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BICH 411 > EXAM 3 > Flashcards

EXAM 3 Flashcards

1
Q

Lipid digestion is mainly

A

triacylglycerols (90%)

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2
Q

10% of lipid digestion is

A

cholesterol, cholesteryl estres, phospholipids, and free fatty acids

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3
Q

what are the important enzymes for lipid digestion

A

pancreatic lipase
colipase
cholesterol esterase

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4
Q

what are the three sections of lipid metabolism

A

digestion
absorption
transport

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5
Q

T/F In lipid digestion it is possible for micelle formation

A

T

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6
Q

In lipid absorption what occurs

A

formation of chylomicrons

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7
Q

List the different lipoproteins

A

chylomicrons
VLDL
LDL
IDL
HDL

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8
Q

what are the major form of energy storage in humans

A

triacylglycerols

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9
Q

The oxidation of fatty acids occurs in a repetitive four step process known as

A

β-oxidation

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10
Q

The processing of dietary lipids (which is primarily fats) occurs in 8 steps:

A
  1. Bile salts mix with fats in the small intestines to form mixed micelles
  2. Intestinal lipases degrade triacylglycerols to form the products of fatty acids and glycerol
  3. Fatty acids are taken up by the intestinal mucosa and converted into triacylglycerols
  4. Reconverted triacylglycerols are packaged with dietary cholesterol to from lipoprotein
    aggregates called chylomicrons.
  5. Chylomicrons are shuttled through the lymph system and the blood stream to various tissues.
  6. In the capillaries, extracellular lipoprotein lipase is activated by apoC-II to hydrolyze the
    fatty acids and glycerol.
  7. The fatty acids and glycerol are then taken up by cells.
  8. In muscle cells the fatty acids can be used, in adipocytes they are reesterfied for storage
    as triacylglycerols.
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11
Q

Triacylglycerols are ____________ and thus must first be ___________ before they can be digested

A

insoluble
emulsified

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12
Q

define emulsification

A

the process by which fat globules are broken down into
droplets,

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13
Q

emulsification is facilitated by

A

bile salts and lipases

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14
Q

Bile salts/Bile acids are what kind of molecules and where are they synthesized and from what are they synthesized

A

amphiphilic molecules synthesized
from cholesterol in liver

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15
Q

Bile salts or bile acids are stored in and where are they released ?

A

the gall bladder
released into the small intestines for digestion purposes

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16
Q

T/F enzymes operate in an insoluble environment

A

F, operate in soluble environments

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17
Q

T/F Lipid Digestion is very minimal in the mouth and stomach

A

T

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18
Q

Stomach contains __________ __________ where fat droplets are

A

gastric lipase
reduced in size

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19
Q

the action of bile salts producing solubilized fat globules like micelles is known as the process

A

emulsification

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20
Q

define emulsification

A

the breaking up of fat globules into smaller emulsion droplets

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21
Q

list the amphiphilic molecules that are present in biles

A

bile salts and phospholipids

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22
Q

Bile salts help solubilize …..

A

fat droplets into micelles

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23
Q

fat globules produced by bile salts are targets for

A

lipases

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24
Q

General characteristics of lipases

A

a class of esterases

hydrolyze glycerol backbones of lipids at specific locations of triacylglycerols (C1 or C3)

produced in the pancreas

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25
Q

define interfacial activation

A

phenomenon that describes rate enhancement of lipase when it contacts the lipid-water
interface.

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26
Q

Pancreatic Lipase is enhanced by a process known as

A

interfacial activation

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27
Q

interfacial activation process requires three molecules/proteins what are they ?

A

bile salts, mixed micelles of
phosphatidylcholine, and colipase

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28
Q

function of colipase

A

facilitates a hydrophobic platform that aids in binding lipid surfaces

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29
Q

T/F Lipase and colipase functions in a 2:1 ratio

A

F, they function on a 1:1 ratio

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30
Q

How does the presence of micelles affect lipase and colipase interactions in the active site

A

causes a change in the complex such that there is no longer access to the active site

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31
Q

Digestion of Lipids produces a mixture of

A

Fatty acids
mono- and diacylglycerols

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32
Q

mono- and diacylglycerols must be
absorbed by

A

mucosal cells in the small
intestines

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33
Q

what can be absorbed by mucosal cells and what can’t?

A

Free monoglycerides
and fatty acids

NOT micelles

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34
Q

How do bile salts also aid in absorption ?

A

by better facilitating diffusion of lipids into mucosal cells

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35
Q

Intestinal fatty acid-binding protein interacts with

A

fatty acids forming a complex inside the intestinal cells, increasing solubility

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36
Q

Lipids are transported as lipoproteins to other tissues for

A

storage and catabolism

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37
Q

Once inside the mucosal cell, what happens to FAs

A

they are reesterfied into TAGs

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38
Q

what molecules are packaged together to form chylomicrons

A

TAGs, cholesterol esters, apoproteins,
and vitamins

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39
Q

name a transport protein in lipids that is part of the exogenous pathways

A

chylomicrons

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40
Q

Chylomicrons are transported via the

A

lymph system

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41
Q

List the Major Structural Components of Lipoproteins

A
  1. Triacylglycerol
  2. Phospholipid
  3. Cholesterol
  4. Apoprotein
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42
Q

what are the building blocks of proteins

A

amino acids

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43
Q

dietary proteins are digested into

A

tripeptides
dipeptides
amino acids

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44
Q

excess amino acids carbon skeletons can be salvaged for

A

GNG
FA biosynthesis
Ketone bodies biosynthesis

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45
Q

what are the three functions of Protein Degradation

A
  1. to store nutrients for times of need in the form of proteins
  2. to eliminate proteins that are harmful to the cell and could accumulate
  3. to permit regulation of cellular metabolism
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46
Q

List 3 proteolytic enzymes

A

Chymotrypsin
Trypsin
elastase
Serine Protease

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47
Q

trypsin

A

cleaves R,K

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48
Q

Chymotrypsin

A

cleaves aromatic A.A W,Y

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49
Q

Serine Protease

A

contains catalytic triad
Asp, His, Ser

cleaves peptide bonds

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50
Q

where does digestion of proteins occur

A

stomach

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51
Q

proteins are cleaved by

A

porteolytic enzymes

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52
Q

elastase

A

cleaves non polar A.A
Gly,Ala

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53
Q

what is the function of storing nutrients for times of need in form of proteins important in

A

muscles

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54
Q

what can the elimination of proteins that are harmful to cells and accumulate cause

A

aggregation issues
mismanaged production of metabolites

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55
Q

what roles does permitting regulation of cellular metabolism via protein degradation have

A

controls level of enzymes directly
control levels of regulatory proteins that impact enzymatic activity

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56
Q

extracellular and intracellular proteins may be disgested by

A

lysosomal proteases

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57
Q

proteins can be degraded by

A

lysosomes
poly-ubiquitination

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58
Q

Proteasome function

A

unfolds proteins in an ATP-dependent process and degrades them

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59
Q

Lysosome characteristics

A

contain over 50 proteases
pH is 5
Nonspecific degradation of proteins
rapid degradation of proteins

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60
Q

T/F lysosomes are Single-membrane vesicles found in all eukaryotic cells

A

F, found in ALMOST all eukaryotic cells

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61
Q

what is the main function of lysosomes

A

degradation of incoming materials of all kinds like organelles proteins and lipids

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62
Q

what is the pH of lysosomes

A

4.5-5

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63
Q

why is it important for pH of lysosomes to be about 5

A

because its roles i degradation and having an acidic environment destabilizes protein folding making it an easier target for degradation

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64
Q

How do cargoes ( proteins) that need to be degraded by lysosomes get there?

