CELLULAR RESPIRATION CONCEPT GLYCOLYSIS LINK REACTION KREBS CYCLE

CELLULAR RESPIRATION

• • CONCEPT GLYCOLYSIS LINK REACTION KREB’S CYCLE ELECTRON TRANSPORT CHAIN CHEMIOSMOSIS ALTERNATIVE PATHWAYS ANAEROBIC REACTION

GLYCOLYSIS • Location – cytosol • Biochemical pathway 1 Glucose (6 C) 2 Pyruvates (3 C) • Names and structures of enzymes involved not required except hexokinase and phosphofructokinase) • Net production of 2 ATP and 2 NADH

• Glyco= sweet, sugar; lysis = split • Catalysed by specific enzymes dissolves in cytosol • Occurs whether or not O 2 is present • 2 phase: – Energy Investment Phase (2 ATP used) – Energy Yielding Phase (4 ATP and 2 NADH are produced) How many net ATP produced?

Phosphorylation • ATP is used to phosphorylate other substrate ATP Substrate ADP Substrate P • Phosphorylation – adding of phosphate group into a molecule making them chemically active

GLYCOLYSIS ENERGY INVESTMENT PHASE

STEP 4~splitting STEP 1~ 2~ phosphorylation isomerization STEP 3~ phosphorylation STEP 5~isomerization • Fructose-1, 6 • • C 6 of glucose ~isan is Isomerization • C 1 of fructose-6 -phosphate diphosphate is splitcatalyses phosphorylated • Isomerase isomerasethe catalyses the phosphorylated into tworeversible isomeris 3 C • rearrangement catalysed by hexokinase conversion of glucose-6 • requires anotherproducing ATP sugar produces: requires an two G 3 P’s to ATP its isomer, • produce • phosphate fructose-1, 6 -diphosphate dihydroxyacetoneph • fructose-6 -phosphate makes glucose chemically osphate (DHAP) & reactive glyceraldehydes-3 - • produces glucose-6 phosphate (G 3 P) phosphate

GLYCOLYSIS ENERGY PAYOFF PHASE/ ENERGY YEILDING PHASE

Step 6: 7 STEP 10 8 STEP & phosphorylation Phoshate Substrate-level group oxidation Substrate-level phosphorylation translocation • Glyceraldehyde-3 -phosphate phosphorylation (G 3 P) is oxidized & NAD+ is • ATP A phosphate is produced group byreduced • ATP is produced by + to NADH + H on C 3 is transferred substrate level substrate-level • For each glucose molecule, 2 Step 9: to C 2 phosphorylation NADH are produced Removal of water • A Produce phosphate group • For each glucose • Glyceraldehyde-3 -phosphate molecule is then phosphorylated 2 -phosphoglycerate is transferred from (G 3 P) molecule, 2 ATP are onproduced C 1 • PEP Creates a double bond to ADP • The phospate source is between C 1 & C 2 of the • For each glucose • Produce inorganic phosphate (not ATP!), substrate molecule, 2 ATP are which 3 -phosphoglycerate present in the cytosol • produced Produce • Produce phosphoenolpyruvate • Produce pyruvate 1, 3 -diphosphoglycerate (PEP) (3 C)

Oxidative Decarboxylation LINK REACTION (FORMATION OF ACETYL COA)

1. Decarboxylation – Pyruvate (3 C) is converted into 2 C molecule by removing one CO 2 2. Reduction – pyruvate is reduced producing 2 H+, NAD+ accept H+ and becomes NADH + H+ 3. The 2 C compound called acetyl attaches to coenzyme A and form acetyl Co. A

KREB CYCLE

REDOX • Oxidation and reduction at the same time • AH + B A + BH • A is oxidized • B is reduced

