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-triangle²-enoyl-CoA

• 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: L-beta-hydroxy-acyl-CoA

• 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: beta-ketoacyl-CoA

• 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

Which enzyme catalyzes the cleavage of 3-ketoacyl CoA in fatty acid oxidation?

1. 3-hydroxyacyl CoA dehydrogenase

2. 3-hydroxyacyl CoA hydrolyase

3. β-ketothiolase

4. acyl CoA dehydrogenase

5. fatty acid thiokinase

3. β-ketothiolase

Which reaction in the β-oxidation pathway yields FADH₂?

1. oxidation of acyl CoA

2. cleavage of 3-ketoacyl CoA

3. oxidation of 3-hydroxyacyl CoA

4. carboxylation of propionyl CoA

5. hydration of trans-Δ2-enoyl CoA

1. oxidation of acyl CoA

Which reaction product is formed from trans-Δ²-enoyl CoA by 3-hydroxybutyryl-CoA dehydratase?

1. Butyric acid

2. 3-ketoacyl CoA

3. 3-hydroxyacyl CoA

4. 3-hydroxyacetyl CoA

5. Acetyl CoA

3. 3-hydroxyacyl CoA

Which reaction in the β-oxidation pathway yields NADH?

1. carboxylation of propionyl CoA

2. cleavage of 3-ketoacyl CoA

3. oxidation of acyl CoA

4. hydration of trans-Δ²-enoyl CoA

5. oxidation of 3-hydroxyacyl CoA

5. oxidation of 3-hydroxyacyl CoA

Which enzyme catalyzes the formation of 3-ketoacyl CoA in the β-oxidation pathway?

1. fatty acid thiokinase

2. 3-hydroxyacyl CoA hydrolyase

3. acyl CoA dehydrogenase

4. β-ketothiolase

5. 3-hydroxyacyl CoA dehydrogenase

5. 3-hydroxyacyl CoA dehydrogenase

How many energy-rich molecules are formed after b-oxidation of butyryl CoA (C4-acid)?

1. 2 FADH₂ + NADH + acetyl CoA

2. FADH₂ + NADH + 2 acetyl CoA

3. FADH₂ + NADH + acetyl CoA

4. FADH₂ + 2 NADH + acetyl CoA

5. 2 FADH₂ + 2 NADH + 2 acetyl CoA

2. FADH₂ + NADH + 2 acetyl CoA

Fatty acid breakdown primarily takes place in the:

1. cytoplasm.

2. Golgi apparatus.

3. nucleoli.

4. inner membrane of mitochondria.

5. matrix of mitochondria.

5. matrix of mitochondria.

Which hormones stimulate the mobilization/release of fatty acids from adipose tissue to meet energy demands?

1. insulin and glucagon

2. cortisol and insulin

3. glucagon and epinephrine

4. insulin and epinephrine

3. glucagon and epinephrine