The first step of cellular respiration What the [email protected] is Glycolysis? The word glycolysis is constructed from glycose, an older term for glucose, and –lysis, which means breakdown. (Greek for “sugar splitting”) The metabolic pathway that converts glucose, C6H12O6 into pyruvate, CH3COCOO− + H+. The products formed are adenosine triphosphate (ATP), and nicotinamide adenine dinucleotide (NADH) The 10 Steps of Glycolysis Glycolysis is split up into 10 different steps. In the first 3 steps, energy in the form of ATP is invested to be reused later. In the next 2 steps, the energy allows glucose to be split into 2 smaller molecules. In the last 5 steps, energy is released as ATP and NADH. Click Link for an Animation http://www.johnkyrk.com/glycolysis.s wf Step 1: ATP phosphorylates glucose to G6P Hexokinase is an enzyme that uses ATP to phosphorylate glucose. This investment of energy prepares glucose for releasing energy later on. Results in Glucose 6-phosphate. ADP is released. FIRST STEP IS IRREVERSIBLE Step 2: G6P rearranged to F6P The enzyme phosphoglucose isomerase catalyzes the opening of the ring form of G6P into the open ring form. Carbonyl group of G6P changes position from the 1st to the 2nd carbon on the chain. Fructose 6-phosphate is formed by this reaction. Phosphoglucose isomerase catalyzes F6P into its ring form. G6P to F6P You are HERE… Step 3: ATP phosphorylates F6P to F 1, 6-BP Enzyme phosphofructokinase uses ATP to phosphorylate F6P. ADP is released, and the molecule fructose 1, 6bisphosphate is formed. Steps 1-3 all include an investment of energy in the form of ATP that will be repaid in the later steps of glycolysis. F6P to F1,6BP Step 4: Splitting up F 1, 6-BP Begins with the opening of the ring for of F 1, 6-BP into the open chain form. The enzyme aldolase cleaves F 1, 6-BP into 2 molecules. One molecule formed is glyceraldehyde 3phosphate. The other molecule formed is dihydroxyacetone phosphate. Cleaving the Hexose Ring Step 5: DHAP converted to G3P The enzyme triophosphate isomerase catalyzes the isomerization of dihydroxyacetone phosphate (DHAP) into G3P. This reaction is similar to step 2. Result is 2 molecules of G3P. These 2 steps break down the molecules formed in the first 3 steps into smaller molecules. DHAP to G3P Step 6: BPG and NADH Steps 6-10 are the energy generating steps of glycolysis. NAD+ is used to oxidize G3P An inorganic phosphorus bond is connected to the molecule to form 1,3 biphosphoglycerate. Hydrogen atoms reduce NAD+ to NADH G3P to BPG Step 7: BPG to 3PG The high energy phosphate group in BPG is dephosphorylated. The phosphate group is transferred to ADP, which becomes ATP The 3 carbon molecule is now 3-phosphoglycerate. Reaction occurs twice, 2 ATP molecules generated. The energy usage has been paid back. BGP to 3GP Step 8: 3PG rearranged to 2PG 3-phosphoglycerate is transformed by an enzyme into 2-phosphoglycerate. 3GP to 2PG Step 9: 2PG converted into PEP Enzyme removes a water molecule from 2- phosphoglycerate, creating phosphoenolpyruvate. The loss of the water molecule redistributes the energy within the molecule. Creates phosphate group with high free energy of hydrolysis. 2PG to PEP Step 10: PEP converted to pyruvate Enzyme transfers the phosphate group from PEP into ADP, creating ATP and pyruvate. PEP to Pyruvate Summary In the first part of glycolysis, ATP is invested to be used later. In the second part, the bigger molecules are split up into smaller ones. In the third part, many of the reactions release energy in the form of ATP and NADH. Net energy: 2 ATP molecules and 2 NADH molecules. http://www.youtube.com/watch?v=O5eMW4b29r g Mitochondria Mitochondria (singular: mitochondrion) sausage shaped organelles that are usually scattered through a cell’s cytoplasm. Glycolysis takes place in the cytoplasm. Pyruvate oxidation, the Krebs cycle, and electron transport and chemiosmosis take place in the mitochondria. Only eukaryotic cells contain mitochondria Mitochondria Mitochondria Mitochondria possess a double membrane; a smooth outer membrane and a folded inner membrane. Folds of inner membrane called cristae Mitochondrial matrix is a protein-rich liquid filling the innermost space of a mitochondrion. Mitochondrion possess their own DNA, called mtDNA, RNA, and ribosomes.