Citric acid cycle Flashcards by Leen Tarik

what is the primary function of TCA cycle?

the oxidation of acetylCoA to CO2

How well did you know this?

Not at all

Perfectly

the citric acid cycle is also called…….

Krebs cycle

Tricarboxylic Acid Cycle

How well did you know this?

Not at all

Perfectly

does TCA cycle requires oxygen?

yes, its an aerobic reaction..

How well did you know this?

Not at all

Perfectly

the energy released from this reaction is saved as what?

NADH, FADH2, and GTP

How well did you know this?

Not at all

Perfectly

true or false?

the TCA cycle accounts for more than two-third of the ATP generated from fuel oxidation!

true..

How well did you know this?

Not at all

Perfectly

why is the TCA called amphibolic

cuz it plays both catabolic and anabolic pathways
for the catabolic reaction, acetylCoA is oxidized to CO2, H2O giving out energy
for the anabolic reactions, Intermediates of TCA cycle plays a role in synthesis like heme formation, FA synthesis, Cholesterol, Steroid synthesis.

How well did you know this?

Not at all

Perfectly

the cellular respiration is a process in which the cell consume …………….. and produce ……………….. as a waste product.

O2, CO2

How well did you know this?

Not at all

Perfectly

TRUE OR FALSE

the glycolysis provides more energy (ATP) from glucose than cellular respiration.

false

How well did you know this?

Not at all

Perfectly

the cellular respiration occurs in three major stages, what are they?

AcetylCoA production
AcetylCoA oxidation
Electron transfer and oxidative phosphorylation

How well did you know this?

Not at all

Perfectly

in respiration stage 1:

Acetyl-CoA production happens, what is generated?

generates some ATP, NADH, FADH2

How well did you know this?

Not at all

Perfectly

in respiration stage 2:

acetyl CoA oxidation happens, what is generated?

Generates more NADH, FADH2, and one GTP

How well did you know this?

Not at all

Perfectly

in respiration stage 3:

oxidative phosphorylation happens, what is generated?

generates a lots of ATP

How well did you know this?

Not at all

Perfectly

what is the catalyst or enzyme that is used when pyruvate is oxidized to Acetyl CoA?

pyruvate dehydrogenase complex (PDH)

How well did you know this?

Not at all

Perfectly

the PDH is activated by what in the liver? and what in the brain and nerves?

in the liver by the insulin, and in the brain the nerves the enzyme is not responsive to hormones

How well did you know this?

Not at all

Perfectly

as we know, Coenzymes are not a permanent part of the enzymes’ structure. They associate, fulfill a function, and dissociate, so what is the function of the CoA?

to accept and carry acetyl groups

How well did you know this?

Not at all

Perfectly

what are the 5 coenzymes that catalyze the pyruvate to acetyl CoA?

Thiamine Pyrophosphate (TPP),lipoic acid, and FAD are prosthetic groups
NAD+ and CoA-SH are co- enzymes

How well did you know this?

Not at all

Perfectly

pyruvate dehydrogenase complex is a multi-enzyme complex, what are the advantages of it?

‒short distance between catalytic sites allows channeling of substrates from one catalytic site to another
‒channeling minimizes side reactions
‒ regulation of activity of one subunit affects the entire complex

How well did you know this?

Not at all

Perfectly

true or false..

formation of acetyl CoA (product 1) happens in step 2 by enzyme 2.

false, it happens in step 3 in enzyme 2

How well did you know this?

Not at all

Perfectly

true or false

the regeneration of the oxidized FAD cofactor forming NADH happens in step 5 in enzyme 3

true

How well did you know this?

Not at all

Perfectly

what inhibits pyruvate dehydrogenase?

its inhibited by its products acetyl coa and NADH

How well did you know this?

Not at all

Perfectly

what does pyruvate dehydrogenase kinase does?

Pyruvate dehydrogenase kinase (PDH Kinase) phosphorylates PDH and converts it to inactive form. Anything regulates kinase activity directly affect PDH activity.
the kinase is activated by ATP acetyl coa and NADH, the presence of these the PDH is inhibited

How well did you know this?

Not at all

Perfectly

during starvation, which enzyme increase? pyruvate dehydrogenase kinase or phosphatase?

pyruvate dehydrogenase kinase increase, because it needs to minimize the glyconeogenesis and the energy have to be saved instead of being wasted..

How well did you know this?

Not at all

Perfectly

during starvation, the result is the inhibition of pyruvate dehydrogenase, why its inhibited?

The resulting inhibition of Pyruvate Dehydrogenase prevents muscle and other tissues from catabolizing glucose & gluconeogenesis precursors.

How well did you know this?

Not at all

Perfectly

in the muscle, what stimulates the phosphatase and activates pyruvate dehydrogenase?

calcium

How well did you know this?

