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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

PowerPoint Art Slides for World of the Cell, Sixth Edition

Wayne Becker, Lewis Kleinsmith, and Jeff Hardin

Chapter 9

Chemotrophic Energy Metabolism: Glycolysis and Fermentation

Metabolism

• All chemical reactions within cell

• Metabolic pathway

– Series of reactions in an ordered sequence to accomplish a biochemical operation

• Anabolic

– Synthesis

– ↑ in molecular order

• ↓ in entropy

• =energy requiring or ENDERGONIC

• Catabolic

– b/d of cellular constituents

• Give rise to metabolites

– ↓ in molecular order

↑ in entropy

• =energy liberating or EXERGONIC

Why catabolism

• catabolic pathways

• a. provide energy for anabolic reactions

• b. involved with breaking down larger molecules

• c. decreasing molecular order & complexity as the reaction proceeds

• d. usually exergonic

• e. catabolism provides energy for anabolic reactions

• (1) energy sometimes captured

• in form of ATP

• (2) energy sometimes captured

• in form of an ion gradient

• f. catabolism results in building blocks

• (1) eg: sugars from carbohydrates

• (2) eg: amino acids from proteins

• (3) eg: nucleic acids (ADP, GDP, TDP, CDP) from RNA and DNA

• g. catabolism method to recycle cellular components

– cells must recycle the buildings blocks

• (a) eg: unneeded enzymes and other proteins

• are broken down to amino acids

• (b) eg: unneeded mRNA is broken down

• to nucleic acids when no longer needed

Figure 9-1 ATP Hydrolysis and Synthesis

ATP = adenosine triphosphate

structure

a. aromatic base: adenine

b. 5-C sugar: ribose

c. 3-phosphate groups

connected by phosphoanhydride bonds

d. adenine + ribose = adenosine

phosphoanhydride bonds

charge repulsion

(a) each phosphate has negative charge

(b) repelling negative charges destabilizes the phosphoanhydride bond holding the two P atoms together

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Figure 9-2 Decreased Resonance Stabilization of the Phosphate and Carboxyl Groups Due to Bond Formation

resonance stabilization

Probably more important than charge repulsion

(b) structure of phosphate ion

(c) when Pi removed, both the Pi and the ADP

are stabilized by more resonance structures

that was not possible when the

Pi is attached to the ADP in the form of ATP

entropy favors two molecules rather than one

more stability associated

with two molecules (ADP and Pi)

relative to one molecule of ATP

(b) therefore, ATP tends to breakdown

to form ADP and Pi

-the equilibrium is shifted to the right

-thus, the ∆G is more negative

Table 9-1 Standard Free Energies of Hydrolysis for Phosphorylated Compounds Involved in Energy Metabolism

Figure 9-4 The ATP/ADP System as a Means of Conserving and Releasing Energy Within the Cell

Summary ATP

• Energy liberated by hydrolysis of anhydride bond >that for phosphoester bond.

• Group transfer reactions

– Phosphate group

– ATP/ADP intermediate

– ATP—PO4-donor

– ADP –PO4 acceptor

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Figure 9-5 The Structure of NAD+ and Its Oxidation and Reduction

NAD serves as e- acceptor

Terms

• Oxidation

• Reduction

• Aerobes

• Anaeobes

• Facultative (Aerobes)

• Fermentation

Figure 9-6 The Glycolytic Pathway from Glucose to Pyruvate, with Two Fermentation Alternatives Figure 9-7 The Thermodynamic Instability of Phospoenolpyruvate

Figure 9-8 The Fate of Pyruvate Under Aerobic and Anaerobic Conditions Figure 9-9 Carbohydrate Catabolism by the Glycolytic Pathway

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Figure 9-10 Phosphorolytic Cleavage of Storage Polysaccharides Figure 9-11 Pathways for Glycolysis and Gluconeogenesis Compared

Figure 9-12 The Regulation of Glycolysis and Gluconeogenesis Figure 9A-1 What Happens to the Sugar?

Figure 9A-2 The Cori Cycle: The Link Between Glycolysis in Muscle Cells and Gluconeogenesis in the Liver