The laws of thermodynamics show that energy in living things comes from the sun, flowing from plants to animals. Photosynthesis and other life activities increase entropy. Living things offset positive entropy by taking in negative entropy. They are dissipative structures far from equilibrium.

Bio chemical reactions occur spontaneously when the Gibbs free energy ＜0. We derived the formula of Gibbs function, and discussed cases of endothermic and exothermic reaction, entropy increase and decrease.

ATP, or adenosine triphosphate is the immediate energy source for biological processes. It is cycling between hydrolysis and synthesis and is reused over and over again in metabolism. Therefor ATP is also called energy currency or coin.

Factors that affect enzyme activity are: temperature, pH, activator, inhibitor, substrate concentration, and enzyme concentration. Enzymes are not always active at the same level.

Most enzymes are proteins, and factors that alter the protein structure can affect enzyme activity. They include temperature, pH, freeze and concentration.

Substances that decrease enzyme activity are called inhibitors(non-competitive i​nhibitor,competitive i​nhibitor, irreversible Inhibitor, reversible Inhibitor), while substances that increase enzyme activity are called activators.

Respiration breaks down glucose into water and carbon dioxide and releases energy. It is categorized into anaerobic and aerobic respiration. Fermentation is another way to obtain energy from organic matter under no oxygen conditions.

Catabolism or breakdown path decomposes organelles or bio macromolecules to produce energy. Aerobic cellular respiration makes ATP via redox reactions. Its efficiency is about 40%. Activation energy stabilizes organic matter at room temperature.

There are 5 common anaerobic respirations: denitrification or Nitrate Reduction, Anaerobic ammonia oxidation or Anammox, Sulfide and Sulphur respiration, Bicarbonate respiration, Iron respiration by iron-reducing bacteria. What is role of anaerobic respiration in ecosystems?

Homolactic acid fermentation and homoalcoholic fermentation use organic matter as electron acceptors to extract electrons from NADH. Heterolactic fermentation produces lactic acid, alcohol and carbon dioxide.

Homolactic fermentation is used for food, beverage preservation and flavoring. We also introduce the process of lactic acid fermentation. It's also the basic unit of biodegradable PLA that is used in medical implants and food packaging.

A journey of exploration and discovery of plant photosynthesis. From ancient to modern times. 18th century: photosynthesis purifies air. 19th century: chloroplasts, energy conservation, starch, chemical equations. 20th century: light reactions, dark reactions, C3 cycle, NADPH and chemiosmotic hypothesis.

Photoautotrophs get their food from photosynthesis, which occurs in chloroplasts. They're also food for heterotrophs. Photosynthesis formula, products, reactants. They are divided into dark reactions and light reactions.

Calvin cycle for biological carbon fixation is also named as dark reaction, C3 pathway, light-independent reaction, photosynthetic carbon reduction (PCR) cycle. Carbon dioxide is fixed by a pentose. Then, they're reduced to triose by ATP, NADPH. Finally, new pentose are synthesized again for the next cycle.

Photorespiration is also known as Glycolate Pathway, C2 cycle. In C3 plant photosynthesis, 30-50% of saccharide is broken down during photorespiration. It protects plants from damage by excessive high-energy chemical.

C3 plant vs C4 plant, C3 pathway vs C4 cycle, Hatch-Slack pathway. The simpler Calvin cycle or C3 cycle can directly utilize CO₂. C4 photosynthesis is more efficient but consumes more ATP. C4 pathway allocate the carbon fixation in different types of cell.

CAM cycle is also called Crassulacean Acid Metabolism. Although photosynthesis occurs in the same cell, the time is divided into day and night. CAM plants are divided into desert plants, aquatic plants and epiphytes. Obligate CAM and Facultative CAM are 2 common pathway.