STEP 4: 5: OXIDATIVE SUBSTRATE DECARBOXYLATION LEVEL PHOSPHORYLATION • -Ketoglutarate removes CO 2 = • Succinyl decarboxylation Co. A is converted to 4 C 7: HYDRATION STEP Succinate NAD+ is reduced to NADH + H+ = Water is added to Fumarate which • ATP dehydrogenation/oxidation produces = Substrate level STEP 3: OXIDATIVE DECARBOXYLATION rearranges the chemical bonds. STEP to form 6: 4 C phosphorylation Malate DEHYDROGENATION/OXIDATION • Attachment of Co. A to form 4 C Succinyl 2 major events: • Breakdown Co. A (high energy of Succinyl bond). Co. A is STEP 8: • Succinate is oxidized to 4 C coupled to the phosphorylation of DEHYDROGENATION/OXIDATION • Isocitrate loses CO 2 leaving a 5 C Fumarate and FAD is reduced. GDP to GTP. STEP 2: ISOMERIZATION compound = decarboxylation. STEP 1: ENTRY OF ACETYL GROUP Malate is oxidized and NAD+ is • to 2 H are transferred to FAD to form • GTP then transfers its phosphate • Citrate is rearranged by two reactions. reduced to NADH + H+ • 5 C compound is oxidized and NAD+ is FADH 2 • Unstable bond attaching the Acetyl group to Co. A breaks. ADP to+ form reduced to NADH H+ to. ATP. produce 5 C • The first reaction, is removed. 4 C water Oxaloacetate is regenerated. ketoglutarate = dehydrogenation/oxidation. • 2 C Acetyl Co. A becomes attached to a 4 C Oxaloacetate, • Then water is added. • Forming 6 C Citrate. • Through these two reactions Citrate is • Co. A is free to combine another 2 C Acetyl group. converted to itswith isomer, 6 C Isocitrate • The process is repeated.

STEP 1 • The unstable bond attaching the acetyl group to Co. A breaks. • The 2 C Acetyl Co. A becomes attached to a 4 C oxaloacetate molecule, • Forming citrate, a 6 C molecule with 3 carboxyl groups. • Co. A is free to combine with another 2 C group. • The process is repeated

STEP 2 • The citrate is rearranged by two preparation reactions. • The first reaction, water is removed. • Then water is added. • Through these two reactions citrate is converted to its isomer, isocitrate

STEP 3 • Isocitrate loses CO 2 leaving a 5 C compound (decarboxylation). • The 5 C compound is oxidized and NAD+ is reduced to NADH + H+ to produce ketoglutarate (dehydrogenation)

STEP 4 • -Ketoglutarate undergoes decarboxylation (removal of CO 2) • and dehydrogenation (NAD+ is reduced to NADH + H+) • Attachment of Co. A to form 4 C compound, succinyl Co. A (high energy bond).

STEP 5 • Succinyl Co. A is converted to succinate • Substrate level phosphorylation takes place (ATP produced). • The breakdown of succinyl Co. A is coupled to the phosphorylation of GDP to GTP. • GTP then transfers its phosphate to ADP to form ATP

STEP 6 • Succinate is oxidized to fumarate and FAD is reduced. • 2 H are transferred to FAD to form FADH 2

STEP 7 • Water is added to fumarate which rearranges the chemical bonds to form malate

STEP 8 • Malate is oxidized and NAD+ is reduced to NADH + H+ • Oxaloacetate is regenerated

SUBSTRATE LEVEL PHOSPHORYLATION Only few ATPs are directly produced by this Phosphorylation. 2 net ATP per glucose from Glycolisis 2 ATP per glucose in Krebs cycle

1. At the end of Krebs cycle, most energy extracted from glucose is in molecules of 6 NADH + H+ and 2 FADH 2 2. These reduced compounds link glycolisis and Krebs Cycle to ETC by passing those electrons down to ETC to O 2. 3. The transfer of electrons to O 2 is exergonic leads to the formation of ATP

• NAD+ + H+ + 2 e- NADH (NAD is reduced, substrate is oxidized) • NADH NAD+ + H+ + 2 e(NAD is oxidized, substrate is reduced)

FOR 1 GLUCOSE. . GLYCOLYSIS • 2 net ATP produced • 2 NADH enter mitochondria as NADH/FADH (depend on the type of shuttles) • Malate-aspetate shuttle: NADH • Glycerol-phosphate shuttle: FADH 2

Malate-aspertate shuttle

Glycerol-phosphate shuttle

FOR 1 GLUCOSE. . GLYCOLYSIS • 2 net ATP produced • 2 NADH enter mitochondria as NADH/FADH KREB CYCLE • 6 NADH (3 X 2 , 2 pyruvate) • 2 FADH (1 X 2, 2 pyruvate) • 2 ATP (1 X 2, 2 pyruvate)

In Electron Transport Chain, • 1 molecule of NADH will generate 3 ATP • And 1 molecule of FADH 2 will generate 2 ATP. PROCESS GLYCOLYSIS LINK REACTION KREB CYCLE TOTAL PRODUCT ATP 2 NADH /FADH 6 ATP 2 NADH 6 ATP 6 NADH 18 ATP 2 FADH 4 ATP 2 ATP 38 ATP / 4 ATP / 36 ATP