A

endocytosis
autophagy

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65
Q

endocytosis for degradation of protein

A

comes from outside the cell crossing membrane to cytoplasm where lysosomes are

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66
Q

define autophagy for degradation of proteins and where it goes

A

comes from inside the cell itself, in the cytoplasm and goes to lysosome

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67
Q

how are products generated from lysosomal degradation released

A

diffuse out of the lysosome

actively transported to cytosol by lysosomal proteins for the re-use by the cell

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68
Q

define non essential amino acids

A

body can biosynthesize it within itself does not come from diet

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69
Q

define essential amino acids

A

A.A that only come from our diets
OR
the breaking down of proteins that are no longer needed that contain the essential amino acids

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70
Q

why is lysosomal protein degradation used in essential amino acids

A

helps us obtain amino acids that come from our diet

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71
Q

amino acids can be ….

A

glucogenic
ketogenic
both

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72
Q

carbon skeletons of glucogenic amino acids are degraded to

A

pyruvate
a-KG
succinyl CoA
fumarate
OAA

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73
Q

carbon skeletons of ketogenic amino acids are degraded to …. and what can they converted to

A

acetyl-CoA

fatty acids or Ketone Bodies

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74
Q

ubiquitination characteristics

A

a selective ATP-dependent ubiquitin mediated pathway

Specific protein degradation

covalent bond formed between target and ubiquitin

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75
Q

T/F ubiquitin is a small 76 residue protein found in ALL eukaryotic cells

A

T

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76
Q

c terminus of ubiquitin function

A

contains a carboxylate side chain that will form a covalent bond to tagged protein

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77
Q

Lysine residue function

A

attachment point for multiple ubiquitin

joining of lys residues form isopeptide bond

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78
Q

what is the tag that gets recognized by proteasome

A

poly-ubiquitin tag

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79
Q

T/F For proteins to be targeted by proteasome it needs a poly-ubiquitinated protein

A

T

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80
Q

name the 3 enzymes of ubiquitination

A

ubiquitin activating enzyme
ubiquitin carrier protein ( ubiquitin conjugating enzyme)
ubiquitin protein ligase

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81
Q

function of ubiquitin activating enzyme

A

utilizes ATP to form thioester bond with C-terminus of ubiquitin

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82
Q

function of ubiquitin carrier protein

A

transfer ubiquitin to a specific cys-thiol bond of E2 ( to maintain energy from thioester bond)

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83
Q

function of ubiquitin protein ligase

A

selects proteins for degradation

forms binding sites for each of 2 substrates

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84
Q

how does ubiquitin protein ligase form binding sites for 2 substrates

A

Binds E2-S-ubiquitin

transfer ubiquitin to lysine residues of target protein by breaking the thioester bond

will continue to go through cycle to get polyubiquitinated

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85
Q

function of Cap in proteasome

A

allows for the entry of poly-ubiquitinated protein into proteasome

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86
Q

what is the fate of ubiquitinated proteins

A

proteasomes

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87
Q

ubiquitin marks proteins for

A

proteasome degradation

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88
Q

which proteins get ubiquitinated?

A

N-terminal amino acid with shorter half lives

PEST sequence ( pro-glu-ser-thre)

regulated ubiquitination ( slide 17)

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89
Q

KFERQ- Motif is specific for what kind of degradation

A

lysosomal

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90
Q

lost from tissues that atrophy affects protein degradation how?

A

increases the rate of degradation

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91
Q

where can the KFERQ-Motif sequence be found

A

in cytosolic proteins as a target for lysosomal degradation under fasting conditions as part of autophagy

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92
Q

the KFERQ sequence is recognized by

A

chaperone mediated autophagy pathways

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93
Q

function of chaperone mediated autophagy in lysosomal degradation

A

is a recognition protein that will look for specific sequence to bring it to lysosome so that autophagy can occur

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94
Q

KFERQ meaning in terms of AA

A

K and R= up to 2 positively charged residues (R,K)

F = up to 2 hydrophobic residues ( I,F,L,V)

E = single negatively charged residue (E,D)

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95
Q

define transanimation

A

transfer of amino groups

moving it from one molecule to another

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96
Q

aspartate aminotransferase function in matrix

A

OAA makaes a-KG while Glutamate and a-KG make aspartate

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97
Q

aspartate amino transferase functino in intermembrane space

A

takes apartate and a-KG to regenerate glutamate and OAA

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98
Q

what molecule do transaminases use ( known as E)

A

PLP (pyridoxal-5-phosphate)

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99
Q

PLP is covalently attached to

A

enzyme lysyl residue via a Schiff’s base

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100
Q

why is a schiff’s base conjugate to the pyrimidine ring in transaminases

A

it is the center of activity

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101
Q

as an amine is transferred PLP becomes

A

pyridoxamine-5-phosphate (PMP)

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102
Q

transaminases are a class of enzymes that utilize what kind of mechanism

A

ping pong mechanism

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103
Q

purpose of ping pong mechanism in transaminases

A

to transfer amino groups from amino acids to for a-keto acids and new A.A

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104
Q

Transamination reactions occur in two stages what are they

A

conversion of an A.A to a-keto acid

Conversion of an a-keto acid to an A.A

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105
Q

T/F transamination is a key reaction of AA metabolism and requires PLP

A

T

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106
Q

increased concentrations of specific transaminases high in the blood are indicative of

A

Heart attack
Liver damage

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107
Q

how can the organs such as heat and liver show damage in amino acid metabolism

A

leak intracellular contents to the blood stream

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108
Q

where can glutamate DH be found

A

in the mitochondria

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109
Q

Glutamate DH in terms of usage of electron acceptors

A

only known enzyme that can use either NAD+ or NADP+ as electron acceptors

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110
Q

how does Glu DH remove NH4+

A

Oxidative deamination

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111
Q

T/F Glu DH has a low Km for Glu , meaning high affinity

A

F, it has a High Km therefore a low affinity for Glu

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112
Q

T/F Glu DH is a reversible enzyme

A

T

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113
Q

Glutamate DH is a regulatable enzyme, under what conditions will it be inhibited and when will it be activated

A

High energy , GTP and NADH inhibit

Low energy, ADP and NAD+ activates

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114
Q

what is the intermediate GDH undergoes in its mechanism

A

a-Iminoglutarate

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115
Q

Ammonia intoxication produces

A

a comatose state

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116
Q

T/F Ammonia is not toxic to animals

A

F, it is

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117
Q

high concentrations of ammonia shift equilibriums to

A

favor glutamine

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118
Q

Glutamate and its derivative GABA are NT, the shift in equilibrium does what

A

lowers the concentration of these NT

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119
Q

Draw the Urea Cycle, include name of enzymes , and structures

A

slide 37 of amino acid metabolism

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120
Q

In the liver, energy is produced in the form of glucose thus the formation of ____________ is favored, important for _________ __________ as ________

A

pyruvate
nitrogen removal
urea

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121
Q

Draw the cycle of using amino acid alanine in the muscle and liver ( Hint: similar to Cori Cycle)

