Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biochemistry > ch 10 - Carbohydrate Metabolism II > Flashcards

ch 10 - Carbohydrate Metabolism II Flashcards

1
Q

Krebs cycle

A

also called citric acid cycle or the tricarboxylic acid (TCA) cycle. In mitochondria. Main function: oxidation of acetyl-CoA to CO2 and H2O. Also produces high energy e-carrying molecules NADH and FADH2.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Acetyl-CoA

A

obtained through the metabolism of carbs, fatty acids and amino acids. Key molecule in crossroads of many metabolic pathways

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

pyruvate dehydrogenase complex (review from ch 9)

A

located in mitochondrial matrix; multienzyme complex that catalyzes oxidation of decarboxylation of pyruvate in the mitochondrion (pyruvate is a product of glycolysis of glucose)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

five enzymes that make up pyruvate dehydrogenase complex

A 
pyruvate dehydrogenase (PDH), 
dihydrolipyl transacetylase, 
dihydrolipoyl dehydrogenase, 
pyruvate dehydrogenase kinase, 
and pyruvate dehydrogenase phosphatase
final two regulate action of PDH
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

coenzyme A (coA)

A

a thiol, containing an -SH group, resulting in formation of thioester which contains sulfur instead of typical oxygen ester -OR. This is very energy taxing but when hydrolyzed it gives off so much energy that it can drive other reactions such as citric acid (Krebs) cycle forward

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Order of pyruvate dehydrogenase complex enzymes needed to catalyze acetyl-CoA formation

A
  1. Pyruvate dehydrogenase (PDH) - pyruvate oxidized yielding CO2 while remaining 2-C molecule binds covalently to thaimine pyrophosphate
  2. Dihydrolipoyl transacetylase - 2-C molec from previous transferred to lipoic acid which creates an acetyl group which binds to acid via thiolester linkage. Then this catalyzes the CoA-SH interaction with new thioester link, causing transfer of an acetyl group to form acetyl-CoA.
  3. Dihydrolipoyl dehydrogenase: after previous step lipoic acid is in reduced state. FAD(flavin adenine dinucleotide) reoxidizes it and it aids in future acetyl-CoA formation. FAD is reduced to FADH2 in the process. And reoxidized in the future while NAD is reduced to NADH
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Fatty Acid oxidation (beta-oxidation)

A

in cytosol, process called activation - thioester bond forms bt carboxyl groups of fatty acids and CoA-SH. Activated fatty acyl-CoA taken to intermembrane space of mito. then transferred to carnitine by transesterification. Then acyl-carnitine, it crosses the inner membrane and transfers fatty acyl group to mitochondrial CoA-SH. Once acetyl-CoA is formed in matrix beta-oxidation can occur, which removes 2-C fragments from the carboxyl end

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Amino acid catabolism

A

used to form acetyl-CoA. must lose their amino group via transamination, C skeletons then form ketone bodies. These amino acids are called ketogenic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Ketones to form acetyl-CoA

A

Acetyl-CoA is normally used to produce ketones when pyruvate dehydrogenase is inhibited but reverse rxn can occur also

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Alcohol to form acetyl-CoA

A

in moderate amounts the enzymes alcohol dehydrogenase and acetaldahyde dehydrogenase convert this to acetyl-CoA; used to synthesize fatty acids because this rxn causes a build up of NADH which inhibits the Krebs cycle.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

overall rxn of pyruvate dehydrogenase

A

pyruvate + NAD+ + CoA-SH -> acetyl-CoA + CO2 + NADH + H+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

NADH and FADH2 (reminder)

A

energy carriers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Citric Acid Cycle overview