Intermembrane space ATP Synthase FADH 2 Complex I Co. Q Complex III Cyt C Complex IV FAD : NADH Dehydrogenase : Coenzyme Q : Succinate Dehydrogenase : Cytochrome bc 1 : Cytochrome C : Cytochrome c Oxidase

Intermembrane space ATP Synthase FADH 2 FAD 1. NADH + H+ oxidizes, transfer H+ and 2 e to complex I

Intermembrane space ATP Synthase FADH 2 FAD 2. The transfer of electron cause complex I to pump H+ to intermembrane space

Intermembrane space ATP Synthase FADH 2 FAD 3. Complex I then transfer e to Co. Q, a lipid soluble mobile electron carrier

Intermembrane space ATP Synthase FADH 2 FAD 4. Co. Q transfer e to complex III

Intermembrane space ATP Synthase FADH 2 FAD 5. This transfer of e cause complex III to pump H+ to intermembrane space

Intermembrane space ATP Synthase FADH 2 FAD 6. Complex III then transfer e to cyt c, another mobile e carrier

Intermembrane space ATP Synthase FADH 2 FAD 7. Cyt c transfer e to complex IV, again H+ is pumped to intermembrane space

Intermembrane space ATP Synthase FADH 2 FAD 8. Complex IV lastly transfer e to O 2 (last e acceptor)

Intermembrane space ATP Synthase FADH 2 FAD 9. O 2 acccept 4 e with 4 H+ and becomes 2 water molecules O 2 + 4 e- + 4 H+ 2 H 2 O

Intermembrane space ATP Synthase FADH 2 FAD REMEMBER: complex I, III and IV has been pumping H+ to the intermembrane space! This create a H+ gradient: H+ concentration in intermembrane space higher than in matrix.

Intermembrane space ATP Synthase FADH 2 FAD This concentration gradient switch on the ATP synthase for CHEMIOSMOSIS. H+ will be pumped back to matrix. This pumping generate ATP synthase add inorganic phosphate (Pi) to ADP ATP

Intermembrane space ATP Synthase FADH 2 FAD How about complex II? Complex II undergo the same process but only accepts H+ from FADH 2, Complex II is a peripheral proteins, it cant pump H+

Intermembrane space ATP Synthase FADH 2 FAD Complex II except e from FADH 2, pass it to Co. Q and then to complex III FADH 2 will not encounter complex I, thus, for FADH 2, H+ will be pumped twice.

Cellular respiration ANAEROBIC AND ALTERNATIVE PATHWAY

ANAEROBIC RESPIRATION & OTHER MACROMOLECULES METABOLIC PATHWAYS OBJECTIVES: 1. DEFINITION OF ANAEROBIC RESPIRATION. 2. DIFFERENCES BETWEEN AEROBIC AND ANAEROBIC RESPIRATION. 3. PRODUCTS OF GLYCOLISIS. 4. FERMENTATION – LACTIC ACID & ETHANOL FORMATION. 5. IMPORTANCE OF FERMENTATION IN INDUSTRY 6. OTHER MACROMOLECULES METABOLIC PATHWAYS. Raven - Johnson - Biology: 6 th Ed. - All Rights Reserved Mc. Graw Hill Companies

Overview of Glucose Catabolism 1. Anaerobic Respiration – In the absence of oxygen, some organisms can still respire anaerobically, using inorganic molecules to accept electrons. • Methanogens • Sulfur Bacteria Raven - Johnson - Biology: 6 th Ed. - All Rights Reserved - Mc. Graw Hill Companies

Fig. 9. 9 Raven - Johnson - Biology: 6 th Ed. - All Rights

RELATED METABOLIC PROCESSES 1. FERMENTATION ● enables some cells to produce ATP without the presence of O 2. ● anaerobic catabolism of organic nutrients. ► Oxidizing agent : NAD+ , not O 2. ► Involves glycolisis followed by pyruvate reduction by NADH. ► Result: 2 ATPs. Raven - Johnson - Biology: 6 th Ed. - All Rights Reserved Mc. Graw Hill Companies

Anaerobic Routes of ATP Formation • Fermentation pathways – Bacteria, yeasts and protistans – Intensive Exercising • Glycolysis - first step • Net yield of two ATP • Final product is lactate or ethanol Raven - Johnson - Biology: 6 th Ed. - All Rights Reserved Mc. Graw Hill Companies

