INTRODUCTION TO CELLULAR RESPIRATION 6.1 Photosynthesis and cellular respiration provide energy for life Cellular respiration makes ATP and consumes O2 During the oxidation of glucose to CO2 and H2O

Photosynthesis uses solar energy Photosynthesis uses solar energy To produce glucose and O2 from CO2 and H2O CO2 H2O Glucose O2 ATP ECOSYSTEM Sunlight energy Photosynthesis in chloroplasts Cellular respiration in mitochondria (for cellular work) Heat energy + Figure 6.1

6.2 Breathing supplies oxygen to our cells and removes carbon dioxide 6.2 Breathing supplies oxygen to our cells and removes carbon dioxide Breathing provides for the exchange of O2 and CO2 Between an organism and its environment CO2 O2 Bloodstream Muscle cells carrying out Cellular Respiration Breathing Glucose + O2 CO2 +H2O +ATP Lungs Figure 6.2

6.3 Cellular respiration banks energy in ATP molecules 6.3 Cellular respiration banks energy in ATP molecules Cellular respiration breaks down glucose molecules And banks their energy in ATP C6H12O6 CO2 6 H2O ATPs Glucose Oxygen gas Carbon dioxide Water Energy O2 + Figure 6.3

6.4 The human body uses energy from ATP for all its activities CONNECTION 6.4 The human body uses energy from ATP for all its activities ATP powers almost all cellular and body activities Table 6.4

6.5 Cells tap energy from electrons “falling” from organic fuels to oxygen Electrons lose potential energy During their transfer from organic compounds to oxygen

STAGES OF CELLULAR RESPIRATION AND FERMENTATION 6.6 Overview: Cellular respiration occurs in three main stages Cellular respiration Occurs in three main stages

Stage 1: Glycolysis Occurs in the cytoplasm Breaks down glucose into pyruvate, producing a small amount of ATP

Stage 2: The citric acid cycle Takes place in the mitochondria Completes the breakdown of glucose, producing a small amount of ATP Supplies the third stage of cellular respiration with electrons

Stage 3: Oxidative phosphorylation Occurs in the mitochondria Uses the energy released by “falling” electrons to pump H+ across a membrane Harnesses the energy of the H+ gradient through chemiosmosis, producing ATP

An overview of cellular respiration An overview of cellular respiration NADH FADH2 GLYCOLYSIS Glucose Pyruvate CITRIC ACID CYCLE OXIDATIVE PHOSPHORYLATION (Electron Transport and Chemiosmosis) Substrate-level phosphorylation Oxidative phosphorylation Mitochondrion and High-energy electrons carried by NADH ATP CO2 Cytoplasm Figure 6.6

6.7 Glycolysis harvests chemical energy by oxidizing glucose to pyruvate In glycolysis, ATP is used to prime a glucose molecule Which is split into two molecules of pyruvate NAD+ NADH H+ Glucose 2 Pyruvate ATP 2 P 2 ADP + Figure 6.7A

PREPARATORY PHASE (energy investment) In the first phase of glycolysis ATP is used to energize a glucose molecule, which is then split in two  Steps      –   A fuel molecule is energized, using ATP. 1 3 Glucose PREPARATORY PHASE (energy investment) ATP Step 1 ADP P Glucose-6-phosphate 2 P Fructose-6-phosphate ATP 3 ADP P P Fructose-1,6-diphosphate  Step      A six-carbon intermediate splits into two three-carbon intermediates. 4 4 Figure 6.7C

In the second phase of glycolysis ATP, NADH, and pyruvate are formed Glyceraldehyde-3-phosphate (G3P)  Step     A redox reaction generates NADH. 5 6 9 NAD  5 NAD  ENERGY PAYOFF PHASE NADH P 6 NADH P 6 +H +H P P P P 1,3 -Diphosphoglycerate  Steps     –      ATP and pyruvate are produced. 6 9 ADP ADP 6 7 7 ATP ATP P P 3 -Phosphoglycerate 7 P P 8 8 2-Phosphoglycerate 8 H2O H2O P P Phosphoenolpyruvate (PEP) ADP 9 ADP 9 9 ATP ATP Pyruvate Figure 6.7C

Acetyl CoA (acetyl coenzyme A) 6.8 Pyruvate is chemically groomed for the citric acid cycle Prior to the citric acid cycle Enzymes process pyruvate, releasing CO2 and producing NADH and acetyl CoA CO2 Pyruvate NAD+ NADH + H+ CoA Acetyl CoA (acetyl coenzyme A) Coenzyme A Figure 6.8 2 1 3

6.9 The citric acid cycle completes the oxidation of organic fuel, generating many NADH and FADH2 molecules In the citric acid cycle The two-carbon acetyl part of acetyl CoA is oxidized CoA CO2 NAD+ NADH FAD FADH2 ATP P CITRIC ACID CYCLE ADP + 3 + 3 H+ Acetyl CoA 2 Figure 6.9A

The two carbons are added to a four-carbon compound, forming citrate Which is then degraded back to the starting compound

