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#‼️BIOCHEMISTRY - PLE TOPNOTCH 2020 > LIPIDS > Flashcards

LIPIDS Flashcards

1
Q

IMPORTANT FATTY ACIDS

A
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2
Q

FA naming

A
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3
Q

ACTIVATION OF FATTY ACIDS

A
  • 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

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4
Q

End product of mammalian FA synthesis (Lipogenesis)

A

Palmitic acid

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5
Q

rate liming step of Lipogenesis

A

Acetyl CoA + HCO 3 – + ATP → Malonyl CoA

Enzyme: Acetyl CoA carboxylase​

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6
Q

Substrate and product of Lipogenesis

A

Acetyl CoA

Palmitoyl CoA

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7
Q

Citrate Shuttle

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

A
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8
Q

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

A

Citrate and Insulin

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9
Q

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

A

Glucagon and epinephrine

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10
Q

Sources of NADPH for Lipogenesis:

A
  • Pentose phosphate pathway
  • Malic enzyme
  • Isocitrate dehydrogenase
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11
Q

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

A

Condensation → Reduction → Dehydration → Reduction

“CoRe DR

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12
Q

Fatty acids are stored as ______

A

TRIACYLGLYCEROL

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13
Q

Enzyme that breaks down TAG to Glycerol and Fatty Acids

A

Hormone Sensitive lipase

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14
Q

Beta Oxidation / Lipolysis

A
  • 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
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15
Q

Substrate for Lipolysis

A

Palmitate

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16
Q

What are the products of Lipolysis?

A

8 Acetyl CoA, 7 NADH, 7 FADH 2

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17
Q

Rate limiting step of BETA-OXIDATION or LIPOLYSIS.

A

Translocation of fatty acyl CoA from the cytosol to the mitochondria

Enyzme: Carnitine-palmitoyl transferase​

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18
Q

How many NADPH are consumed in LIPOGENESIS

A

14

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19
Q

What shuttle is used in Beta oxidation?

A

Carnitine shuttle

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20
Q

TRANSPORT OF FATTY ACYL COA TO THE MITOCHONDRIA

A
  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
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21
Q

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

A

Oxidation → Hydration → Oxidation → Thiolysis​

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22
Q

Enzymes collectively known as fatty acid oxidase​ in Lipolysis.

A

“DeHyDeThy”

o Fatty acyl CoA dehydrogenase

o Δ2 enol CoA hydratase

o 3-hydroxyacyl-CoA dehydrogenase

o Thiolase

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23
Q

ATP YIELD of PALMITATE

A
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24
Q

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

A

Propionyl CoA

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25
Q

Differentiate Lipogenesis from Beta Oxidation

A
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26
Q
  • 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
A

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)

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27
Q

CARNITINE-PALMITOYL TRANSFERASE I DEFICIENCY

A
  • Affects the liver
  • Reduced fatty acid oxidation, leading to severe hypoglycemia, coma, and even death
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28
Q

CARNITINE-PALMITOYL TRANSFERASE II DEFICIENCY

A
  • Affects primarily cardiac and skeletal muscle
  • Cardiomyopathy, muscle weakness with myoglobinemia after prolonged exercise
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29
Q
  • 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
A

JAMAICAN VOMITING SICKNESS

30
Q

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

A

REFSUM DISEASE

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

Accumulation of phytanic acid blocks β-oxidation.

31
Q
  • Cerebrohepatorenal syndrome
  • Inherited absences of peroxisomes in all tissues leads to marked accumulation of very-long-chain, saturated, unbranched fatty acids in liver and central nervous system
A

ZELLWEGER SYNDROME

  • Liver dysfunction with jaundice
  • Marked mental retardation, weakness, hypotonia
  • Craniofacial dysmorphism (high forehead, shallow orbits, hypertelorism, high arched palate, abnormal helices of ears, retrognathia)
  • Early death
32
Q

Inability to transport VLCFAs across the peroxisomal membrane leads to accumulation in the brain, adrenals, and testes

A

ADRENOLEUKODYSTROPHY (ALD)

o Neurodegeneration (Initial apathy and behavioral change, followed by visual loss, spasticity, and ataxia)

o Adrenocortical insufficiency

o Hypogonadism

33
Q

Where does ketogenesis occur?

A

liver mitochondria

34
Q

Substrate for ketogenesis

A

o Acetyl CoA

* Ketone bodies are alternate fuel sources for tissues like the brain during the fasting phase. They are derived from acetyl CoA. Recall tha acetyl CoA comes from glycolysis when you are well fed, but from beta oxidation when you are fasting.

35
Q

Products of ketogenesis

A

o Acetoacetate

o β-hydroxybutyrate

o Acetone

*Of the three ketone bodies, only acetoacetate and β-

hydroxybutyrate can be used as fuel.

36
Q

rate limiting step of KETOGENESIS

A

Acetoacetyl CoA + Acetyl CoA → HMG CoA

Enzyme: HMG CoA Synthase​

37
Q
A

During fasting, there’s almost no glucose available to be converted to acetyl CoA. Free fatty acids in the blood will be sent to the liver to be broken down into acetyl CoA units which can enter ketogenesis. KBs will then be made. KBs are small, can travel to blood & can enter the BBB. As KBs travel in the blood, some KBs can be excreted in the urine &/or one of the KBs (acetone) will be exhaled in the lungs. Once KBs reach the target tissue (extrahepatic), KBs will undergo ketolysis and be converted to AcetylCoA that then enters Krebs cycle (producing 10 ATPs per cycle). Ketogenesis & ketolysis are opposittes but both occur during fasting.

