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DS1101 - S1 Y1 > Week 5 - Citric Acid Cycle (TCA) > Flashcards

Week 5 - Citric Acid Cycle (TCA) Flashcards

1
Q

What is the citric acid cycle

A
  • A central catabolic pathway in the mitochondria which produces energy in the form of GTP and the reduced electron carriers NADH and FADH2
  • It requires acetyl-CoA hence from the glycolysis pathway there’s an additional step to convert the pyruvate into Acetyl-CoA
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2
Q

Where does the citric acid cycle occur

A

Mitochondrial Matrix

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3
Q

What reaction occurs before the TCA

A

oxidative decarboxylation

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4
Q

What is oxidative decarboxylation

A
  • Process which occurs before TCA to convert pyruvate from glycolysis and transform it into Acetyl-CoA
  • This occurs in Aerobic conditions
  • 5 steps
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5
Q

What is the equation for oxidative decarboxylation

A
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6
Q

Where does oxidative decarboxylation occur

A

Matrix of the mitochondria

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7
Q

What is the enzyme complex involved in oxidative decarboxylation

A

pyruvate dehydrogenase

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8
Q

What is the input for TCA

A

acetyl-CoA

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9
Q

What is step 1 of the TCA

A

Acetyl CoA enters at step 1 and syntheses with oxaloacetate (which was produced from the last step in TCA) and releases CoA (Coenzyme A) to be recycled

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10
Q

What is step 3 of TCA

A

NAD+ is reduced to form NADH which is the first step (3) where we’re actually creating energy. And is the first point where CO2 is loss

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11
Q

What occurs in step 4 of TCA

A

CO2 is loss again and NAD+ is reduced to NADH

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12
Q

What occurs in step 5 of TCA

A

Create the first direct energy usable molecule GTP

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13
Q

What occurs in step 6 of TCA

A

Forms another electron proton carrier, FADH2 through the reduction of FAD

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14
Q

What occurs in step 8 of TCA

A

Captures energy again to make another NADH through the reduction of NAD+

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15
Q

What are the oxidation steps in TCA

A

Step 3, 4, 6, 8
(molecules are being reduced hence other molecules must be oxidized)

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16
Q

What steps produce NADH

A

Step 3, 4, 8

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17
Q

How is NADH produced in TCA

A

NAD+ is reduced to form NADH and releases CO2 (makes the process a form of respiration)

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18
Q

When is GTP produced in TCA

A

Step 5

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19
Q

When is FADH2 created

A

Step 6

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20
Q

What is the change of carbon chain during the TCA

A
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21
Q

What is the RDS in TCA

A

Step 3 (NAD+ is reduced to form NADH which is the first step (3) where we’re actually creating energy)

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22
Q

What is step 1 of TCA

A
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23
Q

What is step 3 of TCA

A
24
Q

What is step 4 of TCA

A
25
Q

Which steps of TCA is regulated

A
  • Step 1
  • Step 3
  • Step 4
26
Q

What is the enzyme which catalyzes step 1 of TCA

A

citrate synthase

27
Q

What is the enzyme which catalyzes step 3 of TCA

A

isocitrate dehydrogenase

28
Q

What is the enzyme which catalyzes step 4 of TCA

A

a-ketoglutarate dehydrogenase complex

29
Q

What is step 1 regulated by

A

Inhibited by ATP and NADH, succinyl-CoA (S4) and the product citrate

30
Q

What is step 3 regulated by

A

activated by ADP and NAD+
inhibited by ATP and NADH

31
Q

What is step 4 regulated by

A

activated by ADP and NAD+
inhibited by ATP and NADH and product of this step succinyl-CoA

32
Q

What is the overall reaction of the TCA cycle

A
33
Q

What occurs after the TCA

A

Oxidative phosphorylation
The remaining energy is located in redox/H+ carriers FADH2 and NADH, it is now converted into available energy using an ATP synthase in the mitochondrial inner membrane

