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Bluegrass Technical
and Community College
CHAPTER
Elaine N. Marieb
Katja Hoehn
24
PART A
Human
Anatomy
& Physiology
SEVENTH EDITION
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Nutrition,
Metabolism,
and Body
Temperature
Regulation
Nutrition



Nutrient – a substance that promotes normal
growth, maintenance, and repair
Major nutrients – carbohydrates, lipids, and
proteins
Other nutrients – vitamins and minerals (and
technically speaking, water)
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
USDA Food Guide Pyramid
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.1a
Nutrition
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.1b
Carbohydrates

Complex carbohydrates (starches) are found in
bread, cereal, flour, pasta, nuts, and potatoes

Simple carbohydrates (sugars) are found in soft
drinks, candy, fruit, and ice cream
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Carbohydrates

Glucose is the molecule ultimately used by body
cells to make ATP

Neurons and RBCs rely almost entirely upon
glucose to supply their energy needs

Excess glucose is converted to glycogen or fat and
stored
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Carbohydrates

The minimum amount of carbohydrates needed to
maintain adequate blood glucose levels is 100
grams per day

Starchy foods and milk have nutrients such as
vitamins and minerals in addition to complex
carbohydrates

Refined carbohydrate foods (candy and soft
drinks) provide energy sources only and are
referred to as “empty calories”
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Lipids



The most abundant dietary lipids, triglycerides, are
found in both animal and plant foods
Essential fatty acids – linoleic and linolenic acid,
found in most vegetables, must be ingested
Dietary fats:

Help the body to absorb vitamins

Are a major energy fuel of hepatocytes and skeletal
muscle

Are a component of myelin sheaths and all cell
membranes
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Lipids

Fatty deposits in adipose tissue provide:

A protective cushion around body organs

An insulating layer beneath the skin

An easy-to-store concentrated source of energy
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Lipids


Prostaglandins function in:

Smooth muscle contraction

Control of blood pressure

Inflammation
Cholesterol stabilizes membranes and is a
precursor of bile salts and steroid hormones
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Lipids: Dietary Requirements

Higher for infants and children than for adults

The American Heart Association suggests that:

Fats should represent less than 30% of one’s total
caloric intake

Saturated fats should be limited to 10% or less of
one’s total fat intake

Daily cholesterol intake should not exceed 200 mg
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Proteins


Complete proteins that meet all the body’s amino
acid needs are found in eggs, milk, milk products,
meat, and fish
Incomplete proteins are found in legumes, nuts,
seeds, grains, and vegetables
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Proteins


Proteins supply:

Essential amino acids, the building blocks for
nonessential amino acids

Nitrogen for nonprotein nitrogen-containing
substances
Daily intake should be approximately 0.8g/kg of
body weight
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Proteins: Synthesis and Hydrolysis

All-or-none rule


All amino acids needed must be present at the same
time for protein synthesis to occur
Adequacy of caloric intake

Protein will be used as fuel if there is insufficient
carbohydrate or fat available
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Proteins: Synthesis and Hydrolysis

Nitrogen balance




The rate of protein synthesis equals the rate of
breakdown and loss
Positive – synthesis exceeds breakdown (normal in
children and tissue repair)
Negative – breakdown exceeds synthesis (e.g.,
stress, burns, infection, or injury)
Hormonal control

Anabolic hormones accelerate protein synthesis
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Essential Amino Acids
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.2
Vitamins

Organic compounds needed for growth and good
health

They are crucial in helping the body use nutrients
and often function as coenzymes

Only vitamins D, K, and B are synthesized in the
body; all others must be ingested

Water-soluble vitamins (B-complex and C) are
absorbed in the gastrointestinal tract

B12 additionally requires gastric intrinsic factor to
be absorbed
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Vitamins

Fat-soluble vitamins (A, D, E, and K) bind to
ingested lipids and are absorbed with their
digestion products

Vitamins A, C, and E also act in an antioxidant
cascade
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Minerals

