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.

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

C 6 H 12 O 6 + 6O 2 6CO H 2 O 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

Substrate-level phosphorylation Oxidative phosphorylation

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.

Peter Mitchell ( ) Nobel Laureate… …1961 paper introducing the chemiosmotic hypothesis. Chemiosmosis

Proton-motive force Oxidative phosphorylation

A protein complex, ATP synthase, in the cristae actually makes ATP from ADP and P i. 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

Aerobic Anaerobic

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