Energy and Metabolism

Energy

• the capacity to perform change

• cannot be created nor destroyed, only transferred

Where do biological systems store energy

In chemical bonds

Bonds

• breaking bonds releases energy but also requires an investment

• the balance between the investment and payback defines a reaction as exothermic or endothermic

Exothermic reactions

• more common than endothermic reactions

• release excess energy (as heat) not stored in the products’ bonds

Endothermic reactions

• less common

• take energy from their surroundings, reducing the temperature (heat) around them

Enzymes

• proteins that increase the efficiency of chemical reactions by reducing the energy of activation of a reaction (does not change if exo or endo thermic)

• provide a pocket (active site) where chemical reactions are carried out

• not directly consumed by the chemical reactions they catalyze, but degrade over time by the products released by the reaction

How do biological systems transfer energy from one reaction to another?

They use ATP

• the primary source of ATP in eukaryotic cells is cellular respiration