A

reminder: does not require O2 directly but will not proceed w/o it because NADH and FADH2 will not mulate. pyruvate (glucose and amino acids) with PDH then forms acetyl-CoA - then citrate and cis-Aconitase forms isocitrate+NAD+ andiocitrate dehydrogenase forms NADH, CO2 and alpha-Ketoglutarate; alpha-Ketoglutarate + NAD+ via alpha-Ketoglutarate dehydrogenase = NADH, CO2 and Succinyl-CoA; Succinyl-CoA + GDP+Pi via succinyl-CoA synthetase = GTP and succinate; succinate + FAD and succinate dehydrogenase (complex II) = Fumarate and FADH2; Fumarate forms malate and fumarase; Malate forms oxaloacetate and NADH and NAD+ via malate dehydrogenase; oxaloacetate feeds back into the cycle and citrate synthase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Step 1 of citric acid cycle

A

citrate formation:
acetyl-CoA and oxaloacetate form citryl-CoA as an intermediate via condensation rxn. Hydrolysis of citryl-CoA = citrate and CoA-SH. This is catalyzed by citrate synthase
acetyl-CoA + oxaloacetate + H2O -> citrate + CoA-SH + H+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Synthases vs synthetases

A

synthases are enzymes that form new covalent bonds w/o needing significant energy. Synthetases create new covalent bonds with energy input.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Step 2 of citric acid cycle

A

citrate isomerized to isocitrate:
citrate isomerized to 1 of 4 isomers of isocitrate. Citrate binds at 3 points to aconitase enzyme, water is lost = cis-aconitate; water is added back to form isocitrate which is a metalloprotein and requires Fe2+.
citrate ->(aconitase, H2O in and out) (aconitase, H2O in and out)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Step 3 of citric acid cycle

A

alpha-Ketoglutarate and CO2 Formation
Isocitrate from step 2 oxidized to oxalosuccinate by isocitrate dehydrogenase. oxalosuccinate decarboxylated to form alpha-ketoglutarate and CO2. First of two Cs from cycle is lost and first NADH produced from intermediates in cycle.
Isocitrate with NAD+ -> NADH + H+ and oxalosuccinate with H+ -> CO2 and alpha-ketoglutarate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

rate-limiting enzyme of the citric acid cycle

A

isocitrate dehydrogenase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

step 4 of citric acid cycle

A

succinyl-CoA and CO2 Formation:
carried out by the alpha-ketoglutarate dehydrogenase complex (similar in mechanism, cofactors and coenzymes to pyruvate dehydrogenase (PDH) complex). alpha-ketoglutarate and CoA come together to give off second and last CO2 lost in cycle. Reduced NAD+ gives another NADH.
alpha-ketoglutarate with CoA-SH, NAD+ ->(alpha-ketoglutarate dehydrogenase complex/TPP, lipoic acid, Mg2+)-> succinyl-CoA + CO2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Step 5 of citric Acid Cycle

A

Succinate Formation:
hydrolysis of thioester bond in CoA-SH = succinate and CoA-SH, rxn coupled to phosphorylation of GDP to GTP (catalyzed by succinyl-CoA synthetase). thioester bonds in acetyl-CoA hydrolysis releases lots of energy. GDP to GTP is driven by this release. Then nucleosidediphosphate kinase catalyzes phosphate transfer from GTP to ADP, producing ATP. ONLY time ATP is directly produced in cycle.
Succinyl-CoA and GDP + Pi->succinyl-CoA synthetase

21
Q

Step 6 of citric acid cycle

A

Fumarate Formation:
Does not take place in mitochondrial matrix but in inner membrane. Succinate oxidized to form fumarate (catalyzed by succinate dehydrogenase which is considered a flavoprotein). FAD is reduced to FADH2. FADH2 molecules each pass electrons to ETC which leads to production of 1.5 ATP

22
Q

Flavoprotein

A

covalently bonded to FAD, e- acceptor in fumarate formation step of citric acid cycle (step 6)

23
Q

Step 7 of citric acid cycle

A

Malate formation:

fumarase catalyzes hydrolysis of alkene bond in fumarate, giving rise to malate. Only L-malate forms in rxn

