Lecture 19: Cellular Respiration.  

By the end of this lecture you should be able to…

Describe respiration as a redox reaction.

Concepts and terms: reductant, oxidant, NADH

Describe the structure of mitochondria

Discuss the major components of cellular respiration.

Concepts and terms: glycolysis, Krebs cycle, electron transport

Describe the major inputs and products of each component of the respiratory pathway.

Describe chemiosmosis.

Concepts and terms: ATP synthase, proton gradient.

Contrast aerobic and anaerobic respiration.Concepts and terms: fermentation, lactic acid

Describe the role of inhibitors in studying respiratory biochemistry.

Assigned reading: Chapter 9 in the text.

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http://cellbio.utmb.edu/cellbio/mitochondria_1.htm#powerhouses

Mitochondria are the cells' power sources. Usually they are rod-shaped; however they can be round.

C6H12O6 + 6O2 6CO2 + 6 H2O

Cellular respiration:

• Electrons from food are transferred initially to NAD+• Some of the energy released from NADH is used to make ATP

NAD: nicotinamide adenine dinucleotide

http://ntri.tamuk.edu/cell/mitochondrion/glycpics.html

Substrate-level phosphorylationOxidative phosphorylation

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Figure 9.11 A closer look at the Krebs cycle (Layer 1)

Figure 9.11 A closer look at the Krebs cycle (Layer 2)

Figure 9.11 A closer look at the Krebs cycle (Layer 3)

Figure 9.11 A closer look at the Krebs cycle (Layer 4)

• The conversion of pyruvate and the Krebs cycle produces large quantities of electron carriers.

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Peter Mitchell (1920 - 1992) Nobel Laureate…

…1961 paper introducing the chemiosmotic hypothesis.

http://www.life.uiuc.edu/crofts/bioph354/lect11.html

Chemiosmosis

Proton-motive forceOxidative phosphorylation

• A protein complex, ATP synthase, in the cristae actually makes ATP from ADP and Pi.

• ATP used the energy of

an existing proton gradient to power ATP synthesis.– This proton gradient

develops between the intermembrane space and the matrix.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 9.14

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AerobicAnaerobic

During extreme exertion…

Initially, stored ATP is metabolized (~5mmol/kg muscle. It’s gone in about 5 s.

Then phosphocreatine is converted to ATP; gone in another 5 s.

Then glycolosis starts (anaerobic respiration)…oops, lactate accumulates.

Anaerobic respiration kicks in after about 2 min.

Feedback mechanisms control cellular respiration