essential knowledge 2.a.2: organisms capture and store free energy for use in biological processes

Enduring Understanding: Growth, reproduction and

maintenance of the organization of living systems require free

energy and matterEssential 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

Cellular respiration in eukaryotes involves a series of coordinated enzyme-catalyzed reactions that harvest free energy from simple carbohydrates

CYTOSOL

MITOCHONDRION

NAD+

NADH

+ H+

2

1 3

PyruvateTransport protein

CO2

Coenzyme A

Acetyl CoA

Cellular respiration in eukaryotes involves a series of coordinated enzyme-catalyzed reactions that harvest free energy from simple carbohydrates 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

Cellular respiration in eukaryotes involves a series of coordinated enzyme-catalyzed reactions that harvest free energy from simple carbohydrates

Acetyl CoACoA—SH

Citrate

H2O

Isocitrate NAD+

NADH+ H+

CO2

-Keto-glutarate

CoA—SH

CO2NAD+

NADH+ H+Succinyl

CoA

CoA—SH

P iGTP GDP

ADP

ATP

SuccinateFAD

FADH2

Fumarate

CitricacidcycleH2O

Malate

Oxaloacetate

NADH+H+

NAD+

1

2

3

4

5

6

7

8

Summary of products from 1 turn of the Krebs Cycle:

2 CO23NADH + H+

1FADH21ATP

Pyruvate

NAD+

NADH+ H+ Acetyl

CoA

CO2

CoA

CoA

CoA

Citricacidcycle

FADH2

FAD

CO22

3

3 NAD+

+ 3 H+

ADP +

P i

ATP

NADH

Summary of products from the end of glycolysis thru the Krebs Cycle per glucose molecule:6 CO28 NADH + H+

2 FADH22ATP

Enduring Understanding 4.A: Interactions within biological systems lead to complex properties (side bar) 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

Free ribosomesin the mitochondrial matrix

Intermembrane space Outer

membrane

Inner membraneCristae Matrix

0.1 µm

The electron transport chain captures free energy from electrons in a series of coupled reactions that establish an electrochemical gradient across membranes. 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.

The electron transport chain captures free energy from electrons in a series of coupled reactions that establish an electrochemical gradient across membranes.

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

The electron transport chain captures free energy from electrons in a series of coupled reactions that establish an electrochemical gradient across membranes.

INTERMEMBRANE SPACE

Rotor

H+

Stator

InternalrodCata-lyticknob

ADP+P ATP

iMITOCHONDRIAL MATRIX

Protein complexof electroncarriers

H+

H+H+

Cyt c

Q

V

FADH2

FADNAD

+NADH(carrying

electronsfrom food)

Electron transport chain

2 H+ + 1/2O2

H2O

ADP +

P i

Chemiosmosis

Oxidative phosphorylation

H+

H+

ATP synthase

ATP

21

The electron transport chain captures free energy from electrons in a series of coupled reactions that establish an electrochemical gradient across membranes.

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

Maximum per glucose:

About36 or 38

ATP

+ 2 ATP

+ 2 ATP

+ about 32 or 34 ATP

Oxidativephosphorylation:

electron transport

andchemiosmosis

Citricacidcycle

2Acety

lCoA

Glycolysis

Glucose

2Pyruva

te

2 NADH

2 NADH

6 NADH

2 FADH2

2 FADH2

2 NADH

CYTOSOL Electron shuttlesspan membrane o

r

MITOCHONDRION

Process NADH FADH2 ATPGlycolysis 2 0 2

Krebs Cycle 8 2 2Oxidative

PhosphorylationTotal x 3 =10 x 3 = 30

Total X 2 =2 x 2 = 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

ATP yield per Glucose at each Stage