Obtaining Energy from Glucose: Cellular Respiration Process, Exams of Chemistry

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Lecture Series 12

Cellular Pathways That

Harvest Chemical Energy

Cellular Pathways That HarvestChemical Energy

A.

A. Obtaining Energy and Electrons from Glucose

Obtaining Energy and Electrons from Glucose

B.

B. An Overview: Releasing Energy from Glucose

An Overview: Releasing Energy from Glucose

C.

C. Glycolysis

Glycolysis: From Glucose to

: From Glucose to Pyruvate

Pyruvate

D.

D. Pyruvate

Pyruvate Oxidation

Oxidation

E.

E. The Citric Acid Cycle

The Citric Acid Cycle

Cellular Pathways In General

• Metabolic pathways occur in small steps,

Metabolic pathways occur in small steps,

each catalyzed by a specific enzyme. each catalyzed by a specific enzyme.

• Metabolic pathways are often

Metabolic pathways are often

compartmentalized and are highly compartmentalized and are highly

regulated. regulated.

A. Obtaining Energy andElectrons from Glucose

• When glucose burns, energy is released as

When glucose burns, energy is released as

heat and light: heat and light:

C

C

6 6

H

H

1212

O

O

6 6

+ 6 O

+ 6 O

2 2

6 CO

6 CO

2 2

+ 6 H

+ 6 H

2 2

0 + energy 0 + energy

• The same equation applies to the metabolism

The same equation applies to the metabolism

of glucose by cells, but the reaction is of glucose by cells, but the reaction is

accomplished in many separate steps so that accomplished in many separate steps so that

the energy can be captured as ATP with the energy can be captured as ATP with

minimal loss as heat. minimal loss as heat.

Energy flow and chemical recycling in ecosystems

An introduction to electron transport chains

Redox Rxns: Transfer Electrons and Energy

A. Obtaining Energy andElectrons from Glucose

• The coenzyme NAD is a key electron carrier

The coenzyme NAD is a key electron carrier

in biological in biological redox

redox reactions.

reactions.

• It exists in two forms, one oxidized (NAD

It exists in two forms, one oxidized (NAD

and the other reduced (NADH + H and the other reduced (NADH + H

NAD as an Electron Carrier and Redox Couple

B. An Overview: ReleasingEnergy from Glucose

• Glycolysis

Glycolysis operates in the presence or

operates in the presence or

absence of O absence of O

2 2

• Under aerobic conditions, cellular respiration

Under aerobic conditions, cellular respiration

continues the breakdown process. continues the breakdown process.

B. An Overview: ReleasingEnergy from Glucose

• Pyruvate

Pyruvate oxidation and the citric acid cycle

oxidation and the citric acid cycle

produce CO produce CO

2 2

and hydrogen atoms carried by

and hydrogen atoms carried by

NADH and FADH NADH and FADH

2 2

• The respiratory chain combines the

The respiratory chain combines the

hydrogens hydrogens with O

with O

22

, releasing enough energy , releasing enough energy

for additional ATP synthesis. for additional ATP synthesis.

B. An Overview: ReleasingEnergy from Glucose

• In eukaryotes,

In eukaryotes, glycolysis

glycolysis and fermentation

and fermentation

occur in the cytoplasm outside of the occur in the cytoplasm outside of the

mitochondria; mitochondria; pyruvate

pyruvate oxidation, the citric

oxidation, the citric

acid cycle, and the respiratory chain operate acid cycle, and the respiratory chain operate

in association with mitochondria. in association with mitochondria.

• In prokaryotes,

In prokaryotes, glycolysis

glycolysis, fermentation, and

, fermentation, and

the citric acid cycle take place in the the citric acid cycle take place in the

cytoplasm; and cytoplasm; and pyruvate

pyruvate oxidation and the

oxidation and the

respiratory chain operate in association with respiratory chain operate in association with

the plasma membrane. the plasma membrane.