Energy Releasing Pathways ATP Aerobic Respiration A redox
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 • C 6 H 12 O 6 + 6 O 2 + 6 H 2 O 6 CO 2 + 12 H 2 O + Energy • Water is both a reactant and a product • Glucose is oxidized to form CO 2 oxidation • C 6 H 12 O 6 + 6 O 2 + 6 H 2 O 6 CO 2 + 12 H 2 O + Energy • Oxygen is reduced, forming water reduction • C 6 H 12 O 6 + 6 O 2 + 6 H 2 O 6 CO 2 + 12 H 2 O + Energy • The electrons produced are used to form ATP
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 G 3 P
PHASE 1 Glucose 2 ATPs used Fructose- 1, 6 -diphosphate 2 glyceraldehyde-3 -phosphate (G 3 P)
Glycolysis • Second phase yields NADH and ATP
G 3 P PHASE 2 G 3 P + 2 NADH + 4 ATP Pyruvate
Pyruvate to acetyl Co. A • A carboxyl group is removed from pyruvate (carbon dioxide is produced) • NADH is produced • acetyl group joins with coenzyme A forming acetyl Co. A • Coenzyme A is made from pantothenic acid
Pyruvate Coenzyme A + NADH + CO 2 acetyl Co. A
Glycolysis acetyl Co. A Krebs Cycle
Acetyl Coenzyme A • • Pyruvate is converted into acetyl Co. A NADH is produced Carbon dioxide is a waste product Occurs in the mitochondria • Yellow- products • Green- reactants
2 pyruvate + 2 NAD+ + 2 Co. A ----> 2 acetyl Co. A + 2 NADH + 2 carbon dioxide
Citric Acid Cycle • • Oxidizes acetyl Co. A 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 FADH 2
Citric Acid Cycle • Acetyl Co. A combines with oxaloacetate, forming citrate • Citrate undergoes conversions, ultimately re-forming exaloacetate • Carbon dioxide is a waste product • ATP, NADH, and FADH 2 are produced
Acetyl Co. A oxaloacetate + 6 NADH + 2 FADH 2 + 2 ATP
One Turn of Citric Acid Cycle* 1. 2 C molecule enters the cycle & joins a 4 C molecule. 2. In a series of steps, the remaining H and high energy e- are removed from the 2 C. 3. 3 NAD+ are converted into 3 NADH & 3 H+. 4. 1 FAD is converted into 1 FADH 2. 5. 1 ATP is made. 6. 2 CO 2 are released. 7. At the end of the cycle, nothing remains of the original glucose molecule. * remember…this is x 2!
Types of Reactions • Dehydrogenation – 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 FADH 2 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 FADH 2 to O 2 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
+ FMN 2 H Complex I NADH Q cyt b FADH 2 + 2 H Complex II cyt cr cyt c cyt a O 2 cyt a 3 H 2 OComplex III
Chemiosmotic Model • 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/ATPSynthesi s/biochem. html
Energy Yield • Efficiency is about 40%; the rest is disseminated as heat • Maximum yield of ATPs – from NADH- 3 ATP – from FADH 2 - 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
GLUCOSE ATP produced
GLUCOSE GLYCOLYSIS 2 ATP produced directly
GLUCOSE 16 1482 ATP 38 ATP 34 2 ATP produced directly GLYCOLYSIS + 2 NADH 6 ATP through electron transport + 6 ATP through electron transport PYRUVIC ACID 2 NADH ACETYL Co. A + 2 ATP produced directly + 6 NADH 18 ATP through electron transport + KREBS CYCLE 2 FADH 2 4 ATP through electron transport
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 Co. A 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 the committed step in glycolysis. Once this step is done then glycolysis will carry through. PFK is inhibited by ATP low p. H 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
http: //micro. magnet. fsu. edu/primer/java/scien ceopticsu/powersof 10/index. html
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