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Biochemistry > Unit 4: Chapter 19 > Flashcards

Unit 4: Chapter 19 Flashcards

1
Q

Each acetyl CoA enters citric acid cycle to become oxidized and loses _____ as ____

A

2 carbon; 2 CO2

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2
Q

First stage of Citric Acid cycle

A
  • 2 carbons are introduced into the cycle by condensation of an acetyl group with a 4 carbon compound, oxaloacetate to produce 6 carbon compound of citrate
  • Citrate undergoes 2 oxidative decarboxylations to releas 2 CO2
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3
Q

Second stage of citric acid cycle

A

Oxaloacetate regenerated

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4
Q

Both stages of citric acid cycle generate

A

High energy electrons that are used to power the synthesis of ATP in oxidative phosphorylation

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5
Q

Cellular Respiration

A

Glucose –> 2 pyruvate (glycolysis) –> CO2 + 2 acetyl CoA (when O2 available in mitochondria –> lose CO2 (citric acid cycle)

REMINDER: acetyl CoA can be made from glucose, fatty acids, and amino acids

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6
Q

Citric acid cycle produces NADH and FADH2 which is important:

A
  • Have the power to generate ATP in later stages up to 9 ATP
  • NADH = 2.5 ATP
  • FADH2 = 1.5 ATP
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7
Q

True or False: Acetyl CoA is just produced by just glucose

A

False: Acetyl CoA can be produced from glucose, fatty acids, and amino acids

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8
Q

Where is location of Acetyl CoA formation/ pyruvate dehydrogenase complex?

A

Mitochondrial Matrix

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9
Q

Where is location of citric acid cycle?

A

Mitochondrial Matrix

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10
Q

Where is location of electron transport chian, proton pump, and ATP synthesis?

A

Intermembrane mitochondria

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11
Q

Electron Transport Chain

A

Membrane protein embedded in the inner mitochondria membrnae

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12
Q

Step 1 of Citric Acid Cycle

A
  • Citrate synthase catalyzes condensation of oxaloacetate (4 carbon) and acetyl CoA (2 carbon) to form citryl CoA intermediate (thioester bond)
  • Citryl CoA is cleaved with water to make citrate (6 carbon) and releases CoA
  • Irreversible reaction
  • Very negative ΔG°’
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13
Q

Why is step 1 of citric acid cyle irreversible reaction?

A

Due to thioester bond in acetyl CoA which is very high energy bond to drive reaction

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14
Q

Synthase

A

enzyme that catalyzes synthetic reaction in which two units are joined usually without the direct participation of ATP or other NTP

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15
Q

Citrate Synthase

A
  • Catalyzes step 1 of citric acid cycle
  • Exhibits induced fit
  • Binds to oxaloacetate and conformational change occurs for formation of binding site for acetyl CoA
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16
Q

Formation of reaction intermediate in step 1 ______ causes a structural change that completes active site formation

A

Citryl CoA

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17
Q

Aconitase

A
  • Catalyzes formation of isocitrate from citrate
  • Switches H and OH location in order for clevage to occur and CO2 to be removed
  • Tertiary alcohol to secondary alcohol
  • Shuts down citric acid cycle and cellular respiration –> role as pesticide
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18
Q

Step 2 of citric acid cycle

A
  • Aconitase catalyzes isomerization of citrate to isocitrate
  • location of H and OH switch
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19
Q

Aconitase is inhibited by

A

metabolite of fluroacetate which acts as suicide/ irreversible inhibitor

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20
Q

Fluroacetate

A

Suicide/ irreversible inhibitor
Found in floweering plants
When ingested, turns into fluroacetyl COA which reacts with citrate to form flurocitrate

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21
Q

What enzyme shuts down citric acid cycle and cellular respiration and acts as pesticide?

A

Aconitase

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22
Q

What enzyme switches H and OH position?

23
Q

Step 3 of citric acid cycle

A
  • Isocitrate dehydrogenase catalyzes oxidative decarboxylation of isocitrate to form alpha ketoglutarate and captures high energy electron as NADH
  • Isocitrate (6 carbon) oxidized to oxalosuccinate intermediate (6 carbon) and decarboxylated to alpha ketoglutarate and releases CO2 (5 carbon)
  • First oxidative decarboxlation (CO2 released)
24
Q

Acetyl CoA introduced 2 carbon unit but 2 carbon will not release as CO2 the ____ but _____

A

first time; second time

25
Q

Step 4 of Citric Acid Cycle

A
  • Alpha ketoglutarate dehydrogenase complex catalyzes the synthesis of succinyl CoA from alpha keto glutarate and generates NADH
  • Second oxidative phosphorylation (releases CO2)
26
Q

Alpha ketoglutarate dehydrogenase complex in step 4 of citric acid cycle is structurally and mechanically similiar to

A

pyruvate dehydrogenase complex

27
Q

In first time of citric acid cycle, the 2 carbon that are released are from where?

