Metabolic Pathways

Multi-step processes involving multiple enzymes

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• Break-down of complex molecules to simple molecules
• Stored Energy Can be Used for work

• Assembly of complex molecules
• Requires energy for work

• Cells use energy stored in organic molecules
• Capacity to do work

• Energy can be transferred, but never created or destroyed
• Every enery transfer increases the entropy of the universe. (Entropy is disorder).

More Free Energy

Less Stable

Greater Work Capacity

Less Free Energy

More Stable

Less Work Capacity

Free Energy is released

Often used by cells to drive an endergonic reaction

• Ribose, adnine, and 3 phosphate
• Phosphate is negative charged
• Bone b/t phosphate can be broken to form:
• ADP+energy

10 million molecules per second turnover

Endergonic reaction

Cellular Respiration provides energy

Catalysts

Change chemical rate w/o being consumed

Speed Things Up

Lower barrier of activation energy-energy required to start reaction

Can only speed up reaction that would occur spontaneously

template for substances to come together

stretch or bend molecules

create micro-environment

temporary covalent bonding

1. Environmental Conditions
2. Cofactors (non-protein: metal ions, vitamins)
3. Inhibition (Competitive, noncompetitive)

Molecules Bind to site on the enzyme

Often irreversible if covalent

Used to regulate Cell Metabolism

Turn on/off synthesis of specific enzyme

Control the activity of synthesized enzymes

Allosteric regulation

• Activating/inhibiting molecules binds to a regulatory (allosteric) site
• ATP hydrolysis
• ATP inhibitor and ADP activator act as allosteric regulators

Glucose + Oxygen = Carbon Dioxide, water, and energy

Exergonic Reaction

Energy stored in Glucose is transferred to make ATP

40% efficient, 60% released as heat

Electron acceptor

Oxidizing agent during respiration

Oxygen Required

High ATP yield

No Oxygen Required

Example: Fermentation

Low ATP yield

Glycolysis

Citric Acid Cycle

Oxidative Phosphorylation

Catalysis of glucose in the cytoplams

cost 2 ATP, produces 4 ATP and 2 NADH, net is 2

End product is pyruvate

Pyruvate transported to mitochondria

• Occurs within Mitochondria

1. Decarboxylation of Pyruvate, release of CO₂
2. Oxidation of pyruvate, reduct of NAD⁺ to NADH
3. Coenzyme A attached by an unstable bond

• Electron transport train
• Inner membrane (mitocondria)
• Series of 4 multiprotein complexes
• Prosthetic groups bound to multiprotein
• Electron carriers alternate b/t reduced and oxidized

• Use H+ gradient
• Drives ADP phosphorylation via ATP synthase
• Transfer electrons from NADH & FADH
• pump H+ across membrane