Energy Releasing Pathways ATP

Aerobic Respiration A redox process Glucose contains energy that can be converted to ATP Uses oxygen therefore aerobic

Cellular Energy Transfer Cells transfer energy by redox reactions Remember: oxidation is the loss of electrons reductions is the gain of electrons Oxidation involves loss of energy Reduction involves the gain of energy

Aerobic Respiration- Redox C6H12O6 + 6 O2 + 6 H2O  6 CO2 + 12 H2O + Energy Water is both a reactant and a product Glucose is oxidized to form CO2 Oxygen is reduced, forming water The electrons produced are used to form ATP oxidation reduction

Aerobic Respiration- 4 Stages                                 Glycolysis Formation of acetyl coenzyme A Citric Acid Cycle Electron transport system and chemiosmosis

Glycolysis Glucose is converted to 2 3-carbon molecules of pyruvate ATP and NADH are formed Occurs in the cytosol Yellow- products Green- reactants

Glycolysis Pyruvate Yield Glycolysis means “sugar splitting” One 6-carbon molecule is converted to two 3-carbon molecules Occurs in cytosol Occurs in both aerobic and anaerobic conditions A series of reactions; each catalyzed by a different enzyme Glucose yields two pyruvates

Glycolysis First phase requires ATP investment 2 ATPs used G3P

Glucose Fructose- 1,6-diphosphate 2 glyceraldehyde-3-phosphate (G3P) PHASE 1 Glucose 2 ATPs used Fructose- 1,6-diphosphate 2 glyceraldehyde-3-phosphate (G3P)

Glycolysis Second phase yields NADH and ATP

PHASE 2 G3P Pyruvate G3P Pyruvate + 2 NADH + 4 ATP

Pyruvate to acetyl CoA A carboxyl group is removed from pyruvate (carbon dioxide is produced) NADH is produced acetyl group joins with coenzyme A forming acetyl CoA Coenzyme A is made from pantothenic acid

Pyruvate Coenzyme A + NADH + CO2 acetyl CoA

Glycolysis acetyl CoA Krebs Cycle

Acetyl Coenzyme A Pyruvate is converted into acetyl CoA NADH is produced Carbon dioxide is a waste product Occurs in the mitochondria Yellow- products Green- reactants

2 pyruvate + 2 NAD+ + 2 CoA ----> 2 acetyl CoA + 2 NADH + 2 carbon dioxide

Citric Acid Cycle Oxidizes acetyl CoA Also known as Krebs cycle Occurs in mitochondria (matrix) Series of steps ultimately reforming oxaloacetate All of the energy of glucose is carried by NADH and FADH2

Citric Acid Cycle Acetyl CoA combines with oxaloacetate, forming citrate Citrate undergoes conversions, ultimately re-forming exaloacetate Carbon dioxide is a waste product ATP, NADH, and FADH2 are produced

Acetyl CoA oxaloacetate + 6 NADH + 2 FADH2 + 2 ATP

One Turn of Citric Acid Cycle* 2C molecule enters the cycle & joins a 4C molecule. In a series of steps, the remaining H and high energy e- are removed from the 2C. 3 NAD+ are converted into 3 NADH & 3H+. 1 FAD is converted into 1 FADH2. 1 ATP is made. 2 CO2 are released. At the end of the cycle, nothing remains of the original glucose molecule. * remember…this is x2!

Types of Reactions Dehydrogenation Decarboxylations Hydrogens are transferred to a coenzyme (NAD+ or FAD) Decarboxylations Carboxyl groups are removed from the substrate as carbon dioxide Preparation reactions molecules are rearranged in preparation for decarboxylations or dehydrogenations

Electron Transport System Chemiosmosis Electrons that originated in glucose are transferred via NADH and FADH2 to a chain of electron acceptors Hydrogen ions are pumped across the inner mitochondrial membrane ATP is produced by chemiosmosis

Electron Transport Chain Coupled to ATP synthesis Transports e- from NADH and FADH2 to O2 Electrons  FMN  a series of cytochromes and coenzyme Q