A

slide 44 in amino acid metabolism

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122
Q

ornithine is also used in ___________ _____________ - involves nitrogen

A

polyamine biosynthesis

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123
Q

Inhibition of polyamine biosynthesis effects

A

stops/diminishes cell growth

making it an attractive drug target of fast acting cancers

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124
Q

What other 3 molecules can ornithine be converted to

A

Putrescine
Spermidine
Spermine

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125
Q

what is the mitochondrial enzyme that is usually the rate limiting step of Urea Cycle

A

Carbamoyl Phosphate Synthetase I

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126
Q

What activates the carbamoyl P synthetases I

A

high levels of N-acetyl Glutamate
high levels of amino acid glutamate
high levels of urea and ammonia

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127
Q

acetyl-CoA + Glu –>

A

N-acetyl glutamate

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128
Q

mutations which reduce efficiency of urea cycle can lead to

A

hyperammonemia
lethargy
mental retardation

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129
Q

how can mutation that reduce efficiency of urea cycle be treated

A

change in diet
adding NAG ( N-acetyl-glu) analogs
increasing arginine

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130
Q

what enzyme is involved:

2 ATP + HCO3- + NH3 –> carbamoyl P + 2 ADP + 2 Pi

A

carbamoyl P synthetase I

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131
Q

name the enzyme that is a 3 step reaction that is the rate-limiting step for urea formation

A

carbamoyl P synthetase I

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132
Q

Describe the three step reaction of carbamoyl P synthetase I

A
  1. ATP is used to activated bicarbonate to form carboxyphosphate
  2. Ammonia (NH3) attacks carboxyphosphate to form carbamate and inorganic phosphate
  3. A second ATP serves as a phosphate donor to form carbamoyl-phosphate
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133
Q

ornithine transcarbamylase function

A

allows for the formation of citrulline by using carbamoyl phosphate and ornithine

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134
Q

what molecule that is part of the urea cycle gets exported from the matrix into cytosol

A

citrulline

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135
Q

What is the cost of argininosuccinate synthetase in the urea cycle

A

2 ATP

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136
Q

In the urea cycle , what serves as the source for the second nitrogen

A

Aspartate

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137
Q

describe the reaction of argininosuccinate synthetase in the urea cycle

A

Aspartate comes into play in this enzyme
AND
Citrulline is activated by ATP, and PPi is hydrolyzed to drive reaction

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138
Q

function of arginosuccinase in the urea cycle

A

removes the nitrogen from aspartate forming arginine and fumarate

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139
Q

what enzyme facilitates the formation of argininosuccinate

A

argininosuccinate synthetase

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140
Q

what amino acid is the precursor of urea

A

arginine

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141
Q

function of arginase

A

uses hydrolysis to form urea as a waste product and forms ornithine
(gets transported back to matrix to go through cycle again)

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142
Q

Arginine –> urea + ornithine

catalyzed by what enzyme

A

arginase

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143
Q

arginosuccinate –> Arg + fumarate

catalyzed by what enzyme

A

arginosuccinase

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144
Q

citrulline + Asp –> arginosuccinate

catalyzed by what enzyme

A

arginosuccinate synthetase

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145
Q

what are the fates of fumurate apart from the urea cycle

A
  1. reenters mitochondria to malate-aspartate shuttle to promote TCA
  2. converted to malate via fumarase to OAA cia malate DH —> GNG
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146
Q

why is the formation of alanine and a-KG favored in the muscle

A

because amino acid biosynthesis allows for muscle repair

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147
Q

tyrosine is formed by

A

phenylalanine hydroxylase

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148
Q

Lipids are transported as lipoproteins to other tissues for

A

storage or catabolism

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149
Q

list the different types of lipoproteins based on their protein content ( low to highest)

A

chylomicrons
VLDL
IDL
LDL
HDL

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150
Q

chylomicrons are composed of

A

dietary TAGs, cholesterol, and cholesteryl esters

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151
Q

where are chylomicornos formed

A

in the intestinal mucosal cells after absorption

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152
Q

describe the exogenous pathway as it relates to chylomicrons

A

gets released to intestinal lymph for transport through lymphatic vessels to large veins for delivery throughout the body

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153
Q

what lipoproteins are synthesized by the liver to transport internally produced triacylglycerols and cholesterol from the liver to the tissues

A

VLDL , IDL, LDL

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154
Q

what lipoprotein transportscholesterol and other lipids to the liver from the
tissues

A

HDL

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155
Q

function of VLDL

A

transport TAGs and FAs from liver to tissues

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156
Q

where are VLDLs released

A

to the blood stream as part of the endogenous pathways

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157
Q

where is VLDL biosynthesized and what does it use

A

biosynthesized in the liver using cholesterol-rich chylomicron remnants and TAGs

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158
Q

what two lipoproteins are deliverers of triacylglycerol to cells in the body

A

Chylomicrons and VLDL

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159
Q

chylomicrons and VLDL have the same function how are they different?

A

Chylomicrons
- are formed in intestinal epithelial cells for transport
- dietary triacylglycerols are delivered to muscle cells and adipose tissue
- exogenous pathway

VLDL
- remnants of chylomicrons, as VLDL is biosynthesized in the liver
- part of endogenous pathway
- release to the blood stream

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160
Q

what lipoprotein is known as the transition particle between TAG transport and cholesterol transport

A

Intermediate density lipoprotein (IDL)

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161
Q

How is IDL formed

A

from the remnants of VLDL after removal of TAGs

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162
Q

how can HDL form more LDL

A

gets reabsorbed by liver
picking up cholesteryl esters from HDL

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163
Q

function of LDL

A

delivers cholesterol to cells where it is used in membranes ,

biosynthesis of bile salts in the liver, and

synthesis of steroid hormones

MAJOR cholesterol carrier in the blood stream

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164
Q

what lipoprotein is known as the major cholesterol carrier in the blood stream

A

low density lipoprotein

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165
Q

As VLDL is stipped of TAGs, they are remodeled in the liver to become ……..

A

IDL and ultimately LDL , part of endogenous pathway

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166
Q

what are the major contributor of HDL

A

extra-hepatic cells

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167
Q

why are extra-hepatic cells the major contributors of HDL

A

cells cannot metabolize cholesterol

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168
Q

The HDL precursor is biosynthesized and secreted by

A

liver and small intestine

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169
Q

Lecithin- cholesterol
acyltransferase

A

an enzyme activated by
apolipoprotein A-1 that converts
cholesterol to cholesterol-esters

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170
Q

what is the only place where cholesterol can be
consumed for production of bile
acids

A

liver

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171
Q

what lipoprotein is involved in transport of cholesterol from the tissues to the liver – sometimes called reverse cholesterol transport

A

High density lipoprotein

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172
Q

Where is HDL biosynthesized and where is it released

A

in the liver and intestines for release in blood stream as a protein rich particle

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173
Q

Functions of HDL

A

used for cholesterol recovery ( cleans up excess cholesterol from blood for excretion)

delivers cholesterol to steroidogenic tissues ( adrenal glands, ovaries, testes)

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174
Q

define apoproteins and their functions

A

protein portion of lipoproteins ( coating surface) that dictate interactions

w/o lipid association

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175
Q

list the three examples of apoproteins

A

ApoA-1
ApoB-100
ApoE

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176
Q

Apolipoprotein A-1 (ApoA-1) binding occurs in ….. and what is their effect

A

chylomicrons and HDL
adds a high degree of hydrophilicity

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177
Q

what is known as a homotetramer producing a structure that can ideally wrap around and HDL particle

A

ApoA-1

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178
Q

Function of ApoAI

A

help clear fats and cholesterol from
white blood cells in arterial walls, helping ensure health of white blood cells.

