Download Discover Biology, 5th Ed., C8

Discover Biology, 5th Ed., C8
Energy, Metabolism, & Enzymes
pp 186-203
Metabolism
• All chemical reactions in an organism that
– Capture energy
• Photosynthesis & chemosynthesis (autotroph)
• Harvest from other organisms (heterotroph)
– Store energy
• ATP; GTP; NADH; NADPH; FADH2; chemical bond P.E.
• Elastic potential energy
– Use energy
• Anabolism (make molecules)
• Catabolism (degrade molecules)
Metabolic pathways
• Chemical reactions are LINKED
– Temporally
– Spatially
• Substrates react to form products
– Biomolecules for structure & function
– Signals for cell-cell & cell-environment interaction
• Enzymes catalyze these reactions
– Proteins, usually, but also RNA as ribozymes
– Lower activation energy
ENERGY = ability to do work
• Potential energy
– Gravitational
– Chemical bond
– Elastic
• Kinetic energy (motion)
– Nuclear
– Electromagnetic
– Sound
- Mechanical
- Light (Radiant)
- Heat (thermal)
Laws of Thermodynamics
• First Law
– Energy is neither created nor destroyed
– Energy can be converted to other forms
• Second Law
– Entropy (disorder) increases in the universe
– As order increases in a cell, disorder increases in
its surroundings
– External energy must be used to maintain order in
a cell/ living system
“Lost” Energy
• Heat accompanies motion
– Friction
– Brownian motion
• Metabolic heat accompanies biochemical
reactions
– Dissipates
– Unusable
– Disorganized
Photosynthesis: Light Reaction
• Sun radiant energy excites chlorophyll a’s electrons
– Located in thylakoid membranes/ grana of chloroplast
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Electrons move from Photosystem II to Photosystem I
NADP+ + electron reduction NADPH (e- carrier)
2H2O  4H+ (Protons) + 4 e- + O2 at Photosystem II
Electrons move down ETC [e- transport chain]
Proton gradient supplemented by H+ pump
H+ move passively via ATP Synthase across thylakoid
ATP is generated in stroma of chloroplast
Photosynthesis: Chemiosmosis
Photosynthesis: Anabolism
Catabolism
• Cellular respiration
– Glycolysis: Glucose  2 (pyruvates + ATP + NADH)
– Fermentation: Pyruvate Ethanol + CO2lactic acid + NAD+
– Aerobic respiration: Pyruvate Kreb’s cycle
• Kreb’s cycle (Citric acid cycle)
– Acetyl CoA enters mitochondrial matrix
– Acetyl CoA + oxaloacetate  citric acid
– Generates 2 CO2 + 3 NADH, 1 GTP, & 1 FADH2
Glycolysis
Mitochondrial Chemiosmosis
Redox Reaction
• Paired together: 6CO2 + 6H2O + ATP C6H12O6
• Reduction reactions
– Gain electrons
– CO2 is reduced
• Oxidation reactions
– Lose electrons
– H atoms are oxidized in H2O
– 4 Fe + 3O2  2 Fe2O3 (rust)
Enzymes = Biological Catalysts
Induced Fit Model