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Chapter 8: An Introduction to Metabolism - Coggle Diagram
Chapter 8: An Introduction to Metabolism
An Organism’s Metabolism
Metabolism: total chemical reactions in an organism
Metabolic Pathway
Series of enzyme-catalyzed steps
Specific molecule -> final product
Catabolic Pathways
Break down molecules
Release energy
Example: cellular respiration
Anabolic Pathways
Build complex molecules
Consume energy
Example: protein synthesis
Bioenergetics
Study of how energy flows through living organisms
Energy & Thermodynamics
Energy: capacity to cause change
Forms of Energy
Kinetic energy – motion
Thermal energy – heat (kinetic)
Potential energy – position/structure
Chemical energy – potential energy in bonds
First Law of Thermodynamics
Energy is conserved
Energy can’t be created or destroyed
Second Law of Thermodynamics
Entropy (disorder) increases
Energy transformations release heat
Spontaneous Processes
Occur without energy input
Increase entropy
Free Energy & Reactions
Gibbs Free Energy (ΔG)
ΔG = ΔH – TΔS
ΔH: enthalpy (total energy)
T: temperature in Kelvin
ΔS: entropy
Spontaneous Reactions
ΔG < 0
Exergonic – releases energy
Nonspontaneous Reactions
ΔG > 0
Endergonic – requires energy
Equilibrium
Forward and reverse reactions equal
No net change
System at maximum stability
Metabolism in Cells
Reactions never reach equilibrium
Open system – materials flow in/out
ATP Powers Cellular Work
ATP Structure
Adenine
Ribose
3 phosphate groups
Hydrolysis of ATP
Releases energy
ATP -> ADP + Pi
Drives endergonic reactions
Types of Cellular Work
Chemical – driving reactions
Transport – pumping substances
Mechanical – movement (muscles, cilia)
Phosphorylation
ATP transfers phosphate to a molecule
Makes molecule more reactive
ATP Cycle
ATP regenerated from ADP
Energy comes from catabolic reactions
Enzymes Speed Up Reactions
Enzymes
Biological catalysts (usually proteins)
Speed up reactions without being consumed
Substrate Specificity
Enzyme binds specific substrate
Forms enzyme-substrate complex
Activation Energy (EA)
Energy needed to start reaction
Enzymes lower EA
Induced Fit
Active site changes shape to fit substrate
Enzyme Mechanisms
Orient substrates
Strain bonds
Provide microenvironment
Participate in reaction
Factors Affecting Activity
Temperature
pH
Cofactors (metal ions, vitamins)
Enzyme Inhibitors
Competitive – block active site
Noncompetitive – bind elsewhere, change shape
Allosteric Regulation
Molecules bind at regulatory sites
Can activate or inhibit
Feedback Inhibition
End product inhibits pathway
Prevents waste
Localization
Enzymes in organelles (e.g. mitochondria)