lipid metabolism (breakdown)

where are triacylglycerols (TAGs) stored? (male vs female)

• adipose tissue

  • male = abdomen, glute

  • female = abdomen, breast, glute

TAG are exported from the liver and packaged with what other molecules?

• cholesterol esters

• phospholipids

• combined together → different lipoprotein particles

what hormone helps activate fat breakdown?

• epinephrine

what are lipoproteins made of ? what is each layer’s function?

• apolipoproteins (recognition particles)

• monolayer of phospholipids (amphipathic )

• core of nonpolar lipids (TAG, C, CE)

where are fats degraded into fatty acids and glycerol?

• cytoplasm of adipocytes

beta oxidation of fatty acids occurs in the _______

• mitochondria

how can fatty acids diffuse freely across mitochondrial membranes?

• small fatty acids (<12 carbons) = diffuse freely across mitochondrial membranes

• larger fatty acids (>12 carbons) = transported via acyl-carnitine/carnitine transporter

hydrolysis of TAG is catalyzed first by _____ _____ ____

• hormone-sensitive lipase

  • and then by other lipases

what is formed by hormone sensitive lipase ? what about after other lipases?

• hormone sensitive lipase

  • 2-acyl glycerol/ monoacyl glycerol(-2COOH/esters)

    • at C1 & C3

  • hydrolysis of TAG

• other lipases

  • glycerol (-COOH)

steps to activate/deactivate hormone-sensitive lipase (HSL)

1. low insulin, high epinephrine

2. epinephrine x receptor

3. adenyl cyclase activated → increase cAMP

4. cAMP activates protein kinase

5. protein kinase phosphorylates HSL

   • phosphorylated HSL = active

6. HSL hydrolyzes TAG → free fatty acids

7. phosphatase dephosphorylates HSL → inactive

chylomicron vs LDL ratio

• chylomicron = TAG >> cholesterol

• LDL = cholesterol >> TAG

explain the steps for carnitine transport

1. fatty acid reacts w/ CoA-SH → acyl CoA

2. acyl CoA + carnitine → acyl-carnitine (loses CoA-SH)

3. Carnitine acyltransferase 1 (outer membrane)

4. Carnitine acyltransferase 2 (inner membrane)

5. acyl-carnitine loses carnitine → fatty acid acyl CoA form

   • carnitine returns back to outer membrane

to enter matrix, fatty acids need to be in _____ ____ form

• acyl CoA

what are the 3 stages of fatty acid oxidation? (general)

• stage 1

  • beta oxidation of acetyl CoA

• stage 2

  • acetyl CoA → TCA cycle

• stage 3

  • ATP generation from NADH & FADH₂ (electron transport chain)

what are the type of reactions in 4 step in the beta oxidation pathway

1. oxidation

2. re-hydration

3. oxidation

4. thiolysis

each pass (4-step sequence) removes one ____ group

• acetyl group (acetyl CoA)

1 molecule of acetyl CoA = ___ ATP

12

1 mole of C16 fat will produce how many ATP ?

• n/2 = 16/2 = 8 molecule of acetyl CoA x 12 = 96 ATP

• n/2 -1 = 16/2 -1 = 7 cycles x 5 ATP (NADH & FADH₂) = 35 ATP

• 96 + 35 = 131 ATP

C20 fatty acid will produce what total number of ATP ?

• n/2 = 20/2 = 10 molecule of acetyl CoA x 12 = 120 ATP

• n/2 -1 = 20/2 -1 = 9 cycles x 5 ATP (NADH & FADH₂) = 45 ATP

• 120 + 45 = 165 ATP

describe step 1 (enzyme, location, product, type, etc)

• enzyme: acyl-CoA dehydrogenase

• location: inner mitochondrial membrane

• product: trans double bond

• type of reaction: oxidation

• redox factor: FAD → FADH2

step 1 of beta oxidation is analogous to the ____ ____ reaction in the citric acid cycle

• succinate dehydrogenase

describe step 2

• enzyme: enoyl-CoA hydratase

• product: alcohol

• type of reaction: re-hydration

  • hydrolysis of alkene

  • addition of water

step 2 of beta oxidation is analogous to the ___ reaction in the citric acid cycle

• fumarase

step 3

• enzyme: beta-hydroxyacyl CoA dehydrogenase

• product: ketone

• type of reaction: oxidation

• redox factor: NAD+ → NADH

step 3 of beta oxidation is analogous to ____ _____ reaction of the citric acid cycle

• malate dehydrogenase reaction of the citric acid cycle

describe step 4

• enzyme: acyl-CoA acetyltransferase / thiolase

• type of reaction: thiolysis / nucleophilic reaction

• electrophile: ketone carbon in beta-ketoacyl-CoA

• nucleophile: -SH in CoA-Sh

• product: releases on molecule of acetyl-CoA + Acyl-CoA (original)

where does beta oxidation occur?

• mitochondrial matrix

the 2 carbon units are released as ____ ___

• acetyl CoA