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SFM Exam 1 > Lipid Metabolism > Flashcards

Lipid Metabolism Flashcards

1
Q

Functions of lipids

A

Fuel stores (provide energy)
Structural components of plasma membranes
Signaling molecules (participate in pathways that regulate growth, survival and immune response)
Other roles include providing insulation, generating heat and fat digestion

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2
Q

What is the major source of carbon for FA synthesis?

A

Dietary carbohydrates

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3
Q

What are the major steps in FA synthesis?

A

Phase 1: cytosolic entry of acetyl CoA
Phase 2: generation of malonyl CoA
Phase 3: FA chain formation

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4
Q

What is the RLE for FA synthesis?

A

Acetyl CoA carboxylase which converts acetyl CoA to malonyl CoA

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5
Q

What are the reactions catalyzed by FAS?

A

Condensation, reduction, dehydration, reduction and product release

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6
Q

Synthesis of longer chain FAs (elongation)

A

Palmitate converted to longer chain FA in SER or mitochondria
Brain cells need longer chain FAs (C18-24)
FA lengthened 2 carbons at a time
NADPH used as reducing power

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7
Q

The SER pathway of FA elongation uses what as the carbon donor?

A

Malonyl CoA

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8
Q

The mitochondrial pathway of FA elongation uses what as the carbon donor?

A

Acetyl CoA

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9
Q

Where does desaturation/unsaturation occur?

A

In the SER and it uses NADPH/NADH and oxygen

Catalyzed by acyl CoA desaturases

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10
Q

How many desaturases do humans have?

A

Four: delta 4, 5, 6 and 9 that cannot make a double bound beyond carbon 9 (C9-10) and the methyl end
Ex. Omega 3 and 6 FAs (which is why they need to be in the diet)

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11
Q

What are the essential FAs?

A

Linoleic (18:2 omega 6) and linolenic acid (18:3 omega 3)

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12
Q

What is linoleic acid used to make?

A

Arachidonic acid (omega 6) a precursor for eicosanoids (prostaglandins, leukotrienes and thromboxanes)

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13
Q

What is linolenic acid used to make?

A

Eicosapentaenoic acid (EPA omega 3) and docosahexanoic acid (DHA omega 3)

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14
Q

What is the storage form of FA?

A

TAGs

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15
Q

What are the 4 major lipases?

A

ATGL (adipose triglyceride lipase), hormone sensitive lipase (HSL), lipoprotein lipase (LPL) and monoacylglycerol lipase (MAG lipase)

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16
Q

The activity of HSL is modulated by what?

A

Phosphorylation

17
Q

What two major signals promote mobilization of TAGs?

A

Hunger and exercise

18
Q

What are the major controllers of the signaling that promotes mobilization of TAGs?

A

Glucagon (secreted in response to hunger) and epinephrine (secreted in response to exercise)
Both phosphorylate HSL (activate) and promote lipolysis in adipocytes

19
Q

What inhibits the mobilization of TAGs?

A

Fed status

Insulin (secreted in response to a high carb meal) dephosphorylates HSL via activation of PP1 to inhibit lipolysis

20
Q

What are perilipin?

A

A family of proteins that coat lipid droplets in adipocytes and muscle cells
Regulate lipolysis by controlling physical access to HSL
They are regulated by PKA (phosphorylation allows association with HSL) which promotes lipolysis

21
Q

What are the major steps in FA oxidation?

A

Phase I: transport of FA into the mitochondria

Phase II: beta oxidation

22
Q

What are the 4 major steps of beta oxidation?

A

Oxidation, hydration, oxidation and thiolysis

23
Q

CPT I deficiency

A

Defect in the catabolism of FAs
Defect in carnitine palmitoyltransferase I (CPT I)
Associated organelle: mitochondria

24
Q

CACT deficiency

A

Defect in the catabolism of FAs
Defect in carnitine acylcarnitine translocase (CACT)
Associated organelle: mitochondria

25
Q

CPT II deficiency

A

Defect in the catabolism of FAs
Defect in carnitine palmitoyltransferase II (CPT II)
Associated organelle: mitochondria

26
Q

MCAD deficiency

A

Defect in the catabolism of FAs
Defect in medium chain acyl CoA dehydrogenase (MCAD)
Associated organelle: mitochondria

27
Q

Zellweger syndrome

A

Defect in biogenesis of peroxisomes (affects FA catabolism)

28
Q

Infantile Refsum disease

A

Defect in assembly of peroxisomes (affects FA catabolism)

29
Q

X-linked adrenoleukodystrophy

A

Defect in transport of very long chain FAs into peroxisomes

30
Q

Adult Refsum disease

A

Defect in the catabolism of FAs
Defect in degradation of phytanic acid
Associated organelle: peroxisome

31
Q

Describe MCAD deficiency (detailed)

A

Disorder of beta oxidation that impairs breakdown of MCFAs
Leads to secondary carnitine deficiency due to excessive excretion of MCA carnitine in urine
Pts depend on glucose as energy source
Gluconeogenesis impaired due to low activity of pyruvate carboxylase due to low ATP & acetyl CoA

32
Q

What are the 3 important KBs?

A

Acetoacetate, beta hydroxybutyrate and acetone

33
Q

Where are KB produced?

A

In the liver ONLY

34
Q

What are the sources of NADH that are used as a reducing power for FA synthesis?

A

Malic enzyme and PPP

SFM Exam 1 (8 decks)

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