Seven minerals are required in moderate amounts

Calcium, phosphorus, potassium, sulfur, sodium,
chloride, and magnesium

Dozens are required in trace amounts

Minerals work with nutrients to ensure proper
body functioning

Calcium, phosphorus, and magnesium salts harden
bone
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Minerals

Sodium and chloride help maintain normal
osmolarity, water balance, and are essential in
nerve and muscle function

Uptake and excretion must be balanced to prevent
toxic overload
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Metabolism


Metabolism – all chemical reactions necessary to
maintain life
Cellular respiration – food fuels are broken down
within cells and some of the energy is captured to
produce ATP


Anabolic reactions – synthesis of larger molecules
from smaller ones
Catabolic reactions – hydrolysis of complex
structures into simpler ones
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Metabolism

Enzymes shift the high-energy phosphate groups of
ATP to other molecules

These phosphorylated molecules are activated to
perform cellular functions
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Stages of Metabolism

Energy-containing nutrients are processed in three
major stages



Digestion – breakdown of food; nutrients are
transported to tissues
Anabolism and formation of catabolic
intermediates where nutrients are:

Built into lipids, proteins, and glycogen

Broken down by catabolic pathways to pyruvic
acid and acetyl CoA
Oxidative breakdown – nutrients are catabolized to
carbon dioxide, water, and ATP
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.3
Oxidation-Reduction (Redox) Reactions

Oxidation occurs via the gain of oxygen or the loss
of hydrogen

Whenever one substance is oxidized, another
substance is reduced

Oxidized substances lose energy

Reduced substances gain energy

Coenzymes act as hydrogen (or electron) acceptors

Two important coenzymes are nicotinamide
adenine dinucleotide (NAD+) and flavin adenine
dinucleotide (FAD)
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Mechanisms of ATP Synthesis:
Substrate-Level Phosphorylation
 High-energy
phosphate groups are
transferred directly
from phosphorylated
substrates to ADP

ATP is synthesized
via substrate-level
phosphorylation in
glycolysis and the
Krebs cycle
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.4a
Mechanisms of ATP Synthesis:
Oxidative Phosphorylation

Uses the chemiosmotic process whereby the
movement of substances across a membrane is
coupled to chemical reactions
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Mechanisms of ATP Synthesis:
Oxidative Phosphorylation
 Is carried out by the electron transport proteins in
the cristae of the mitochondria

Nutrient energy is used to pump hydrogen ions into
the intermembrane space

A steep diffusion gradient across the membrane
results

When hydrogen ions flow back across the
membrane through ATP synthase, energy is
captured and attaches phosphate groups to ADP (to
make ATP)
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Mechanisms of ATP Synthesis:
Oxidative Phosphorylation
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.4b
Carbohydrate Metabolism
 Since all carbohydrates are transformed into
glucose, it is essentially glucose metabolism



Oxidation of glucose is shown by the overall
reaction:
C6H12O6 + 6O2  6H2O + 6CO2 + 36 ATP + heat
Glucose is catabolized in three pathways

Glycolysis

Krebs cycle

The electron transport chain and oxidative
phosphorylation
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Carbohydrate Catabolism
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.5
Glycolysis


A three-phase pathway in which:

Glucose is oxidized into pyruvic acid

NAD+ is reduced to NADH + H+

ATP is synthesized by substrate-level
phosphorylation
Pyruvic acid:

Moves on to the Krebs cycle in an aerobic pathway

Is reduced to lactic acid in an anaerobic
environment
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Glycolysis
Glycolysis
ATP
Krebs
cycle
ATP
Electron transport chain
and oxidative
phosphorylation
ATP
Glucose
Phase 1
Sugar
activation
Key:
= Carbon
atom
Pi = Inorganic
phosphate
2 ATP
2 ADP
Fructose-1,6bisphosphate
P
P
Phase 2
Sugar
Dihydroxyacetone
cleavage
phosphate
P
Pi
Glyceraldehyde
phosphate
P
2 NAD+
4 ADP
2 NADH+H+
Phase 3
Sugar
oxidation
and formation
of ATP
4 ATP
2 Pyruvic acid
2 NADH+H+
O2
To Krebs
cycle
(aerobic
pathway)
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
O2
2 NAD+
2 Lactic acid
Figure 24.6
Glycolysis
Glycolysis
ATP
Krebs
cycle
ATP
Electron transport chain
and oxidative
phosphorylation
ATP
Glucose
Phase 1
Sugar
activation
2 ATP
2 ADP
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Key:
= Carbon
atom
Pi = Inorganic
phosphate
Figure 24.6
Glycolysis
Glycolysis
ATP
Krebs
cycle
ATP
Electron transport chain
and oxidative
phosphorylation
ATP
Glucose
Phase 1
Sugar
activation
2 ATP
2 ADP
Fructose-1,6bisphosphate
P
P
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Key:
= Carbon
atom
Pi = Inorganic
phosphate
Figure 24.6
Glycolysis
Glycolysis
ATP
Krebs
cycle
ATP
Electron transport chain
and oxidative
phosphorylation
ATP
Glucose
Phase 1
Sugar
activation
2 ATP
2 ADP
Fructose-1,6bisphosphate
P
P
Phase 2
Sugar
Dihydroxyacetone
cleavage
phosphate
P
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Key:
= Carbon
atom
Pi = Inorganic
phosphate
Glyceraldehyde
phosphate
P
Figure 24.6
Glycolysis
Glycolysis
ATP
Krebs
cycle
ATP
Electron transport chain
and oxidative
phosphorylation
ATP
Glucose
Phase 1
Sugar
activation
2 ATP
2 ADP
Fructose-1,6bisphosphate
P
P
Phase 2
Sugar
Dihydroxyacetone
cleavage
phosphate
P
Pi
Key:
= Carbon
atom
Pi = Inorganic
phosphate
Glyceraldehyde
phosphate
P
2 NAD+
2 NADH+H+
Phase 3
Sugar
oxidation
and formation
of ATP
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.6
Glycolysis
Glycolysis
ATP
Krebs
cycle
ATP
Electron transport chain
and oxidative
phosphorylation
ATP
Glucose
Phase 1
Sugar
activation
2 ATP
2 ADP
Fructose-1,6bisphosphate
P
P
Phase 2
Sugar
Dihydroxyacetone
cleavage
phosphate
P
Pi
Key:
= Carbon
atom
Pi = Inorganic
phosphate
Glyceraldehyde
phosphate
P
2 NAD+
4 ADP
2 NADH+H+
Phase 3
Sugar
oxidation
and formation
of ATP
4 ATP
2 Pyruvic acid
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.6
Glycolysis
Glycolysis
ATP
Krebs
cycle
ATP
Electron transport chain
and oxidative
phosphorylation
ATP
Glucose
Phase 1
Sugar
activation
2 ATP
2 ADP
Fructose-1,6bisphosphate
P
P
Phase 2
Sugar
Dihydroxyacetone
cleavage
phosphate
P
Pi
Key:
= Carbon
atom
Pi = Inorganic
phosphate
Glyceraldehyde
phosphate
P
2 NAD+
4 ADP
2 NADH+H+
Phase 3
Sugar
oxidation
and formation
of ATP
4 ATP
2 Pyruvic acid
O2
To Krebs
cycle
(aerobic
pathway)
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.6
Glycolysis
Glycolysis
ATP
Krebs
cycle
ATP
Electron transport chain
and oxidative
phosphorylation
ATP
Glucose
Phase 1
Sugar
activation
Key:
= Carbon
atom
Pi = Inorganic
phosphate
2 ATP
2 ADP
Fructose-1,6bisphosphate
P
P
Phase 2
Sugar
Dihydroxyacetone
cleavage
phosphate
P
Pi
Glyceraldehyde
phosphate
P
2 NAD+
4 ADP
2 NADH+H+
Phase 3
Sugar
oxidation
and formation
of ATP
4 ATP
2 Pyruvic acid
2 NADH+H+
O2
To Krebs
cycle
(aerobic
pathway)
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
O2
2 NAD+
2 Lactic acid
Figure 24.6
Glycolysis: Phase 1 and 2