24
Q

Step 8 of citric acid cycle

A

oxaloacetate formed anew:
malate oxidized to oxaloacetate by malate dehydrogenase. Last molecule of cycle of NAD+ reduced to NADH. Oxaloacetate ready to start over in cycle.
succinate with FAD by succinate dehydrogenase -> FADH2 and fumarate, add H20 -> malate, add NAD+ by malate dehydrogenase -> NADH and H+ and oxaloacetate

25
Q

substrates of citric acid cycle

A 
Please, Can I Keep Selling Seashells For Money, Officer?
Pyruvate
Citrate
Isocitrate
alpha-Ketoglutarate
Succinyl-CoA
Succinate
Fumarate
Malate
Oxaloacetate
26
Q

Net yield for Citric Acid Cycle

A

pyruvate dehydrogenase complex produces 1 acetyl-CoA, 1 NADH.
In cycle: 3 NADH, 1 FADH2, 1 GTP, 2 C leave in form of CO2.
Total ATP: 4 NADH at 2.5 ATP per NADH = 10 ATP
1 FADH2 at 1.5 ATP per FADH2 = 1.5 ATP
1 GTP = 1 ATP
total is 25 per glucose

27
Q

production of ATP in glycolysis

A

30-32

28
Q

Regulation in citric acid cycle

A

Energy carriers inhibit energy producing processes.

  • isocitrate dehydrogenase inhibited by ATP, NADH and FADH2
  • acetyl-CoA production inhibited by phosphorylating PDH (facilitated by pyruvate dehydrogenase kinase, reactivated by pyruvate dehydrogenase phosphatase in response to high levels of ADP) and inhibited by itself
  • PDH inhibited by ATP and NADH as markers of cell being energetically satisfied
29
Q

Three Control Points of citric acid cycle

A
  • Citrate synthase (ATP, NADH as products inhibit, and succinyl-CoA, citrate directly inhibit)
  • Isocitrate dehydrogenase: inhibited by energy products
  • alpha-Ketoglutarate dehydrogenase complex: succinhyl-CoA and NADH and ATP are inhibitors. ADP and calcium ions stimulate
30
Q

proton-motive force

A

in the ETC, the inner mitochondrial membrane uses this to produce ATP; it is an electrochemical proton gradient generated by the complexes of the ETC

31
Q

final (two) step(s) of aerobic respiration

A

E- transport along inner mitochondrial membrane and generation of ATP via ADP phosphorylation

32
Q

reduction potential

A

in ETC, physical property that determines that direction of e- flow, proteins along inner membrane must transfer the elections donated by NADH and FADH2 in a specific order and direction.
Reminder: if you pair 2 molecules with different reduction potentials molecule with higher potential will be reduced and other will be oxidized

33
Q

Complex I in e- flow of ETC

A

NADH-CoQ oxidoreductase:
transfers electrons to coQ. Receives e-s from NADH
passing high-energy electrons from NADH to CoQ to form CoQH2
-NADH + H+ + FMN (flavin mononucleotide) -> NAD+ + FMNH2
-FMNH2 + 2 Fe-S (oxidized) -> FMN + 2 Fe-S (reduced) + 2 H+
-2 Fe-S (reduced) + CoQ + 2 H+ -> 2 Fe-S (oxidized) + CoQH2
Overall: NADH + H+ + CoQ -> NAD+ + CoQH2

34
Q

Complex II in e- flow of ETC

A

Succinate-CoQ oxidoreductase:
transfers electrons to CoQ. However, receives electrons from succinate (citric acid cycle intermediate which is oxidized to fumarate when interacting with FAD which is covalently bonded to this complex) Oxidation of succinate reduces FAD to FADH2 which then reduces iron-sulfur protein and goes back to FAD. iron-sulfur reduces coQ and is reoxidized. No contribution to proton gradient in this step.
-succinate + FAD -> fumarate + FADH2
-FADH2 + Fe-S(oxidized) -> FAD + Fe-S (reduced)
-Fe-S(reduced) + CoQ + 2H+ -> Fe-S(oxidized) + CoQH2
overall: succinate + CoQ = 2H+ -> fumarate + CoQ2

