4/15 TCA and Glucose Metabolism

pyruvate can go through either aerobic or anaerobic pathway t or f

t

when can pyruvate go into the mitochondria

when there is a sufficient supply of oxygen

• starts TCA cycle

• starts oxidative phosphorylation

• ETC

• large amount of energy

under anaerobic conditions what can pyruvate be converted to in the muscle

lactate

NADH → NAD+

in cytosol

lactate in liver back to pyruvate through the cori cycle

What is pyruvate converted to in yeast under anaerobic cond

ethanol NADH → NAD+

what concentrations are fixed

NAD+/NADH ATP/ADP stays constant

having a lot of NADH means you have a lot of

energy because means glycolisis is happening producing ATP

what happens if NAD+ runs out what does the body resort to

glycolisis won’t continue because 6 step needs it

Body still generates 2 ATP per glucose

what is the purpose of anaerobic pathways

to regenerate NAD+ so glycolysis can continue and we can use the two generate ATP

Ethanol is converted to what where

acetate in the liver when ingested - regenerates NADH molecule

only during sufficient O2 supply

what cycle converts lactose to pyruvate in the liver

cori cycle

what two things can pyruvate do

anaerobic path

oxaloacetate

where does the TCA cycle take place

mitochondria

what is the starting material of the TCA cycle

pyruvate

what is the structure of the mitochondira

two lipid bilayer membrane

inner mitochondrial membrane

outer mitochondrial membrane

characteristics of inner mitochondrial membrane

highly folded with a large surface area, very impermeable, shape defining , houses machinery

characteristics of outer mitochondrial membrane

porins, permeable

what is the spcae bw 2 mitochondiral membrane

intermembrane space, inside

first step of citric acid cycle

pyruvate once in matrix of mitochondria (sufficient o2 supply)

pyruvate → pyruvate dehydrogenase → acetyl-CoA

NAD+ → NADH

Coash - CO2

decarboxylation and redox

structure of pyruvate dehydrogenase

three subunits which electrons flow through to eventually get NAD+ received 2 electrons

E1 - 60 TTP

E2- 60 lipoamide

E3 - 12 FAD

What bond is important in Acetyl-CoA and why

high energy thio-ester bond drives reaction

Step 1. Pyruvate Dehydrogenase

E1 subunit - decarboxylation of pyruvate to form hydroxyethyl-TPP

Step 2. Pyruvate Dehydrogenase

Hydroxyethyl TPP transfers two carbon acetyl molecule to E2 lipoamide, effectively reducing the disulfide bond

Step 3. Pyruvate Dehydrogenase

The E2 lipoamide is transfered to coenzyme A forming acetyl CoA, need to restore lipoamide

Step 4. Pyruvate Dehydrogenase

Oxidize the disulfide bond of E2 cofactor in E3 by FAD molecule

Step 5. Pyruvate Dehydrogenase

The FAD reduced generated donates electrons to NAD+, forming NADH and regenerating the oxidized form of E3.

final product of the catalytic system

how is pyruvate dehydrogenase regulated

pyruvate dehydrogenase is regulated by pyruvate dehydrogenase kinase which phosphorylates the E1 enzyme

• pyruvate dehydrogenase kinase is activated by high levels of ATPand NADH, inhibiting the complex.

• because it signals that energy is abudnant so we don’t need to keep making more

• shuts down conversion of pyruvate to acetyl co - a which is the first step of the citric acid cycle

What is the outcome of the TCA cycle

3 NADH, QH2, GTP (ATP)

First step of the TCA cycle

condensation of Acetyl-COA with Oxaloacetate to form a citrate molecule - catalyzed by citrate synthase,

the hydrolysis of the Acetyl-CoA thioester bond drives the reaction forward releasing CoA, also a water molecule is input

Why are conc of oxaloacetate kept low in the mitochondria

because its constantly being used in the TCA cycle

what is complex two

succinate dehydrogenase - membrane enzyme ETC TCA

what regulates the tca cycle

three irreversible steps

step two of TCA cylcle

aconitase catalyzes moving OH group on symmetrical citrate to unsymmetrical isocitrate , releasing water in the process

which steps of the TCA cycle generate an NADH molecule

3, 4, 8

what step of the TCA cycle resembles pyruvate dehydrogenase

step 4 - a ketoglutarate dehydrogenase because theres a oxidation and a decarboxylatoin resulting in NADH

which step of the TCA cycle produces a GTP

5 Succinyl CoA synthetase

step 3 TCA

isocitrate dehydrogenase , and decarboxylation

isocitrate to a-ketoglutarate , first NADH molecule

step 4 TCA

a-ketoglutarate dehydrogenase

a-ketoglutarate to succinyl CoA, also producing NADH

step 5 TCA

succinyl CoA sythentase

succinyl CoA to succinate

producing GTP from thio-ester bond since first step drove reaction forward and only substrate level phosphorylation

step 6

succinate dehydrogenase (complex 2 of etc)

succinate to fumurase double bond

everythingg w fad to qh2

inner membrane

step 7

fumarase

fumarate to malate with the addition of water

step 8

malate dehydrogenase

malate to oxaloacetate with the last NADH molecule produced finish the TCA cycle and even though its endergonic it goes forward because conc kept low bc its constantly used for tca cycle

inhibition of the TCA cycle

high conc of NADH inhibits three key enzymes

citrate synthase

isociatrate dehydrogenase and a-ketoglutarate dehydrogenasein the cycle, thus slowing down the overall process.