Phase 1: Sugar activation


Two ATP molecules activate glucose into
fructose-1,6-diphosphate
Phase 2: Sugar cleavage

Fructose-1,6-bisphosphate is cleaved into two
3-carbon isomers

Bishydroxyacetone phosphate

Glyceraldehyde 3-phosphate
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Glycolysis: Phase 3

Phase 3: Oxidation and ATP formation

The 3-carbon sugars are oxidized (reducing NAD+)

Inorganic phosphate groups (Pi) are attached to
each oxidized fragment

The terminal phosphates are cleaved and captured
by ADP to form four ATP molecules
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Glycolysis: Phase 3

The final products are:

Two pyruvic acid molecules

Two NADH + H+ molecules (reduced NAD+)

A net gain of two ATP molecules
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Krebs Cycle: Preparatory Step

Occurs in the mitochondrial matrix and is fueled
by pyruvic acid and fatty acids
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Krebs Cycle: Preparatory Step

Pyruvic acid is converted to acetyl CoA in three
main steps:

Decarboxylation

Carbon is removed from pyruvic acid

Carbon dioxide is released
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Krebs Cycle: Preparatory Step


Oxidation

Hydrogen atoms are removed from pyruvic acid

NAD+ is reduced to NADH + H+
Formation of acetyl CoA – the resulting acetic acid
is combined with coenzyme A, a sulfur-containing
coenzyme, to form acetyl CoA
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Krebs Cycle


An eight-step cycle in which each acetic acid is
decarboxylated and oxidized, generating:

