Discover Biology, 5 th Ed., C8 Energy, Metabolism, & Enzymes pp

Metabolism All chemical reactions in an organism that – Capture energy Photosynthesis & chemosynthesis (autotroph) Harvest from other organisms (heterotroph) – Store energy ATP; GTP; NADH; NADPH; FADH 2 ; 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- Mechanical – Electromagnetic- Light (Radiant) – Sound- 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 Electrons move from Photosystem II to Photosystem I NADP + + electron  reduction  NADPH (e - carrier) 2H 2 O  4H + (Protons) + 4 e - + O 2 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 + CO 2 lactic 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 CO NADH, 1 GTP, & 1 FADH 2

Glycolysis

Mitochondrial Chemiosmosis

Redox Reaction Paired together: 6CO 2 + 6H 2 O + ATP  C 6 H 12 O 6 Reduction reactions – Gain electrons – CO 2 is reduced Oxidation reactions – Lose electrons – H atoms are oxidized in H 2 O – 4 Fe + 3O 2  2 Fe 2 O 3 (rust)

Enzymes = Biological Catalysts

Induced Fit Model