LACTIC ACID FERMENTATION 1. Intensive exercising, O 2 is scarce, human muscle cells switch from aerobic respiration to lactic acid fermentation. ● Lactate accumulates. ● Gradually it is carried to liver, to be converted back to pyruvate when O 2 is available. (O 2 Debt) 2. Commercial Importance: cheese production, yoghurt. Raven - Johnson - Biology: 6 th Ed. - All Rights Reserved Mc. Graw Hill Companies

Lactate Fermentation • Muscle cells in animals • Quick ATP production • Some bacteria

ALCOHOL FERMENTATION 1. 2. 3. 4. 5. Pyruvate loses CO 2. Pyruvate is converted to 2 C Acetaldehyde. NADH is oxidized to NAD+. Acetaldehyde is reduced to ethanol. Examples: Yeast, Bacteria Raven - Johnson - Biology: 6 th Ed. - All Rights Reserved Mc. Graw Hill Companies

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Alcohol Fermentation • Acetaldehyde is intermediate product • Yeasts Raven - Johnson - Biology:

FERMENTATION & RESPIRATION: COMPARISON 1. Similarity: ● Both use glycolisis to oxidize glucose and other substrates to pyruvate. ● Produce 2 ATPs by substrate-levelphosphorylation. ● Use NAD+ as oxidizing agent in glycolisis. Raven - Johnson - Biology: 6 th Ed. - All Rights Reserved Mc. Graw Hill Companies

2. Differences: ● Fermentation produce NAD+ during the reduction of pyruvate to form lactate or ethanol and CO 2. ● Aerobic respiration produce NADH during the oxidation of intermediates. Raven - Johnson - Biology: 6 th Ed. - All Rights Reserved Mc. Graw Hill Companies

3. Final electron acceptor: ● Fermentation: pyruvate acts as the final electron acceptor. ● Cell respiration: O 2 is the final electron acceptor. Raven - Johnson - Biology: 6 th Ed. - All Rights Reserved Mc. Graw Hill Companies

4. Amount of energy harvested: ● Fermentation yields net 2 ATPs by substrate- level phosphorylation. ● Cell respiration: 18 times more by substrate-level phosphorylation and oxidative phosphorylation. Raven - Johnson - Biology: 6 th Ed. - All Rights Reserved Mc. Graw Hill Companies

5. Requirement of O 2: ● Fermentation does not require O 2. ● Cell

6. Occurrence: ● Fermentation happens in cytosol. ● Cell Respiration occurs in cytosol and

OTHER METABOLIC PATHWAYS 1. Glycolisis and Krebs Cycle can connect to many other metabolic pathways. 2. Cell respiration can oxidize organic molecules other than glucose to make ATP. Raven - Johnson - Biology: 6 th Ed. - All Rights Reserved - Mc. Graw Hill Companies

Fig. 9. 21 Raven - Johnson - Biology: 6 th Ed. - All Rights

1. PROTEINS - hydrolyzed to amino acids. 2. Excess Amino Acids - enzymatically converted to intermediates of glycolisis & Krebs Cycle. (Pyruvate, Acetyl Co. A, -ketoglutarate). 3. This conversion deaminates amino acids, nitrogenous waste are excreted & carbon skeleton can be oxidized. Raven - Johnson - Biology: 6 th Ed. - All Rights Reserved Mc. Graw Hill Companies

1. FATS - rich in hydrogens. (high energy electrons) 2. Oxidation of 1 g of fat produces 2 times more ATP than 1 g of Carbohydrate. 3. Fats- digested into glycerol and fatty acids. 4. Glycerol can be converted into glyceraldehydes phosphate (intermediate of glycolisis). 5. Fatty acids – converted into Acetyl Co. A by βoxidation. The 2 C compounds enter Krebs Cycle. Raven - Johnson - Biology: 6 th Ed. - All Rights Reserved Mc. Graw Hill Companies

Review • Chemical Energy Drives Metabolism • Glucose Catabolism – Glycolysis – Pyruvate Oxidation – Krebs Cycle – Electron Transport Chain • Aerobic Respiration Summary • Energy Storage • Fermentation Raven - Johnson - Biology: 6 th Ed. - All Rights Reserved Mc. Graw Hill Companies

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Fig. 9. 9 b - Biology: 6 th Raven - Johnson Ed. - All

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• The conversion of pyruvate and the Krebs cycle produces large quantities of electron carriers. Raven - Johnson - Biology: 6 th Fig. 9. 12 Ed. - All Rights Reserved Copyright. Hill © Companies 2002 Pearson Education, Inc. , publishing as Benjamin Cummings Mc. Graw