Three molecules of NADH + H+

One molecule of FADH2

Two molecules of CO2

One molecule of ATP
For each molecule of glucose entering glycolysis,
two molecules of acetyl CoA enter the Krebs cycle
PLAY
Krebs Cycle
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Cytosol
Pyruvic acid from glycolysis
Glycolysis
ATP
Krebs
cycle
Electron
transport chain
and oxidative
phosphorylation
NAD+
CO2
CoA
Acetyl CoA
ATP
Mitochondrion
(fluid matrix)
NADH+H+
ATP
Oxaloacetic acid
(pickup molecule)
NADH+H+
Citric acid
CoA (initial reactant)
NAD+
Isocitric acid
Malic acid
NAD+
Krebs cycle
CO2
NADH+H+
a-Ketoglutaric acid
Fumaric acid
CO2
FADH2
FAD
Key:
Succinic acid
Succinyl-CoA
CoA
NAD+
NADH+H+
CoA
= Carbon atom
GTP
GDP + Pi
ADP
ATP
Pi = Inorganic phosphate
CoA = Coenzyme A
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.7
Pyruvic acid from glycolysis
Glycolysis
ATP
Krebs
cycle
Electron
transport chain
and oxidative
phosphorylation
ATP
CO2
CoA
Acetyl CoA
Cytosol
NAD+
NADH+H+
Mitochondrion
(fluid matrix)
ATP
Key:
= Carbon atom
Pi = Inorganic phosphate
CoA = Coenzyme A
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.7
Pyruvic acid from glycolysis
Glycolysis
ATP
Krebs
cycle
Electron
transport chain
and oxidative
phosphorylation
ATP
Cytosol
NAD+
CO2
CoA
Acetyl CoA
NADH+H+
Mitochondrion
(fluid matrix)
ATP
Oxaloacetic acid
(pickup molecule)
Citric acid
CoA (initial reactant)
Krebs cycle
Key:
= Carbon atom
Pi = Inorganic phosphate
CoA = Coenzyme A
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.7
Cytosol
Pyruvic acid from glycolysis
Glycolysis
ATP
Krebs
cycle
Electron
transport chain
and oxidative
phosphorylation
ATP
NAD+
CO2
CoA
Acetyl CoA
NADH+H+
Mitochondrion
(fluid matrix)
ATP
Oxaloacetic acid
(pickup molecule)
Citric acid
CoA (initial reactant)
Isocitric acid
Krebs cycle
Key:
= Carbon atom
Pi = Inorganic phosphate
CoA = Coenzyme A
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.7
Cytosol
Pyruvic acid from glycolysis
Glycolysis
ATP
Krebs
cycle
Electron
transport chain
and oxidative
phosphorylation
ATP
NAD+
CO2
CoA
Acetyl CoA
NADH+H+
Mitochondrion
(fluid matrix)
ATP
Oxaloacetic acid
(pickup molecule)
Citric acid
CoA (initial reactant)
Isocitric acid
NAD+
Krebs cycle
CO2
NADH+H+
a-Ketoglutaric acid
Key:
= Carbon atom
Pi = Inorganic phosphate
CoA = Coenzyme A
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.7
Cytosol
Pyruvic acid from glycolysis
Glycolysis
ATP
Krebs
cycle
Electron
transport chain
and oxidative
phosphorylation
ATP
NAD+
CO2
CoA
Acetyl CoA
Mitochondrion
(fluid matrix)
NADH+H+
ATP
Oxaloacetic acid
(pickup molecule)
Citric acid
CoA (initial reactant)
Isocitric acid
NAD+
Krebs cycle
CO2
NADH+H+
a-Ketoglutaric acid
CO2
Succinyl-CoA
CoA
NAD+
NADH+H+
Key:
= Carbon atom
Pi = Inorganic phosphate
CoA = Coenzyme A
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.7
Cytosol
Pyruvic acid from glycolysis
Glycolysis
ATP
Krebs
cycle
Electron
transport chain
and oxidative
phosphorylation
ATP
NAD+
CO2
CoA
Acetyl CoA
Mitochondrion
(fluid matrix)
NADH+H+
ATP
Oxaloacetic acid
(pickup molecule)
Citric acid
CoA (initial reactant)
Isocitric acid
NAD+
Krebs cycle
CO2
NADH+H+
a-Ketoglutaric acid
CO2
Succinic acid
Key:
Succinyl-CoA
CoA
NAD+
NADH+H+
CoA
= Carbon atom
GTP
GDP + Pi
ADP
ATP
Pi = Inorganic phosphate
CoA = Coenzyme A
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.7
Cytosol
Pyruvic acid from glycolysis
Glycolysis
ATP
Krebs
cycle
Electron
transport chain
and oxidative
phosphorylation
NAD+
CO2
CoA
Acetyl CoA
ATP
Mitochondrion
(fluid matrix)
NADH+H+
ATP
Oxaloacetic acid
(pickup molecule)
Citric acid
CoA (initial reactant)
Isocitric acid
NAD+
Krebs cycle
CO2
NADH+H+
a-Ketoglutaric acid
Fumaric acid
CO2
FADH2
FAD
Key:
Succinic acid
Succinyl-CoA
CoA
NAD+
NADH+H+
CoA
= Carbon atom
GTP
GDP + Pi
ADP
ATP
Pi = Inorganic phosphate
CoA = Coenzyme A
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.7
Cytosol
Pyruvic acid from glycolysis
Glycolysis
ATP
Krebs
cycle
Electron
transport chain
and oxidative
phosphorylation
NAD+
CO2
CoA
Acetyl CoA
ATP
Mitochondrion
(fluid matrix)
NADH+H+
ATP
Oxaloacetic acid
(pickup molecule)
Citric acid
CoA (initial reactant)
Isocitric acid
Malic acid
NAD+
Krebs cycle
CO2
NADH+H+
a-Ketoglutaric acid
Fumaric acid
CO2
FADH2
FAD
Key:
Succinic acid
Succinyl-CoA
CoA
NAD+
NADH+H+
CoA
= Carbon atom
GTP
GDP + Pi
ADP
ATP
Pi = Inorganic phosphate
CoA = Coenzyme A
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.7
Cytosol
Pyruvic acid from glycolysis
Glycolysis
ATP
Krebs
cycle
Electron
transport chain
and oxidative
phosphorylation
NAD+
CO2
CoA
Acetyl CoA
ATP
Mitochondrion
(fluid matrix)
NADH+H+
ATP
Oxaloacetic acid
(pickup molecule)
NADH+H+
Citric acid
CoA (initial reactant)
NAD+
Isocitric acid
Malic acid
NAD+
Krebs cycle
CO2
NADH+H+
a-Ketoglutaric acid
Fumaric acid
CO2
FADH2
FAD
Key:
Succinic acid
Succinyl-CoA
CoA
NAD+
NADH+H+
CoA
= Carbon atom
GTP
GDP + Pi
ADP
ATP
Pi = Inorganic phosphate
CoA = Coenzyme A
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.7
Electron Transport Chain