Not at all

Perfectly

what are the diseases involved in pyruvate dehydrogenase complex deficiency?

beri beri diseases: deficiency in the thiamine or niacin, no enough ATP is produced throught the TCA cycle if the PDH is inactive lactic acidosis: deficiency in the E1 results in inability to convert pyruvate to acetyl CoA. Leigh syndrome: gene mutation in the PDH that causes less mitochondrial production of ATP

where does the TCA cycle takes place ?

in the mitochondria matrix

in the citric acid cycle, step 1 is ?

Step 1: C-C bond formation to make citrate

in citric acid cycle, step 2 is ?

Step 2: Isomerization via dehydration/rehydration

in citric acid cycle, step 3-4 is ?

Steps 3–4: Oxidative decarboxylations to give 2 NADH

in the citric acid cycle, in step 5?

Step 5: Substrate-level phosphorylation to give GTP

in the citric acid cycle, in step 6?

Step 6: Dehydrogenation to give reduced FADH2

in citric acid cycle, in step 7?

Step 7: Hydration

in the citric acid cycle, in step 8?

Step 8: Dehydrogenation to give NADH

what is the enzyme used in step 1 in the citric acid cycle? and what is special about this reaction?

citrate synthase the only reaction with C-C bond

what is the enzyme used in the second step?

acotinase

what is the enzyme used in the 3rd step?

isocitrate dehydrogenase

what enzyme is used in the 4th step ?

alpha ketoglutarate dehydrogenase

in the 5th step, the succinylcholine CoA is produced, what is special about this reaction?

* Last oxidative decarboxylation. Carbons not directly from glucose because carbons lost came from oxaloacetate * Succinyl-CoA is another higher-energy thioester bond * Highly thermodynamically favorable/irreversible. Regulated by product inhibition

the enzyme alpha ketoglutarate dehydrogenase is similar to another enzyme, what is this enzyme?

pyruvate dehydrogenase

in step 5, the succinate synthesis happens, which enzyme is used in this reaction?

succinylcholine CoA synthetase

in step 6, the fumarate is generated, what is the enzyme that runs this reaction?

succinate dehydrogenase | in this reaction, FADH2 is generated

in step 7, malate is formed, what is the enzyme that runs this reaction?

fumarate

in step 8, oxaloacetate is generated, what is the enzyme used?

malate dehydrogenase

what is the net result of the citric acid cycle?

2CO2 + 3NADH + FADH2 + GTP

what is the TOTAL energy produced by the citric acid cycle?

32 ATP

what are the enzymes that help in the regulation f the TCA cycle?

Those catalyze the reaction with highly negative △G°: citrate synthase (1st step), isocitratedhydrogenase (3rd step) α–ketoglutatrate dehydrogenase complex (4th step).

what are the irrevesible steps of the TCA cycle ?

1st, 3rd and 4th steps are IRREVERSIBLE | High product concentration inhibits the cycle

TCA cycle is used in many pathways, state them..

1. amino acid synthesis 2. fatty acid synthesis 3. heme synthesis 4. glyconeogenesis 5. Neurotransmitter (brain)

``` Which of the following coenzymes is unique to α– ketoglutatrate dehydrogenase complex ? A. NAD+ B. FAD C. GDP D. H2O E. Lipoic Acid ```

e. lipoic acid

``` Coenyzme A is synthesized from which of the following vitamins? A. Niacin B. Riboflavin C. Vitamin A E. VitaminC D. Pantothenate ```

d. pantothenate

``` A patient diagnosed wşth the thiamine deficiency exhibited fatigue and muscle cramps. The muscle crampsi have been related tı an accumulation of metabolic acids. Which of the following metabolic acids is most likely yo accumulate in a thiamine defiency? A. Isocitric acid • B.Pyruvic acid • C. Succinic acid • D. Malic acid • E. Oxaloacetic acid ```

``` How many NADH molecules are generated from the complete oxidation of one Glucose? A. 5 B. 7 D. 16 E. 32 C. 10 ```

In what form is the energy released from TCA cycle oxidation?

NADH FADH2 GTP (guanosine triphosphate)

TCA Cycle accounts for more than one-third of the adenosine | triphosphate (ATP) generated from fuel oxidation.

False | its two-third

TCA has both catabolic and anabolic roles.

True

Which of the following is not true? A. Cellular respiration provides more energy (ATP) from glucose than glycolysis B. Only a small amount of energy available in glucose is captured in glycolysis C. glycolysis captures energy stored in lipids and amino acids D. Cellular respiration is used by animals, plants, and many microorganisms

C Cellular respiration captures energy stored in lipids and amino acids

What are the three basic steps of cellular respiration?

