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Chapter 4
Cellular Metabolism and
Reproduction:
Mitosis and Meiosis
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Introduction to Cellular Metabolism
• Metabolism: total cellular chemical
changes
– Anabolism: process of building up
– Catabolism: process of breaking down
• Calorie: measure of energy contained in
food
• ATP: energy source available to the cell
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Anabolism
Anabolism provides the materials needed for cellular
growth and repair
Dehydration synthesis
• type of anabolic process
• used to make polysaccharides, triglycerides, and
proteins
• produces water
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Anabolism
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Catabolism
Catabolism breaks down larger molecules into smaller ones
Hydrolysis
• a catabolic process
• used to decompose carbohydrates, lipids, and proteins
• water is used to split the substances
• reverse of dehydration synthesis
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Catabolism
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Control of Metabolic Reactions
Metabolic pathways
• series of enzyme-controlled reactions leading to formation of a
product
• each new substrate is the product of the previous reaction
Enzyme names commonly
• reflect the substrate
• have the suffix – ase
• sucrase, lactase, protease, lipase
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Control of Metabolic Reactions
Cofactors
• make some enzymes
active
• non protein component
• ions or coenzymes
Coenzymes
• organic molecules
that act as cofactors
• vitamins
Factors that alter enzymes
• heat
• radiation
• electricity
• chemicals
• changes in pH
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Energy for Metabolic Reactions
Energy
• ability to do work or change something
• heat, light, sound, electricity, mechanical energy, chemical
energy
• changed from one form to another
• involved in all metabolic reactions
Release of chemical energy
• most metabolic processes depend on chemical energy
• oxidation of glucose generates chemical energy to promote
cellular metabolism
• cellular respiration releases chemical energy from molecules
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and makes it available for cellular use
Cellular Metabolism or
Biochemical Respiration
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ATP Molecules
• each ATP molecule has three parts:
• an adenine molecule
• a ribose molecule
• three phosphate molecules in a chain
• third phosphate attached by high-energy bond
• when the bond is broken, energy is transferred
• when the bond is broken, ATP becomes ADP
• ADP becomes ATP through phosphorylation
• phosphorylation requires energy released from cellular respiration
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Glycolysis
• Breakdown of glucose
• Anaerobic or aerobic process
• Final outcome
– 2 pyruvic acid molecules, 2 ATP molecules
(anaerobic), 8 ATP molecules (aerobic)
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The Krebs Citric Acid Cycle
• Pyruvic Acid > Acetic Acid > Acetyl-CoA
• Acetyl-CoA enters Krebs cycle in
mitochondria
• Final outcome
– 6 CO2, 8 NADH2, 2 FADH2, 2 ATP (GTP)
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The Electron Transport (Transfer)
System
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Series of reduction/oxidation reactions
Requires O2
Electron carriers
Number of ATP molecules dependent on
electron carrier
• Water is a waste product
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Summary of ATP Production
• During glycolysis, the citric acid cycle, and
electron transport
• Glycolysis: 8 ATP (aerobic)
• Krebs cycle and electron transport
– 28 ATP + 2 GTP or
– 30 ATP
• 1 glucose molecule yields 38 ATP
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Anaerobic Respiration
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Fermentation
• Yeast breaks down glucose anaerobically
• Pyruvic acid broken down by
decarboxylase
– Forms carbon dioxide and acetaldehyde
• Final products: 2 ATP, CO2, ethyl alcohol
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Anaerobic Production of ATP by
Muscles
• Pyruvic acid converted to lactic acid
– Accumulation of lactic acid causes fatigue in
muscles
– When oxygen supplied, lactic acid turns back
into pyruvic acid
• 2 ATP produced per glucose molecule
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Production of ATP from
General Food Compounds
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Production of ATP from General
Food Compounds (cont’d.)
• Carbohydrates fit into cellular furnace at
same level as glucose
– Can be stored in liver or as fat
• Fats digested into fatty acids and glycerol
– Glycerol enters at PGA stage of glycolysis
– Fatty acids enter Krebs citric acid cycle
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Production of ATP from General
Food Compounds (cont’d.)