Food (glucose) is oxidized and the released
hydrogens:

Are transported by coenzymes NADH and FADH2

Enter a chain of proteins bound to metal atoms
(cofactors)

Combine with molecular oxygen to form water

Release energy
The energy released is harnessed to attach
inorganic phosphate groups (Pi) to ADP, making
ATP by oxidative phosphorylation
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Mechanism of Oxidative Phosphorylation

The hydrogens delivered to the chain are split into
protons (H+) and electrons


The protons are pumped across the inner
mitochondrial membrane by:

NADH dehydrogenase (FMN, Fe-S)

Cytochrome b-c1

Cytochrome oxidase (a-a3)
The electrons are shuttled from one acceptor to the
next
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Mechanism of Oxidative Phosphorylation

Electrons are delivered to oxygen, forming oxygen
ions

Oxygen ions attract H+ to form water

H+ pumped to the intermembrane space:

Diffuses back to the matrix via ATP synthase

Releases energy to make ATP
PLAY
InterActive Physiology ®:
Muscular System: Muscular Metabolism
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Glycolysis
Krebs
cycle
Electron
transport chain
and oxidative
phosphorylation
ATP
ATP
ATP
H+
H+
H+
H+
Intermembrane
space
Core
Cyt c
e-
eQ
1
3
2
Inner
mitochondrial
membrane
2 H+ +
FADH2
NADH +
Mitochondrial
matrix
O2
H2O
FAD
ATP
ADP + Pi
H+
(carrying efrom food)
1
2
NAD +
H+
Electron Transport Chain
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
ATP Synthase
Figure 24.8
Glycolysis
Krebs
cycle
Electron
transport chain
and oxidative
phosphorylation
ATP
ATP
ATP
H+
Core
Intermembrane
space
Cyt c
Q
1
3
2
Inner
mitochondrial
membrane
NADH + H+
(carrying efrom food)
Mitochondrial
matrix
NAD +
Electron Transport Chain
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.8
Glycolysis
Krebs
cycle
Electron
transport chain
and oxidative
phosphorylation
ATP
ATP
ATP
H+
H+
Core
Intermembrane
space
Cyt c
eQ
1
3
2
Inner
mitochondrial
membrane
FADH2
NADH +
(carrying efrom food)
Mitochondrial
matrix
FAD
H+
NAD +
Electron Transport Chain
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.8
Glycolysis
Krebs
cycle
Electron
transport chain
and oxidative
phosphorylation
ATP
ATP
ATP
H+
H+
H+
Core
Intermembrane
space
Cyt c
e-
eQ
1
3
2
Inner
mitochondrial
membrane
FADH2
NADH +
(carrying efrom food)
Mitochondrial
matrix
FAD
H+
NAD +
Electron Transport Chain
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.8
Glycolysis
Krebs
cycle
Electron
transport chain
and oxidative
phosphorylation
ATP
ATP
ATP
H+
H+
H+
H+
Intermembrane
space
Core
Cyt c
e-
eQ
1
3
2
Inner
mitochondrial
membrane
FADH2
NADH +
(carrying efrom food)
Mitochondrial
matrix
FAD
H+
NAD +
Electron Transport Chain
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
ATP Synthase
Figure 24.8
Glycolysis
Krebs
cycle
Electron
transport chain
and oxidative
phosphorylation
ATP
ATP
ATP
H+
H+
H+
H+
Intermembrane
space
Core
Cyt c
e-
eQ
1
3
2
Inner
mitochondrial
membrane
FADH2
NADH +
(carrying efrom food)
Mitochondrial
matrix
FAD
ATP
ADP + Pi
H+
NAD +
H+
Electron Transport Chain
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
ATP Synthase
Figure 24.8
Glycolysis
Krebs
cycle
Electron
transport chain
and oxidative
phosphorylation
ATP
ATP
ATP
H+
H+
H+
H+
Intermembrane
space
Core
Cyt c
e-
eQ
1
3
2
Inner
mitochondrial
membrane
2 H+ +
FADH2
NADH +
Mitochondrial
matrix
O2
H2O
FAD
ATP
ADP + Pi
H+
(carrying efrom food)
1
2
NAD +
H+
Electron Transport Chain
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
ATP Synthase
Figure 24.8
Electronic Energy Gradient

