Download ELECTRON TRANSPORT CHAIN (student)

ELECTRON TRANSPORT CHAIN
Stage 4:
How far have we come?
• We began with our simple glucose molecule
• Through the processes of...
– GLYCOLYSIS
– PYRUVATE OXIDATION
– KREBS CYCLE
...we have used the energy stored in the C-C
bonds of glucose to help ATP
• Directly (substrate-level phosphorylation)
• Indirectly (oxidative phosphorylation)
Energy Totals
• GLYCOLYSIS
• PYRUVATE
OXIDATION
• KREBS CYCLE
ATP
USED
ATP
produced
NADH
produced
FADH2
produced
2
4
2
0
ATP USED ATP
produced
NADH
produced
FADH2
produced
2
4
0
ATP USED ATP
produced
NADH
produced
FADH2
produced
2
10
2
4
6
So what’s the deal with ATP??
• C6H12O6 + 6O2  6CO2 + 6H2O + 36 ATP
• We need to produce 36 ATP in Cell. Resp.
• After 3 stages, we have only produced 6 ATP
through substrate-level oxidation
• Thus, there are 30 ATP left to create
– We produce the remaining 30 ATP through
oxidative phosphorylation in the ETC
ELECTRON-TRANSPORT-CHAIN
• In this step, we will utilize
the energy provided by the
electron carriers
NADH and FADH2
•Extremely
EXERGONIC
∆G = -2870 kJ/Mol
How it works
• NADH + FADH2 eventually transfer the electrons they carry to a series
of proteins that are located in the inner membrane
• The components of the ETC
are arranged in order of
increasing electronegativity
• Thus, allowing the electrons to
flow, or BE TRANSPORTED,
between the compounds
• Every step involves oxidation
and reduction rxns.
How it works
• Every time an electron moves from one molecule to the next,
free energy is released
• The free energy is used to pump H+ ions, or PROTONS, from the
mitochondrial matrix into the
INTERMEMBRANE SPACE
• The ETC needs a highly
electronegative compound
to oxidize the last protein
– OXYGEN is used here, as it is one
of the most electronegative
compounds on earth
How it works
• An oxygen atom removes two é from the final protein complex
• Oxygen then combines with 2 protons (H+) in the mitochondrial
matrix to form an H2O molecule
Diagram
• The red path shows the path
that é travel through the ETC
• KNOW NAMES OF THESE
MOLECULES
How it works
UBIQUINONE (Q)
cytochrome C
CYTOCHROME
OXIDASE COMPLEX
NADH
DEHYDROGENASE
CYTOCHROME b-c1
COMPLEX
NADH + FADH2... Not so similar
• NADH passes its electrons to the first protein complex
– NADH DEHYDROGENASE
• FADH2 passes its electrons to Q (or ubiquinone)
• This distinction means that:
– NADH = 3 H+ pumped out
– FADH2 = 2 H+ pumped out
• SO...
– NADH produces 3 ATP
– FADH2 produces 2 ATP
NADH + FADH2... Not so similar
• The NADH you produced in glycolysis works differently than the
NADH produced in pyruvate oxidation and Krebs cycle
– Why?
• Glycolysis occurs in the
cytoplasm, thus NADH has to
travel through the double
membrane of mitochondria
– it can’t pass the inner membrane
• NADH passes its é through a
protein transport to FAD thus
forming FADH2
ATP PRODUCTION
• Electrochemical Gradient: A concentration gradient created by
pumping ions into a space surrounded by a membrane that is
impermeable to the ions
– This is exactly what we are doing when we pump H+ ions into the
intermembrane space using the ETC
– Thus, the inner membrane becomes a H+ reservoir
– An potential difference, or VOLTAGE, is created across the
membrane
• +ve charge in the intermembrane space
• –ve charge in the mitochondria matrix
+
-------
-
ATP PRODUCTION
• H+ ions can not diffuse back through the innermembrane
• They need to be pumped back by the transport protein
ATP SYNTHASE
• As H+ ions are passed through
ATP SYNTHASE, the free energy
of the gradient is reduced, thus
releasing enough energy to
produce ATP
• ADP + Pi  ATP
ATP PRODUCTION
• This process was coined: CHEMIOSMOSIS
• ATP synthesized was caused by the ‘osmosis of H+ ions’
• Chemiosmosis is said to be COUPLED to the ETC
Final Energy Tally
Theoretical Yield vs. Actual Yield
•
It is possible that we will not always obtain
36 ATP for every glucose molecule that we
used
•
2 reasons:
1.
Some H+ ions may make it through the inner mitochondrial
membrane reducing the number of H+ ions that pass
through ATP synthase.
Some of the protons in the H+ reservoir might get used up
in other cellular reactions
2.