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FOM > FOMweek2a > Flashcards

FOMweek2a Flashcards

1
Q

what is the main storage form of FAs in the body?

A

Triacylglycerols (TAGS)

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2
Q

how is isocitrate dehydrogenase regulated?

A

isocitrate dehydrogenase

**inhibitted by high NADH/NAD+ (high energy conditions)

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3
Q

2 functions of pyruvate/malate cycle?

A

1) transport acetyl CoA from mito to cytosol

2) malic enzyme generates NADPH to power FAS

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4
Q

What is the key regulatory step in FAS? And what is its cofactor?

A

acetyl CoA —> malonyl CoA
catalyzed by Acetyl CoA carboxylase
***biotin is cofactor

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5
Q

How is acetyl CoA carboxylase regulated (feed forward)?

A

Citrate allosterically activates
insulin increases transcription
Xylulose 5-p “ “
Insulin stimulates dephosphorylation, activating ACC

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6
Q

How is acetyl CoA carboxylase regulated (product)?

A

palmitoyl CoA allosterically inhibits
phosphorylation by AMP-PK inhibits
glucagon–>cAMP–>PKA–>inhibitory phosphorylation

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7
Q

HOw does malonyl CoA affect FAS

A

inhibits carnitine polmitoyl transferase I (CPTI) by preventing b-oxidation of new FAs

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8
Q

FAS

A

makes FA

*happens in cytosol & 1 enzyme carries out all steps

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9
Q

General steps in FAS

A

bond formation
reduction
dehydration
reduction

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10
Q

Describe the structure of enzyme fatty acid synthase

A

large enzyme w/ multiple activities

  • *phophopantetheinyl group linked to serine residue
  • *cysteine sidechain = other subunit
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11
Q

Bond formation in FAS

A
  • 2 C’s (acetyl CoA & has w C) added to p-Sulfur
  • then added to growing acyl chain on c-Sulfur
  • subsequent 2 C units come from malonyl CoA
  • **? C group from c-Sulfur transferred onto p-Sulfur chain
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12
Q

1st reduction in FAS

A

keto group reduced to an alcohol

*NADPH+ & H+ powers the rxn

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13
Q

Dehydration in FAS

A

removes water and introduces a C=C double bond

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14
Q

2nd reduction in 1 cycle of FAS

A

C=C double bond is reduced

**also powered by NADPH+ & H+

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15
Q

Dehydration in FAS

A

removes water and introduces a C=C double bond

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16
Q

2nd reduction in 1 cycle of FAS

A

C=C double bond is reduced

**also powered by NADPH+ & H+

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17
Q

unsaturation constrictions

A

*body can unsaturate C-C bonds if they are at least 9 C’s away from w end

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18
Q

2 most important dietary unsaturated FAs?

A

linoleic (18:29, 2)

linolenic (18:39, 12,15)

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19
Q

At what point does FAS stop adding 2 C units?

A

once FA chain has reached 16 C = palmitate

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20
Q

how can arachidonic acid be made?

A
  • cannot be made de novo

* can convert linolenic acid from diet innto arachadonic acid by introducing a C=C, elongating, then adding another C=C

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21
Q

unsaturation process

A

Process:

  • uses Fatty acyl CoA desaturase
  • energy ultimately comes from NADH+ & H+
  • Oxygen is the e- acceptor
  • makes 2 H2o as by products
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22
Q

How do FAs get into cells?

A
  • VLDLs circulate & react with lipoprotein lipase (LPL)
  • LPL cleases of FA so can enter cells
  • get B-oxidized for energy in muscle & stored as TAGs in adipocytes
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23
Q

TAGs are made up of what components?

A

3 FAs linked to a glycerol backbone (glycerol 3-p from glycolysis)

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24
Q

cardiolipin

A
  • component of inner mito membrane
  • formed from phosphatidyl glycerol and CDP diacylglycerol
  • inner mito membrane is rich in cardiolipin
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25
Q

What happens during TAG packaging?

A

TAGs are packaged in Golgi w/ apoprotein B-100 –>VLDL

*form secretory vesicles that fuse to plasma membrane & release VLDL’s into blood

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26
Q

How do FAs get into cells?