The transfer of energy from NADH + H+ and
FADH2 to oxygen releases large amounts of energy

This energy is released in a stepwise manner
through the electron transport chain
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Electronic Energy Gradient


The electrochemical proton gradient across the
inner membrane:

Creates a pH gradient

Generates a voltage gradient
These gradients cause H+ to flow back into the
matrix via ATP synthase
PLAY
Electron Transport
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.9
ATP Synthase

The enzyme consists of three parts: a rotor, a knob,
and a rod

Current created by H+ causes the rotor and rod to
rotate

This rotation activates catalytic sites in the knob
where ADP and Pi are combined to make ATP
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Structure of ATP Synthase
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.10
Summary of ATP Production
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.11
Glycogenesis and Glycogenolysis


Glycogenesis –
formation of glycogen
when glucose supplies
exceed cellular need for
ATP synthesis
Glycogenolysis –
breakdown of glycogen
in response to low blood
glucose
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.12
Gluconeogenesis

The process of forming sugar from
noncarbohydrate molecules

Takes place mainly in the liver

Protects the body, especially the brain, from the
damaging effects of hypoglycemia by ensuring
ATP synthesis can continue
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Lipid Metabolism

Most products of fat metabolism are transported in
lymph as chylomicrons

Lipids in chylomicrons are hydrolyzed by plasma
enzymes and absorbed by cells

Only neutral fats are routinely oxidized for energy
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Lipid Metabolism

Catabolism of fats involves two separate pathways

Glycerol pathway

Fatty acids pathway
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Lipid Metabolism

Glycerol is converted to glyceraldehyde phosphate

Glyceraldehyde is ultimately converted into acetyl
CoA

Acetyl CoA enters the Krebs cycle
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Lipid Metabolism

Fatty acids undergo beta oxidation which
produces:

Two-carbon acetic acid fragments, which enter the
Krebs cycle

Reduced coenzymes, which enter the electron
transport chain
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Lipid Metabolism
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.13
Lipogenesis and Lipolysis

Excess dietary glycerol and fatty acids undergo
lipogenesis to form triglycerides

Glucose is easily converted into fat since acetyl
CoA is:

An intermediate in glucose catabolism

The starting molecule for the synthesis of fatty
acids
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Lipogenesis and Lipolysis

Lipolysis, the breakdown of stored fat, is
essentially lipogenesis in reverse

Oxaloacetic acid is necessary for the complete
oxidation of fat

Without it, acetyl CoA is converted into ketones
(ketogenesis)
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Lipogenesis and Lipolysis
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.14
Lipid Metabolism:
Synthesis of Structural Materials

Phospholipids are important components of myelin
and cell membranes
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Lipid Metabolism:
Synthesis of Structural Materials


The liver:

Synthesizes lipoproteins for transport of
cholesterol and fats

Makes tissue factor, a clotting factor

Synthesizes cholesterol for acetyl CoA

Uses cholesterol to form bile salts
Certain endocrine organs use cholesterol to
synthesize steroid hormones
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Protein Metabolism


Excess dietary protein results in amino acids being:

Oxidized for energy

Converted into fat for storage
Amino acids must be deaminated prior to oxidation
for energy
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Protein Metabolism


Deaminated amino acids are converted into:

Pyruvic acid

One of the keto acid intermediates of the Krebs
cycle
These events occur as transamination, oxidative
deamination, and keto acid modification
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Amino Acid Oxidation
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 24.15