1. TEK B.4B
Concept:
Investigate and Identify Cellular Processes Including Energy Production and Synthesis of New Molecules

3. Glucose is the primary food molecule that living organisms use for energy production in the cells. The first pathway for energy release from glucose takes place in the cytoplasm and is called glycolysis. If oxygen is present, glycolysis is followed by two pathways. The first pathway is the citric acid cycle, or Krebs cycle, followed by the electron transport chain. These two pathways make up cellular respiration, which is the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen. Cellular respiration takes place in the mitochondria. If oxygen is not present, the pathway that follows glycolysis is fermentation. Fermentation releases energy from food molecules by producing ATP in the absence of oxygen. The tow main types of fermentation are alcoholic fermentation and lactic acid fermentation. Yeast cells use alcoholic fermentation, forming ethyl alcohol and carbon dioxide as wastes. Alcoholic fermentation causes bread dough to rise. When oxygen is not present in muscle cells, lactic acid fermentation results, causing a painful burning sensation that may lead to muscle stiffness.