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179
Q

ABCG1 transporter function

A

role in lipid homeostasis by controlling both tissue lipid levels and efflux of cellular cholesterol to HDL

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180
Q

ABCA1 transporter function

A

mediates efflux of cholesterol and phospholipids to lipid-poor apolipoproteins like ApoAI to form nacent HDL

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181
Q

how does ApoA1 intereact with HDL

A

it facilitates interactions with SR-B1 receptor within HDL at the liver

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182
Q

once ApoAI binds HDL to SR-BI and transfers its component lipids to the cell what occurs

A

Depleted HDL dissociates from the receptor and re enters circulation for scavenging cholesterol

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183
Q

LDL contains what kind of apolipoprotein

A

ApoB-100

in a ratio 1:1

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184
Q

what is LDL major role

A

major cholesterol carrier in the blood stream

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185
Q

function of ApoB-100

A

plays a role in LDL-receptor-mediated endocytosis

covers half the surface of LDL

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186
Q

LDL-receptors that target ApoB-100 are

A

transmembrane glycoproteins

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187
Q

the LDL-receptors specifically target ApoB-100 in

A

clathrin-coated pits that produce a clathrin-coated vesicle for endocytosis

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188
Q

ApoB-100 and cholesteryl-esters are hydrolyzed producing

A

amino acids , fatty acids, and cholesterol

189
Q

Apolipoprotein E binds to

A

VLDL and chylomicrons

190
Q

As VLDL is converted to LDL via IDL, what can remain bound to IDL

A

ApoE

191
Q

Function ApoE

A
  • enhance binding to LDL-receptors in liver and CNS
  • facilitate the transfer of cholesterol to neurons in CNS
192
Q

defects in ApoE4 have been correlated/linked to

A

increased chances of developing Alzeihmer’s

193
Q

stored fats are mobilized for

A

energy production (in animals)

194
Q

activity of the enzyme hormone-sensitive triacylglycerol lipase is regulated by

A

high glucagon and epiniphrine levels

195
Q

function of albumin

A

aids in transport of the predominantly hydrophobic FA coming from free FA and glycerol entering the bloodstream

196
Q

High glucagon and epinephrine levels activate

A

cAMP dependent protein kinase A

197
Q

once levels of cAMP are increased what occurs in terms of lipid metabolism

A

lipid droplets are more accessible to hormone-sensitive lipase

198
Q

the rate of HSL hydrolysis dictates

A

rate of diffusion of FA passing across the adipocyte membrane to bloodstream

199
Q

FA transported in blood via

A

serum albumin and enters muscle cells via FA transporter

200
Q

FA are catabolized in

A

mitochondria

201
Q

CD36 function

A

directly related to influx of FAs into the cell , they recognize FA chains

202
Q

carnitine carries _______ _______ into the ___________ for ________

A

Fatty acids
mitochondria
oxidation

203
Q

carnitine acyl-transferase I is inhibited by

A

High levels malonyl-CoA used for FA synthesis

204
Q

once in the cytosol of muscle cells, FAs

A

must be activated and requires 2ATP investment for activation

205
Q

Fatty acids in the cytosol of the cell must be activated by the attachment of

A

Coenzyme A

206
Q

The priming reaction, or addition of CoA,in B ox is catalyzed by

A

acyl-CoA synthetases

207
Q

function of acyl-CoA syntheetase

A

condenses FAs wtih CoA with simultaneous hydrolysis of ATP to AMP and PPi

208
Q

T/F Formation of CoA ester is inexpensive energetically

A

F, it is expensive energetically

209
Q

why does the activation of FA require the investment of 2 ATP

A

reaction barely break with 1 ATP hydrolysis

BUT

subsequent hydrolysis of PPi drives rxn forward

210
Q

what enzyme has acyl-adenylate intermediate in its mechanism

A

Acyl CoA Synthetase

211
Q

draw acyl-coA synthetase mechanism

A

slide 35 and 37 of lipid metabolism

212
Q

activated acyl -CoA occurs in the _____________, but the process of fatty acid oxidation within the __________

A

cytosol
mitochondria

213
Q

carrier carnitine function

A

accepts the acyl portion of activated FA through a transesterification reaction

214
Q

what catalyzes the transesterification reaction in carnitine transport

A

carnitine palmitoyl transferase

occurs in outer mitochondrial membrane

215
Q

what is released after the reaction carnitine palmitoyl transferase I

A

releases CoA in cytosol for use in more activation reactions

216
Q

products from B-ox feed into

A

citric acid cycle
ETC/Oxidative Phosphorylation

217
Q

define B-oxidation

A

the process of FA degradation in 2C units through an oxidative process involving the B-carboxyl group

218
Q

Define Ketone bodies

A

special source of fuel and energy for ceratin tissues

219
Q

some of the acetyl-CoA produced by FA ox in liver mitochondria is converted to

A

acetone
acetoacetate
b-hydroxybutyrate

( aka ketone bodies)

220
Q

Ketone bodies are cource of fuel for

A

brain - during starvation
heart - fat burning mode
muscle

221
Q

T/F ketone bodies are transportable forms of acetyl-CoA

A

T

222
Q

why are ketone bodies useful as a special energy source

A

they are transportable forms of acetyl-CoA

223
Q

Location of Ketogenesis

A

occurs in the liver mitochondria

224
Q

first step in ketone body biosynthesis used what enzyme and where have we seen this before

A

thiolase (acetyl-CoA acetyltransferase)

reverse of last step in B-ox

225
Q

what is a key intermediate in both ketone body and cholesterol biosynthesis

A

HMG-CoA

(hydroxymethylglutaryl-CoA)

226
Q

what enzyme is the first committed step in the ketone body biosynthesis

A

HMG-CoA lyase

227
Q

function of thiolase in ketogenesis

A

combines 3 acetyl CoA molecules allowing for release and production of energy in the form of CoA

228
Q

what are the final two products made for HMG-CoA lyase

A

acetoacetate and acetyl CoA

229
Q

Draw B-Hydroxy-B-methylglutaryl-CoA

A

Slide 5 of KB

230
Q

where are acetoacetate and acetyl CoA released

A

acetyl CoA remains in the liver
acetoacetate gets released in the bloodstream

231
Q

what are the fates of acetoacetate

A

gets converted to B-hydroxybuterate

can get converted to acetone

232
Q

how does acetoacetate convert to B-hydroxybutyrate

A

redox reaction catalyzed by B-hydroxybutyrate DH

233
Q

how does acetoacetate convert to acetone

A

undergoes a non-enzymatic decarboxylation since it is a B-keto acid

234
Q

what dictates the fates of acetoacetate

A

based on the ratio of NADH/NAD

235
Q

T/F the conversion to acetoacetate and D-B-Hydroxybutyrate is irreversible

A

F, it is reversible

236
Q

during pro-longed periods of fasting, where glucose is limiting, the energy source of the body becomes? what pathway will kick in

A

breakdown of products of fats and thus KB

GNG will kick in to meet brains demands

237
Q

T/F Ketone bodies are used for energy

A

T

238
Q

KB are transported from the liver to other tissues in the bloodstream where _____________ and ___________________ can be converted to _______________ to produce energy

