Key Themes (2) “Think Like a Biologist”: Understand What Life Is. “Unity” of life: What are common features of eukaryotes? Energy conversions: Sugar breakdown & mitochondrial ATP formation 1 Lecture 7: Cellular Respiration

Yesterday’s Exit Ticket –Energy-releasing reactions: Large, complex  smaller, simpler Release energy and increase entropy e.g. ATP  ADP and P i e.g. respiration (glucose + O 2  H 2 O + CO 2 + ATP) –Energy-requiring reactions: Smaller, simpler  large complex Decrease entropy e.g. ADP + Pi  ATP e.g. photosynthesis (light E + H 2 O + CO 2  glucose + O 2 )

Food-to-Energy Fig. 9.1 Fig. 8.3 Respiration 3

Cellular respiration breaks down energy-rich molecules to CO 2 & water, extracting their energy. Fig. 9.2 Light energy ECOSYSTEM Photosynthesis in chloroplasts CO 2 + H 2 O Cellular respiration in mitochondria Organic molecules + O 2 ATP powers most cellular work Heat energy ATP High energy Low energy C-H bond “burned” with O 2 to H 2 O + CO 2 4

Photosynthesis: Respiration: ATP Since ATP is too unstable, C-H bonds in sugars are used for energy storage. Converts solar energy to ATP and uses ATP to make sugars Converts the energy of sugars back to ATP as needed. Sugar [CH 2 O] x + O 2 CO 2 + H 2 0 ATP Light (energy) H + & e - 5

What is the goal of cellular respiration? Food  ATP Release the energy in C-H bonds Harness that energy to create ATP 6-C sugar Glucose + O 2 (6-C sugar) ATP + CO 2 + H 2 0 (energy) 3-C sugars + some ATP CO 2 + some ATP H 2 O + ATP H + & e - O2O2 paraibaparadise.com 6

What is the goal of cellular respiration? 6-C sugar 3-C sugars + some ATP CO 2 + some ATP H 2 O + ATP H + & e - O2O2 Step 1: Glycolysis Step 2: Citric Acid Cycle Step 3: Oxidative Phosphorylation 7

Step 1: Glycolysis Occurs in: cytosol Starts with: glucose, NAD +, ADP, P i Produces: pyruvate, NADH, and ATP Glucose (6-C sugar) Pyruvates (3-C sugars) + some ATP H + & e - 8

Cytosol Fig. 9.6 GlucosePyruvate Glycolysis Electrons carried off by NADH ATP Some Step 1: Glycolysis Occurs in: cytosol Starts with: glucose, NAD +, ADP, P i Produces: pyruvate, NADH, and ATP 9

Pyruvates (3-C sugars) + some ATP Glucose (6-C sugar) Step 1: Glycolysis Occurs in: cytosol Starts with: glucose, NAD +, ADP, P i Produces: pyruvate, NADH, and ATP H + & e - NAD + NADH Glycolysis can occur with or without O 2 !! 10

Pyruvates (3-C sugars) + some ATP CO 2 + some ATP H + & e - Step 2: Citric Acid Cycle Occurs in: mitochondrial matrix (fluid space) Starts with: pyruvate, NAD +, FAD, ADP, P i Produces: NADH, FADH 2, CO 2 and ATP 11

Fig. 9.6 Mitochondrion Electrons carried off by NADH & FADH 2 Citric acid cycle ATP GlucosePyruvate Glycolysis Electrons carried off by NADH Some ATP Some Cytosol Step 2: Citric Acid Cycle Occurs in: mitochondrial matrix (fluid space) Starts with: pyruvate, NAD +, FAD, ADP, P i Produces: NADH, FADH 2, CO 2 and ATP 12

CO 2 + some ATP H + & e - Step 2: Citric Acid Cycle Occurs in: mitochondrial matrix (fluid space) Starts with: pyruvate, NAD +, FAD, ADP, P i Produces: NADH, FADH 2, CO 2 and ATP NAD + FAD NADH FADH 2 Pyruvates (3-C sugars) + some ATP 13

Step 3: Oxidative Phosphorylation (Using oxygen to phosphorylate ADP) Occurs in: mitochondrial inner membranes Starts with: O 2, NADH, FADH 2, ADP, P i Produces: H 2 O, ATP, NAD +, FAD H 2 O + ATP NADH O2O2 FADH 2 ADP P i 14

Electron transport and ATP synthase Mitochondrion ATP Electrons carried off by NADH & FADH 2 Citric acid cycle ATP GlucosePyruvate Glycolysis Electrons carried off by NADH Fig. 9.6 Some ATP Lots of Cytosol Step 3: Oxidative Phosphorylation (Using oxygen to phosphorylate ADP) Occurs in: mitochondrial inner membranes Starts with: O 2, NADH, FADH 2, ADP, P i Produces: H 2 O, ATP, NAD +, FAD 15

