2- Biochemical Pathways: Cellular Respiration Chapter 6.

2- Biochemical Pathways: Cellular Respiration Chapter 6

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- Energy and Organisms Organisms are classified based on the kind of energy they use. Autotrophs Use the energy from sunlight to make organic molecules (sugar) Use the energy in the organic molecules to make ATP Heterotrophs Obtain organic molecules by eating the autotrophs Use the energy in the organic molecules to make ATP Autotrophs use photosynthesis. To use the energy from light to make organic molecules All organisms use cellular respiration. To harvest the energy from organic molecules and use it to make ATP

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- Energy Transformation

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- Cellular Respiration Respiration is a metabolic pathway of Redox Reactions Respiration oxidizes carbohydrates and transfers the energy to produce ATP The type of molecule that is reduced determines the type of respiration The energy produced is in the form of ATP

5- Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cellular Respiration Three Types of Respiration 1. Aerobic Respiration - Oxygen is reduced to produce water 2. Anaerobic Respiration - A molecule other that oxygen is reduced - may produce acids, methane, etc. 3. Fermentation - Another carbohydrate is reduced to produce alcohols

5- Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1. Aerobic Respiration Glucose is Oxidized to become Carbon Dioxide Oxygen is reduced to become water The protons and electrons from the oxidation of glucose are used to produce ATPs

5- Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1. Aerobic Respiration C 6 H 12 O 6 + 6 O 2 6 H 2 O + 6 CO 2 + Energy C 6 H 12 O 6 + 6O 2 + 38 ADP + 38 P 6 H 2 O + 6CO 2 + 38 ATP

5- Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1. Aerobic Respiration Aerobic Respiration is a three stage process: Stage 1: Glycolysis Stage 2: The Krebs Cycle Stage 3: Oxidative Phosphorylation (Electron Transport Chain) Each of these stages produce ATP At the end of all three stages, there is a net gain of ~38 ATPs

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- Stage 1: Glycolysis Glycolysis is a 10 step metabolic pathway that cleaves glucose Glyo-lysis = splitting glucose Glycolysis occurs in the cells cytoplasm

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- Stage 1: Glycolysis Glycolysis splits glucose to make two pyruvate molecules Produces 4 ATP molecules 4 ATP made -2 ATP invested = net production of 2 ATP Reduces 2 NAD + to make 2 NADH

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- Stage 1: Glycolysis During Glycolysis, Glucose (a 6 carbon molecule) is chopped up into 2 Pyruvates (pyruvate is a 3 carbon molecule) This is a 9 step metabolic process

Figure 6_07

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- 9 Steps of Glycolysis Summary 1. Glucose is phosphorylated - costs 1 ATP to become Glucose-6-Phosphate 2. Glucose-6-P is converted to Fructose-6-P 3. Fructose-6-P is phosphorylated - costs 1 ATP to become Fructose-1,6-bisphosphate 4. Fructose-1,6-bisphosphate is split into two molecules - each with 3 carbons and a phosphate: Dihydroxyacetone (DHAP) Glyceraldehyde-3-Phoshate (G-3-P)

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- 9 Steps of Glycolysis Summary G-3-PDHAP 5. G-3-P is phosphorylated to 5. DHAP is phosphorylated to become 1,3-bisphosphoglycerate become 1,3 bisphosphoglycerate 6. 1,3-bisphosphglycerate gives up 6. 1,3-bisphosphoglycerate gives up a a phosphate to an ADP, G-3-P left phosphate to an ADP, G-3-P left 7. G-3-P converted to 7. G-3-P converted to 2-Phosphoglycerate 2-Phospoglycerate 8. 2-Phosphoglycerate converted to 8. 2-Phosphoglycerate converted to Phosphoenolpyruvate Phosphoenolpyruvate 9. Phosphoenolpyruvate gives up 9. Phosphoenolpyruvate gives up its phosphate to an ADPits phosphate to an ADP

Glucose Pyruvate1 Pyruvate 2 2 ATP 4 ATP, 2 NADH

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- NAD +, NADH NAD + is an electron carrier for the redox reactions of cellular respiration NAD + accepts 2 electrons and 1 proton to become NADH Functions of NAD +, NADH NAD + is reduced so Redox reactions can occur NAD + is used to carry electrons from one part of the cell to another NAD + keeps protons out of solution