38
Q

Substrate for Cholesterol Synthesis

A

Acetyl CoA

39
Q

The liver is NOT able to use ketone bodies as fuel because it lacks the enzyme ___

A

succinyl CoA-acetoacetate-CoA transferase (thiophorase)

40
Q

Describe the structure of cholesterol

A

o 27-carbon compound

o Steroid nucleus: four fused hydrocarbon rings (A-D)

o An eight-carbon, branched hydrocarbon chain attached to carbon 17 of the D ring

o Hydroxyl group at carbon 3 of the A ring

o Double bond between carbon 5 and 6 of the B ring

41
Q

Primary bile acids

A

o Cholic acid

o Chenodeoxycholic acid

42
Q

Secondary bile acids

A

o Deoxycholic acid

o Lithocholic acid

43
Q

• Bile salts

A

o Conjugated to taurine and glycine (e.g., taurocholic acid, glycocholic acid)

44
Q

Cholesterol Synthesis

A
  1. Acetyl CoA is produced from glucose
  2. Acetoacetyl-CoA and acetyl-CoA condense to form HMG-CoA
  3. HMG-CoA is reduced to mevalonate
  4. Mevalonate is converted to C-5 isoprenoid, isoprenyl pyrophosphate
  5. Two isoprenyl pyrophosphates condense to form C-10 compound, geranyl pyrophosphate, which reacts with another C-5 compound to form C-15 farnesyl pyrophosphate
  6. Squalene is formed from two C-15 units, and then oxidized and cyclized to form lanosterol
  7. Lanosterol is converted to cholesterol
45
Q

Rate limiting step for Cholesterol Synthesis

A

Hydroxymethylglutaryl-CoA (HMG CoA) → Mevalonate

Enzyme: HMG-CoA Reductase Requirement: 2 NADPH​

46
Q

are drugs used for the treatment of hypercholesterolemia, to reduce the risk for cardiovascular diseases. They are competitive inhibitors of HMG CoA reductase.​

A

Statins

47
Q

• 7-dehydrocholesterol reductase deficiency

  • Leading to low plasma cholesterol and elevated 7dehydrocholesterol
  • Presents with dysmorphic facial features, microcephaly, mental retardation, congenital heart disease, other malformations, often stillborn
A

SMITH-LEMLI-OPITZ SYNDROME

48
Q
  • Precipitation of cholesterol in the gallbladder
  • Results when more cholesterol enters the bile than can be solubilized by the bile salts and phosphatidyl choline present
A

CHOLELITHIASIS

49
Q

o Most common form of CAH (>90%)

o Mineralocorticoids and glucocorticoids are absent or deficient

o Overproduction of androgens leads to masculinization of external genitalia in females and early virilization in males

A

21 -α-Hydroxylase deficiency

50
Q
  • Largest diameter
  • Lowest density

• Highest TAG content

A

Chylomicron

51
Q

o Decrease in serum cortisol, aldosterone, and corticosterone

o Increased production of deoxycorticosterone causes fluid retention (low-renin hypertension)

o Overproduction of androgens causes masculinization and virilization

A

11-β1-Hydroxylase Deficiency

52
Q
  • Autoimmune destruction of the adrenal cortex leads to adrenocortical insufficiency
  • Acute addisonian crisis precipitated by stress (infection, trauma, surgery, vomiting, diarrhea, or noncompliance with replacement steroids)
  • Hyperpigmentation due to excess ACTH stimulating melanocytes to produce melanin
A

ADDISON DISEASE

53
Q

Highest cholesterol content

A

LDL

54
Q

• Highest protein content

A

HDL

55
Q
  • Cofactor of lecithin:cholesterol acyltransferase (LCAT)
  • Structural component of HDL
A

Apo A-1

56
Q
  • Mediates assembly and secretion of VLDL
  • Structural protein of VLDL, IDL, LDL
A

Apo B-100

57
Q

Main apoprotein and mediates secretion of chylomicrons from small intestines

A

Apo B-48

58
Q

Cofactor of lipoprotein lipase

Found in Chylomicrons, VLDL IDL, HDL

A

Apo C-II

59
Q

Mediates uptake of chylomicron remnants and IDLs

Found in Chylomicron remnants, VLDL, IDL, HDL

A

Apo E

60
Q

Type I

Familial Lipoprotein Lipase Deficiency

A
61
Q

Type IIa

Familial Hypercholesterolemia

A
62
Q

Type III

Familial dysbetalipoproteinemia

A
63
Q

Type IV

Familial Hypertriacylglycerolemia

A
64
Q

Familial Lipoprotein (a) Excess

A
65
Q

Familial hyperalphalipoproteinemia

A
66
Q

Abetalipo-proteinemia

A
67
Q

Familial alpha-lipoprotein deficiency

Tangier disease

Fish-eye disease

Apo A-1 deficiencies

A
68
Q

Metabolism of Chylomicrons

A
69
Q

VLDL Metabolism

A
70
Q

HDL Metabolism

A

#‼️BIOCHEMISTRY - PLE TOPNOTCH 2020 (13 decks)

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