A

Acetoacetate
B-hydroxybutyrate
Acetyl CoA

239
Q

when does the brain use ketone bodies

A

starvation

240
Q

the heart gets much of its energy from

A

KB but also uses alot of FAs

241
Q

why do we use KB for energy and not FA

A

KB are fast acting source for energy because of its quicker conversion to acetyl CoA , FA takes longer

242
Q

fates of acetone

A

incorporated into lipid and skeleton structures

get excreted out as urine

gets exhaled

243
Q

if NADH levels are higher than NAD+ what does this tell us in terms of BHB and acetone

A

B-hydroxybutyrate will be higher

244
Q

fates of B-hydroxybutyrate

A

excreted as urine
used in metabolism by oxidative phosphorylation

245
Q

function of B-hydroxybutyrate DH

A

takes any B-HB that has been generate and converts it it AcAc

uses NAD+ forming NADH as the electron acceptor

246
Q

3-ketoacyl-CoA transferase function

A

uses succinyl CoA as a substrate producing acetoacetyl CoA and succinate

247
Q

how are ketone bodies brought into the cell

A

monocarboxylate transporters

248
Q

where does ketolysis occur

A

happens in other cells and NOT in the liver

249
Q

liver lacks what enzyme thats important for ketolysis

A

3-ketoacyl CoA Transferase

250
Q

why is it important for the liver to lack 3-ketoacyl CoA Transferase

A

liver is able to make its own energy and utilize other sources through B-Ox

so we want out other cells to have acces to KB for energy

251
Q

what enzyme ensure that ketolysis will occur in target cells

A

3-ketoacyl CoA Transferase

252
Q

define ketosis

A

accumulation of excess ketone bodies

253
Q

define ketoacidosis

A

even larger amount of ketone bodies accumulate lowering the bodies pH to acidic levels

254
Q

define diabetic ketoacidosis

A

associated with diabetic who cant use glucose in high amounts to keep up with energy demands , increasing the KB and acidic levels in blood stream

255
Q

alcholic ketoacidosis

A

messe with the NADH/NAD+ polls

256
Q

alcohol characteristics in ketoacidosis

A

diminishes hepatic GNG
decreases insulin secretion
increases lipolysis
impaired FA ox and ketogenesis

257
Q

define nutritional ketosis

A

a diet high in fat and protein but low in carbs ( below 20g)

258
Q

In nutritional ketosis it relies on what for glucose in the brain ? what about peripheral tissues

A

liver to keep up with glucose for the brain

fats and KB are supplied to peripheral tissues

259
Q

if glucagon and cAMP levels are high and insulin levels are low what is occuring in nutritional ketosis

A

enhances glycogen breakdown and GNG activation

decreases lipid synthesis

260
Q

what can a ketogenic diet that’s used as part of dietary therapy helpful in treating

A

epilepsy
migraines
dementia
autism

261
Q

define anaerobic exercise and what is its primary fuel

A

shorter bursts of energy such as weight training/high intensity interval training

carbs are used as the primary fuel

262
Q

define aerobic exercise and what is its primary fuel

A

cardio excercise , low intensity and steady state for fat burning

relies on Fats

263
Q

what causes a decrease in blood pH in ketoacidosis

A

increased concentration of acetoacetate and D-B-hydroxybutyrate in ionized form

264
Q

cholesterols are precursors of

A

bile
steroid hormones
atherosclerotic plaques

265
Q

cholesterol has structural and metabolic roles what are they

A

modulates membrane fluidity
serves as precursors for many molecules

266
Q

atherosclerotic plaques are cause by _________ & what are the potential side effects

A

aggregation
heart attack and stroke

267
Q

why is cholesterol prone to aggregation

A

it has a high degree of hydrophobicity

268
Q

be able to recognize cholesterol

A

slide 2 on cholesterol powerpoint

269
Q

Where can the only hydrophilic region of cholesterol be found

A

A ring of cholesterol

270
Q

what makes cholesterol rigid

A

4 fused rings

271
Q

what makes cholesterol weakly amphilic

A

lone hydroxyl group in A ring

272
Q

cholesterol is synthesized from __________ ______ that comes from ________________

A

acetyl CoA
isoprene units

273
Q

define isoprene units

A

5 C skeletons

274
Q

fates of isoprene units

A
  1. cholesterol
  2. Fat Soluble Vitamins; Ubiquinone;hormones;carotenoids
275
Q

how does cholesterol maintain fluidity of membranes

A

helps maintain order at high temps

helps offer a better barrier at low temps

276
Q

how does cholesterol maintain order at high temps

A

offers rigidity for increased movement of FA tails

277
Q

how does cholesterol offer a better barrier at low temps

A

increases interactions when movement stops at lower temps

phase change from fluid to gel-like solid

278
Q

first step in cholesterol synthesis is the same as ketone body synthe except that it occurs in

A

cytoplasm

279
Q

the second step in cholesterol is also same as KB , what occurs in this step in terms of cholesterol synthesis

A

uses HMG-CoA synthetase and attaches 2 C unit form acetyl Coa and forms HMG-CoA

280
Q

draw HMG-CoA Synthase mechanism

A

slide 10 form cholesterol

281
Q

what is the first committed step toward isoprene unit synthesis

A

HMG-CoA reductase

282
Q

function of HMG-CoA reductase( cholesterol)

A

uses 2 NADPH to form mevalonate , resulting in a loss of CoA

283
Q

Look at the mechanisms for HMG-Reductase I and II

A

slide 13 and 14 of cholesterol

284
Q

List 6 characteristic of Cholesterol Biosynthesis

A
  1. occurs in the liver
  2. begins in the cytosol with synthesis of mevalonate from acetyl Coa
  3. First step is a thiolase rxn
  4. second step makes HMG-CoA
  5. Third step - HMG-CoA reductase
  6. HMG-CoA reductase is site of action of cholesterol

slide 16 on cholesterol ppt

285
Q

define statin inhibitors of HMG-reductase

A

effective inhibitors that mimic the transition state

286
Q

what enzyme is the principal site of regulation in cholesterol synthesis

A

HMG-CoA Reductase

287
Q

How is HMG-CoA reductase regulated

A
  1. Phosphorylation by cAMP (low energy status)
  2. degradation via ubiquitin
  3. gene expression
288
Q

how does phosphorylation by cAMP affect HMG-CoA reductase

A

inhibits reductase therefore stopping biosynthesis pathway

289
Q

if we have high levels of cholesterol how does this effect HMG-CoA Reductase

A

degrades HMG-CoA stopping biosynthesis

290
Q

if we have high levels of gene expression how does this affect HMG-CoA

A

activates cholesterol biosynthesis , activates reductase

291
Q

function of mevalonate-5-phosphotransferase

A

utilizes ATP as a phosphate donor to attach it to mevalonate to form phosphomevalonate

292
Q

what enzyme of cholesterol synthesis begins the process of adding PPi tail

A

mevalonate-5-phosphotransferase

293
Q

Thiolase utilizes an _______________ mechanism to allow for activation of nucleophilic attacks
with the reaction driven by the release of _________ ( cholesterol biosynthesis)

A

acid-base
CoA

294
Q

function of phosphomevalonate kinase in cholesterol biosynthesis

A

adds a second phosphate using ATP as a donor forming 5-pyrophosphomevalonate

295
Q

what enzyme in cholesterol biosynthesis completes the synthesis of PPi tail ( high energy leaving group)