1. Acetyl CoA production 2. Acetyl CoA oxidation 3. Electron transfer and oxidative phosphorylation

``` Acetyl CoA can be from all except A. Fatty acid B. Ketone bodies C. Amino acids D. Acetate E. Lactate ```

E. Lactate

What is the enzyme that catalyzes the oxidative decarboxylation of pyruvate to form acetyl-CoA?

Pyruvate Dehydrogenase Complex (PDH)

Which of the following is true about PDH? A. PDH complex is part of TCA cycle B. its is one of the enzymes in glycolysis C. In the liver, it is activated by insulin, whereas in the brain and nerves, its not responsive to hormones D. All

C PDH complex is not part of the TCA cycle but it supplies substrate for the cycle.

Which of the following is true about acetyl-CoA A. Coenzymes are not a permanent part of the enzymes’ structure B. The function of CoA is to accept and carry acetyl groups C. CoA contains thiol group, pantothenic acid, and ribose 3 phosphate D. All

``` Which of the following is not among the coenzymes required for conversion of pyruvate to Acetyl-CoA? A. Thiamine Pyrophosphate (TPP) B. lipoic acid C. Palmitate D.FAD E.NAD+ F. CoA-SH ```

``` C Thiamine Pyrophosphate (TPP),lipoic acid, and FAD are prosthetic groups while NAD+ and CoA-SH are coenzyme ```

Which of the following is not advantage of multienzyme complexes? A. channeling minimizes side reactions B. regulation of activity of one subunit affects the entire complex C. short distance between catalytic sites allows channeling of substrates from one catalytic site to another D. None

Which of the following is true? A. Enzyme 1 catalyze the first and second step B. Enzyme 2 work in re oxidation of lipoamide cofactor C. Enzyme 3 works in regenerating oxidized FAD cofactor forming NADH D. Oxidation of aldehyde to carboxylic acid is performed by Enzyme 2 E.A and B F.A and c

F Enzyme 1 Step 1: Decarboxylation of pyruvate to an aldehyde Step 2: Oxidation of aldehyde to a carboxylic acid Enzyme 2 Step 3: Formation of acetyl-CoA (product 1) Enzyme 3 Step 4: Re oxidation of the lipoamide cofactor Step 5: Regeneration of the oxidized FAD cofactor Forming NADH (product 2)

``` Which of the following match is true? A.Pyruvate Dhydrogenase -E1 B.Dihydrolipoyl Dehydrogenase -E2 C.Dihydrolipoyl Trasnacetlylase E3 D.All ```

A | B and C are reversed.

Which of the following is false A.NADH competes with NAD+ for binding to E3 B.Acetyl CoA competes with CoA for binding to E2 C.PDH is inhibited by Acetyl CoA and NADH D.Kinase is inhibited by ATP, Acetyl CoA, and NADH E.None

D | Kinase is activated by ATP, Acetyl CoA and NADH. In the presence of these, PDH complex is turned off.

Pyruvate dehydrogenase kinase (PDH Kinase) phosphorylates PDH and converts it to inactive form. True/ False

True

Which of the following is true about what happens during starvation? I.PDH kinase increases while PDH phosphate decrease II.Metabolism shift toward fat utilization III.Gluconeogenesis is maximized IV.Glucose is spared for use by the brain and RBC A.I, II, III B.I, III, IV C.II, III, IV D.I, II, IV

D | Gluconeogenesis is minimized.

The increased cytosolic Ca 2+ stimulates the phosphatase, & dephosphorylation activates ……………

- Pyruvate Dehydrogenase.

``` Which of the following is not one of Pyruvate Dehydrogenase Complex Deficiency? A.Beri Beri Disease B.Hemolytic anemia C.Lactic Acidosis D.Leigh syndrome ```

B | its glycolytic disorder

Which of the following is not true? A.a-ketoglutarate synthesis and oxaloacetate synthesis generates NADH B.Synthesis of Succinyl CoA is irreversible C.a-ketoglutarate dehydrogenase and pyruvate have similar complexes. D.Succinate synthesis produces GTP and is a substrate-level phosphorylation E.Fumarate synthesis produce FADH2 F.None

What is the net product of the citric acid cycle?

``` 2 CO2 3 NADH 1 FADH2 1GTP 1 CoA 3 H+ ```

1 NADH=.......ATP | 1 FADH2=......ATP

2. 5 | 1. 5

``` Which enzymes catalyze the reaction with high negative delta G (irreversible)? A.citrate synthase ( 1st step) B.Fumerase ( 7th step) C.isocitratedhydrogenase (3rd step) D.dehydrogenase complex (4th step) E.All except B F.All except D ```

``` Which of the following is wrongly matched with its function? A.A-ketoglutarate - Aminoacid synthesis B.Succinyl CoA- heme synthesis C.Malate- fatty acid synthesis D.Oxaloacetate- amino acid synthesis ```

C Malate- gluconeogenesis Citrate- fatty acid synthesis

Which steps produce NADH?

Oxaloacetate synthesis (8th step) a-ketoglutarate synthesis (3rd step) Succinyl CoA synthesis (4th step)

Citric acid cycle Flashcards

(76 cards)