Nutrient Role in Bioenergetics
Chapter 4
Bioenergetics
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Bioenergetics refers to the flow of
energy within a living system.
Energy is the capacity to do work.
Aerobic reactions require oxygen.
Anaerobic reactions do not require
oxygen.
Bioenergetics

First law – Energy is neither created nor
destroyed, but instead, transforms from
one state to another without being used
up.
Bioenergetics

There are six forms of interchangeable
energy states:
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Chemical
Light
Electric
Mechanical
Heat
Nuclear
Bioenergetics
The process of photosynthesis is a
chemical reaction.
 Chlorophyll absorbs radiant energy:
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To synthesize glucose from carbon
dioxide and water
To release oxygen.
Solar energy and photosynthesis
provide power to the animal world
through food and oxygen.
Bioenergetics
Photosynthesis

What is the
equation for the
chemical reaction
of
photosynthesis?
Bioenergetics
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Respiration is the
reverse of
photosynthesis.
C6H12O6 + O2 →
6CO2 + 6H2O
Cellular Respiration

Organism transforms the chemical
energy into a form it can use.

Cellular Respiration-Step by step process
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Glucose
Lipids
Amino acids
Heat
Bioenergetics
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Takes one of three forms:
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Mechanical work of muscle contraction
Chemical work for synthesizing cellular
molecules
Transport work that concentrates diverse
substances in body fluids
Bioenergetics

Potential energy
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Kinetic energy
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Energy associated with a substance’s
structure or position.
Energy of motion.
Potential energy and kinetic energy

The total energy of any system.
Bioenergetics
Adenosine Triphosphate
Bioenergetics

Cellular Oxidation–Reduction
Reactions

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Constitute the mechanism for energy
metabolism
Redox reactions power the transfer
process of energy
Bioenergetics

Oxidation–reduction reactions couple:
•
Oxidation = a substance loses electrons

•
Transfer oxygen, hydrogen, or electrons
Reduction = a substance gains electrons

Atoms gain an electron-reducing valence
Coupled Reactions
Coupled Reactions

Reduction Reaction
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→ 2C3H6O3
LDH
Pyruvate (gains 2 e-) → Lactate
2C3H4O3 + 2H
Coupled Reactions

Oxidation Reaction
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→
LDH
Lactate (loses 2 e-)
2C3H6O3 - 2H
2C3H4O3
Pyruvate
Bioenergetics

ATP – energy currency

Potential energy extracted from food
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ATP
Chemical energy extracted for biologic
work
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Cells
Muscle contraction
Phosphate Bond

Stored or potential energy

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High energy bonds
ATP – hydrolysis
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ATP + H2O → ADP + P – 7.3 kCal/mole
ATPase
Bioenergetics
Bioenergetics

Phosphocreatine (PC) is also a highenergy phosphate compound.
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ATP-PC (phosphagens)
Releases energy when bonds between
creatine and phosphate are broken.
Sustains all out exercise ~ 5-8 s
Resynthesis of ATP used – reservoir
Stored in muscle - anaerobic
Bioenergetics
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Cells store 4-6 times more PCr than ATP
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Muscle
Provide a reservoir of high-energy
phosphate bonds
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ATP + H2O  ADP + Pi
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ATPase
ADP + C~P  ATP + C

Creatine kinase
Bioenergetics
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Phosphorylation
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Refers to energy transfer through
phosphate bonds
Oxidative phosphorylation
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Synthesizes ATP by transfer of electrons
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NADH and FADH2
Cellular Oxidation-Reduction
Reactions
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Mechanism for energy metabolism
Involves transfer of hydrogen atoms
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Loss of hydrogen: oxidation
Gain of hydrogen: reduction
Cellular Oxidation

Mitochondria
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NAD and FAD → NADH and FADH2
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Cytochromes – Electron Transport Chain
(ETC)
Transfer of electrons (H+)
Energy conserved – high energy phosphate
bonds
Figure 4.11
Bioenergetics
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Sources for ATP formation include:
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Glucose derived from liver glycogen
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Free fatty acids - circulating
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Glycogenolysis
Triacylglycerol and glycogen stored in muscle
Triacylglycerol in liver, adipocytes
Lipoprotein complexes - circulating
Amino acids

Intramuscular and liver-derived carbon
skeletons
Bioenergetics