34
Q

What processes occur in oxidative phosphorylation

A
  • electron transport chain
  • Chemiosmosis
35
Q

Where does oxidative phosphorylation occur

A

inner membrane of the mitochondrion

36
Q

What are the electron carriers in the electron transport chain

A

coenzyme Q and cytochrome C

37
Q

What is the process of the electron transport chain

A
  1. NADH approaches complex 1 and gives up its protons and electrons to form NAD+, in turn donating its electron to complex 1 - supercharging it
  2. Supercharged complex 1 has the energy to pump protons (H+) from the mitochondrial matrix into the intermembrane space - creating an accumulation of protons on this side (forming a proton gradient)
  3. Complex 1 passes its electron to CoQ
  4. FADH2 gives up it’s electrons to complex 2 to form FAD, however complex 2 cannot pump protons
  5. Complex 2 transfers its electron to CoQ
  6. Electrons in CoQ are passed to complex 3 - providing it energy to pump more protons from the mitochondrial matriz into the intermembrane space
  7. Complex 3 passes its electrons to Cytochrome C
  8. Cytochrome C passes it’s electrons to complex 4 which then becomes supercharged and pumps more protons into the intermembrane space adding to the strong proton gradient
  9. Complex 4 passes its electrons to oxygen (O2) forming 2 oxygen ions, and then protons are added, forming 2 water molecules
38
Q

What is chemiosmosis

A

the process which takes the stored electrochemical energy in the ion gradient and converts it into a high energy bond in ATP.
This uses an ATP synthase

39
Q

What is the protein which brings about the synthesis of ATP oxidative phosphorylation

A

ATP synthase

40
Q

What is the chemiosmotic theory

A

the flow of H+ through ATP synthase due to the proton gradient lead to conformational changes in ATP synthase which

  1. binds ADP
  2. phosphorylates ADP into ATP
  3. releases the ATP

This occurs in a binding change mechanism within the ATP synthase. ATP synthase may be regarded as a rotating molecular motor, as a flow of protons turns the motor clockwise.

41
Q

What is the overall reaction of oxidative phosphorylation

A
42
Q

Why is anaerobic metabolism used instead of aerobic metabolism when active

A

Aerobic metabolism releases energy at a low rate so when someone is running they will switch to anaerobic metabolism and the body will deal with the build of lactic acid in their muscles because anaerobic metabolism will release energy at a greater rate.

43
Q

What is the ATP yield of the whole aerobic glycolysis + TCA + OxPhos

A

36 ATP
(30-38 ATP)

44
Q

What is the ATP yield of anaerobic glycolysis

A

net 2 ATP from the conversion of 1 molecule of glucose to 2 molecules of lactic acid

45
Q

How much ATP is produced by the NADH produced from glycolysis and TCA

A

Glycolysis NADH = 2 ATP
TCA NADH = 3ATP

46
Q

Why does the NADH produced in glycolysis produce less ATP than the NADH produced in TCA

A

For NADH to be converted into ATP from the electron transport chain it must be in the mitochondria
Hence NADH from glycolysis is in the cytosol and uses up some energy to get into the mitochondria
On the other hand NADH from TCA is already in the mitochondria

47
Q

How many ATP molecules are produced from oxidative decarboxylation

A

6
as it produces 2 NADH (from 2 pyruvate molecules) (1 NADH = 3 ATP)

48
Q

How many ATP molecules are produced from TCA and oxidative phosphorylation

A

24

49
Q

What does the electron transport chain create

A

A proton gradient (pH) gradient) across the membrane which represents stored potential energy - a voltage gradient

50
Q

what is a voltage gradient

A

Difference in concentration of H+ ions across the membrane
It is an electrochemical potential

51
Q

How many H+ are pumped out per NADH

A

6 H+

52
Q

How many H+ are pumped out per FADH2

A

4H+

53
Q

What is the terminal electron acceptor in ETC

A

O2 (oxygen)

54
Q

What is the overall reaction from the citric acid cycle combined with oxidative phosphorylation

A
55
Q

What is the overall reaction for just electron transport chain

A

DS1101 - S1 Y1 (63 decks)

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