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Anatomy & Physiology
SIXTH EDITION
Chapter 25, part 2
Metabolism and Energetics
PowerPoint® Lecture Slide Presentation prepared by
Dr. Kathleen A. Ireland, Biology Instructor, Seabury Hall, Maui, Hawaii
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Frederic H. Martini
Fundamentals of
SECTION 25-3
Lipid Metabolism
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Lipid catabolism
• Lipolysis
• Lipids broken down into pieces that can be
converted into pyruvate
• Triglycerides are split into glycerol and fatty
acids
• Glycerol enters glycolytic pathways
• Fatty acids enter the mitochondrion
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Lipid catabolism
• Beta-oxidation
• Breakdown of fatty acid molecules into
2-carbon fragments
• Enter the TCA
• Irreversible
• Lipids and energy production
• Cannot provide large amounts in ATP in a
short amount of time
• Used when glucose reserves are limited
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Figure 25.9 Beta Oxidation
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Figure 25.9
Figure 25.9 Beta Oxidation
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Figure 25.9
Lipid synthesis (lipogenesis)
• Almost any organic molecule can be used to form
glycerol
• Essential fatty acids cannot be synthesized and
must be included in diet
• Linoleic and linolenic acid
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Figure 25.10 Lipid Synthesis
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Figure 25.10
Lipid transport and distribution
• 5 types of lipoprotein
• Lipid-protein complex that contains large
glycerides and cholesterol
• Chylomicrons
• Largest lipoproteins composed primarily
of triglycerides
• Very low-density lipoproteins (VLDLs)
• contain triglycerides, phospholipids and
cholesterol
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Lipid transport and distribution
• 5 types of lipoprotein (continued)
• Intermediate-density lipoproteins (IDLs)
• Contain smaller amounts of triglycerides
• Low-density lipoproteins (LDLs)
• Contain mostly cholesterol
• High-density lipoproteins (HDLs)
• Equal amounts of lipid and protein
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Lipoprotein lipase
• Enzyme that breaks down complex lipids
• Found in capillary walls of liver, adipose tissue,
skeletal and cardiac muscle
• Releases fatty acids and monglycerides
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Figure 25.11 Lipid Transport and Utilization
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Figure 25.11a
Figure 25.11 Lipid Transport and Utilization
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Figure 25.11b
SECTION 25-4
Protein Metabolism
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Amino acid catabolism
• If other sources inadequate, mitochondria can
break down amino acids
• TCA cycle
• removal of the amino group (-NH2)
• Transamination – attaches removed amino
group to a keto acid
• Deamination – removes amino group
generating NH4+
• Proteins are an impractical source of ATP
production
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Figure 25.12 Amino Acid Catabolism
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Figure 25.12
Figure 25.12 Amino Acid Catabolism
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Figure 25.12a
Figure 25.12 Amino Acid Catabolism
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 25.12b
Figure 25.12 Amino Acid Catabolism
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Figure 25.12c
Protein synthesis
• Essential amino acids
• Cannot be synthesized by the body in adequate
supply
• Nonessential amino acids
• Can be synthesized by the body via amination
• Addition of the amino group to a carbon
framework
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Figure 25.13 Amination
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Figure 25.13
Figure 25.14 A Summary of the Pathways of
Catabolism and Anabolism
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Figure 25.14
SECTION 25-5
Nucleic Acid Metabolism
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Nucleic acid metabolism
• Nuclear DNA is never catabolized for energy
• RNA catabolism
• RNA molecules are routinely broken down and
replaced
• Generally recycled as nucleic acids
• Can be catabolized to simple sugars and
nitrogenous bases
• Do not contribute significantly to energy
reserves
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Nucleic acid synthesis
• Most cells synthesis RNA
• DNA synthesized only when preparing for
division
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