H (electrons and H + ) removed from high energy C-H bonds CO 2 + some ATP H 2 O + ATP H + & e - (via NADH) O2O2 Pyruvates (3-C sugars) + some ATP Glucose (6-C sugar) H + & e - (via NADH & FADH 2 ) 16

I H - C - OH (CHOH) 6 (= C 6 H 12 O 6 sugar) I to O = C = OCO 2 Where does H go? H (electrons and H + ) are loaded onto electron carriers NADH & FADH 2 H (electrons and H + ) removed from high energy C-H bonds (all the way to CO 2 in the citric acid cycle) 17

H (electrons and H + ) removed from high energy C-H bonds CO 2 + some ATP H 2 O + ATP H + & e - (via NADH) O2O2 Pyruvates (3-C sugars) + some ATP Glucose (6-C sugar) H + & e - (via NADH & FADH 2 ) 18

ATP Mitochondrion ATP Electrons carried off by NADH & FADH 2 Citric acid cycle ATP Cytosol GlucosePyruvate Glycolysis Electrons carried off by NADH Fig ~34 Most ATP is formed by electron transport chain through oxidative phosphorylation Electron transport and ATP synthase 19

Smooth outer membrane Folded inner membrane: Matrix: Citric acid cycle Mitochondria Electron transport chain & ATP formation Fig

Fig Potential energy (ion gradient) used for ATP formation Fig

Protein complex of electron carriers H+H+ H+H+ H+H+ Cyt c Q    VV FADH 2 FAD NAD + NADH (carrying electrons from food) Electron transport chain & pumping of protons 2 H / 2 O 2 H2OH2O ADP + P i H+H+ H+H+ ATP synthase ATP 2 1 The electron transport chain pumps protons against the concentration gradient; builds up a high H + concentration in intermembrane space. Intermembrane space Mitochondrial matrix Inner membrane Fig ATP synthesis via H + flow Step 3: Oxidative Phosphorylation 22

Smooth outer membrane Folded inner membrane Intermembrane space Mitochondria Fig Matrix 23

Protein complex of electron carriers H+H+ H+H+ H+H+ Cyt c Q    VV FADH 2 FAD NAD + NADH (carrying electrons from food) Electron transport chain & pumping of protons 2 H / 2 O 2 H2OH2O ADP + P i H+H+ H+H+ ATP 2 1 Intermembrane space Mitochondrial matrix Inner membrane Fig ATP synthesis via H + flow INTERMEMBRANE SPACE Rotor H+H+ Stator Internal rod Cata- lytic knob ADP + P ATP i MITOCHONDRIAL MATRIX Fig Oxygen (O 2 ) is the final electron (and H + ) acceptor ATP synthase Protons flow downhill through the ATP synthase, driving phosphorylation of ADP to ATP. Step 3: Oxidative Phosphorylation 24

Let’s take a look at the whole sequence: Step 1: Glycolysis Step 2: Citric Acid Cycle Step 3: Oxidative Phosphorylation 25

Electron Donors and Electron Acceptors CO 2 + some ATP H 2 O + ATP H + & e - (via NADH) O2O2 Pyruvates (3-C sugars) + some ATP Glucose (6-C sugar) H + & e - (via NADH & FADH 2 ) Original electron donor in cellular respiration Electron donors for mitochondrial electron transport chain Electron acceptor from mitochondrial electron transport chain 26

ATP links the energy from breakdown of energy-rich food molecules to cellular work P i ADP + Energy from breakdown of energy-rich molecules Energy for cellular work ATP + H2OH2O Energy loaded onto ATP Energy released from ATP Fig

Proteins Carbohydrates Amino acids Sugars Fats GlycerolFatty acids Glycolysis Glucose Glyceraldehyde-3- Pyruvate P NH 3 Acetyl CoA Citric acid cycle Oxidative phosphorylation Fig The cellular respiration pathway for Carbohydrates Fats 28

Predict how the enzymes that function early in glycolysis, and start the breakdown of glucose, should be regulated: The enzymes should A) not be regulated. B) be turned off when enough (ATP) energy is available. C) be turned on when more (ATP) energy is needed. D) be regulated in a dual way, both by activation when more ATP energy is needed and by inactivation when enough ATP energy is available. 29

5 min break 30

Key Themes Energy conversions: Sugar breakdown without oxygen via glycolysis + fermentation 31