A

phosphomevalonate Kinase

296
Q

function of pyrophosphate mevalonate decarboxylase

A

forms isoprene unit using energy from decarboxylation and couple it with ATP

297
Q

how does ATP fit into the reaction catalyzed by pyrophosphomevalonate decarboxylase

A

as decarboxylation occurs we leave behind e- and OH group has to leave so it occurs via ATP

w/o ATP it wouldn’t be enough to hydrolyze P bond

298
Q

product form from pyrophosphomevalonate decarboxylase

A

isopentenyl pyrophosphate

298
Q

isopentenyl pyrophosphate is isomerized to produce dimethylallyl
pyrophosphate via what enzyme

A

isopentenyl pyrophosphate isomerase

298
Q

T/F hydrolysis of ATP drive long chain of otherwise unfavorable e- transfers in third step cholesterol biosynthesis

A

F, it is the fourth step

299
Q

what are the two isoprene units forms in cholesterol biosynthesis

A

isopentenyl pyrophosphate
dimethylallyl pyrophosphate

300
Q

function of isopentenyl pyrophosphate isomerase

A

allows for the two isoprene units to be easily interconverted

301
Q

what allows for the 5C units to easily form long chains/ condense

A

via cleavage and hydrolysis of PPI

302
Q

function of prenyltransferase, product formed ( give number of C) , and direction of reaction

A

combines 2 5C units by releasing PPi
to form geranyl pyrophosphate (10C)

moves in head to tail direction

303
Q

what can prenyltransferase also do other than condensing a 5C units to forming a 10 C unit

A

releases another PPi
AND
combines geranyl pyrophosphosphate (10C) and isopentyl pyrophosphate (5C) to produce farnesyl-pyrophosphate ( 15C)

head to tail

304
Q

head to head condensation to form squalene with the use of NADPH is catalyzed by what enzyme

A

squalene synthase

305
Q

function of squalene synthetase

A

NADPH dependent enzyme, that catalyzes the condensation of two farnesyl pyrophosphates
to produce squalene

306
Q

squalene from mevalonate is driven by

A

ATP hydrolysis, decarboxylation and PPi hydrolysis

307
Q

condensation of 3 mevalonate forms

A

farnesyl PPi

308
Q

two farnesyl PPi link to form

A

squalene

309
Q

function of squalene epoxidase

A

catalyzes addition of an epoxide ring forming 2-3 oxidosqualene

310
Q

cleavage of epoxide ring leads to

A

cascade of e- movement that conversts polyisoprene into lanosterol

311
Q

squalene monooxygenase converts

A

squalene to squalene-2,3-epoxide

312
Q

a ____________ converts the epoxide to lanosterol

A

cyclase

313
Q

the conversion of squalene to epoxide occurs in

A

the ER membrane

314
Q

acyl Coa cholesterol transferase

A

transfers acyl CoA moeitey to cholesterol at C3 and forms and ester bond

315
Q

cholesterol is exported form liver as

A

VLDL

316
Q

ApoC-II activates

A

extracellular lipoprotein lipase in capillaries and unloads TAG

317
Q

TAG are unloaded via

A

ApoC-II and Lipoprotein

318
Q

regular, vigorous exercises raises ______ and a low fat diet that avoids red meat reduces __________ ___________ __________

A

HDLs
serum cholesterol levels

319
Q

ApoB-100 binds _______ ____________ and delivers ______________ to peripheral tissue

A

LDL receptors
cholesterol

320
Q

in response to the bodies response to high cholesterol levels , when decreased HMG-CoA reductase causes

A

decrease mRNA levels
increase enzyme degradation

both of these will decrease cholesterol synthesis

321
Q

in response to high cholesterol levels, there is a decreased LDL receptors which causes

A

reduces uptake of cholesterol in the blood

322
Q

In response to high cholesterol levels, when some cholesterol is shipped back to liver via HDL how is this done

A

activates ABCA1 transport protein which binds cholesterol inside the cell and passes it out to blood stream in form of HLDL

in liver some cholesterol is turned to bile transported to the intestine

323
Q

what is the bodies response when there is high cholesterol levels

A

decrease in cholesterol biosynthesis
decrease in HDL levels
decrease in bile salts
decrease in absorption
decrease in LDL receptors
increase in VLDL receptors

324
Q

what happens to cholesterol in excess VLDL and LDL

A

some deposited on walls of blood vessels forming plaque

atherosclerosis

325
Q

define familial hypercholesterolemia FH

A

genetic lack of LDL receptors

326
Q

define tangier disease

A

lack of ABCA1 transporter
causing a decrease in HDL receptors

327
Q

The consequence of the loss of LDL
receptors is two-fold:

A

levels of LDL (and VLDL) rise in the blood stream and
(2) the uptake of LDL in
extrahepatic cells decreases, leading to a decrease in HDL

328
Q

Diminished levels of HDL coupled with increased levels of
VLDL/LDL lead to a buildup of cholesterol that leads to

A

a buildup of cholesterols that lead to pro-inflammatory response, leading to calcification of plaques in arteries and blood vessel damage

329
Q

many drugs that lower serum cholesterol are

A

mevalonate analogs that inhibit HMG-CoA reductase

330
Q

tricarboxylate transport system function

A

transfers acetyl-CoA in form of citrate into the cytosol for fatty acid synthesis

331
Q

FA synthesis begins with

A

carboxylation of acetyl-CoA to generate malonyl-CoA

332
Q

fatty acid synthase enzyme function

A

carries out seven reactions and lengthens a fatty acid two carbons at a time

333
Q

function of elongases

A

add extra carbons to the FA

334
Q

function of desaturases

A

allows for DBs to form

335
Q

TAGs are synthesized from

A

from glycerol and fatty acids

336
Q

what is the major way that acetyl CoA gets transported out of the cell in the form

A

of citrate

337
Q

how is citrate formed

A

combining acetyl CoA with OAA in TCA via citrate synthase

338
Q

how does pyruvate get converted to OAA

A

anaplerutic reaction using pyruvate carboxylase

339
Q

what is the major source of cytosolic acetyl CoA

A

Citrate via ATP citrate lyase

340
Q

what serves as the building blocks for malonyl-CoA

A

Acetyl CoA

341
Q

Acetyl-CoA is generated in the mitochondrion by either

A

pyruvate dehydrogenase complex or beta oxidation

342
Q

ATP-citrate lyase function

A

catalyzes the
conversion of citrate to oxaloacetate and acetyl-CoA in the cytosol

343
Q

what is going to happen when our energy levels are high

A

decrease in TCA
AND
increase in citrate

344
Q

draw the tricarboxylate transport system

A

slide 6 on FA biosynthesis

345
Q

to synthesize lipids must export

A

acetyl CoA to cytoplasm via citrate

346
Q

why not stop OAA conversion at malate in the cytosol

A

we want increase in NADPH level for reductive biosynthesis

347
Q

acetate units need for FA biosynthesis are activated by

A

the formation of Malonyl-CoA at the expense of ATP

348
Q

driving force of the condensation reaction is the ……….. in FA biosynthesis

A

exergonic decarboxylation of Malonyl CoA

349
Q

chain elongation stops at

A

palmitoyl CoA

350
Q

what enzyme commits acetate to FA synthesis

A

acetyl-CoA carboxylase

351
Q

what must occur first to be committed step in FA biosynthesis

A

carboxylation of acetyl CoA to form malonyl CoA

352
Q

what are the three enzymes of ACC

A

biotin carboxyl carrier
biotin carboxylase
transcarboxylase

353
Q

what enzyme utilizes biotin and ATP to activate CO2 for carboxylation of acetyl-CoA

