Gluconeogenesis, Tca Cycle

Front 1

Where does the tricarboxylic acid (TCA) cycle/citric acid cycle/Krebs cycle occur?

Back 1

Mitochondria

Front 2

Where does the pyruvate in the first step come from?

Back 2

glycolysis (two molecules pyruvate for each molecule glucose)

Front 3

What disease does thiamine deficiency causes and what are symptoms?

Back 3

Beriberi

severe lethargy and fatigue

Serious neurological and cardiovascular problems result bc thiamine is a cofactor in several reactions of carbohydrate metabolism.

Front 4

What is thiamine pyrophosphate?

Back 4

TPP

Works as a coenzyme in many enzymatic reactions

Front 5

TCA cycle

Step 1

Back 5

Oxaloacetate + Acetyl CoA + H20 --> citrate + CoA + H+

Condensation of oxaloacetate with Acetyl CoA to produce citrate

Enzyme is citrate synthase

Front 6

Citrate synthase: what is it for and what regulates it?

Back 6

Enzyme catalyzing step 1 of TCA cycle

Condensation of oxaloacetate with Acetyl CoA to produce citrate

<b> Presence of citrate inhibits it </b>

Front 7

TCA cycle

Step 2

Back 7

Citrate <---> Isocitrate

Enzyme is aconitase

Even though it's an equilibrium reaction, it's favorable because product is constantly being removed.

Front 8

Aconitase

Back 8

Isomerizes citrate to Isocitrate

Front 9

TCA cycle

Step 3

Back 9

isocitrate + NAD+ --> alpha-ketoglutarate + NADH + H+ + CO2

1st NADH generated

Catalyzed by isocitrate dehydrogenase

Front 10

Isocitrate dehydrogenase: what is it for and what regulates it?

Back 10

Catalyzes step 3 of TCA cycle

conversation of isocitrate + NAD+ --> NADH + H+ + CO2 + alpha-ketoglutarate

<b> Activated by ADP and Ca2+. Inhibited by NADH (NADH is product of rxn). </b>

Front 11

TCA cycle

Step 4

Back 11

Oxidative decarboxylation of alpha ketoglutarate results in formation of succinyl CoA

alpha-ketoglutarate + NAD+ + CoA --> succinyl CoA + NADH + CO2

Catalyzed by alpha-ketoglutarate dehydrogenase

Front 12

alpha-ketoglutarate hydrogenase: what is it for and what regulates it?

Back 12

Catalyzes step 4 of TCA cycle

2nd time NADH is generated

alpha-ketoglutarate + NAD+ + CoA --> succinyl CoA + NADH + CO2

<b> Inhibited by NADH and succinyl CoA; Activated by Ca2+ </b>

Front 13

TCA cycle

Step 5

Back 13

Conversion of succinyl CoA into succinate with formation of high energy phosphate compound

succinyl CoA + Pi + GDP &lt;--> Succinate + GTP + CoA

Succinyl CoA synthase is enzyme

Front 14

Succinyl CoA synthase

Back 14

Catalyzes step 5 of TCA cycle

succinyl CoA + Pi + GDP <--> Succinate + GTP + CoA

Front 15

TCA Cycle

Step 6

Back 15

Regeneration of oxaloacetate by oxidation of succinate

succinate + FAD <--> fumarate + FADH2

Catalyzed by succinate dehydrogenase, enzyme linked directly to electron transport chain

Front 16

TCA Cycle

Step 7

Back 16

Regeneration of oxaloacetate by oxidation of succinate

fumarate + H20 <--> L-malate

Enzyme is fumarase

Front 17

Succinate dehydrogenase

Back 17

Step 6 of TCA cycle, involved in Regeneration of oxaloacetate by oxidation of succinate

Front 18

Fumarase

Back 18

Step 7 of TCA cycle, involved in Regeneration of oxaloacetate by oxidation of succinate

Front 19

TCA Cycle

Step 8

Back 19

Regeneration of oxaloacetate by oxidation of succinate

malate + NAD+ <--> NADH + oxaloacetate

Catalyzed by malate dehydrogenase.

This reaction works as a brake in the TCA cycle.

Front 20

Net reaction of TCA Cycle

Back 20

Acetyl CoA + 3NAD+ + FAD + GDP + Pi + 2h2o --> 2CO2 + FADH2 + 3NADH + 3H + GTP

Front 21

How many molecules of NADH, FADH2, and GTP per molecule of Acetyl CoA?

Back 21

3NADH

1FADH2

1 GTP

Front 22

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How many molecules of NADH, FADH2, and GTP per molecule of glucose?

Back 22

6 NADH

2 FADH2

2 GTP

Front 23

What molecules are inhibitors of TCA cycle (in excess?)

What molecules are activates

Back 23

Inhibitors: ATP, NADH

Activators: ADP (signals use of ATP)

Front 24

Pyruvate dehydrogenase complex (connection with glycolysis): What inhibits and activates it?

Back 24

Inhibitors: Excess Acetyl CoA, NADH, ATP

Activators: Pyruvate, NAD+, CoA

When levels of glucose are high, TCA cycle gets activated

Front 25

Malate dehydrogenase: what is it for and what inhibits it?

Back 25

Regeneration of oxaloacetate by oxidation of succinate

malate + NAD+ <--> NADH + oxaloacetate

<b> Inhibited by NADH </b>

Front 26

Will ATP ever activate the TCA cycle enzymes?

Back 26

NO. TCA cycle is to prepare for electron transport chain to generate ATP. Excess ATP means it's not needed.

Front 27

Anaplerotic reactions

Back 27

Anaplerosis is the act of replenishing TCA cycle intermediates that have been extracted for biosynthesis.

Example of such can be the TCA Cycle (also called the Krebs or citric acid cycle). In normal function of this cycle for respiration, concentrations of TCA intermediates remain constant; however, many biosynthetic reactions also use these molecules as a substrate.