• Proteins digested into amino acids
– Enter into Krebs cycle at different stages
• Dependent on chemical structure
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Introduction to Cellular
Reproduction
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Introduction to Cellular
Reproduction (cont’d.)
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Process of cell duplication
Mitosis: duplication of genetic material
Cytokinesis: duplication of organelles
Meiosis: reduction division only in gonads
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The Structure of the DNA
Molecule
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The History of the Discovery of
DNA
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Friedrich Miescher, 1869: first discovery
P.A. Levine, 1920s: composition
Rosalind Franklin: helical structure
Watson and Crick: three-dimensional
structure
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The Anatomy of the DNA Molecule
• Double helical chain of nucleotides
– Phosphate group
– Five-carbon sugars (deoxyribose)
– Nitrogen-containing base
• Pyrimidines (thymine and cytosine)
• Purines (adenine and guanine)
– Pyrimidines pair with purines
– Chains held together by hydrogen bonds
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The Anatomy of the DNA Molecule
(cont’d.)
• Gene: sequence of base pairs that codes
for polypeptide or protein
• Human Genome Project
– 3 billion base pairs that code for 30,000 genes
• Duplication of DNA molecule
– Helicase separates at hydrogen bonds
– DNA polymerase adds new nucleotides
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The Cell Cycle
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Introduction
• All reproduction begins at cellular level
• Interphase
– Previously called resting stage
• Mitosis
• Cytokinesis
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Interphase
• Time between divisions
– G1: Primary growth phase
– S: DNA duplication
– G2: Centrioles complete duplication,
mitochondria replicate, chromosomes
condense and coil
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Mitosis
• Prophase
– Chromosomes become visible as chromatids
joined by centromere
– Two kinetochores at the centromere
– Centrioles move to opposite poles
– Nuclear membrane breaks down
– Microtubules attach kinetochores to spindle
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Mitosis (cont’d.)
• Metaphase
– Chromatids align at equator of cell
– Centromere divides
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Mitosis (cont’d.)
• Anaphase
– Divided centromere pulls chromatids to
opposite pole
– Cytokinesis begins
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Mitosis (cont’d.)
• Telophase
– Chromosomes uncoil and decondense
– Spindle apparatus breaks down
– New nuclear membrane forms
– Cytokinesis nearly complete
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Animation - Mitosis
• Stop and watch a 3-D presentation of
mitosis.
[Insert mitosis.swf]
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Cytokinesis
• Animal cells
– Cleavage furrow forms
– Cell is pinched into daughter cells
• Plant cells
– Cell plate forms at equator
– Cell plate becomes new cell wall
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Meiosis: A Reduction Division
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Introduction
• Occurs only in the gonads
• Reduces genetic material from diploid to
haploid
• Two divisions resulting in four cells
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Stages of Meiosis
• Prophase I: homologous chromosomes
pair and cross over
• Metaphase I: chromosomes align along
equator
• Anaphase I: centromeres pulled to poles
– One member to each pole
• Telophase I: one of each pair is at each
pole
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Stages of Meiosis (cont’d.)
• Prophase II: spindle forms; centrioles
move to poles
• Metaphase II: chromosomes line up at
equator
• Anaphase II: centromeres divide
• Telophase II: chromatids at each pole; new
nuclear membrane forms
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Animation - Meiosis
• Now that you have learned about the
stages of meiosis, watch the meiosis
animation for a visual of this process.
• [Insert meiosis.swf]
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Gametogenesis: The
Formation of the Sex Cells
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Gametogenesis: The Formation of
the Sex Cells (cont’d.)
• Spermatogenesis
– Four cells produced
– Develop into sperm
• Oogenesis
– Four cells produced
– Only one becomes functional egg
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Animation – Cancer Metastasizing
• Refer to the Common Disease, Disorder or
Condition box on Cancer in your textbook
and read about the growth of cancer cells.
Now watch the 3-D Cancer Metastasizing
animation.
• [Insert cancer metastasizing.swf]
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Summary
• Discussed how glucose is converted into
ATP in the presence of oxygen
• Discussed how glucose is converted into
ATP in the absence of oxygen
• Described how fats and proteins are
converted into ATP
• Discussed the cell cycle
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