Ch. 6 Glycolysis-krebs-ETC (1)

•  Cellular respiration oxidizes sugar and produces ATP in three main stages

– Glycolysis occurs in the cytoplasm

– The Krebs cycle and the electron transport chain occur in the mitochondria

6.8 Overview: Respiration occurs in three main stages

STAGES OF CELLULAR RESPIRATION AND FERMENTATION

Mitochondrion

CO2 CO2

High-energy electrons carried by NADH

CITRIC ACID CYCLE

GLYCOLYSIS Pyruvate Glucose

and FADH2

Substrate-level phosphorylation

OXIDATIVE PHOSPHORYLATION

(Electron Transport and Chemiosmosis)

Oxidative phosphorylation

ATP ATP

Cytoplasm Inner mitochondrial membrane

Remember NADP+/NADPH from Photosynthesis???

•  It was a high energy electron carrier!

•  In respiration we have NAD+ that carries high energy electrons and a hydrogen ion in the form of NADH

•  FAD is also an electron and hydrogen ion carrier and becomes FADH2

•  These will become important in the ETC

REDOX reactions

•  LEO goes GER

•  Lose electron- oxidation

•  Gain electron- reduction

6.6 Overview: Cellular respiration occurs in three main stages

•  Stage 1: Glycolysis

– Glycolysis begins respiration by breaking glucose, a six-carbon molecule, into two molecules of a three-carbon compound called pyruvate

– This stage occurs in the cytoplasm

6.9 Glycolysis harvests chemical energy by oxidizing glucose to pyruvic acid

Figure 6.9A

Glucose Pyruvic acid

* Pyruvic acid = Pyruvate

Summary of Glycolysis

•  In

Glucose (6-C)

2 NAD+

•  Out

2 pyruvate; 2(3-C)

2 ATP (net)

2 NADH

Questions

•  Where does glycolysis take place?

•  Glycolysis energy yield?

•  Breaks glucose into TWO ________.

•  Animation

•  Stage 2: The citric acid (Krebs) cycle

– The Krebs cycle breaks down pyruvate into carbon dioxide and supplies the third stage with electrons

– This stage occurs in the mitochondria

•  Each pyruvic acid molecule is broken down to form CO2 and a two-carbon acetyl group, which enters the Krebs cycle

6.10 Pyruvic acid is chemically groomed for the Krebs cycle

Figure 6.10

Pyruvic acid

Acetyl CoA (acetyl coenzyme A)

•  The Krebs cycle is a series of reactions in which enzymes strip away electrons and H+ from each acetyl group

6.11 The Krebs cycle completes the oxidation of organic fuel, generating many NADH and FADH2 molecules

Figure 6.11A

Acetyl CoA

KREBS CYCLE

Citric Acid Production

The Krebs Cycle Section 9-2

Mitochondrion

Citric Acid Production

Figure 9–6 The Krebs Cycle Section 9-2

Mitochondrion

Summary

•  In

Pyruvate -> Acetyl CoA

•  Out

CO2 (as waste)

(LOTS OF ELECTRONS!!)

Questions

•  Where does the Krebs cycle take place?

•  How many ATP are produced?

Animation

•  Stage 3: Oxidative phosphorylation/Electron Transport Chain

– During this stage, electrons are shuttled through the electron transport chain

– As a result, ATP is generated through oxidative phosphorylation associated with chemiosmosis

– This stage occurs in the inner mitochondrion membrane

•  The electrons from NADH and FADH2 travel down the electron transport chain to oxygen

•  Energy released by the electrons is used to pump H+ into the space between the mitochondrial membranes

•  In chemiosmosis, the H+ ions diffuse back through the inner membrane through ATP synthase complexes, which capture the energy to make ATP (same as photosynthesis!)

Chemiosmosis powers most ATP production

Intermembrane space

Inner mitochondrial membrane

H+ NAD+

Mitochondrial matrix

Electron flow

Electron carrier

Protein complex of electron carriers

FADH2 FAD

ATP synthase

P ADP +

Chemiosmosis

OXIDATIVE PHOSPHORYLATION

Electron Transport Chain

Summary

Oxygen

NADH (carrying electrons)

FADH2 (carrying electrons)

LOTS OF ATP!!!!!

What’s the take away message???

•  Glycolysis breaks down glucose into pyruvate

•  Pyruvate is made into acetyl- CoA (releasing CO2)

•  Krebs uses up acetyl- CoA and produces 2 ATP, more CO2, and LOTS OF ELECTRONS CARRIED BY NADH AND FADH2!

•  For each glucose molecule that enters cellular respiration, chemiosmosis produces up to 38 ATP molecules

6.14 Review: Each molecule of glucose yields many molecules of ATP

KREBS CYCLE

Electron shuttle across membranes

Cytoplasmic fluid

GLYCOLYSIS

Glucose 2

Pyruvic acid

2 Acetyl CoA

KREBS CYCLE

ELECTRON TRANSPORT CHAIN

AND CHEMIOSMOSIS

Mitochondrion

by substrate-level phosphorylation

used for shuttling electrons from NADH made in glycolysis

by substrate-level phosphorylation

by chemiosmotic phosphorylation

Maximum per glucose: Figure 6.14

The Mystery of the Toxic Flea Dip….

6.11 CONNECTION: Certain poisons interrupt critical events in cellular respiration

•  There are three different categories of cellular poisons that affect cellular respiration

– The first category blocks the electron transport chain (for example, rotenone, cyanide, and carbon monoxide)

– The second inhibits ATP synthase (for example, oligomycin)

– Finally, the third makes the membrane leaky to hydrogen ions (for example, dinitrophenol)

1 - 2 H+ NAD+ NADH

FADH2 FAD

P ADP +

Chemiosmosis

Electron Transport Chain

H+ H+ H+

Rotenone Cyanide, carbon monoxide

Oligomycin

ATP synthase

Rotenone

•  Rotenone is a common pesticide

•  Rotenone interrupts the electron transport chain

•  It prevents NADH from transferring its electrons and therefore prevents the production of ATP

•  If NADH cannot transfer its electrons, there will be a substantial decrease of NAD+ molecules

Ch. 6 Glycolysis-krebs-ETC (1)

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