Glucose Glycolysis Pyruvate CYTOSOL MITOCHONDRION Fig Step 1 of cellular respiration: Glycolysis outside mitochondria From glucose (6 C) to 2 pyruvate (3 C) Citric acid cycle 32

Glucose Glycolysis Pyruvate CYTOSOL O 2 present: Aerobic cellular respiration MITOCHONDRION Acetyl CoA Citric acid cycle Fig Only when oxygen is present can glucose be broken down completely in the mitochondria for high energy yield 33

Glucose Glycolysis Pyruvate CYTOSOL No O 2 present: Fermentation MITOCHONDRION Acetyl CoA Ethanol or lactate Citric acid cycle Fig

Alcoholic fermentation (forms ethanol plus CO 2 ) by yeasts and bacteria under anaerobic conditions Glycolysis & fermentation 2 ADP + 2 P i 2 ATP GlucoseGlycolysis 2 Pyruvate 2 NADH2 NAD H + CO 2 2 Acetaldehyde 2 Ethanol (a) Alcohol fermentation 2 Fig The solution when oxygen runs out or is unavailable (anaerobic conditions): 35

Glycolysis and fermentationFermentation to ethanol 2 ADP + 2 P i 2 ATP GlucoseGlycolysis 2 Pyruvate 2 NADH2 NAD H + CO 2 2 Acetaldehyde 2 Ethanol (a) Alcohol fermentation 2 Fig. 9.18(a) Yeasts use alcoholic fermentation to convert hexoses (from sugar cane sucrose or corn starch or cellulose) into ethanol for fuels Production of Foods & Fuels 36

Alcohol fermentation (forms ethanol plus CO 2 ) Yeasts & bacteria Anaerobic conditions Glycolysis & fermentation 2 ADP + 2 P i 2 ATP GlucoseGlycolysis 2 Pyruvate 2 NADH2 NAD H + CO 2 2 Acetaldehyde 2 Ethanol (a) Alcohol fermentation 2 Fig Do all organisms use alcohol fermentation when oxygen is in short supply? 37

Alcohol fermentation (forms ethanol plus CO 2 ) Yeasts & bacteria Anaerobic conditions Glycolysis & fermentation without oxygen (anaerobic conditions) 2 ADP + 2 P i 2 ATP GlucoseGlycolysis 2 Pyruvate 2 NADH2 NAD H + CO 2 2 Acetaldehyde 2 Ethanol (a) Alcohol fermentation 2 Glucose 2 ADP + 2 P i 2 ATP Glycolysis 2 NAD + 2 NADH + 2 H + 2 Pyruvate 2 Lactate (b) Lactic acid fermentation Fig Lactic acid fermentation Other fungi & bacteria Also in muscle cells under anaerobic conditions 38

Production of Foods and Fuels by Microbes in home & industry Yeasts for beer & wine [alcohol fermentation] & for bread leavening [from the CO 2 gas formed]; lactic acid bacteria for fermented products from milk or other foods [lactic acid fermentation]. 39

Fermentation versus aerobic respiration Different human muscle fibers use different metabolism ( See also Table 49.1): Glucose Glycolysis Pyruvate CYTOSOL Fermentation Aerobic cellular respiration MITOCHONDRION Acetyl CoA Lactate Citric acid cycle Fig

Fermentation versus aerobic respiration Different human muscle fibers use different metabolism ( See also Table 49.1): Glucose Glycolysis Pyruvate CYTOSOL Fermentation Aerobic cellular respiration MITOCHONDRION Acetyl CoA Lactate Citric acid cycle Fig Fast-twitch glycolytic fibers (for sprint) use glycolysis - quick, but does not provide much energy. Glycogen 41

Fermentation versus aerobic respiration Different human muscle fibers use different metabolism ( See also Table 49.1): [Glucose] Glycolysis Pyruvate CYTOSOL Fermentation Aerobic cellular respiration MITOCHONDRION Acetyl CoA Lactate Citric acid cycle Fig Fast-twitch glycolytic fibers (for sprint) use glycolysis - quick, but does not provide much energy. Slow-twitch oxidative fibers (with many mitochondria for extended exercise) use oxidative respiration - slower, but yields much more energy. Fats 42

Glucose Glycolysis Pyruvate CYTOSOL No O 2 present: Fermentation O 2 present: Aerobic cellular respiration MITOCHONDRION Acetyl CoA Ethanol or lactate Citric acid cycle Fig Fermentation in absence of O 2 Aerobic respiration in presence of O 2 43

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Hank’s Crash Course in Cellular Respiration 3:30-end GuQ&feature=relmfu 45

Today’s Exit Ticket Glucose Process: Location: # ATPs: Process: Location: Products Released: Location: Products Released: # ATPs: Process: 46