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Chapter 8

Harvesting Energy: Glycolysis and Cellular Respiration

Chapter 8: Glycolysis and Cellular Respiration

What is Glucose Metabolism?

Photosynthesis:

= 6 CO2

Carbon

dioxide

+ 6 H2O

Water

C6H12O6

Glucose

+ 6 O2

Oxygen

Glucose Metabolism:

+ Energy

Chemical (40%)

Heat (60%)

Answer: The breakdown of glucose to release energy from

chemical bonds

+ Light

Energy6 CO2

Carbon

dioxide

+ 6 H2O

Water

= C6H12O6

Glucose

+ 6 O2

Oxygen

Major Steps of Glucose Metabolism

Glucose

1) Glycolysis (2 ATP)

PyruvateNo oxygen present

(Anaerobic)

2) Fermentation

Ethanol

Lactate

Oxygen present

(Aerobic)

3) Cellular Respiration(36 ATP)

Carbon Dioxide

Water

Cytoplasm

Mitochondria


Glucose Metabolism:


Figure 8.1 – Audesirk2 & Byers

1) Glycolysis (Greek: “To break down a sweet”)

• Ancient biochemical pathway (all organisms do it...)

• Occurs in cytoplasm; does not require oxygen

Major Steps:

A) Glucose Activation: Initiation of the reaction (takes energy…)

2 ATP 2 ADP

(Activation Energy)C C C CCC

Glucose


CCC x 2

P

Glyceraldehyde

3-phosphate

(G3P)

x 2

1) Glycolysis (Greek: “To break down a sweet”)

• Ancient biochemical pathway (all organisms do it...)

• Occurs in cytoplasm; does not require oxygen

Major Steps:

A) Glucose Activation: Initiation of the reaction (takes energy…)

B) Energy Harvesting: Completion of the reaction (… to make energy)


4 ADP 4 ATP

CCC x 2

P

Glyceraldehyde

3-phosphate

(G3P)

2 NAD+ 2 NADH

CCC x 2

Pyruvate

2

Net ATP Gain = 2 ATP


Glycolysis in Review:



Glucose



(Anaerobic)

2) Fermentation

Ethanol

Lactate

Oxygen present

(Aerobic)


Carbon Dioxide

Water


2) Fermentation: Process for regenerating NAD+ for glycolysis

• Crucial for organisms that live where O2 is rare (e.g., intestines / soils / bogs)

A) Lactate Fermentation: Pyruvate converted to lactate (lactic acid)

CCC x 2

Lactate

CCC x 2

Pyruvate

2 NADH 2 NAD+ (Back to glycolysis)


Types of Fermentation:

Does NOT

produce ATP!

Lactate Fermentation:


Figure 8.3 / 8.4 – Audesirk2 & Byers

2) Fermentation: Process for regenerating NAD+ for glycolysis

• Crucial for organisms that live where O2 is rare (e.g., intestines / soils / bogs)

A) Lactate Fermentation: Pyruvate converted to lactate (lactic acid)

B) Alcoholic Fermentation: Pyruvate converted to ethanol and CO2


Types of Fermentation:

Does NOT

produce ATP!

CCC x 2

Ethanol

x 2

Carbon

Dioxide

+CCC x 2

Pyruvate

2 NADH 2 NAD+ (Back to glycolysis)

Alcoholic Fermentation:


Figure 8.3 / 8.5 – Audesirk2 & Byers

Yeast

3


Glucose



(Anaerobic)

2) Fermentation

Ethanol

Lactate

Oxygen present

(Aerobic)


Carbon Dioxide

Water


3) Cellular Respiration: Series of reactions that produces ATP

• Occurs in mitochondria / requires oxygen


= CO2

Carbon

Dioxide

+ H2O

Water

Pyruvate + O2

Oxygen

+ ATP

Chemical

Energy

• Mitochondria have two membranes

• Outer membrane (smooth)

• Inner membrane (folded – cristae)

• Mitochondria have two compartments

• Intermembrane compartment

• Matrix

Recall from Chapter 4:





Sequence of Events:

A) Pyruvate diffuses into mitochondrial matrix

• Travels down concentration gradient (via pores)

B) Pyruvate converted to acetyl CoA:

CC - CoA x 2

Acetyl CoANAD+ NADH

Coenzyme A CO2

C( x 2)

CCC x 2

Pyruvate




Sequence of Events:

C) Krebs Cycle:CC - CoA (x 2)

Acetyl CoA

Krebs

Cycle

2 CO2C( )C(x 2)

FAD

FADH2

(x 2)

3 NAD+

3 NADH

(x 2)

ADP

ATP

(x 2)

DO NOT

COPY!


The True Story:

The Krebs Cycle is also

called the Citric Acid Cycle

Figure E8.3 – Audesirk2 & Byers

Review of Cellular Respiration:


Energy Checklist (per glucose):

1) 2 ATP

2) 10 Electron-carrier Molecules

• NADH (8)

• FADH2 (2)


4




Sequence of Events:

D) Electron Transport Chain:

• Location where electron-carrier molecules unload their electrons

Located in the inner

mitochondrial membrane

Outer

Membrane

Inner

Membrane

Intermembrane Compartment

Matrix

ETC

NAD+

FAD

NADH

FADH2

2e-

H+H+H+

1/2 O2 + 2 H+ H2O

2e-

2e-

Electron Transport Chain: Cyanide


Similar to Figure 8.8 – Audesirk2 & Byers




Sequence of Events:

E) Chemiosmosis:

• Utilizes energy stored in H+ gradient to generate ATP

Located in the inner

mitochondrial membrane

H+

H+H+ H+

H+

H+

H+

H+

H+

H+H+

ATPADP

32 ATP

Outer

Membrane

Inner

Membrane

Intermembrane Compartment

Matrix

ETC

H+ H+ H+

H+ ion

channel

H+(See “A Closer Look - Chemiosmosis: Chloroplasts – Pg. 124)

ATP diffuses out of mitochondria

to provide energy for cellular processes


Chemiosmosis:


Final Tally of Energy

Production:

One Molecule of Glucose

Yields 36 - 38 ATP

Yippee!



Multiple Biomolecules Yield Energy:

(See Health Watch - Pg. 144)

Fats:

• Glycerol Enters glycolysis

• Fatty Acids Enters Krebs cycle

Reversal true as well:

Glucose Fats


Proteins:

• Enter at multiple stages

Figure E8.4 – Audesirk2 & Byers