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how does pyruvate get converted to oxaloacetate

pyruvate carboxylatease converts pyruvate to oxaloacetate in a reaction that requires ATP and biotin as a cofactor.

what happens if u dont have pyruvate carboxylase

can’t ramp up the TCA cycles limited by oxaloacetate

what does pyruvate dehydrogenase kinase do

It phosphorylates and inhibits pyruvate dehydrogenase, reducing the conversion of pyruvate to acetyl-CoA.

How many total ATP made from a singular glucose

30 or 32

why is QH2 equal only 1.5 atp vs NADH which is 2.5 ATP

Because QH2 participates in fewer proton pumping steps in the electron transport chain compared to NADH, resulting in lower ATP yield.

QH2c doesnt go trhough compelx one

Oxaloacetate can combine with NADH to form malate accomplishing what

to get into the mitochondira for the citric acid cycle. - malate transport dependent pathway

32

makes no difference in cytosol or mitochondria

mitochondira dehydrogenase dependent pathway

NADH reacts with a DHAP → glycerol-3-phosphate → donates e pair to mitochondrial dehydrogenase → Q to QH2

• one mol NADH cytosol = 1 QH2 in mitochondria

30

how many protons are transferred per NADH mol

10 protons

how many protons from matrix to intermembrane space for complex one

4

how many protons from matrix to intermembrane space for complex three

4

how many protons from matrix to intermembrane space for complex four

2

what is the final electron reciever

o2

what is complex 2

succinate dehydrogenase step 6 of TCA FAD to QH2 succinate to fumarate oxidation forming a double bond

which complexes generate QH2

1 and 2

complex 1

thru clusters of redox centerstransfers electrons from NADH to Q.

NADH electrons —> FMN recieves 2 electrons —> one electron at a time through FeS clusters → Q to QH2 inside membrane

then diffuse away from complex one

four protons across matrix to intermembrane. space

what is a cytochrome

A cytochrome is a heme-containing protein that plays a crucial role in electron transport chains, facilitating the transfer of electrons through redox reactions. T

complex three

movbe to complex four recieving one elctron at a time from QH2

reduced cytochrome C

Complex 3

Q cycle

• QH2 by membrane released two electrons and two protons

• one electron → iron sulfur complex → cyt c → cyt c 1 → complex 4

• other electron cyt b - matrix and gives it to that naked Q

• Q-

  end of first cycle

  second cycle

• QH2 does same again releases two protons and two e

• one goes to cytochorme c

• Q- picks up the other electron and is Q2-, grabs 2 H’s from matrix side and diffuses away from complex 3

• net consumption of one QH2 bc regenerate one

• 4 protons

complex 4

cyt c from CIII releases the one electron into complex 4

recieved by final e reciver to O2 convert to water molecule

cytochrome oxidase

2 protons

how many protons does one QH2 move across the membrane

six protons

four from ocmplex three

two from 4

6 vs 10

what is the main consequence of the ETC

building up a large proton gradient across the membrane

proton motive force

the potential energy stored in the proton gradient across the inner mitochondrial membrane, driving ATP synthesis.

building up the large potential

what is ATP synthase

An enzyme complex that uses the proton motive force to synthesize ATP from ADP and inorganic phosphate.

proton gradient from ETC drives ATP formatoin

referred to as complex 5 of the etc

what are the two sub units of atp synthase

F0 and F1

F0

A B and C sub unit

A and C associate tg and is the functional unit

B is the arm that holds F1 and F0 tg - more structure

F1 - generates the ATP molecule

alpha gamma beta epsilon

important

Alpha Beta Gamma subunits work together to facilitate ATP synthesis and enzymatic action.

What motion does ATP synthase do

rotates

how does the F0 unit of ATP synthase work

protons flow into the open channel of a sub unit down its conc gradient and binds to a C sub unit, causing rotation and as a new subiunit C reaches A a proton is released

one rotation = 8 protons translocated bc 8 C sub units, releases from itnermembrane space back to matrix by flowing throuugh half the channel at a time

rotate a turbine

converts the potential energy from the proton gradient to kinetic energyto drive ATP synthesis in the F1 complex

how to link rotation of AC F0 turbine to F1 synthesis for ATP

Gamma sub unit of F1 - switch - anchored to turbine rotates with it - switch to a conformational state that activates ATP synthesis. As gamma rotates, it induces changes in the alpha and beta subunits that promote ATP production.

The conformations are loose open and tight

open releases the new atp molecule

tight = ADP + Pi in mechanical force

ADP and Pi orients

tight open and loose

tight = mechanical force puts them tg

open = release and pick them up

loose = orient

rotation based on rotation fo the gamma subunit switch

one rotation of a ab subunit complex generates how many atp

3

How does the free phosphate get in there

H+ gradient from ETC proton pumps, utilizes protein gradient secondary active symporter

ATP from the matrix is coupled with

ADP into the matrix

if the proton gradient doesn’t get used what happens to the electron transport chain

will stop because the point is to build up the gradient

if the ETC stops, the TCA will stop bc NADH will build which inhibits 3 key enzymes in TCA

what enzymes does NADH inhibit in TCA

Thermogenin

.

Protons moving back and forth across the gradient generate body heat if they don’t generate ATP

return of protons to the matrix and proton motive force is released as heat

alternative return route without coupling like bears