35
Q

Complex III in e- flow of ETC

A

CoQH2 cytochrome c oxidoreductase:
transfer of electrons from coQ to cytochrome c. Involve oxidation and reduction of cytochromes: proteins with heme groups where iron is reduced to Fe2+ and reoxidized to Fe3+.
-CoQH2 + 2 cytochrome c [w Fe3+] -> CoQ + 2 cytochrome c [w Fe2+} + 2 H+
contributes to proton-motive force by Q cycle

36
Q

Q cycle

A

complex III of ETC: shuttles e-s and 4 protons are displaced to intermembrane space increasing gradient of proton-motive force across teh inner mitochondrial membrane

37
Q

Complex IV in e- flow of ETC

A

cytochrome c oxidase:
facilitates the culminating step of the ETC: transfer of e-s from cytochrome c to oxygen, final e- acceptor. cytochromes a and a3 make up cytochrome oxidase, works with Cu2+
Overall: -4 cytochrome c [with Fe2+] + 4H+ + O2 -> 4 cytochrome c [w Fe3+] + 2H2O

38
Q

ATP synthase

A

enzyme responsible for harnessing energy to form ATP from ADP and an inorganic phosphate as the electrochemical gradient called proton-motive force is formed in the ETC

39
Q

NADH shuttle mechanisms

A

carriers that can take e-s from NADH across the inner mitochondrial membrane: Glycerol 3-phosphate shuttle, and Malate-aspartate shuttle

40
Q

Glycerol 3-phosphate shuttle

A

generates 1.5 ATP for every molecule of cytosolic NADH. cytosol contains one isoform of glycerol-3-phosphate dehydrogenase which oxidizes cytosolic NADH to NAD+ while forming glycerol 3-phosphate from dihydroxyacetone phosphate (DHAP). Other glycerol-3-phosphate on outside attached to FAD reduces it to FADH2 which transports e-s to ETC via complex II

41
Q

Malate-aspartate shuttle

A

generates 2.5 ATP per molecule of NADH. Cytosolic oxaloacetate is reduced to malate so it can pass inner mitochondrial membrane (done through malate dehydrogenase). Also NADH oxidized to NAD+. malate dehydro turns NAD+ to NADH inside and passes e-s to ETC through complex I. Malate reoxidizes to oxaloacetate and this is transaminated to aspartate which then goes back into the cytosol to start over

42
Q

ATP synthase

A

energy provided for by the ETC, spans the entire inner mitochondrial membrane and protrudes into the matrix; links ATP synthesis and ETC

43
Q

F sub 0 portion

A

part of ATP sythase that spans the membrane, which proton-motive force interacts with; functions as ion channel so protons travel through this along their gradient back into the matrix

44
Q

chemiosmotic coupling

A

during proton movement over their gradient through F0 back to matrix, this allows chem energy of gradient to be harnessed as a means of phosphorylating ADP, forming ATP

45
Q

F sub 1 portion

A

portion of ATP synthase that utilizes energy released from electrochemical gradient related to chemiosmotic coupling as protons travel through F0 portion of ATP synthase to phosphorylate ADP to ATP

46
Q

conformational coupling in oxidative phosphorylationg

A

suggests that relationship bt proton gradient and ATP synthesis is indirect instead of theory of chemiosmotic coupling. ATP is released by the synthase a result of conformational change caused by the gradient

47
Q

Free energy change of reaction when proton-motive force is dissipated through the F0 portion of ATP synthase

A

delta G upper degree prime = -220 kj/mol
highly exergonic.
phosphorylating ADP to form ATP is endergonic so coupling these two rxns allows energy harnessed from one to drive the other

48
Q

key regulators of oxidative phosphorylation - respiratory control

A

O2 and ADP; if O2 is limited rate of oxidative phosphorylation decreases and NADH and FADH2 increase. NADH inhibits citric acid cycle;
in presence of O2 rate is dependent on ADP

Biochemistry (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions