CELLULAR RESPIRATION CHAPTER 6 Sunlight energy ECOSYSTEM Photosynthesis

CELLULAR RESPIRATION CHAPTER 6

Sunlight energy ECOSYSTEM Photosynthesis in chloroplasts CO 2 Glucose H 2 O O 2 Cellular respiration in mitochondria ATP (for cellular work) Heat energy

Cellular Respiration Banks Energy in ATP Molecules C 6 H 12 O 6 Glucose + 6 O 2 Oxygen 6 CO 2 Carbon dioxide + 6 H 2 O Water + ATPs Energy Cellular respiration transfers energy from the bonds of glucose storing it in ATP (~38 ATP/glucose are produced) When the bonds of glucose are broken, electrons are stripped from it and ultimately transferred to oxygen

Cells Tap Energy From Electrons “falling” From Organic Fuels to Oxygen C 6 H 12 O 6 Glucose + 6 O 2 Oxygen 6 CO 2 Carbon dioxide + 6 H 2 O Water + ATPs Energy Oxygen is electronegative, thus pulling these etowards it As electrons move from glucose to oxygen, energy is released in small amounts, stored in a gradient that is used to synthesize ATP Other foods (organic molecules) can be used as a source of energy as well

Cellular Respiration is a Redox Process, As is Photosynthesis Loss of hydrogen atoms (oxidation) C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O + Energy (ATP) Glucose Gain of hydrogen atoms (reduction)

Enzymes are Necessary to Oxidize Glucose and Other Foods The enzyme that removes hydrogens from organic molecule is called dehydrogenase Oxidation Dehydrogenase NAD+ + 2 H 2 H+ + 2 e – Reduction + NADH + H (carries 2 electrons)

Cells Tap Energy From Electrons “falling” from Organic Fuels to Oxygen – Dehydrogenase requires NAD+ (a coenzyme) to carry e- becoming NADH when it accepts e– A related coenzyme, FAD functions like NAD+ (becoming FADH 2 ) – NADH and FADH 2 “carry” eoriginating from glucose over to the proteins embedded in the cristae of the mitochondria called the electron transport chain (ETC ) Copyright © 2009 Pearson Education, Inc.

NADH NAD+ ATP + 2 e– Controlled release of energy for synthesis of ATP H+ El ec tro nt ch ra ain ns po rt 2 e– H+ H 2 O 1 2 O 2

Breathing Supplies Oxygen to Our Cells For Use in Cellular Respiration and Removes Carbon Dioxide Breathing and cellular respiration are closely related – Breathing is necessary for the exchange of CO 2 produced during cellular respiration for atmospheric O 2

O 2 Breathing CO 2 Lungs CO 2 Bloodstream Muscle cells carrying out Cellular Respiration Glucose + O 2 CO 2 + H 2 O + ATP O 2

STAGES OF CELLULAR RESPIRATION

Cellular Respiration Occurs in Three Main Stages Stage 1: Glycolysis – Location: cytoplasm – Purpose: to begin the breakdown of glucose – What happens: A single molecule of glucose is enzymatically cut in half through a series of steps producing two molecules of pyruvate – Redox reactions produce NADH – Substrate-level phosphorylation produces ATP – Products/glucose : 2 pyruvate, 2 NADH, 2 ATP

ENERGY INVESTMENT PHASE Glucose ATP Steps 1 – 3 A fuel molecule is energized, using ATP. 1 ADP P Glucose-6 -phosphate P Fructose-1, 6 -bisphosphate 2 ATP 3 ADP P Step 4 A six-carbon intermediate splits Into two three-carbon intermediates. 4 P Step 5 A redox reaction generates NADH. Glyceraldehyde-3 -phosphate (G 3 P) P NAD+ 5 P NADH 5 NADH + H+ ENERGY PAYOFF PHASE P + H+ P P ADP P P 1, 3 -Bisphoglycerate ADP 6 6 ATP P P 3 -Phosphoglycerate 7 7 P Steps 6 – 9 ATP and pyruvate are produced. P 2 -Phosphoglycerate 8 H 2 O P P ADP Phosphoenolpyruvate (PEP) ADP 9 ATP 8 H 2 O 9 ATP Pyruvate

Substrate-level Phosphorylation § Substrate-level phosphorylation is the enzymatic transfer of a phosphate group from a substrate molecule to ADP, forming ATP Enzyme ADP ATP P Substrate P Product

Pyruvate is Chemically Groomed for The Kreb’s Cycle Grooming Step Location: mitochondrial matrix Purpose: to prepare pyruvate for entry into the Kreb’s cycle What Happens: Occurs in three steps – 1. The removal of a carboxyl group from pyruvate (first release of CO 2) – 2. Oxidization of the remaining 2 -carbon compound forming acetate – 3. Binding of Coenzyme A to the 2 -carbon acetate forming acetyl coenzyme A Products/glucose: 2 CO 2 , 2 NADH, 2 Acetyl Co. A

Pyruvate is Chemically Groomed for The Kreb’s Cycle NADH H+ NAD+ 2 Co. A Pyruvate 1 CO 2 3 Coenzyme A Acetyl coenzyme A