NAD +, NADH

NAD + Reduced to NADH

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- FAD, FADH 2 FAD is very similar to NAD + It has the same functions of collecting and carrying electrons and protons FAD can carry 2 Hydrogen atoms FAD is Reduced to FADH 2

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- Stage 2: Krebs Cycle Also known as The Citric Acid Cycle or the Tricarboxylic Acid (TCA) Cycle The Krebs cycle is a metabolic pathway that further oxidizes pyruvate The Krebs Cycle occurs in the Cell membrane of Prokaryotic Cells and in the mitochondria of Eukaryotic Cells In mitochondria, a multienzyme complex called pyruvate dehydrogenase catalyzes the reaction

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- Stage 2: Krebs Cycle The Krebs Cycle begins with pyruvate (from Glycolysis) Remember, there are 2 pyruvates made from each Glucose, so there are 2 Krebs Cycles for every glucose molecule During a Krebs Cycle the pyruvate (a 3 carbon molecule) will be completely oxidized to become 3 carbon dioxide molecules (one carbon atom each)

5- Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cellular Respiration C 6 H 12 O 6 + 6O 2 6H 2 O + 6CO 2 + Energy Glucose Oxygen Water Carbon Dioxide The Krebs Cycle produces the CO 2 that we exhale

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- Stage 2: Krebs Cycle Important steps in the Krebs Cycle Pyruvate is converted to acetyl-CoA Acetyl-CoA combine with Oxaloacetate (in the mitochondria) to make Citrate The cycle ends with the production of oxaloacetate, ready for anther turn of the cycle

Figure 6_05

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- Stage 2: Krebs Cycle During the Krebs Cycle enough energy is released from one pyruvic acid molecule to produce: 1 ATP 4 NADH from 4 NAD + 1 FADH 2 from 1 FAD.

Figure 6_08

Glucose Pyruvate1 Pyruvate 2 2 ATP 4 ATP, 2 NADH 2 ATP 1 ATP, 2 CO 2 4 NADH, 1 FADH 2 Pyruate converted to Acetyl Co-A

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- Stage 2: Krebs Cycle After glycolysis and the Krebs cycle glucose has been completely oxidized to form: 6 CO 2 ~5 ATP ~10 NADH ~2 FADH 2 We are still short of our 36-38 ATP goal The third stage of cellular respiration uses the protons and electrons of the hydrogens on the NADHs and FADH 2 s that were produced during the first 2 stages

Glucose Pyruvate1 Pyruvate 2 2 ATP 4 ATP, 2 NADH 2 ATP 2 ATP, CO 2 8 NADH, 2 FADH 2 Electron Transport Chain NADH, FADH 2 34 ATP Pyruate converted to Acetyl Co-A

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- Stage 3: Electron-Transport System The electron transport chain (ETC) is a series of membrane-bound electron carrier molecules called cytochromes embedded in the mitochondrial inner membrane Electrons from NADH and FADH 2 are transferred to cytochromes of the ETC Each cytochrome transfers the electrons to the next cytochromes in the chain

Fig. 7.13a

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- Stage 3: Electron-Transport System As the electrons are transferred, some electron energy is released with each transfer This energy is used by the cytochromes to pump protons (H + ) across the membrane from the matrix to the inner membrane space A proton concentration gradient is established

Stage 3: Electron Transport Chain

Figure 6_06

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- Stage 3: Electron-Transport System There are other channel proteins in the membrane known as ATP synthases ATP synthases provide a channel for protons to rush through by diffusion The rushing protons provides the energy for ATP synthase to phosphorylate ADP to ATP

Figure 6_06

Figure 6_09

5- Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cellular Respiration Recall Three Types of Respiration 1. Aerobic Respiration - Oxygen is reduced to produce water 2. Anaerobic Respiration - A molecule other that oxygen is reduced - may produce acids, methane, etc. 3. Fermentation - Another carbohydrate is reduced to produce alcohols