A
  • VLDLs circulate & react with lipoprotein lipase (LPL)
  • LPL cleases of FA so can enter cells
  • get B-oxidized for energy in muscle & stored as TAGs in adipocytes
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27
Q

most important sphingolipid

A

sphingophospholipid sphingomyelin!

in myelin sheaths of nerve fibers w/ choline head group

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28
Q

ether glycerolipids

A

aka plasmalogens

  • have ether linkage on 1 C of glycerol backbone
  • 1 FA tail
  • 1 head group
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29
Q

sphingolipids

A

use ceramide instead of glycerol for their backbones

*ceramide is derived from serine & palmitoyl CoA

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30
Q

most important sphingolipid

A

sphingophospholipid sphingomyelin!

in myelin sheaths of nerve fibers w/ choline head group

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31
Q

gangliosides

A

serine backbone
oligosaccharides
NANA

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32
Q

cerebrosides

A

serine backbone

ceramide AND either glucose or galactose attached at hydroxy-methyl group

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33
Q

globosides

A

cerebroside but w/ 2 or more sugars

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34
Q

Adiponectin

A

complementary to leptin

*adiponectin receptors signal thru AMP-PK & PPAR, leading to suppression of FAS & increases FA oxidation

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35
Q

what does ratio of sphingomyelin to dipalmit…… in amniotic fluid tell us

A

indicates gestational term

  • as ratio of phosphatidylcholine to sphingomyelin gets larger = the later in the pregnancy it is
  • in few weeks before birth, ratio may decrease some
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36
Q

how does adipose function as endocrine tissue?

A

release peptide hormones leptin & adiponectin

37
Q

Leptin

A

satiety hormone

  • TAGs are hi, leptin secretion increases
  • leptin acts thru JAK/STAT receptors in hypothalmus to depress appetite
38
Q

cerebrosides

A

serine backbone

ceramide AND either glucose or galactose attached at hydroxy-methyl group

39
Q

globosides

A

cerebroside but w/ 2 or more sugars

40
Q

lung surfactant

A
  • prevent aveolar collapse
  • most abundant: dipalmitoylphosphatidylcholine
  • sphingomyelin is another example
41
Q

what does ratio of sphingomyelin to dipalmit…… in amniotic fluid tell us

A

indicates gestational term

  • as ratio of phosphatidylcholine to sphingomyelin gets larger = the later in the pregnancy it is
  • in few weeks before birth, ratio may decrease some
42
Q

how does adipose function as endocrine tissue?

A

release peptide hormones leptin & adiponectin

43
Q

Leptin

A

satiety hormone

  • TAGs are hi, leptin secretion increases
  • leptin acts thru JAK/STAT receptors in hypothalmus to depress appetite
44
Q

importance of gangliosides, cerebrosides, & globosides

A

severe mental retardation is often caused by inability to break down these molecules
*lysosomal storage diseases

45
Q

+ Nitrogen balance

A

eating more protein then can be excreted

46
Q
  • N balance
A

eating enough protein that all of it can be secreted

47
Q

Nitrogen balance

A

excrete as much N as consumed

48
Q

examples of (-) N balance diseases

A

chachexia, anorexia, kwashiorkor

49
Q

Nitrogen balance equation

A

N balance= N intake-urinary urea N- X

50
Q

what is ammonia metabolism

A

fuel generation from AA

  • derived C –> CO2 & H2o & energy
  • derived N –> Urea & other N products –> urine
51
Q

Which ion can cross membranes; NH4+ or NH3

A

NH3

*in a ammonia solution w/ pH 9.3 the ratio of NH4+ = NH3

52
Q

AA transport into gut lumen/turnover

A
  • use secondary active transport gets AA & Na+ into cell
  • facilitated diffusion gets AA to other tissues
  • Na/K+ pump maintains balance w/in cell (expends lots of energy)
53
Q

Glutamate role & conjugate ketoacid?

A
  • a-ketoglutarate

* amino group pool of the cell, for body to use

54
Q

Aspartate rle & conjugate?

A
  • oxaloacetate

* donates both free and fixed N to the urea cycle

55
Q

Alanine role & conjugate?

A
  • pyruvate
  • in fasted condition when muscle is working =break down of protein, so alanine is releasedin circulation where C-skeleton is used to replacedietary glucose (key role in gluconeogenesis)
56
Q

glutamine role & conjugate?

A
  • glutamate

* transports N to liver for urea cycle

57
Q

Fed State protein digestion & AA turnover

A
  • dietary protein is broken down into AA in the gut
  • insulin promotes storage of protein
  • AAs enter blood, enter muscle cells, & cycle thru AA & protein pools
  • **FAs from VLDL & carbs are main fuel sources
58
Q

Fasted state protein digestion & AA turnover

A
  • glucagon, cortisol, epinephrine & norepinephrine promote mobilization of stored proteins
  • protein from muscles is broken down into AAs in muscles
  • N is donated to glutamine (kidney or gut) or alanine (liver) to be carried outside muscle cell
  • FAs from adipose (freed thru lipolysis) & carbs (gluconeogenesis) are fuel sources
59
Q

glutamate dehydrogenase properties

A
  • makes a-ketoglutarate from glutamate
  • can fix free ammonium!
  • reversible process
  • can use NAD+/NADH or NADP+/NAdPH as e- acceptor/donor
60
Q

function of the urea cycle

A

convert N to urea–>urine excretion

61
Q

regulation of the urea cycle is done by what?

