Bioenergetics - Eastern Michigan University

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Transcript Bioenergetics - Eastern Michigan University

Bioenergetics
Components of a typical cell
Cellular Structures
• Cell membrane
– semi-permeable
– encloses internal components of cell
– regulates flux of metabolites and nutrients
• Nucleus
– contains genetic material (DNA)
– regulates protein production
• Cytoplasm
– fluid portion of the cell which contains organelles,
enzymes etc.
Mitochondria
• “power station” for the cell
• All “aerobic” respiration takes place within
the mitochondria
• “anaerobic” glycolysis occurs in the
cytoplasm
ATP Generation
• The purpose of glycolysis and aerobic
respiration is to produce ATP
• All of the systems we study in Exercise
Physiology relate to ATP production
ADP and ATP structures
ATP as universal energy donor that drives energy
needs of cells
Breakdown of glucose to CO2 + H2O via cellular
oxidation releases energy (Big Picture)
The First Step
Glycolysis: part 1
glycolysis: part 2
Glycolysis Yields Potential and Direct
Energy
• The glycolytic process yields NADH from
NAD+
– NADH transported into mitochondria to
produce ATP in electron transport
• Glycolysis also yields ATP directly by
“substrate level phosphorylation”
Substrate Level Phosphorylation
Production of Lactate
Why Produce Lactate?
Fate of Glucose (Glycolysis)
• glucose is broken down to pyruvate
• pyruvate can then enter the Krebs Cycle
(aerobic)
• or
• pyruvate can form lactate (lactic acid)
– anaerobic, feel the burn
The Krebs Cycle
The Krebs Cycle
• pyruvate enters the Krebs from glycolysis
• fatty acids also enter the Krebs cycle
• together pyruvate and fatty acids drive the Krebs
to produce a lot of ATP
Krebs in Detail
Electrons enter respiratory chain from
glycolysis and Krebs
Electron transport
Electron transport 1
Electron transport 2
Chemiosmotic theory of aerobic ATP
production
Movement of protons across
membrane and electrons along
ETC
• Animation of Electron transport in
Mitochondria.htm
A high proton gradient enables ATP to be
generated
Movement of protons through ATPase generates ATP
• Animation of ATP synthesis in
Mitochondria.htm
ATP tally from breakdown of 1 glucose molecule
Metabolic
Process
High energy
products
ATP from
oxidative
phosphorylation
ATP subtotal
Glycolysis
2ATP
2 NADH
-6
2 (if anaerobic)
8 (if aerobic)
Pyruvic acid to
acetyl-CoA
2 NADH
6
14
Krebs Cycle
2 GTP
6 NADH
2 FADH
-18
4
Grand Total
16
34
38
38 ATP
Putting it together
• Glycolysis occurs
in the cytosol
• Glycolysis feeds
the Krebs cycle
• Krebs occurs in
the mitochondria
Pathways of Catabolism
Energy Transformation
• Exergonic vs. endergonic rxns
– exergonic produces energy
– endergonic requires energy input
• Coupled rxns
– by coupling exergonic rxn, energy can run
endergonic rxn
Coupling exergonic and endergonic reactions
The energy systems
• Anaerobic vs aerobic systems
• Anaerobic (non-oxidative)
– ATP-PC (Phosphocreatine or phosphagen)
• PC + ADP => ATP + C
– Glycolysis
• breakdown of glucose to form 2 pyruvate or lactate
• Aerobic
– Krebs Cycle (TCA or oxidative phosphorylation)
The Phosphocreatine (PC)
System
Phosphogen Reactions
PCr + ADP + H+ <=> ATP + Cr
Creatine Kinase
ADP + ADP <=> ATP + AMP
Adenylate Kinase
Phosphagen System as
Bioenergetic Regulator
• Phosphagen system produces ATP at high
rate to maintain energy state
Enzymes
–
–
–
–
necessary for almost all biological processes
lower Energy of Activation
work in a “lock and key” type of mechanism
very sensitive to temperature and pH
• remember body temp regulated in narrow range
Enzymes catalyze reactions by lowering
energy of activation
Lock and Key model of enzyme action
Take Home Message
• enzymes catalyze reactions by bringing the
reactants into close proximity
• this means less energy is required to
activate the reaction
Fuels for Exercise
• Carbohydrates
• Fats
• Proteins
Carbohydrates-”A quick fix”
• Simple sugars
– glucose, fructose, sucrose, maltose
• Complex carbs (polysaccharides)
– starch, cellulose, glycogen
– storage form of glucose is glycogen
• Glycogenolysis
– process by which glycogen is broken down into
glucose for use by the body
Fats-”Energy for the long haul”
• More efficient storage form of energy than CHO
(9 kcal/gram vs 4 kcal/gram)
• Kinds of fats
– fatty acids, triglycerides, phospholipids, steroids
• Fatty acids and triglycerides are used for energy
• Phospholipids and steroids are used for structural
and regulatory purposes
Proteins-”The building blocks”
• Composed of sub-units called amino acids
• Primarily used for structural purposes
(muscle tissue, tendons, ligaments)
• Also serve as enzymes
• Can be used for energy (4 kcal/gram), but
not readily
Metabolism of Proteins, Carbohydrates and Fats