For each turn of the cycle Two CO2 molecules are released The energy yield is one ATP, three NADH, and one FADH2 and Steps CITRIC ACID CYCLE Oxaloacetate CoA 2 carbons enter cycle Acetyl CoA Citrate leaves cycle + H+ NAD+ NADH CO2 Alpha-ketoglutarate ADP P ATP + Succinate FAD FADH2 Malate Step Acetyl CoA stokes the furnace. NADH, ATP, and CO2 are generated during redox reactions. Redox reactions generate FADH2 and NADH. Figure 6.9B 1 5 2 4 3

6.10 Most ATP production occurs by oxidative phosphorylation 6.10 Most ATP production occurs by oxidative phosphorylation Electrons from NADH and FADH2 Travel down the electron transport chain to oxygen, which picks up H+ to form water Energy released by the redox reactions Is used to pump H+ into the space between the mitochondrial membranes

Driving the synthesis of ATP In chemiosmosis, the H+ diffuses back through the inner membrane through ATP synthase complexes Driving the synthesis of ATP Intermembrane space Inner mitochondrial membrane Mitochondrial matrix Protein complex Electron flow Electron carrier NADH NAD+ FADH2 FAD H2O ATP ADP ATP synthase H+ + P O2 Electron Transport Chain Chemiosmosis . OXIDATIVE PHOSPHORYLATION + 2 1 2 Figure 6.10

Cyanide, carbon monoxide CONNECTION 6.11 Certain poisons interrupt critical events in cellular respiration Various poisons Block the movement of electrons Block the flow of H+ through ATP synthase Allow H+ to leak through the membrane H+ O2 H2O P ATP NADH NAD+ FADH2 FAD Rotenone Cyanide, carbon monoxide Oligomycin DNP ATP Synthase + 2 ADP Electron Transport Chain Chemiosmosis 1 Figure 6.11

OXIDATIVE PHOSPHORYLATION (Electron Transport and Chemiosmosis) 6.12 Review: Each molecule of glucose yields many molecules of ATP Oxidative phosphorylation, using electron transport and chemiosmosis Produces up to 38 ATP molecules for each glucose molecule that enters cellular respiration Electron shuttle across membrane Mitochondrion Cytoplasm 2 NADH 2 NADH (or 2 FADH2) 2 NADH 6 NADH 2 FADH2 GLYCOLYSIS OXIDATIVE PHOSPHORYLATION (Electron Transport and Chemiosmosis) Glucose 2 2 Acetyl CoA CITRIC ACID CYCLE Pyruvate + 2 ATP + 2 ATP + about 34 ATP by substrate-level phosphorylation by substrate-level phosphorylation by oxidative phosphorylation About 38 ATP Maximum per glucose: Figure 6.12

6.13 Fermentation is an anaerobic alternative to cellular respiration 6.13 Fermentation is an anaerobic alternative to cellular respiration Under anaerobic conditions, many kinds of cells Can use glycolysis alone to produce small amounts of ATP

In lactic acid fermentation In lactic acid fermentation NADH is oxidized to NAD+ as pyruvate is reduced to lactate 2 Lactate NAD+ NADH 2 ATP 2 ADP + 2 2 Pyruvate GLYCOLYSIS P Glucose Figure 6.13A

In alcohol fermentation In alcohol fermentation NADH is oxidized to NAD+ while converting pyruvate to CO2 and ethanol NAD+ NADH 2 GLYCOLYSIS 2 ADP + 2 P ATP Glucose 2 Pyruvate released CO2 2 Ethanol Figure 6.13B Figure 6.13C

INTERCONNECTIONS BETWEEN MOLECULAR BREAKDOWN AND SYNTHESIS 6.14 Cells use many kinds of organic molecules as fuel for cellular respiration

OXIDATIVE PHOSPHORYLATION (Electron Transport and Chemiosmosis) Carbohydrates, fats, and proteins can all fuel cellular respiration When they are converted to molecules that enter glycolysis or the citric acid cycle OXIDATIVE PHOSPHORYLATION (Electron Transport and Chemiosmosis) Food, such as peanuts Carbohydrates Fats Proteins Sugars Glycerol Fatty acids Amino acids Amino groups Glucose G3P Pyruvate Acetyl CoA CITRIC ACID CYCLE ATP GLYCOLYSIS Figure 6.14

6.15 Food molecules provide raw materials for biosynthesis 6.15 Food molecules provide raw materials for biosynthesis Cells use some food molecules and intermediates from glycolysis and the citric acid cycle as raw materials This process of biosynthesis Consumes ATP ATP needed to drive biosynthesis ATP CITRIC ACID CYCLE GLUCOSE SYNTHESIS Acetyl CoA Pyruvate G3P Glucose Amino groups Amino acids Fatty acids Glycerol Sugars Carbohydrates Fats Proteins Cells, tissues, organisms Figure 6.15

6.16 The fuel for respiration ultimately comes from photosynthesis 6.16 The fuel for respiration ultimately comes from photosynthesis All organisms Can harvest energy from organic molecules Plants, but not animals Can also make these molecules from inorganic sources by the process of photosynthesis Figure 6.16