17

Water soluble; can diffuse directly to blood and be used by non-liver tissue, especially the brain