PHSC 208, L28

Purpose of electron transport system

move electrons that were gathered from the co-enzymes (co-enzymes got electrons from oxidizing carbons)

• use energy from electrons being shuttled around

• bring electrons and move them from each complex and finally move to oxygen to make water

How do we regenerate the NAD+ and FAD we need to run glycolysis and the citric acid cycle?

the electron transport system

What happens in the mitochondria that gets you sick??

pesticides, antibiotics, carbon minoxides, etc get into mitochondria and inhibit electron transport system

The energy released during mitochondrial electron transfer is used for…

1. ATP synthesis

2. Ca2+ uptake when cell overloaded with calcium

3. Thermogenesis (heat generation)— how animals survive winter

What are the cons of the electron transport system?

• shuttling electrons and having oxygen at the terminal acceptor is dangerous— causing problems in aging

• oxidation/reduction of unwanted things

Mitochondrial outer membrane contains ____

Porins (proteins that will make a hole)

• smaller than 10,000 daltons (ions and small metabolites) can come in and out

Inner membrane of mitochondria is ______ to _______

impermeable to almost everything else

• O2, CO2, and H2O can diffuse in/out

• H2O comes in through the aquaporin

• things can go through it by concentration gradient or transporters

Explain the Malate-Aspartate Shuttling System

• oxaloacetate reduces into malate

  • allows electrons move into malate

  • malate gives electrons back into NADH to make NAD+

• Can now run electron transport system bc electrons from cytoplasm

Glycerol-3-Phosphate Shuttle

oxidize NADH to NAD+ and convert dihydroxyacetone phosphate to glycerol-3-phosphate

• good at giving up electrons to FADH2

• electrons can be shuttle into ETS of Complex II

What are electron carriers?

molecules that can hold one or more electrons

Mobile carriers can move ______ complexes

between

Ubiquinone (UQ or Co-enzyme Q)

is a mobile electron carrier in the electron transport chain that accepts electrons from various donors and passes them to Complex III

ubuquinone (UQ) is the ____ form

oxidized

ubiquinol (UQH2) is the _____ form

reduced

How does Statin lower cholesterol?

by inhibiting synthesis of cholesterol

• CON- also inhibits CoQ10

What is Cytochrome C (cyto c)?

a small protein with a heme molecule in the middle

• only carries one electron and no protons

• special electron carrier, carries from complex III→ complex IV

What happens when cyto c is released from mitochondria?

undergoes apoptosis (programmed cell death)

Complex I is known as ____

NADH dehydrogenase

Complex II is known as ______

succinate dehydrogenase

(also citric acid cycle)

Complex III is known as _______

cytochrome bc1 complex

What is cytochrome c in relation to Complex IV?

moble electron carrier that takes us to Complex IV

Complex IV is known as _____

cytochrome oxidase

Complex I (NADH dehydrogenase)

• dehydrogenase take electrons on NADH and move to FMH2

• 2 electrons moves through wire system and moves to ubiquinol (reduced form UQH2)

• 4 protons pumped out of the matrix

• NADH carries its electrons to Complex I, release electrons to ubiquinol

  Redox reaction: NADH + H⁺ + UQ (CoQ) → NAD⁺ + UQH2 (CoQH2) +4H

Complex II (succinate dehydrogenase)

• only enzyme that participate in both the citric acid cycle and ETS

  Redox reaction: succinate + UQ → fumarate +UQH2

• no electrons pump out of the matrix in Complex II

• FADH2 is in Complex II, release electrons to ubiquinol

Complex III (Q cycle)

• 2 electrons released from NADH and FADHs to ubiquinol, ubiquinol takes them to Complex III

• 2 ubiquinols come in, 1 ubiquinol and 1 ubiquinone leaves

Complex IV

• move electron from cyto c, move through wire and drop on wire

• 2 Cu forms Cu-Cu and 3rd Cu forms Fe-Cu center with cytochrome a3

• 4 protons pumped out to intermembrane space

  • 4 additional protons from matrix used to make 2 water molecules

iClicker: Which statement is TRUE regarding mobile elctron carriers entering/moving between the electron transport complexes?

a. electrons form NADPH enter ETS at Complex I

b. FADH2 enters ETS at Complex 2

c. Ubiquinol (UQH2) moves electrons from Complex 3 → Complex 4

d. cytochrome c carries two electrons

e. all of the above

b. FADH2 enters ETS at Complex 2