A

acetyl CoA carboxylase

354
Q

draw the acetyl coA carboxylase mechanism

A

slide 11 FA biosynthesis

355
Q

protomers

A

inactive/inhibit
T state in ACC

356
Q

polymers

A

multiple protomers together
R state ( active )

357
Q

what is positive allosteric ACC enzyme

A

Citrate

358
Q

what is the negative allosteric ACC enzyme

A

Palmitoyl CoA

359
Q

what are the effects of citrate on ACC

A

it activates it
favors R state and therefore favors polymer formation

360
Q

what are the effects of Palmitoyl CoA on ACC

A

inhibits ACC
stabilized T state therefore in favors protamers

361
Q

ACC hormonal control involves

A

phosphorylation of Ser79

362
Q

hormonal control of ACC is catalyzed by

A

AMP-dependent protein Kinase that is part of cAMP independent pathway

363
Q

AMPK effec on ACC

A

leads to inactivation of ACC

364
Q

when levels of glucagon and epinephrine are high how does this affect ACC

A

activates protein kinase A which phosphorylates ACC leading to inhibition

365
Q

T/F ACC can exist in different isoforms based on tissue specificity

A

T

366
Q

Adipose tissue contains what kind of ACC isoform

A

cytosolic ACC1 where FA biosyn occurs

367
Q

tissues that lack FA biosyn have much higher ratios of

A

ACC2

368
Q

Function of ACC2

A

produces malonyl CoA as a way to inhibit the carnitine transporter so FA cant enter matrix for B ox and differe stop FA biosynthesis

369
Q

why does the liver have both ACC1 and ACC2 forms

A

relies on its own ability to do its own FA biosynthesis and relies on FATS for energy source

370
Q

define nonalcoholic fatty liver disease

A

hepatic accumulation of excess triglycerides

371
Q

what is the leading cause of morbidity and mortalinty in atients with NAFLD

A

cardiovascular disease

372
Q

effects of high insulin levels on ACC

A

activates ACC
Increasing FA biosynthesis
Increase energy

373
Q

Compare and contrast B-ox and FA biosynthesis

A

B-Ox:
- occurs in matrix
- tagged by CoA as carrier group
- e- flow through ox. of carbon compounds to produce e- carriers NADH and FADH2
- in the l configuration
- Acetyl CoA used as C2 unit

FA:
- occurs in cytoplasm
- tagged by ACP as carrier group
- go through reduction reactions to form FAs and use NADPH
- in D configuration
- uses malonyl CoA as C2 unit

374
Q

what is the condensing enzyme of FA biosynthesis

A

B-ketoacyl-ACP synthase

375
Q

high levels of fatty acyl-
CoAs serve

A

feedback inhibitors for FA metabolism

376
Q

Acetyl Transacylase function

A

takes acyl portion of acetyl CoA and transfers to acyl
carrier protein (ACP), releasing CoA

377
Q

Malonyl Transacylase function

A

malonyl portion of malonyl CoA is
transferred to ACP, release CoA

378
Q

what enzymes are required to produce the substrates for β-ketoacyl-ACP synthase

A

Acetyl Transacylase

Malonyl Transacylase

379
Q

β-ketoacyl-ACP synthase function

A

serves to condense malonyl-ACP
and acetyl-ACP,forms acetoacetyl-ACP

380
Q

how does B-ketoacyl-ACP synthase condense malonyl ACP and acetyl ACP

A

via decarboxylation occurs allowing for the formation of the
4-carbon unit acetoacetyl bound to ACP

381
Q

β-Ketoacyl ACP reductase function

A

uses NADPH to reduce a ketone
producing a hydroxyl group in
formation of β-hydroxybutyryl-
ACP

382
Q

3-Hydroxyacyl-ACP dehydratase function

A

removes water in a dehydration
reaction, forming a double bond in
the product α,β-trans-butenoyl-
ACP

383
Q

Enoyl ACP-reductase function

A

reduces the
double bond using NADPH to form
butyryl-ACP

384
Q

what is the final step of FA biosynthesis after the 7 reactions

A

palmitoyl thioesterase (TE)

385
Q

function palmitoyl thioesterase

A

allows for the release from acyl carrier protein sulfhydryl group so that palmitate gets released

386
Q

elongation beyond 16 C occurs in

A

in ER and mitochondria

387
Q

what is the substrate for elongation beyond 16 C

A

acyl CoA

388
Q

T/F all natural double bonds in FA are cis

A

T

389
Q

fatty acid synthase contains how many active sites

A

six active sites for seven reactions

390
Q

what is the key intermediate for synthesis of TAG and other complex lipids

A

phosphatidic acid

391
Q

what are the enzymes required to take dihydroxyacetone phosphate to phosphatidic acid

A

glycerol-3-phosphate DH

glycerol-3-phosphate acyltransferase

1-acylglycerol-3-phosphate acyltransferase

392
Q

what are the precursor of glycerophospholipid and what is the function of glycerophospholipid

A

1,2-diacylglycerol phosphatidic acid

lipid in membranes

393
Q

what are the precursor of spingolipid-sphingomyelins and its function

A

1,2-diacylglycerol phosphatidic acid

lipid in membranes

394
Q

what is the precursor of sphingoglycolipids ( cerebrosides and gangliosides) and their functoin

A

palmitoyl-CoA serine

lipids in membrane

395
Q

what lipid gets metabolized from arachidonic acid

A

prostaglandins

396
Q

what is the precursor of prostaglandins and function

A

C20 FA - arachidonate

inflammation

397
Q

PLA2 releases arachidonic acid is precursor of

A

eicosanoids

398
Q

T/F eicosanoids are local hormones

A

T

399
Q

tissue injury and inflammaation triggers

A

release of arachidonate and eicosanoid synthesis

400
Q

T/F eicosanoids are precursors of arachidonic acid

A

T

401
Q

characteristics of eicosanoids

A

exert effects a very low concentrations

have very short half lifes

act at sites near their biosynthesis

synthesized from arachidonic acid in ER

402
Q

release of eicosanoids is stimulated by

A

histaines , hormones, and proteases

403
Q

eicosanoids are also produced when

A

tissues are injured producing inflammation and pain

404
Q

thromboxane A2 is produced by

A

platelets to stimulated platelet aggregation

405
Q

COX2 is produced in high levels in rensponse

A

to pain

406
Q

coxibs become important for

A

treatment of inflammatory diseases like arthritis

407
Q

what is the activated form of FA

A

fatty acyl CoA

408
Q

where is abnormal adrenoleukodystrophy protein found

A

peroxisome

409
Q

function of ALD protein

A

responsible for breaking down very long chain FAs

410
Q

the accumulation of very long FAs damages

A

myelin sheath results in neurological problems

encoded by ABCD1 gene

411
Q

function of peroxisomes

A

takes really long FAs and helps break them down as a way to help and speed up function of mitochondria

