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Cellular Respiration: Electron Transport Chain Ch. 9. Ms. Springstroh AP Biology Adapted from Ms. Gaynor-Day and Mr. Grant. What’s the point?. The point is to make ATP !. ATP. ATP accounting so far…. Glycolysis  2 ATP Kreb’s cycle  2 ATP

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Cellular respiration electron transport chain ch 9

Cellular Respiration: Electron Transport ChainCh. 9

Ms. Springstroh

AP Biology

Adapted from Ms. Gaynor-Day and Mr. Grant


What’s thepoint?

The pointis to makeATP!

ATP


Atp accounting so far
ATP accounting so far…

  • Glycolysis 2ATP

  • Kreb’s cycle 2ATP

  • Life takes a lot of energy to run, need to extract more energy than 4 ATP!

There’s got to be a better way!

I need a lotmore ATP!

A working muscle recycles over 10 million ATPs per second


Stage 3 oxidative phosphorylation electron transport chain etc chemiosmosis
Stage #3: Oxidative Phosphorylation(Electron Transport Chain (ETC) + Chemiosmosis)

  • Chemiosmosisis a process which connects the processes of electron transport and ATP synthesis

  • NADH and FADH2

    • Drop off e-’s at ETC, which powers ATP synthesis using oxidative phosphorylation

      **OCUURS IN CRISTAE

      (folds of inner membrane)


Mitochondria
Mitochondria

  • Double membrane

    • outer membrane

    • inner membrane

      • highly folded cristae

      • enzymes & transport proteins

    • intermembrane space

      • fluid-filled space between membranes

Oooooh!Form fits function!


What is oxidative phosphorylation
What is “oxidative phosphorylation”?

  • Recall…

    • Take H+/e-’s away, molecule = “oxidized”

    • Give H+/e-’s, molecule = “reduced”

    • Give phosphate  molecule = “phosphorylated”

  • So…oxidative phosphorylation= process that couples removal of H+’s/ e-’s from one molecule (NADH or FADH2) & giving phosphate molecules to another molecule (ADP)


Difference between oxidative phosphorylation substrate level phosphorylation
Difference between oxidative phosphorylation & substrate-level phosphorylation

Oxidative phosphorylation: generates ATP when electrons are taken from NADH or FADH2 (which become oxidized) and go down the electron transport chain. This causes Pi (inorganic phosphate) to join with ADP to form ATP.

Substrate-level phosphorylation: generates ATP when an enzyme takes a phosphate from a substrate molecule and gives it directly to ADP.


The pathway of electron transport
The Pathway of Electron Transport

  • In the ETC…

    • e-’s fall from glucose to oxygen not directly, rather in a series of steps. As the e-’s fall from step to step, energy is released in manageable amounts.

      **NEEDS O2 TO PROCEED

      (unlike glycolysis)


Etc characteristics
ETC Characteristics

  • Occurs in cristae, which increase surface area of inner mitochondrial membrane  allows more ATP to be produced

  • ETC takes e-’s from NADH/FADH2and gives them toO2

  • O2 “pulls” e-’s “down” ETC due to electronegativity (high affinity for e-’s)


What happens at the end of the ETC chain?

  • Electrons are passed to oxygen, forming water

    • O2 = final e- acceptor


How etc generates atp
How ETC generates ATP

  • ETC does NOT make ATP directly but provides the stage for chemiosmosis to occur

    • The energy from “falling” e-’s (exergonic) in the ETC is used to pump H+’s from mitochondrial matrix to intermembranespace

      • Results in a H+ (proton) gradientinside mitochondria

        • Inside (matrix) = low [H+]

        • Outside (intermembrane space)

          = high [H+]


http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120071/bio11.swf::Electron%20Transport%20System%20and%20ATP%20Synthesishttp://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120071/bio11.swf::Electron%20Transport%20System%20and%20ATP%20Synthesis

Inner

Mitochondrial

membrane

Oxidative

phosphorylation.

electron transport

and chemiosmosis

Glycolysis

ATP

ATP

ATP

H+

H+

H+

H+

Cyt c

Protein complex

of electron

carriers

Intermembrane

space

Q

IV

I

III

ATP

synthase

II

Inner

mitochondrial

membrane

H2O

FADH2

2 H+ + 1/2 O2

FAD+

NADH+

NAD+

ATP

ADP +

P i

(Carrying electrons

from, food)

H+

Mitochondrial

matrix

Chemiosmosis

ATP synthesis powered by the flow

Of H+ back across the membrane

Electron transport chain

Electron transport and pumping of protons (H+),

which create an H+ gradient across the membrane

Oxidativephosphorylation

Figure 9.15

  • Chemiosmosis and the electron transport chain


Chemiosmosis
Chemiosmosishttp://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120071/bio11.swf::Electron%20Transport%20System%20and%20ATP%20Synthesis

  • Utilizes ATP synthase

    • the enzyme that actually makes ATP from ADP and Pi

  • A mechanism which uses energy stored in the H+ gradient across any membrane to drive cellular work

    • Cellular work in this case = synthesis of ATP


Chemiosmosis the energy coupling mechanism

INTERMEMBRANE SPACEhttp://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120071/bio11.swf::Electron%20Transport%20System%20and%20ATP%20Synthesis

H+

H+

H+

H+

H+

H+

H+

H+

ADP

+

ATP

P i

MITOCHONDRIAL MATRIX

Figure 9.14

Chemiosmosis: The Energy-Coupling Mechanism

ATP Synthase


Electron shuttleshttp://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120071/bio11.swf::Electron%20Transport%20System%20and%20ATP%20Synthesis

span membrane

MITOCHONDRION

CYTOSOL

2 NADH

or

2 FADH2

2 FADH2

2 NADH

2 NADH

6 NADH

Glycolysis

Oxidative

phosphorylation:

electron transport

and

chemiosmosis

Citric

acid

cycle

2

Acetyl

CoA

2

Pyruvate

Glucose

+ 2 ATP

+ about 32 or 34 ATP

by substrate-level

phosphorylation

by substrate-level

phosphorylation

by oxidative

phosphorylation

About

36 or 38 ATP

Maximum per

glucose:

Figure 9.16

  • There are three main processes in this metabolic enterprise

+ 2 ATP


We will cover the following two slides when we learn about photosynthesis, but you can preview them now if you want. You’ll probably understand most of them!


A comparison of chemiosmosis in chloroplasts and mitochondria
A Comparison of Chemiosmosis in Chloroplasts and Mitochondria

  • Chloroplasts and mitochondria

    • Generate ATP by the SAME basic mechanism: chemiosmosis

    • But use different sources of energy to accomplish this

    • http://student.ccbcmd.edu/~gkaiser/biotutorials/cellresp/atpase_flash.html


  • The spatial organization of Mitochondriachemiosmosis differs in chloroplasts and mitochondria

  • In both organelles

    • electron transport chains generate a H+ gradient across a membrane

  • ATP synthase

    • Uses this proton-motive force to make ATP


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