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Definition: A series of chemical reactions in the cytoplasm and mitochondria of cells, where chemical energy (glucose) from food is transferred to ATP. ATP is a chemical that carries the energy to power every reaction and process that goes on in all living things. It is then recharged from food molecules by cellular respiration. ATP can store chemical energy until it is needed by the cell. Aerobic Respiration: C6H12O6 + 6 02 glucose Requires oxygen to work; has four distinct stages (see later). --- 6 CO2 + 6 H2O + 36 ATP + heat + oxygen --- carbon dioxide + water + energy + heat Anaerobic Respiration: Does not require oxygen. Only a small amount of ATP is produced. Occurs in complex animals, some bacteria and fungi (eg. yeast). - Alcohol Fermentation: In plants and micro-organisms. eg. Yeast (a fungi) uses fermentation and produces alcohol and CO2, used by humans for making beer, wine and bread. - Lactic Acid Fermentation: In animals and some bacteria. eg. In human muscle cells this occurs when not enough oxygen is available during rapid exercise. It results in a build-up of lactic acid which causes muscle fatigue and soreness. http://micro.magnet.fsu.edu/cells/mitochondria/mitochondria.html http://academic.brooklyn.cuny.edu/biology/bio4fv/page/mito.htm STRUCTURE: Mitochondria are oval-shaped organelles with two plasma membranes, an outer membrane and a highly folded inner membrane that gives a larger surface area for chemical reactions. The intermembrane space is the space between the outer and inner membranes. The folding of the inner membrane divides the mitochondrion into different areas to provide a larger surface area and produces membrane compartments (cristae) that hold different materials. The inner membrane allows only certain molecules to pass through it and is much more selective than the outer membrane. The matrix is the gel-like fluid substance within the inner membrane. The cristae protrude into the matrix. Many enzymes are also found in the mitochondria – some are dissolved in the fluid matrix, while some form part of the inner membrane. FUNCTION: The main chemical reactions occurring inside the mitochondria are the last stages of aerobic respiration. Respiration is the breakdown of chemicals from food to convert the energy they contain into ATP. Materials for this reaction are transported from the cytoplasm into the mitochondria which allows the cell to control these reactions. The ATP produced in respiration is transported out of the mitochondria to where it is needed and used by the cell. NUMBER OF MITOCHONDRIA IN CELLS: The density of mitochondria in a cell reflects the cell’s energy requirements. Cenerally they are clustered where the action is. Cells such as muscle, kidney and liver cells have hundreds of mitochondria because they have a high energy demand so must produce large amounts of ATP. Muscle cells work hard contracting so need lots of energy. Kidney and liver cells carry out a number of different reactions needing ATP. Sperm cells also have lots of mitochondria as they require large amounts of ATP energy to swim to the ovum (egg). STAGE LOCATION SUMMARY PRODUCTS Glycolysis “splitting sugar” Cytoplasm Begins the breakdown of glucose. Requires ATP & ADP. No oxygen required. Can be anaerobic. Pyruvate, 2ATP, H, NADH2 Formation of Acetyl Co-enzyme A Mitochondrial matrix Pyruvate is combined with an enzyme (Co-enzyme A) to form Acetyl CoA. CO2, H, Acetyl Co-enzyme A Krebs Cycle or Citric Acid Cycle Mitochondrial matrix A series of reactions in which Acetyl Co-enzyme A is modified. Requires H20 & ADP. No oxygen required. CO2, 2ATP, H, NADH2 Electron Transport Chain Cristae of mitochondria A chain of chemical reactions where Hydrogens (electrons) from previous stages are passed along to release energy used to produce a large amount of ATP. Oxygen is required. Requires H, O2, ADP 32 ATP, H2O Diagram showing the stages of Aerobic Respiration http://canada.canacad.ac.jp/BiologyIBHL1/3104