Cellular Respiration Occurs in Three Main Stages Stage 2: The Kreb’s Cycle (Citric Acid Cycle) – Location: mitochondrial matrix – Purpose: to complete the oxidation of glucose into CO 2 and to form more electron carriers – What Happens: A 2 -C acetate combines with 4 -C oxaloacetate forming 6 -C citrate. – Redox reactions produce NADH and FADH 2 – Substrate-level phosphorylation produces ATP – 4 -C Oxaloacetate is regenerated to bind acetate and begin cycle again – Products/glucose : 4 CO 2, 6 NADH, 2 FADH 2 , 2 ATP,

Co. A Acetyl Co. A 2 carbons enter cycle Oxaloacetate 1 Citrate NADH + H+ NAD+ 5 NAD+ 2 NADH + H+ CITRIC ACID CYCLE CO 2 leaves cycle Malate ADP P FADH 2 4 ATP FAD Alpha-ketoglutarate 3 CO 2 leaves cycle Succinate NADH + H+ Step 1 Acetyl Co. A stokes the furnace. NAD+ Steps 2 – 3 NADH, ATP, and CO 2 are generated during redox reactions. Steps 4 – 5 Redox reactions generate FADH 2 and NADH.

Cellular Respiration Occurs in Three Main Stages Stage 3: Oxidative phosphorylation (along the ETC) – Location: cristae of mitochondria – Purpose: generate a proton gradient to help form ATP – What Happens: NADH & FADH 2 , supply the electrons they are – – carying to the ETC. As e- are transferred from protein to protein, H + are concentrated in the intermembrane space The potential energy of this proton gradient is used to make ATP by chemiosmosis The concentration gradient drives H+ through ATP synthases producing ATP The ETC + chemiosmosis = oxidative phosphorylation Products/glucose: 34 -38 ATP and H 2 O

Oxidative Phosphorylation Intermembrane space Protein complex of electron carriers H+ H+ Electron carrier H+ H+ ATP synthase Inner mitochondrial membrane FADH 2 Electron flow NADH Mitochondrial matrix FAD NAD+ H+ 1 2 O 2 + 2 H+ H+ H+ H 2 O Electron Transport Chain OXIDATIVE PHOSPHORYLATION ADP + P H+ Chemiosmosis ATP

OVERVIEW OF AEROBIC RESPIRATION Electron shuttle across membrane Cytoplasm 2 NADH Mitochondrion 2 NADH (or 2 FADH 2) 6 NADH 2 NADH GLYCOLYSIS Glucose 2 Pyruvate 2 Acetyl Co. A 2 ATP by substrate-level phosphorylation Maximum per glucose: CITRIC ACID CYCLE 2 ATP by substrate-level phosphorylation About 38 ATP 2 FADH 2 OXIDATIVE PHOSPHORYLATION (Electron Transport and Chemiosmosis) about 34 ATP by oxidative phosphorylation

Overview of Cellular Respiration

Fermentation Enables Cells to Produce ATP Without Oxygen Fermentation is an anaerobic energy-generating process – Location: cytoplasm – Purpose: to produce ATP in the absence of oxygen – What Happens? : Glycolysis, and regeneration of NAD+ – Pyruvate accepts electrons generated by redox reactions in glycolysis – Your muscle cells and certain bacteria can oxidize NADH through lactic acid fermentation Copyright © 2009 Pearson Education, Inc.

2 ADP 2 P Glycolysis 2 ATP GLYCOLYSIS Glucose 2 NAD+ 2 NADH Lactic Acid Fermentation 2 Pyruvate 2 NADH Steps to regenerate NAD+ 2 Lactate Lactic acid fermentation

Fermentation Enables Cells to Produce ATP Without Oxygen The baking and winemaking industry have used alcohol fermentation for thousands of years – Occurs in yeast cells (single-celled fungi) – Yeast convert pyruvate to CO 2 and ethanol while oxidizing NADH back to NAD+

2 ADP 2 P Glycolysis 2 ATP GLYCOLYSIS Glucose 2 NAD+ 2 NADH 2 Pyruvate 2 NADH Steps to regenerate NAD+ with a release of CO 2 2 CO 2 released 2 NAD+ 2 Ethanol Alcohol fermentation Alcohol Fermentation

INTERCONNECTIONS BETWEEN MOLECULAR BREAKDOWN AND SYNTHESIS

Cells Use Many Kinds of Organic Molecules as Fuel for Cellular Respiration Although glucose is considered the primary source of sugar for respiration and fermentation, three molecules can serve as substrates for generating ATP – Carbohydrates (disaccharides) – Proteins (after conversion to amino acids) – Fats

Food, such as peanuts Carbohydrates Fats Glycerol Sugars Proteins Fatty acids Amino groups Glucose G 3 P Pyruvate GLYCOLYSIS Acetyl Co. A ATP CITRIC ACID CYCLE OXIDATIVE PHOSPHORYLATION (Electron Transport and Chemiosmosis)

ATP needed to drive biosynthesis ATP CITRIC ACID CYCLE Acetyl Co. A GLUCOSE SYNTHESIS Pyruvate G 3 P Glucose Amino groups Amino acids Proteins Fatty acids Glycerol Fats Cells, tissues, organisms Sugars Carbohydrates

Cellular respiration generates has three stages oxidizes uses ATP produce some (a) C 6 H 12 O 6 energy for produces many (b) (d) to pull to electrons down (c) by process called uses H+ diffuse through ATP synthase uses (e) pumps H+ to create (f)