Download Enduring Understanding: Growth, reproduction and maintenance of

Essential Knowledge 2.A.2: Organisms capture
and store free energy for use in biological
processes

What happens to pyruvate after glycolysis?
◦ Pyruvate is transported from the cytoplasm to the
mitochondrion via a transport protein.
◦ Pyruvate’s carboxyl group (COO-), which is already
fully oxidized, is removed as CO2
◦ The remaining 2 carbon fragment is oxidized,
forming a 2 C compound called acetate and
reducing NAD+ to NADH + H+
◦ Acetate joins with Coenzyme-A, which makes it
very reactive, forming Acetyl Co-A
CYTOSOL
MITOCHONDRION
NAD+
2
1
Pyruvate
Transport protein
NADH +
H+
3
CO2
Coenzyme A
Acetyl CoA

Where does the Krebs Cycle take place?
◦ The matrix of the mitochondria

When Acetyl Co-A enters the Krebs Cycle,
what does it join with?
◦ It joins with OAA (oxaloacetate). The 2 carbons
originally from Pyruvate (and glucose) join with the
4 carbons of OAA to form 6 carbon Citrate.

What happens in the Krebs cycle?
◦ Through a series of enzyme catalyzed reactions the
remaining 2 carbons from pyruvate (originally from
glucose) are oxidized and expelled as CO2. 3 NAD+
are reduced to form 3 NADH + 3H+ and 1 FAD is
reduced to form 1 FADH2. Indirectly 1 ATP is
formed.

How is ATP formed during the Krebs Cycle?
◦ Substrate level phosphorylation
Acetyl CoA
Summary of products
from 1 turn of the
Krebs Cycle:
CoA—SH
NADH
+H
NAD+
2 CO2
3NADH + H+
1FADH2
1ATP
H2 O
1
+
8
Oxaloacetate
2
Malate
H2 O
Citrate
Isocitrate
NAD+
Citric
acid
cycle
7
Fumarate
NADH
+ H+
3
CO2
CoA—SH
6
-Ketoglutarate
4
CoA—SH
5
FADH2
NAD+
FAD
Succinate
GTP GDP
ADP
ATP
P i
Succinyl
CoA
NADH
+ H+
CO2
Pyruvate
CO2
NAD+
Summary of products
from the end of glycolysis
thru the Krebs Cycle per
glucose molecule:
CoA
NADH
+
H+
Acetyl CoA
CoA
CoA
6 CO2
8 NADH + H+
2 FADH2
2ATP
Citric
acid
cycle
2 CO2
FADH2
3
NAD+
3 NADH
FAD
ADP
+
ATP
P
+3
H+
i

Essential Knowledge 4.A.2:The structure and
function of subcellular components, and their
interactions, provide essential cellular processes.
◦ How do mitochondria specialize in energy capture and
transformation?
 Mitochondria have a double membrane that allows
compartmentalization within the mitochondria and is
important to its function
 Matrix (within the inner membrane)
 Intermembrane Space (between the inner & outer membranes)
 The outer membrane is smooth, but the inner membrane is
highly convoluted, forming folds called cristae
 Cristae contain enzymes important to ATP production;
cristae also increase the surface area for ATP production
Intermembrane space
Outer
membrane
Free
ribosomes
in the
mitochondrial
matrix
Inner
membrane
Cristae
Matrix
0.1 µm

Where is the electron transport chain of
cellular respiration?
◦ The Cristae (inner member of mitochondria)
◦ In prokaryotic organisms it is located in the plasma
membrane

What happens at the electron transport chain?
◦ Electrons delivered by NADH and FADH2 are passed
thru a series of electron acceptors as they move
toward the terminal electron acceptor, oxygen.

What happens as electrons move through the
electron transport chain?
◦ The energy released by passage of electrons from
one electron carrier to the next is used to pump H+
from the matrix into the intermembrane space. (In
prokaryotes H+ is pumped outside the plasma
membrane.)
◦ This creates a gradient of H+ across the membrane
called a proton-motive force.
INTERMEMBRANE SPACE
H+
Stator
Rotor

How does the proton
gradient (H+) produce
ATP?
◦ The energy stored in the
proton gradient is
released as H+ move back
across the cristae through
H+ channels provided by
ATP synthases chemiosmosis
Internal
rod
Catalytic
knob
ADP
+
P
i
ATP
MITOCHONDRIAL MATRIX
H+
H+
H+
H+
Cyt c
Protein
complex
of electron
carriers
V
Q



FADH2
NAD
H
(carrying
electrons
FAD
ATP
synthase
2 H + + 1 / 2 O2
NAD
H2 O
ADP + P i
+
from food)
ATP
H+
1 Electron transport chain
Oxidative
phosphorylation
2 Chemiosmosis

Chemiosmosis couples the electron transport
chain to ATP Synthesis…
◦ Electron Transport Chain: Electron transport and
pumping protons (H+), which create an H+ gradient
across the membrane
◦ Chemiosmosis – ATP synthesis powered by the flow
of H+ back across the membrane
Electron shuttles
span membrane
CYTOSOL
MITOCHONDRION
2 NADH
or
2 FADH2
2 NADH
Glycolysis
Glucose
2
Pyruvate
6 NADH
2 NADH
2
Acetyl
CoA
+2
ATP
Citric
acid
cycle
+2
ATP
Maximum per glucose:
About
36 or 38
ATP
2 FADH2
Oxidative
phosphorylation:
electron transport
and
chemiosmosis
+ about 32 or 34 ATP
ATP yield per Glucose at each Stage
Process
NADH
FADH2
ATP
Glycolysis
2
0
2
Krebs Cycle
8
2
2
Oxidative
Phosphorylation
Total x 3 =
10 x 3 = 30
Total X 2 =
2x2=4
34*
Maximum per glucose = 36 to 38
*depends on which shuttle transports electrons from NADH in
cytosol – may cost 2 ATP in that case OP = 32