Digestion

• Digestion is the process by which larger food molecules are broken down into smaller ones that can enter into our cells to be used. This is accomplished both mechanically, by way of chewing and transport through the digestive system, and chemically with enzymes and digestive juices. One of the end products of carbohydrate digestion is glucose, which is used in aerobic respiration to produce ATP.
  
  

Cell Structure

• All cells consist of an outer cell membrane or wall, cytoplasm and organelles. The cell membrane or wall functions to permit or deny the entrance of various molecules into the cell. The cytoplasm is a jelly-like fluid that fills our cells and suspends our organelles. There are a number of different types of organelles, which are small specialized structures; each performs a different function. Mitochondria are organelles that are known as the energy pumps of cells, as it is here that ATP ultimately is produced.
  
  

Respiration Stages

• Aerobic respiration takes place in three stages: glycolysis, the Krebs or citric acid cycle and the electron transport process. Glycolysis occurs in the cytoplasm and does not require the presence of oxygen. The Krebs or citric acid cycle and the electron transport process take place in our mitochondria, and both require the use of oxygen, according to BioTopics.
  
  

Reaction Products

• The resulting products of aerobic respiration are water, carbon dioxide and ATP. Water is either used by our bodies or excreted; carbon dioxide is a waste product that is transported to the lungs to be breathed out. ATP is the energy unit or fuel used by our cells to perform three types of functions: to transport molecules through cell membranes, to provide energy to fuel chemical reactions and to allow the movement of muscle cells.
  
  

Anaerobic Respiration

• Anaerobic respiration is the process by which our cells convert glucose to ATP in the absence of oxygen. Without oxygen present, the chemical reactions of the last two stages of respiration will differ. According to The Royal Society of Chemistry, anaerobic respiration is less efficient than aerobic, producing fewer molecules of ATP. Anaerobic respiration also will produce the waste product lactic acid instead of carbon dioxide. A buildup of lactic acid can result in muscle cramps.