CELL RESPIRATION The Big Picture This lesson meets the following DoE Specific Curriculum Outcomes for Biology 11: 314-2 and 314-9

MITOCHONDRIA Mitochondria (singular: mitochondrion) are round or sausage-shaped organelles that are usually scattered throughout the cytoplasm of eukaryotic cells. Prokaryotic cells have no mitochondria - they carry out cellular respiration within the cytoplasm.

MITOCHONDRIA Mitochondria possess a double membrane (referred to as an envelope) composed of a smooth outer membrane and a highly folded inner membrane. The folds of the inner membrane are called cristae (singular: crista). The outer membrane plays a role similar to that of the cell membrane The inner membrane is associated with cell respiration.

MITOCHONDRIA The inner membrane creates two compartments within the mitochondrion. The mitochondrial matrix is a protein- rich liquid that fills the innermost space of a mitochondrion. A fluid-filled intermembrane space lies between the inner and outer membrane. Both these compartments play a critical role in aerobic respiration.

CELL RESPIRTION Def - the process in which a cell breaks down sugar or other organic compounds to release energy used for cellular work; may be anaerobic or aerobic, depending on the availability of oxygen. Aerobic can be summarized by the following formula: C6H12O6 + 6O2  6H20 + 6CO2 + energy (36 ATP)

GOALS of CELL RESPIRATION C6H12O6 + 6O2  6CO2 + 6H2O + 36ATP Cell respiration has three goals: Break the bonds between the six carbon atoms of glucose, resulting in six carbon dioxide molecules. Move hydrogen atom electrons from glucose to oxygen, forming six water molecules. Trap as much of the free energy released in the process as possible in the form of ATP.

STAGES of CELL RESPIRATION Stage 1: Glycolysis - a 10-step process occurring in the cytoplasm. Stage 2: Pyruvate oxidation - a one-step process occurring in the mitochondrial matrix.

STAGES of CELL RESPIRATION Stage 3: The Krebs cycle (also called the tricarboxylic acid cycle, the TCA cycle, or the citric acid cycle) - an eight-step cyclical process occurring in the mitochondrial matrix. Stage 4: Electron transport and chemiosmosis (oxidative phosphorylation) - a multistep process occurring in the inner mitochondrial membrane.

Stage 1 Glycolysis

GLYCOLYSIS For each molecule of glucose, glycolysis creates two molecules of Pyruvate (Pyruvic Acid). All reactions (steps) take place in the cytoplasm. The process is anaerobic - does not require oxygen.

GLYCOLYSIS Two ATP molecules phosphorylates glucose by adding phosphate groups to both ends of the sugar molecule. The glucose molecule then splits into two PGAL molecules. Each of the two PGAL molecules is oxidized to BPG. The hydrogen each gives up is used to form a NADH molecule.

GLYCOLYSIS Each of the BPG molecules is further oxidized to form 3PG molecules. The phosphate groups they give up are used to form ATP. Each 3PG molecule is finally oxidized to form Pyruvate (Pyruvic Acid) molecules and yield another ATP molecule.

GLYCOLYSIS ENERGY YIELD In the process of converting one glucose molecule to two Pyruvate molecules… Four ATP are produced but two are required resulting in a net gain of two ATP. Two NADH are produced.

FERMENTATION Cells that contain mitochondria (Eukaryotes) normally carry out Aerobic Cell Respiration. Pyruvate produced by Glycolysis enters the mitochondria and is catabolised by the Kreb’s Cycle and Electron Transport Chain. The latter process requires the presence of free oxygen.

FERMENTATION Prokaryotic cells do not have mitochondria. Their cell respiration is anaerobic and takes place in the cytoplasm. Unlike glycolysis that produces Pyruvate molecules, anaerobic cell respiration produces either ethyl alcohol or lactic acid. This process is called Fermentation.

ALCOHOL FERMENTATION In alcohol fermentation, glucose is split into two Pyruvate molecules using two ATP’s. Each Pyruvate is then converted to ethanol yielding two ATP’s (net) and releasing CO2. Alcohol fermentation takes in yeast and is used to make beer, wine and bread.

LACTIC ACID FERMENTATION In lactic fermentation, pyruvate is converted to lactic acid and two ATP’s (net). Takes place in bacteria cells. Can happen in eukaryotic cells during periods of excess exercise. Muscle cells demands for ATP outstrips O2 supply (oxygen dept). Cell switches to anaerobic respiration and produces lactic acid but reverses after rest.