Biology Bioenergetics

Photosynthesis uses energy to convert carbon dioxide and water into oxygen and glucose. It takes place in chloroplasts in plant cells, chlorophyll absorbs light. 

The reaction is endothermic, the surroundings get colder and it requires energy (from light).

Factors that affect the rate of photosynthesis are light intensity, concetration of carbon dioxide and chlorophyll and temperate. 

Glucose can be used in five different ways: For respiration, can convert into other useful substances. Making cellulose, aid strong plant walls. Making amino acids, combined with nitrate ions to be made into proteins. Stored as oils or fats (lipids) to be stored in seeds. Stored as starch, ready to use when photosynthesis is not happening. 

Organisms need energy for many things: Construction, Contraction and Homeostasis. 

Anaerobic respiration is without oxygen, glucose is not completely broken down and making it a less efficient way of transferring energy. In animals, glucose is converted to lactic acid. In plants and yeast cells, glucose is converted into ethanol and carbon dioxide. It is called fermentation in yeast cells. 

Aerobic respiration is with oxygen. It reacts with oxygen in the mitochondria of cells to give carbon dioxide, water and energy. 

Metabolism is the sum of all the chemical reactions that happen in an orgranism. Metabolic reactions include: Breaking down excess proteins, which is excreted in urine. Converting glucose to starch (plants), glycogen (animals) and cellulose (plants). Making lipids, combining glycerol and fatty acid to make lipid molecules. Making amino acids, combine glucose and nitrate ions. 

Oxygen debt is the extra oxygen required to oxidise lactic acid and remove it from cells.