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- 1. Aerobic Respiration Oxygen is the final molecule to receive the electrons as they are passed down the Electron Transport Chain Oxygen is reduced with two electrons and picks up two protons The result is water: 2O 2 + 8e - s and 8H + s 4H 2 O Oxygen is the Final Electron Acceptor in Aerobic Respiration

The Electron Transport Chain

Glucose Pyruvate1 Pyruvate 2 2 ATP 4 ATP, 2 NADH 2 ATP 2 ATP, CO 2 8 NADH, 2 FADH 2 Electron Transport Chain NADH, FADH 2 30+ ATP And H 2 O Pyruate converted to Acetyl Co-A

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- Aerobic Cellular Respiration: Overview

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- Total Yields for Aerobic Cellular Respiration per Glucose Molecule Glycolysis 2 ATP 2 NADH (converted to 2 FADH 2 ) Krebs cycle 2 ATP 8 NADH 2 FADH 2 Electron transport chain Each NADH fuels the formation of 3 ATP. 8 NADH x 3 ATP = 24 ATP Each FADH 2 fuels the formation of 2 ATP. 4 FADH2 x 2 ATP = 8 ATP Total ATP=2+2+24+8=36 ATP made from the metabolism of one glucose molecule.

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- 2. Anaerobic Cellular Respiration Some cells do not require O 2 as the final electron acceptor for the electron transport chain These cells perform Anaerobic Respiration Anaerobic Respiration produces fewer ATPs per glucose molecule compared to Aerobic Respiration it is not as efficient and the exact amount of ATP production depends on the organism and the electron acceptors that are used

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- 2. Anaerobic Cellular Respiration Anaerobic respiration by methanogens methanogens use CO 2 CO 2 is reduced to CH 4 (methane) Anaerobic respiration by sulfur bacteria inorganic sulphate (SO 4 ) is reduced to hydrogen sulfide (H 2 S)

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- 3. Fermentation Fermentation reduces organic molecules as the final electron acceptors Ethanol fermentation occurs in yeast fermentation of sugars produces alcohol Lactic acid fermentation occurs in animal cells (especially muscles) electrons are transferred from NADH to pyruvate to produce lactic acid

Figure 6_10

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- Alcoholic Fermentation Starts with glycolysis Glucose is metabolized to pyruvic acid. A net of 2 ATP is made. During alcoholic fermentation Pyruvic acid is reduced to form ethanol. Carbon dioxide is released. Yeasts do this Leavened bread Sparkling wine

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- Lactic Acid Fermentation Starts with glycolysis Glucose is metabolized to pyruvic acid. During lactic acid fermentation Pyruvic acid is reduced to form lactic acid. No carbon dioxide is released. Muscle cells have the enzymes to do this, but brain cells do not. Muscle cells can survive brief periods of oxygen deprivation, but brain cells cannot. Lactic acid burns in muscles.

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- Metabolizing Other Molecules Cells will use the energy in carbohydrates first. Complex carbohydrates are metabolized into simple sugars. Cells can use the energy in fats and proteins as well. Fats are digested into fatty acids and glycerol. Proteins are digested into amino acids. Cells must convert fats and proteins into molecules that can enter and be metabolized by the enzymes of glycolysis or the Krebs cycle.

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- Fat Respiration Fats are broken down into Glycerol Fatty acids Glycerol Converted to glyceraldehyde-3-phosphate Enters glycolysis Fatty acids Converted to acetylCoA Enter the Krebs cycle Each molecule of fat fuels the formation of many more ATP than glucose. This makes it a good energy storage molecule.

Preparatory Steps Amino Acids Lipids

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- Protein Respiration Proteins are digested into amino acids. Then amino acids have the amino group removed. Generates a keto acid (acetic acid, pyruvic acid, etc.) Enter the Krebs cycle at the appropriate place

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- The Interconversion of Fats, Carbohydrates and Proteins

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6- Energy Resources Carbohydrates, fats and proteins can all be used for energy. Glycolysis and the Krebs cycle allow these types of molecules to be interchanged. If more calories are consumed than used The excess food will be stored. Once the organism has all of the proteins it needs And its carbohydrate stores are full The remainder will be converted to and stored as fat.

2- Biochemical Pathways: Cellular Respiration Chapter 6.

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Transcript of 2- Biochemical Pathways: Cellular Respiration Chapter 6.