Lecture - Energy 1 Glycolysis 2.pptx (1).pdf

Glycolysis and TCA cycle Lecture BIOL2020 The mitochondria has two membranes and most metabolic pathways have some connection with them ● ● ● 2 membranes ○ Inner and outer Cristae Matrix ○ Enzymes ○ mtDNA The process of metabolism involves many interconnected cellular pathways to ultimately pro...

Glycolysis and TCA cycle Lecture BIOL2020 The mitochondria has two membranes and most metabolic pathways have some connection with them ● ● ● 2 membranes ○ Inner and outer Cristae Matrix ○ Enzymes ○ mtDNA The process of metabolism involves many interconnected cellular pathways to ultimately provide cells with the energy required to carry out their function. Metabolic pathways are anabolic if they make large molecules or catabolic if they break them Anabolic pathways Require energy (endergonic) ΔG>0 Catabolic pathways Release energy (exergonic) ΔG<0 Metabolic pathways are anabolic if they make large molecules or catabolic if they break them Anabolic pathways CO2 CO2 CO2 Require energy (endergonic) ΔG>0 CO2 Catabolic pathways CO2 CO2 Release energy (exergonic) ΔG<0 Proteins use the energy released during ATP hydrolysis in several ways Cells Obtain Energy by the Oxidation of Organic Molecules Oxidation refers to the removal of electrons Reduction means the addition of electrons. New molecules! NAD and FAD are coenzymes of redox reactions and electron carriers Oxidized ● ● ● coenzymes are organic molecules that bind to the active sites of certain enzymes NAD and FAD accept electrons (become reduced) during catabolic steps in the breakdown of organic molecules. NADH and FADH2 donate these electrons to some other biochemical reaction normally involved in a process that is anabolic (like the synthesis of ATP). Reduced Glucose is one of the most important oxidizable substrates in energy metabolism. Reason 1: Its oxidation is highly exergonic ∆G change in Gibbs free energy Reason 2: Many polysaccharides break into Glucose ● Starch, Glycogen, cellulose enzymes catalyze oxidation via a series of small steps in which free energy is transferred in conveniently sized packets to carrier molecules—most often ATP and NADH. Glycolysis is a metabolic pathway that entails the oxidation of glucose molecules into two pyruvate molecules Glycolysis is a 10 enzymatic reaction process that break glucose into pyruvate Glucose → 2 Pyruvate + 2 NADH + 2 ATP ● Phase 1: Add two phosphates and cleave ● Phase 2: Oxidation and ATP ● Phase 3: Make Pyruvate and ATP Disaccharides are broken into three monosaccharides Glucose, Galactose and Fructose. Enzyme names match substrate names sucrase for sucrase, lactase for lactose and maltase for maltose. Lactose: Sucrose: Maltose: Other monosaccharides (eg Fructose and Galactose) are converted into Glycolysis intermediates a kinase is an enzyme that phosphorylates Pyruvate is the branchpoint between aerobic and anaerobic metabolism ● ● If high [O2] PDH takes pyruvate If low [O2], LDH make lactate Glycolysis occurs in the cytoplasm of the cell. A Mitochondrial Pyruvate Carrier transports pyruvate into mitochondria ● ● ● GLUT MPC2 glycolysis happens in the cytoplasm the TCA cycle happens in the mitochondria Acetyl-CoA enters the TCA cycle Pyruvate dehydrogenase converts Pyruvate into Acetyl-CoA ● ● ● ● Pyruvate Dehydrogenase (PDH) pyruvate Acetyl-CoA complex reaction adds a CoA removes a carbon releases a lot of energy (-33ΔG) Dehydrogenases are enzymes that remove a pair of hydrogen atoms from a substrate, thereby oxidizing it. Pyruvate Dehydrogenase multienzyme complex E1 metabolite binding sites ● ● ● Metabolize pyruvate It is big ~ 100 subunits Multiples of 3 subunits E2 core of the complex https://pdb101.rcsb.org/motm/153 E3 intermediate enzyme PDH needs a vitamin B1 derivative as cofactor E1 subunit requires thiamine pyrophosphate ● ● Thiamine is NOT Thymine! Thiamine deficiency is linked to PDH Glycolysis stores energy as ATP and NADH molecules if high [O2]: PDH Acetyl-CoA → TCA cycle ● The citric acid cycle is also called the tricarboxylic acid cycle or the Krebs cycle Hans Krebs ~1930 The products of the TCA cycle are CO2, ATP, NADH, and FADH2 Acetyl-CoA → 3 NADH + FADH2 + ATP + 2 CO2 If there are excess amino acids, or if the body is in a state of starvation, some amino acids will be converted into TCA cycle metabolites TCA cycle intermediates can be lost to cataplerotic pathways that provide precursors for biosynthesis ○ ○ cataplerotic pathways provide precursors for biosynthesis anaplerotic pathways regenerate the TCA intermediates Summary Glycolysis Glucose→ 2 Pyruvate + 2 NADH +2 ATP Oxidation of Glucose liberates energy Cytoplasm Pyruvate Dehydrogenase (PDH) Pyruvate → Acetyl-CoA +NADH TCA cycle Acetyl-CoA → CO2 + 3 NADH + FADH2 + ATP cataplerotic and anaplerotic pathways