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Flashcards in LIPIDS Deck (70)
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1

IMPORTANT FATTY ACIDS 

2

FA naming 

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ACTIVATION OF FATTY ACIDS

• A fatty acid must be converted to its activated form before it can participate in metabolic processes

• Enzyme: Fatty acyl CoA synthetase

• Occurs in the cytosol

Activated FA: Acyl-CoA

4

End product of mammalian FA synthesis (Lipogenesis)

Palmitic acid

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rate liming step of Lipogenesis

Acetyl CoA + HCO 3 – + ATP → Malonyl CoA

Enzyme: Acetyl CoA carboxylase​

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Substrate and product of Lipogenesis

Acetyl CoA

Palmitoyl CoA

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Citrate Shuttle 

*Mitochondrial acetyl CoA (from the oxidation of pyruvate) is transported to the cytosol using the citrate shuttle

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Activators of Acetyl-CoA Carboxylase (rate-limiting enzyme of Lipogenesis)

Citrate and Insulin 

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Inhibitors of Acetyl-CoA Carboxylase (rate-limiting enzyme of Lipogenesis)

Glucagon and epinephrine

10

Sources of NADPH for Lipogenesis:

• Pentose phosphate pathway

• Malic enzyme

• Isocitrate dehydrogenase

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Sequence of steps repeated seven times for Elongation of PAlmitoyl COA (Lipogenesis)

Condensation → Reduction → Dehydration → Reduction

"CoRe DR

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Fatty acids are stored as ______

TRIACYLGLYCEROL

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Enzyme that breaks down TAG to Glycerol and Fatty Acids

Hormone Sensitive lipase 

14

Beta Oxidation / Lipolysis

  • Removal of acetyl CoA fragments from the ends of fatty acids, also yielding NADH and FADH2 in the process
    • Acetyl CoA can enter the citric acid cycle
    • NADH and FADH 2 can enter the ETC

15

Substrate for Lipolysis

Palmitate

16

What are the products of Lipolysis?

8 Acetyl CoA, 7 NADH, 7 FADH 2

17

Rate limiting step of BETA-OXIDATION or LIPOLYSIS. 

Translocation of fatty acyl CoA from the cytosol to the mitochondria

Enyzme: Carnitine-palmitoyl transferase​

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How many NADPH are consumed in LIPOGENESIS

14

19

What shuttle is used in Beta oxidation?

Carnitine shuttle

20

TRANSPORT OF FATTY ACYL COA TO THE MITOCHONDRIA

1. Fatty acyl synthetase activates the fatty acid

2. Carnitine acyltransferase-1 attaches fatty acyl to carnitine in the outer mitochondrial membrane

3. Fatty acyl-carnitine is shuttled through the inner membrane

4. Carnitine acyltransferase-2 transfers fatty acyl group back to a CoA in the mitochondrial matrix

21

Sequence of steps repeated seven times in Beta Oxidataion/Lipolysis:

Oxidation → Hydration → Oxidation → Thiolysis​

22

Enzymes collectively known as fatty acid oxidase​ in Lipolysis. 

"DeHyDeThy"

o Fatty acyl CoA dehydrogenase

o Δ2 enol CoA hydratase

o 3-hydroxyacyl-CoA dehydrogenase

o Thiolase

 

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ATP YIELD of PALMITATE 

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produced only during beta oxidation of odd-numbered fatty acids (because beta oxidation removes 2 carbons at a time.

Propionyl CoA

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Differentiate Lipogenesis from Beta Oxidation 

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• Leads to decreased oxidation of fatty acids with 6–10 carbons

• Most common inborn error of fatty acid oxidation o Autosomal recessive disorder with a higher incidence in Northern Europeans

MEDIUM-CHAIN FATTY ACYL COA DEHYDROGENASE (MCAD) DEFICIENCY

o Severe hypoglycemia

o Accumulation of fatty acids (dicarboxylic acids) in the urine

o Can manifest as Sudden Infant Death Syndrome (SIDS)

27

CARNITINE-PALMITOYL TRANSFERASE I DEFICIENCY

• Affects the liver

• Reduced fatty acid oxidation, leading to severe hypoglycemia, coma, and even death

28

CARNITINE-PALMITOYL TRANSFERASE II DEFICIENCY

• Affects primarily cardiac and skeletal muscle

• Cardiomyopathy, muscle weakness with myoglobinemia after prolonged exercise

29

• Caused by eating the unripe fruit of the akee tree

• The toxin hypoglycin inactivates medium- and short-chain acylCoA dehydrogenase, inhibiting β-oxidation and causing hypoglycemia

JAMAICAN VOMITING SICKNESS

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• Deficiency of phytanoyl-CoA hydroxylase leads to accumulation of phytanic acid

REFSUM DISEASE

o Peripheral neuropathy and ataxia, retinitis pigmentosa, and abnormalities of skin and bones

Accumulation of phytanic acid blocks β-oxidation.