Electron Carriers Most electron carriers carry hydrogen atoms Electron carriers transfer energy Electrons lose energy as they are transferred between acceptors NAD+ is a common hydrogen acceptor is respiratory and photosynthetic pathways Nicotinamide adenine dinucleotide

Electron Carriers Nicotine adenine dinucleotide phosphate (NADP+) is involved in photosynthesis

NAD+ is a coenzyme derived from the vitamin nicotinic acid (niacin)

Electron Carriers Flavin Adenine Dinucleotide- FAD+ is involved in cellular respiration

Electron Carriers Cytochromes- proteins containing iron

Electron Transport Chain Electrons lose energy as they pass through the chain

Electron Transport Chain Hydrogen ions (protons) are passed into the intermembrane space of the mitochondria

Electron Transport Chain Electrons are finally passed to oxygen thereby forming water

NADH 2H+ FMN Complex I 2H+ Q FADH2 cyt b 2H+ Complex II cyt cr cyt c O2 H2O cyt a cyt a3 Complex III

Chemiosmotic Model Peter Mitchell 1978 Nobel Prize in Chemistry for a 1961 paper on the chemiosmotic model Cornwall, UK Glynn Research Laboratories Died in 1992 Peter Mitchell

Chemiosmotic model Explains the coupling of ATP synthesis to electron transport A proton gradient is formed across the inner mitochondrial membrane

Chemiosmotic Model Protons diffuse through the channels formed by the enzyme complex ATP synthase Movement of protons catalyze production of ATP

http://telstar. ote. cmu. edu/biology/animation/ATPSynthesis/biochem http://telstar.ote.cmu.edu/biology/animation/ATPSynthesis/biochem.html

Energy Yield Efficiency is about 40%; the rest is disseminated as heat Maximum yield of ATPs from NADH- 3 ATP from FADH2- 2 ATP The NADHs from glycolysis produce fewer ATPs due to the necessity of transport of NADH across the mitochondrial membrane

Energy Yield The NADHs from glycolysis produce fewer ATPs due to the necessity of transport of NADH across the mitochondrial membrane 36 to 38 ATPs yield

ATP produced GLUCOSE

2 ATP GLUCOSE 2 ATP produced directly GLYCOLYSIS

38 ATP 16 ATP 34 ATP 8 ATP 14 ATP 2 ATP 2 NADH 2 NADH 6 NADH 2 FADH2 GLUCOSE 2 ATP produced directly GLYCOLYSIS 6 ATP through electron transport + 2 NADH PYRUVIC ACID 6 ATP through electron transport + 2 NADH 2 ATP produced directly + ACETYL CoA 18 ATP through electron transport + KREBS CYCLE 6 NADH 4 ATP through electron transport + 2 FADH2

Other Nutrients Nutrients other that glucose provide energy Humans gain more energy from oxidation of fatty acids than glucose Lipids contain 9 kcal per gram Lipids are broken down and glycerol enters glycolysis; fatty acids are converted to acetyl CoA and enter the citric acid cycle

Other Nutrients Proteins are broken down into amino acids Amino acids are deaminated (the amino acids are removed) The remaining carbon chain centers at various points Proteins contain about 4 kcal per gram

Regulation of Aerobic Respiration ATP synthesis continues until ADP stores are depleted Enzyme regulation is important An important regulation point is phosphofructokinase

PFK is activated by ADP/AMP PFK is the committed step in glycolysis. Once this step is done then glycolysis will carry through. PFK is inhibited by ATP low pH citrate groups PFK is activated by ADP/AMP

Anaerobic Respiration Various inorganic substances serve as the final electron acceptor like sulfur Yield is only the two ATP molecules from glycolysis Seen is some bacteria

Alcoholic Fermentation Produces ethanol Pyruvate is converted to ethanol to regenerate NAD+ Ethanol is a potentially toxic waste product Yeast carry out alcoholic fermentation when oxygen deprived

Lactate Fermentation Bacteria and some fungi carry out lactate fermentation Pyruvate is converted to lactate to regenerate NAD+ Strenuous exercise in mammals results in lactate fermentation as well

Must Know...

http://micro. magnet. fsu http://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10/index.html