ciclu krebs

Question 1

ce este ciclul krebs

Answer 1

calea finala de oxidare a zaharidelor,lipidelor si aa

Question 2

in ce tipuri de celule se desf ?

Answer 2

celule eucariote
!!! exceptie eritrocite - NU au mitocondrii

Question 3

unde se desf ?

Answer 3

in matricea mitocondriala
in maj tesuturilor, in special in ficat

Question 4

reactia dintre Acetil CoA si H2O

Answer 4

CH3COSCoA + 3H2O -> 2 CO2 + 8H + CoA-SH

Question 5

rolul H

Answer 5

preluat de CoE
oxidare catena de transport de electroni

Question 6

compusul esential al ciclului krebs

Answer 6

acidul oxalilacetic
rol de catalizator
intra in ciclu si se regaseste la final

Question 7

scopul ciclului

Answer 7

generare NADH si FADH2( f reduse)

Question 8

etapa 1

Answer 8

acetil co a + oxaloacetat -> citrat + CoA- SH
enzima - citratsintetaza
proces de condensare aldolica a acetilului activat cu oxalilacetat
delta G < 0 , ireversibila

Question 9

cine inhiba citratsinteza?

Answer 9

ATP si NADH
ciclul Krebs isi adapteaza ritmul la nevoile energetice ale tesuturilor

Question 10

etapa 2

Answer 10

citrat -> isocitrat
enzima - aconitaza
se realizeaza izomerizarea acidului ciric in prezenta aconitazei prin intermediul acidului aconitic
4 Fe/ mol aconitaza
delta G =0

Question 11

etapa 3

Answer 11

isocitrat + NAD -> alfa-cetoglutarat + NADH + CO2
enzima - IZOCITRATDEHIDROGENAZA (ICDH)
produs intermediar - acid oxalilsuccinic ( se decarboxileaza pana la acid alfa-cetoglutaric)
se prod NADH si CO2!!!!

Question 12

enzima NAD dependenta

Answer 12

efector alosteric pozitiv pt ADP
(NAD - f oxidata prez in mitocondrii favorizeaza TCA in scpul formarii ADP, respectiv ATP)

Question 13

enzima NADP

Answer 13

f redusa
inhibata de crestera conc de ADP
nu fav desfasurarea TCA
(cant mari de ADP - valorile energetice ale organismului sunt satisfacute- adaptare TCA )

Question 14

ICDH

Answer 14

izocitrat dehidrogenaza
NAD dependenta (activator ADP)
NADP dependenta(inhibitor ATP)

Question 15

determinanta de viteza

Answer 15

procese de echilibru cu viteza scazuta
influenteaza intregul proces
ex stafeta

Question 16

coenzimele NAD

Answer 16

preponderent in reactiile de oxidare din citoplasma si motcondrie
in exces f oxidata

Question 17

coenzimele NADP

Answer 17

in sinteze reductive
in exces forma redusa

Question 18

etapa 4

Answer 18

alfa-cetoglutarat + CoASH + NAD -> succinilCoA + NADH + CO2
enzima alfa-cetoglutaratdehidrogenaza
proces de decarboxilare
se prod CO2 si NADH!!!!

Question 19

etapa 4

Answer 19

alfa-cetoglutarat + CoASH + NAD -> succinilCoA + NADH + CO2
enzima alfa-cetoglutaratdehidrogenaza
proces de decarboxilare
se prod CO2 si NADH!!!!

Question 20

GDP

Answer 20

guanidindifosfat

Question 21

Pi

Answer 21

fosfat anorganic

Question 22

etapa 5

Answer 22

succinilCoA + GDP + Pi -> acid succinic + GTP + CoASH
enzima succinattiokinaza (STK)
in prezenta Mg2

Question 22

etapa 5

Answer 22

succinilCoA + GDP + Pi -> acid succinic + GTP + CoASH
enzima succinattiokinaza (STK)
in prezenta Mg2
delta G < 0

Question 23

GTP

Answer 23

guanidintrifosfat
GTP + ADP - GDP + ATP
GTP poate fi utilizat in biosinteza proteinelor,a porfirinelor, dar mai ales la obtinerea ATP din ADP

Question 24

etapa 6

Answer 24

succinat + FAD -> fumarat + FADH2 etapa caract de specificitate absoluta - se obtine un izomer (trans-fumarat)

Question 25

SDH

Answer 25

succinildehidrogenaza metalo-enzima(Fe) proteina intrinseca a membranei interne mitocondriale(celelalte enzime- im mitosol)

Question 26

inhibitori SDH

Answer 26

OA, acid malonic, succinimida, malonilamida

Question 27

activstori SDH

Answer 27

acid fumaric, acid succinic

Question 28

etapa 7

Answer 28

fumarat +H2O -> L-malat enzima -fumaraza delta G= 0

Question 29

etapa 8

Answer 29

L malat +NAD -> oxalilacetat +NADH enzima -malatdehidrogenaza(MDH) reactie puternic endergonica ,echilbrul deplasat mult spre stanga delta G > 0

Question 30

in ce etape se obtine FADH?

Answer 30

etapa 6

Question 31

in ce etape se obtine NADH ?

Answer 31

3,4,8

Question 32

enzime mb ext mitocondriala

Answer 32

monoaminooxidaza acil-coenzimsintetaza

Question 33

enzime mb int mitocondriala

Answer 33

citocromii b,c1,a,a,a3 ubichinona succinat dehidrohenaza ATP aza translocaze