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THIRD EDITION
HUMAN PHYSIOLOGY
AN INTEGRATED APPROACH
Dee Unglaub Silverthorn, Ph.D.
Chapter 4
Cellular Metabolism
PowerPoint® Lecture Slide Presentation by
Dr. Howard D. Booth, Professor of Biology, Eastern Michigan University
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
About this Chapter
• Energy for synthesis and movement
• Energy transformation
• Enzymes and how they speed reactions
• Metabolic pathways
• ATP its formation and uses in metabolism
• Synthesis of biologically important molecules
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Energy (E) Transfer Overview
• Energy does work
• Kinetic energy
• Potential energy
• Energy conversion
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Energy (E) Transfer Overview
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Figure 4-1: Energy transfer in the environment
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Chemosynthesis versus Photosynthesis
Chemosynthesis
• 6CO2 + 6H2S → C6H12O6 + 6S
Needs heat added such as from hydrothermal vents
in the deep ocean
Photosynthesis
• 2n CO2 + 2n H2O + photons → 2(CH2O)n + 2n O2
Occurs in Two Stages
Stage 1: Light energy used to form ATP and NADPH
Stage 2: Uses ATP and NADPH to reduce CO2
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Energy and Chemical Reactions
Figure 4-5: Energy transfer and storage in biological reactions
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Adenosine Triphosphate (ATP)
• Source of immediately usable energy for the cell
• Adenine-containing RNA nucleotide with three
phosphate groups
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Adenosine Triphosphate (ATP)
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Figure 2.22
How ATP Drives Cellular Work
Figure 2.23
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Protein
• Macromolecules composed of combinations of 20
types of amino acids bound together with peptide
bonds
Figure 2.16
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Structural Levels of Proteins
• Primary – amino acid sequence
• Secondary – alpha helices or beta pleated sheets
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Structural Levels of Proteins
Figure 2.17a-c
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Structural Levels of Proteins
• Tertiary – superimposed folding of secondary
structures
• Quaternary – polypeptide chains linked together
in a specific manner
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Structural Levels of Proteins
Figure 2.17d, e
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Fibrous and Globular Proteins
• Fibrous proteins
• Extended and strandlike proteins
• Examples: keratin, elastin, collagen, and
certain contractile fibers
• Globular proteins
• Compact, spherical proteins with tertiary and
quaternary structures
• Examples: antibodies, hormones, and enzymes
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Protein Synthesis
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Figure 4-34: Summary of transcription and translation
Post – Translational protein modificaiton
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Figure 4-35: Post-translational modification and the secretory pathway
Post – Translational protein modificaiton
• Folding, cleavage, additions: glyco- lipo- proteins
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Characteristics of Enzymes
• Most are globular proteins that act as biological
catalysts
• Holoenzymes consist of an apoenzyme (protein)
and a cofactor (usually an ion)
• Enzymes are chemically specific
• Frequently named for the type of reaction they
catalyze
• Enzyme names usually end in -ase
• Lower activation energy
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Characteristics of Enzymes
Figure 2.19
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Enzymes speed biochemical reactions
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Figure 4-8: Two models of enzyme binding sites
Mechanism of Enzyme Action
• Enzyme binds with substrate
• Product is formed at a lower activation energy
• Product is released
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Enzymes speed biochemical reactions
•
•
•
•
Lower activation E
Specific
Cofactors
Modulators
• Acidity
• Temperature
• Competitive inhibitors
• Allosteric
• Concentrations
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Protein Denaturation
• Reversible
unfolding of
proteins due to
drops in pH
and/or
increased
temperature
Figure 2.18a
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Protein Denaturation
• Irreversibly denatured proteins cannot refold and
are formed by extreme pH or temperature
changes
Figure 2.18b
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Law of Mass Action
• Defined:
• Equlibrium
• Reversible
Figure 4-17: Law of mass action
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Types of Enzymatic Reactions
• Oxidation–reduction
• Hydrolysis–dehydration
• Addition–subtraction exchange
• Ligation
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Cell Metabolism
• Pathways
• Intermediates
• Catabolic energy
• Anabolic synthesis
Figure 4-18b: A group of metabolic pathways resembles a road map
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Control of Metabolic Pathways
• Feedback inhibition
Figure 4-19: Feedback inhibition
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ATP Production
• Glycolysis
• Pyruvate
• Anaerobic
respiration
• Lactate
production
• 2 ATPs produced
Figure 4-21: Overview of aerobic pathways for ATP Production
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Pyruvate Metabolism
• Aerobic respiration
• In mitochondria
• Acetyl CoA and CO2
• Citric Acid Cycle or Kreb’s Cycle or TCA Cycle
• Energy Produced from 1 Acetyl CoA
• 1 ATP
• 3 NADH
• 1 FADH2
• Waste–2 CO2s
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Pyruvate Metabolism
Figure 4-23: Pyruvate metabolism
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Electron Transport
• High energy electrons
• Energy transfer
• ATP synthesized from ADP
• H2O is a byproduct- In a typical individual
this amounts to approximately 400 ml/day
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Electron Transport
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Figure 4-25: The electron transport system and ATP synthesis
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Biomolecules Catabolized to make ATP
• Complex
Carbohydrates
• Glycogen
catabolism
• Liver storage
• Muscle storage
• Glucose produced
Figure 4-26: Glycogen catabolism
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Protein Catabolism
• Deaminated
• Conversion
• Glucose
• Acetyl CoA
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Protein Catabolism
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Figure 4-27: Protein catabolism and deamination
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Lipid Catabolism
• Higher energy content
• Triglycerides to glycerol
• Glycerol
• Fatty acids
• Ketone bodies - liver
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Fat mass, adipose tissue and energy stores
Liver triglycerides = 450 kcal
Muscle triglycerides =
Liver glycogen = 400 kcal
3000 kcal
Muscle glycogen =
2500 kcal
Adipose tissue triglycerides =
120,000 kcal
Data for a 70 kg lean subject.
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Synthetic (Anabolic) pathways
• Glycogen
synthesis
• Liver storage
• Glucose to
glycogen
• Gluconeogenesis
• Amino acids
• Glycerol
• Lactate
Figure 4-29: Gluconeogenesis
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Lipogenesis
• Acetyl Co A
• Glycerol
• Fatty acids
• Triglycerides
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Figure 4-30: Lipid synthesis
Lipogenesis
Figure 4-30: Lipid synthesis
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Summary
• Energy: chemical, transport, mechanical work
• Reactions: reactants, activation energy,
directions
• Enzymes: characteristics, speed & control
pathways
• Metabolism: catabolic, anabolic
• ATP production: anaerobic, aerobic, glycolysis,
• citric acid cycle, & electron transport
• Synthesis of carbohydrates, lipids and proteins
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