A

Oxaloacetate

28
Q

Alpha ketoglutarate dehydrogenase complex cofactors

A

TPP, Lipoic acid, FAD, coenzyme A, Mg2+

29
Q

Step 5 of Citric Acid Cycle

A
  • Succinyl Coa synthetase catalyzes clevage of thioester linkage of Succinyl CoA and powers formation of ATP and forms succinate
  • Only step ATP generated
  • Only substrate level phosphorylation in cycle
30
Q

Suiccinyl CoA product of step 4 contains

A

thioester bond so compound has high phosphoryl transfer potential

31
Q

Substrate phosphorylation

A

High phosphoryl transfer potential compound donates phosphate to ADP for ATP formation

32
Q

What step of citric acid cycle is only step ATP generated and substrate level phosphorylation?

A

Step 5: Succinyl CoA to Succinate

33
Q

Reaction Mechanism of Succinyl CoA synthetase

A
  • Histidine active site of Succinyl CoA synthetase performs nucleophillitic attack on Succinyl phosphate for succinate to be released
  • Hydrolysis of thioester bond to produce ATP
34
Q

What steps are invovled in regeneration of Oxaloacetate?

A

Steps 6, 7, 8

35
Q

_____ regenerates each citric acid cycle

A

Oxaloacetate (4 carbon)

36
Q

___ and ___ initiates another citric acid cycle

A

Oxaloacetate; acetyl CoA

37
Q

All enzymes in citric acid cycle are found in _____ but for sucinate dehydrogenase (step 6)

A

mitochondrial matrix

38
Q

All enzymes in citric acid cycle are found in mitochondrial matrix but for ___________

A

Succinate Dehydrogenase (step 6) embedded in innermitochondrial membrane

38
Q

Step 6 of citric acid cycle

A
  • Catalyzed succinate dehydrogenase
  • Succinate oxidized to Furmate
  • FAD reduced to FADH2
  • NOT IN MITOCHONDRIAL MATRIX, in innermitochondria membrane
39
Q

Step 7 of citric acid cycle

A
  • Catalyzed by furamase
  • Furmate added water for double bond to form hydroxyl and hydrogen on maltate
40
Q

Step 8 of citric acid cycle

A
  • Catalyzed by maltate dehydrogenase
  • Maltate oxidized to Oxaloacetate
  • NAD+ reduced to NADH
  • Fourth and final oxidation of cycle
  • Very positive ΔG°’
  • Very negative ΔG
  • Rxn pulls citrate synthetase reaction of the next step
41
Q

From glucose, what are the products of the citric acid cycle

A

6 NADH, 2 FADH2, 4 CO2, 2 ATP

Products are doubled starting from glucose as we have 2 acetyl CoA

42
Q

Net reaction of Citric Acid Cycle with 1 acetyl CoA

A

1 acetyl CoA + 3 NAD+ + FADH + ADP + Pi + 2H20 –> 2CO2 + 3NADH + FADH2 + ATP + 2H+ + CoA

43
Q

Per pyruvate generates what and ATP equivalents

A

4 NADH = 10 ATP
1 FADH = 1.5 ATP
1 ATP

Total 12.5 ATP per pyruvate

44
Q

How mcuh ATP is generates from glucose through acetyl CoA formation and citric acid cycle?

45
Q

What is key control point in citric acid cycle?

A

Isocitrate dehydrogenase and alpha ketoglutarate dehydrogenase

46
Q

Citric Acid Cycle must be reeplineshed because

A

Citric Acid cycle provides precursors for biosynthesis so replenishing reactions are needed (anaplerotic)

47
Q

Anaplerotic reactions refers to

A

Replening reactions

48
Q

Prominent anaplerotic reaction is catalyzed by ______ ________

A

pyruvate carboxylase

49
Q

Glyoxylate Cycle

A
  • Similiar to citric acid cycle but bypass 2 decarboxylation steps, allowing synthesis of carbohydrates from fats
  • Not in humans
  • Succinate can be converted into oxaloacetate and into glucose since no carbon is loss
  • prominent in oil rich seeds
50
Q

Pyruvate carboxylase anaplerotic reaction

A

Increase in Acetyl CoA activated pyruvate carboxylase which activates oxaloacetate for repinish

51
Q

Key enzymes of glyoxylate cycle

A

Isocitrate lyase: catalyzes cleavage of isocitrate to glyoxylate and succinate
Maltate synthase: catalyzes reaction of glyoxylate with acetyl CoA to produce maltate

52
Q

Reaction equation of glyoxylate cycle

A

2 acetyl CoA + NAD+ + 2H20 –> succinate + 2 COASH + NADH + 2H+

NO CO2 produced!!
One extra oxaloacetate

Biochemistry (17 decks)

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