A

arginine, amount of N coming into cycle**, & transcriptional regulation
**big part of regulation

62
Q

how does arginine regulate urea cycle?

A

High arginine:

1) increases NAG synthesis, which allosterically activates CPS-I
2) increases arginase activity

63
Q

Defects in Urea cycle Sx’s & common manifestations

A

*usually seen as hyperammonaemia or hyperglutinaemia
*neurons r targeted because glutamate depletion prevents synthesis of NTs
Sx: FTT, seizures, Ataxia, tremors, irritible, not eating

64
Q

6 enzymes, 6 inherited disorders of the urea cycle, what is common among them all?

A

elevated blood [NH4+]

65
Q

characteristic of urea cycle disorders downstream from CPS-I?

A

elevated urinary orotic acid

66
Q

HHH syndrome

A

*ornithine/citrulline antiporter is defective

67
Q

Ways to diagnose inherited disorders of urea cycle?

A
  • measure free ammonium & BUN (blood urea N)
  • AA panel
  • test for orotic acid in urine
  • plasma citrulline test
68
Q

Tx for inherited disorders of urea cycle?

A
  • low protein diet (often 1st step even when unsure of which enzyme is malfunctioning)
  • N-carbamoylglutamic acid
  • eliminate N in other pathways using: benzoic acid, phenylbutyrate, arginine
  • liver transplant/hepatocyte transusion
69
Q

3 key cofactors in AA metabolism

A
  • PLP: transaminations, deaminations, C chain transfers
  • FH4: 1 C transfers
  • BH4: ring hydroxylations
69
Q

3 key cofactors in AA metabolism

A
  • PLP: transaminations, deaminations, C chain transfers
  • FH4: 1 C transfers
  • BH4: ring hydroxylations
70
Q

nonessential vs. essential AA

A

non-essential: we can make from glucose & N of other AA; 11 of them

  • essential; must get in diet; 9 of them
  • **children need arginine in diet, adults dont
70
Q

Essential AAs

A 
M. V. Pitthall
M=methionine
V=valine
P=phenylalanine
I= isoleucine
T= tryptophan
T=threonine
H=histidine
A=arginine*
L=leucine
L=lysine
70
Q

What AA is made from phenylalanine?

A

Tyrosine

*if phenylalanine (or enzyme phenylalanine hydroxylase) is absent, tyrosine becomes essential

70
Q

What is the pathway to get from 3-phosphoglycerate to serine to alanine?

A

3-phosphoglycerate–>serine–>2-phosphoglycerate –>pyruvate –>alanine
**or serine can make cysteine then pyruvate?

70
Q

What AA uses sulfur from methionine to be synthesized?

A

cysteine

71
Q

AA can be derived from and degraded into what 3 intermediate classes?

A
  • Glycolysis intermediates
  • TCA cycle intermediates
  • Acetyl CoA & Acetoacetate (ketogenic AAs)
72
Q

what AA is derived from pyruvate as glycolytic intermediate?

A

alanine

*reversible process

73
Q

where are ALT & AST normally expressed?

A

only in hepatocytes

*in blood =liver damage

74
Q

What is the pathway to get from 3-phosphoglycerate to serine to alanine?

A

3-phosphoglycerate–>serine–>2-phosphoglycerate –>pyruvate –>alanine
**or serine can make cysteine then pyruvate?

75
Q

what is PAPS?

A

activated sulfur

  • structure similar to ATP
  • sulfate donor
76
Q

What are the 2 ways glutamate is produced?

A

glutamate a-ketoglutarate
*enzyme = glutamate dehydrogenase
OR
a-ketoglutarate can be transaminated by aspartate aminotransferase (AST)

77
Q

Name the 3 ammonium fixing enzymes?

A

1) glutamate dehydrogenase
2) glutamine synthetase
3) carbamoyl phosphate

78
Q

WHat AA can be made from a-ketoglutarate in TCA cycle?

A

*glutamate–>proline, glutamate, &/or arginine

79
Q

WHat AA can be made from oxaloacetate in TCA cycle?

A

*aspartate –>aspargine

80
Q

what happens when a-ketoacid dehydrogenase is inactive? (deficient)

A

branched chain AAs can’t be broken all the way down and are stuck in a-keto (conjugate) structure
*a-ketos build up & are secreted in urine
MAPLE SYRUP URINE DISEASE

81
Q

describe the transition/reactions to get to/from glutamate to glutamine

A

glutamate–>glutamine
*uses ATP & NH4+ & glutamine synthetase

glutamine–>glutamate
*uses H2O & glutaminase

82
Q

what is proline’s special role in protein structure?

A

introduces inflexibility into proteins secondary structure

83
Q

3 branched chain AAs are….

A

valine, isoleucine, & leucine

84
Q

why can thiamin (TTP) be effective treatment for MSUD?

A

TTP is also decarboxylase so can make up for a-keto acid dehydrogenase

FOM (6 decks)

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