* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Pyruvic acid is chemically groomed for the Krebs cycle
Survey
Document related concepts
Nicotinamide adenine dinucleotide wikipedia , lookup
Basal metabolic rate wikipedia , lookup
Photosynthesis wikipedia , lookup
Amino acid synthesis wikipedia , lookup
15-Hydroxyeicosatetraenoic acid wikipedia , lookup
Fatty acid synthesis wikipedia , lookup
Specialized pro-resolving mediators wikipedia , lookup
Electron transport chain wikipedia , lookup
Microbial metabolism wikipedia , lookup
Fatty acid metabolism wikipedia , lookup
Adenosine triphosphate wikipedia , lookup
Photosynthetic reaction centre wikipedia , lookup
Light-dependent reactions wikipedia , lookup
Butyric acid wikipedia , lookup
Biosynthesis wikipedia , lookup
Oxidative phosphorylation wikipedia , lookup
Transcript
STAGES OF CELLULAR RESPIRATION AND FERMENTATION Overview: Respiration occurs in three main stages • Cellular respiration oxidizes sugar and produces ATP in three main stages – Glycolysis occurs in the cytoplasm – The Krebs cycle and the electron transport chain occur in the mitochondria Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • An overview of cellular respiration High-energy electrons carried by NADH GLYCOLYSIS Glucose Pyruvic acid Cytoplasmic fluid Figure 6.8 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings KREBS CYCLE ELECTRON TRANSPORT CHAIN AND CHEMIOSMOSIS Mitochondrion Glycolysis harvests chemical energy by oxidizing glucose to pyruvic acid Glucose Figure 6.9A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Pyruvic acid • Details of glycolysis Steps 1 – 3 A fuel molecule is energized, using ATP. Glucose Step PREPARATORY PHASE (energy investment) 1 Glucose-6-phosphate 2 Fructose-6-phosphate 3 Fructose-1,6-diphosphate Step 4 A six-carbon intermediate splits into two three-carbon intermediates. 4 Glyceraldehyde-3-phosphate (G3P) ENERGY PAYOFF PHASE 5 Step 5 A redox reaction generates NADH. 6 Steps 6 – 9 ATP and pyruvic acid are produced. 1,3-Diphosphoglyceric acid (2 molecules) 7 3-Phosphoglyceric acid (2 molecules) 8 2-Phosphoglyceric acid (2 molecules) 2-Phosphoglyceric acid (2 molecules) 9 Figure 6.9B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Pyruvic acid (2 molecules per glucose molecule) Pyruvic acid is chemically groomed for the Krebs cycle • Each pyruvic acid molecule is broken down to form CO2 and a two-carbon acetyl group, which enters the Krebs cycle Pyruvic acid Acetyl CoA (acetyl coenzyme A) CO2 Figure 6.10 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The Krebs cycle completes the oxidation of organic fuel, generating many NADH and FADH2 molecules Acetyl CoA • The Krebs cycle is a series of reactions in which enzymes strip away electrons and H+ from each acetyl group KREBS CYCLE Figure 6.11A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 2 CO2 2 carbons enter cycle Oxaloacetic acid 1 Citric acid CO2 leaves cycle 5 KREBS CYCLE 2 Malic acid 4 Alpha-ketoglutaric acid 3 CO2 leaves cycle Succinic acid Step 1 Acetyl CoA stokes the furnace Steps 2 and 3 NADH, ATP, and CO2 are generated during redox reactions. Figure 6.11B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Steps 4 and 5 Redox reactions generate FADH2 and NADH. Chemiosmosis powers most ATP production • The electrons from NADH and FADH2 travel down the electron transport chain to oxygen • Energy released by the electrons is used to pump H+ into the space between the mitochondrial membranes • In chemiosmosis, the H+ ions diffuse back through the inner membrane through ATP synthase complexes, which capture the energy to make ATP Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Chemiosmosis in the mitochondrion Protein complex Intermembrane space Electron carrier Inner mitochondrial membrane Electron flow Mitochondrial matrix ELECTRON TRANSPORT CHAIN Figure 6.12 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings ATP SYNTHASE Connection: Certain poisons interrupt critical events in cellular respiration Rotenone Cyanide, carbon monoxide ELECTRON TRANSPORT CHAIN Figure 6.13 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Oligomycin ATP SYNTHASE Review: Each molecule of glucose yields many molecules of ATP • For each glucose molecule that enters cellular respiration, chemiosmosis produces up to 38 ATP molecules Cytoplasmic fluid Mitochondrion Electron shuttle across membranes GLYCOLYSIS 2 Glucose Pyruvic acid by substrate-level phosphorylation 2 Acetyl CoA used for shuttling electrons from NADH made in glycolysis KREBS CYCLE by substrate-level phosphorylation KREBS CYCLE ELECTRON TRANSPORT CHAIN AND CHEMIOSMOSIS by chemiosmotic phosphorylation Maximum per glucose: Figure 6.14 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Fermentation is an anaerobic alternative to aerobic respiration • Under anaerobic conditions, many kinds of cells can use glycolysis alone to produce small amounts of ATP – But a cell must have a way of replenishing NAD+ Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • In alcoholic fermentation, pyruvic acid is converted to CO2 and ethanol – This recycles NAD+ to keep glycolysis working released GLYCOLYSIS Glucose 2 Pyruvic acid Figure 6.15A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 2 Ethanol Figure 6.15C • In lactic acid fermentation, pyruvic acid is converted to lactic acid – As in alcoholic fermentation, NAD+ is recycled • Lactic acid fermentation is used to make cheese and yogurt GLYCOLYSIS Glucose 2 Pyruvic acid Figure 6.15B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 2 Lactic acid INTERCONNECTIONS BETWEEN MOLECULAR BREAKDOWN AND SYNTHESIS Cells use many kinds of organic molecules as fuel for cellular respiration • Polysaccharides can be hydrolyzed to monosaccharides and then converted to glucose for glycolysis • Proteins can be digested to amino acids, which are chemically altered and then used in the Krebs cycle • Fats are broken up and fed into glycolysis and the Krebs cycle Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Pathways of molecular breakdown Food, such as peanuts Polysaccharides Fats Proteins Sugars Glycerol Fatty acids Amino acids Amino groups Glucose G3P Pyruvic acid Acetyl CoA GLYCOLYSIS Figure 6.16 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings KREBS CYCLE ELECTRON TRANSPORT CHAIN AND CHEMIOSMOSIS Food molecules provide raw materials for biosynthesis • In addition to energy, cells need raw materials for growth and repair – Some are obtained directly from food – Others are made from intermediates in glycolysis and the Krebs cycle • Biosynthesis consumes ATP Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Biosynthesis of macromolecules from intermediates in cellular respiration ATP needed to drive biosynthesis KREBS CYCLE GLUCOSE SYNTHESIS Acetyl CoA Pyruvic acid G3P Glucose Amino groups Amino acids Fatty acids Glycerol Sugars Proteins Fats Polyscaccharides Cells, tissues, organisms Figure 6.17 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The fuel for respiration ultimately comes from photosynthesis • All organisms have the ability to harvest energy from organic molecules – Plants, but not animals, can also make these molecules from inorganic sources by the process of photosynthesis Figure 6.18 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings