1Anabolism and Catabolism
Key concept: When energy input is greater than output, anabolism builds complex molecules from simple ones. When input is less than output, catabolism breaks complex molecules down for energy.
- Set Energy Input above Energy Output and build a complex organelle (anabolism).
- Then set Energy Output above Energy Input until every structure is back to monomers (catabolism).
Thermodynamics connection: Anabolism (building) requires energy input and decreases entropy locally. Catabolism (breaking down) releases energy and increases entropy.
2Energy Coupling
Key concept: Cells couple energy-releasing (exergonic) reactions with energy-requiring (endergonic) reactions. ATP, the cell's energy currency, links the two.
- Tap the free phosphate to form ATP (phosphorylation).
- Tap ATP's high-energy bond to release energy (hydrolysis).
- ATP hydrolysis powers active transport across membranes
- The electron transport chain couples oxidation to ATP synthesis
- Cellular respiration couples glucose breakdown to ATP formation
Endergonic Reaction +ΔG
Phosphorylation (requires energy)
ADP + Pi + Energy → ATP
Exergonic Reaction -ΔG
Hydrolysis (releases energy)
ATP → ADP + Pi + Energy
3Sequential Metabolic Pathways
Key concept: Energy-related pathways are sequential, allowing controlled energy transfer. Each product becomes the next reaction's reactant.
Objective: Convert all Glucose to ATP
Select an enzyme, then tap a molecule it acts on.
4Loss of Order Results in Death
Key concept: Living systems are highly ordered and require constant energy to maintain that order. Significant loss of order or energy flow results in death.
- Take the cell through all five consequences of energy loss, one step at a time or all at once.
Summary: Life is a constant battle against entropy (disorder). Energy input must exceed energy loss to maintain the highly ordered state we call "alive."
Loss of electrochemical gradients
Cell contents leak out
Loss of cellular structure
Inability to reproduce or repair
Disorder takes over