412
Q

glyoxysomes

A

metod of FA b-ox in plans

413
Q

what are the three enzymes used in B-oxidation in peroxisomes

A

acyl-CoA oxidase, peroxisomal enoyl-CoA hydratase, peroxisomal thiolase

414
Q

Acyl-CoA oxidase catalyzes a reaction using

A

fatty acyl-CoA and molecular oxygen to produce trans-Δ2-enoyl-CoA

and

hydrogen peroxide via a FAD-cofactor, where electrons are transferred directly to O 2
producing H2O2

415
Q

FA oxidation in peroxisomes difference than B-ox

A

produce 1.5 fewer ATP per 2-C units

enzyme catalse is present to address the generation of H2O2

416
Q

how is peroxisomal thiolase different than thiolase in b-ox

A

has specificity for longer FA chains and does not recognize substrates with 8C or less

417
Q

how does transport occur in peroxisome

A

via ALD protein

418
Q

in perozisomes what breaks down hydrogen peroxide to H2O and O2

A

catalase

419
Q

what is the first enzyme in peroxisomal FA oxidation

A

acyl-CoA oxidase

420
Q

describe the process that Fatty Acyl CoA undergoes through in B-Ox

A

proceeds through oxidation in which 2 C units are removed producing acetyl CoA and remainder of fatty acyl CoA molecule until all possible 2 Carbon units have been converted to acetyl-CoA

421
Q

where does B-Ox occur

A

in the mitochondri a

422
Q

what enzyme that is the first step of B-ox that forms a trans-double bond

A

acyl-CoA DH

423
Q

acyl CoA DH converts fatty acyl CoA to

A

trans-Δ2-enoyl-CoA

424
Q

mitochondria has 4 different acyl-CoA DH how do they differ

A

they differ based on their specificity b/c FA can occur in a # if diff length

425
Q

majority of SIDS occur b/c

A

long-chain FA oxidation effects

426
Q

the mechanism of acyl CoA DH involves

A

proton abstraction
double bond formation
hydride removal by FAD

427
Q

function of enoyl CoA hydratse

A

splits H2O across dbl bond

forms 3-L -hydoxyacyl-CoA

428
Q

what enzyme converts trans - Δ2 - enoyl- CoA to 3-L-hydroxyacyl-CoA

A

enoyl-CoA hydratase

429
Q

what is the second enzyme used in B-Ox that is similar to fumarase

A

enoyl-CoA hydratase

430
Q

function of 3-L-hydroxyacyl-CoA DH

A

NAD+ dependent dehydrogenation

converts 3-L hydroxyacyl-CoA to B-ketoacyl-CoA

431
Q

addition of CoA, is catalyzed by a family of enzymes called _________ _________ and can be found in ….

A

acyl-CoA synthetases

endoplasmic reticulum or outer mitochondrial membrane

432
Q

Fatty acids pass through the outer
mitochondrial membrane using

A

carnitine
palmitoyl acyltransferse I

433
Q

The translocation of acyl-carnitine across the inner mitochondrial membrane is mediated by

A

carnitine
carrier protein

434
Q

Upon entry into the matrix, the acyl portion is transferred to CoA using as transesterification reaction catalyzed by

A

carnitine palmitoyl transferase II

435
Q

function of B-ketoacyl CoA thiolase

A

cleaves B-ketoacyl with a thiol group of CoA

converts B-ketoacyl CoA to acetyl coA and remaining acyl CoA is 2C shorter

436
Q

draw B-Ox of palmitic acid

A

slide 16 on B-Ox slides

437
Q

equation used to calc number of rounds of B-ox

A

(C/2)-1

438
Q

equation used to calc number of acetyl CoA

A

C/2

439
Q

Each round of B-Ox Yields

A

1 NADH
1 FADH2
1 acetyl-CoA

440
Q

Each acetyl CoA enters TCA and yiels

A

1 FADH2
1 GTP
3 NADH

441
Q

The process of activation of FA comes in the cost of

A

2 ATP

442
Q

most FAs have Cis db what is the problem with this for B-ox

A

b-ox uses trans double bonds

cis db is not a substrate for the 4 enzymes involved in B-ox

443
Q

what is the solution to monounsaturated FAs when a cis DB is encounteres

A

use of enoyl-CoA isomerase

444
Q

function of enoyl CoA isomerase

A

catalyzes isomerizaation reaction

converts cis- Δ3 double bond to trans- Δ2 double bond

445
Q

list the 3 issues that can arise in the B-ox of Polyunsaturated FAs

A

presence of beta,gamma DB ( need a,B for enoyl CoA hydratase)

presence of Δ4 double bond inhibits enoyl-CoA hydratase

the Δ3 double bond product
is not a substrate for
enzymes in β-oxidation

446
Q

how is the presence of beta,gamma DB resolved in polyunsat FAs

A

enoyl CoA isomerase moves location of DB from Cis-3 to trans-2

447
Q

how is the presence of Δ4 double bond inhibits enoyl-CoA hydratase resolved

A

use of NADPH dependent enzyme 2,4-dienoyl-CoA reductase

in mammals requires 3,2-enoyl-CoA isomerase

448
Q

function 2,4-dienoyl-CoA reductase

A

reduces Δ4 DB to 3,4 trans DB

449
Q

function of 3,2 enoylCoA isomerase

A

flips location of trans DB to C2 and C3

450
Q

how is the Δ3 double bond product
that is not a substrate for
enzymes in β-oxidation resolved

A

3,5-2,4 dienoyl CoA isomerase

451
Q

3,5-2,4 dienoyl CoA isomerase function

A

converts the trans delta 3 DB to a trans delta 2 DB so that it becomes a substrate for 2,4-dienoyl CoA reducatase

452
Q

function of acyl CoA DH

A

creates a trans DB between C2 and C3 of fatty acyl CoA

453
Q

enoyl coA hydratase adds water to create trans DB what happens to OH

A

transferred to C3

454
Q

function of 3-L hydroxylacyl CoA DH

A

oxidizes OH to a ketone using NAD+

455
Q

what is the fate of 3C unit propionyl CoA from odd # B-ox of FA

A

converts to succinyl CoA

456
Q

what are the 3 enzymes involved that converts propionyl CoA to succinyl CoA

A

propionyl CoA carboxylase
methylmalonyl CoA racemase
methylmalonyl CoA mutase

457
Q

what is the cost of a cis DB

A

1 FADH2

458
Q

what is the cost of the presence of a Delta 4 DB

A

1 NADPH but gets repayed later by NADH

cost = 2.5 ATP

459
Q

how do we use propionyl CoA as energy

A

produces malate via 3 enzymes ( succinyl CoA synthetase, succinate DH, fumarase)

transported to matrix via malate asp shuttle

malic enzyme converts it to pyruvate

converted to acetyl CoA via PDHC

fuels TCA cycle

460
Q

proline is made from

A

glutamate

461
Q

function of THF

A

interconverts several one carbon copmds or fragments

462
Q

in bacteria aspartate biosynthesizes

A

Lysin
methionine
threonine

463
Q

leucine isoleucine and valine are derived from

A

pyruvate requires TPP enzyme

464
Q

what amino acids are synthesized from glucose derivative

A

Phe
Tryptophan

Tyr

465
Q

histidine involves

A

5-phosphoribosyl-a-pyrophosphate used in nucleotide biosynthesis

466
Q

Apolipoproteins are lipid binding proteins that aid in

A

the transport of triacylglycerols.

467
Q

apolipoproteins protein moieties are recognized by

A

receptors on cells surfaces of
muscle and fat cells.

BICH 411 (4 decks)

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