Cellular Respiration – Requires Oxygen, Produces Carbon Dioxide

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Metabolism

§ Consists of all of the chemical reactions that take place in a cell. § Can be reactions that break things down. Cellular Metabolism (Catabolism) § Or reactions that build things up. (Anabolism) Biol 105 Read Chapter 3 (pages 63 – 69)

Cellular Metabolism

§ Some of the reactions provide energy for the cell in the form of ATP. § Aerobic Cellular Respiration – requires oxygen, produces carbon dioxide.

§ Anaerobic Fermentation – does not require oxygen, does not produce carbon dioxide.

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Summary of Cellular Respiration Aerobic Cellular respiration

Electrons § In aerobic cellular respiration cells take in sugar transferred by NADH Cytoplasm Blood Electrons (glucose) and break it down to into carbon vessel transferred by NADH dioxide and water, this requires oxygen and

Glucose Plasma Electrons membrane transferred produces CO . by NADH 2

and FADH2 Carrier protein § This process produces energy in the form of Citric Electron Transition Glycolysis Acid Transport Reaction glucose pyruvate Cycle Chain ATP

Oxygen § C H O + 6O → 6CO +6H O + Energy (ATP) Mitochondrion 6 12 6 2 2 2

Extracellular fluid +2 ATP +2 ATP +32 ATP = 36 ATP

Aerobic Cellular respiration

§ There are four steps in aerobic cellular respiration: 1. Glycolysis 2. Transition Reaction 3. Citric Acid Cycle (Krebs Cycle) 4. Electron Transport Chain

Name, Location, Require O2?, Starting Molecule(s),

Ending Molecule, #ATP, #NADH, #FADH2, #CO2

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Cellular Respiration - Glycolysis Cellular Respiration - Glycolysis

§ Phase 1: Glycolysis § Starts with: § 1 glucose (6 carbon molecule) § Occurs in the cytoplasm. § (2 ATP) § Does not require Oxygen § Splits one glucose into two pyruvate § Ends with: molecules. § 2 ATP § 2 NADH § Forms 2 Pyruvate Molecules § 2 pyruvate (3 carbon molecule) § Produces 2 ATP + 2 NADH

Glycolysis

Glycolysis (in cytoplasm)

Cytoplasm

During the first steps, two molecules of ATP are consumed in preparing glucose for splitting. Glucose

2 ATP During the remaining Energy- steps, four molecules of ATP are produced. investment 2 ADP phase 4 ADP In Cytosol

4 ATP Energy- The two molecules of yielding pyruvate then diffuse + 2 NAD phase from the cytoplasm into the inner compartment of the mitochondrion, where they pass through 2 NADH a few preparatory steps (the transition reaction) before entering the citric acid cycle. Two molecules of nicotine adenine dinucleotide 2 Pyruvate (NADH), a carrier of high-energy electrons, also are produced.

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Cellular Respiration – Transition Reaction Transition Reaction

§ Phase 2: Transition Reaction (Intermediate Phase) § Starts with: § 2 pyruvate (3 carbon molecule) § Occurs within the mitochondria. § 2 Coenzyme A § Requires Oxygen. § Coenzyme-A combines with pyruvate and a § Ends with: CO2 is removed from each pyruvate. § 2 CO2 § Forms 2 acetyl CoA molecules. § 2 NADH § Produces 2 NADH. § 2 Acetyl CoA (2 carbon molecule)

§ Produces 2 CO2.

Transition Reaction Cellular Respiration – Citric acid cycle Transition Reaction (in mitochondrion) § Phase 3: Citric Acid Cycle (Krebs Cycle)

§ Occurs in the mitochondria. Pyruvate (from glycolysis) § Requires Oxygen.

One carbon (in the form of CO2) is removed from pyruvate. § 2 Acetyl CoA enter the citric acid cycle and A molecule of NADH is formed when NAD+ gains two electrons combine with oxaloacetate. and one proton. CO2 NAD+ § Oxaloacetate re-forms.

In NADH Coenzyme A § Produces: (electron passes The two-carbon Mitochondria to electron molecule, called § 2 ATP transport chain) an acetyl group, binds to coenzyme A (CoA), forming § 2 FADH2 CoA acetyl CoA, which enters the Acetyl CoA citric acid cycle. § 6 NADH

§ 4 CO2 Citric Acid Cycle

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Citric Acid Cycle Citric Acid Cycle

§ Also called the Krebs Cycle Citric Acid Cycle (in mitochondrion)

Acetyl CoA, the § Starts with: two-carbon compound formed during the transition reaction, enters the citric acid § 2 Acetyl CoA (2 carbon molecule) The citric acid cycle also cycle. yields several molecules of

FADH2 and NADH, carriers of high-energy electrons that Acetyl CoA § Oxaloacetate enter the electron transport CoA chain. CoA Oxaloacetate Citrate § Ends with: NADH CO2 leaves NAD+ § 4 CO cycle 2 NAD+ Malate Citric Acid Cycle § 2 ATP FADH NADH 2 ATP ADP + Pi FAD § 6 NADH In α-Ketoglutarate Succinate CO leaves cycle § 2 FADH2 2 Mitochondria NAD+ NADH The citric acid cycle yields § Oxaloacetate One ATP from each acetyl CoA that enters the cycle, for a net gain of two ATP.

NADH and FADH

§ NADH and FADH2 are important carriers of electrons

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Cellular Respiration The Big Pay Off – Electron Transport Chain

§ Phase 4: Electron Transport Chain § NADH and FADH2 are important carriers of electrons. § Electrons of FADH2 and NADH are transferred from one protein to another, until § They donate electrons to the electron transport they reach oxygen. chain. § Requires oxygen. § Releases energy that results in 32 ATP. § At the end of the chain oxygen accepts the electrons.

Electron Transport Chain

Electron Transport Chain (inner membrane of mitochondrion)

The molecules of NADH and FADH2 produced by earlier phases Inner of cellular respiration pass their electrons to a series of protein molecules embedded in the inner Membrane of membrane of the mitochondrion. Mitochondria High NADH + NAD As the electrons are transferred from one protein to the next, energy is released and used to 2e– make ATP.

FADH2 2e– Membrane proteins FAD Eventually, the electrons are passed to oxygen, which combines Potential energy Potential 2e– with two hydrogens 2e– to form water.

2e– H2O Low + 1 2 H + 2 O2 Energy released is used for synthesis of ATP

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The Big Pay Off – Electron Transport Chain

§ Electron Transport Chain produces ATP using the ATP Synthase protein.

§ The Electron Transport Chain produces 32 molecules of ATP.

How is ATP made using the ETC How is ATP made using the ETC

+ 1. In the mitochondria NADH and FADH2 donate 4. ATP Synthase allows the H to flow down electrons to the electron transport chain (ETC). it’s concentration gradient back to the lumen of the mitochondria. 2. Oxygen is the final electron acceptor from the ETC. 5. The H+ flowing through the ATP Synthase provides the energy for the ATP Synthase 3. The ETC uses the energy from the electrons to to catalyze the reaction of ADP + P → ATP. transport H+ against the concentration gradient, transporting them from the lumen of the mitochondria to the inter-membrane space.

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Summary of Cellular Respiration Summary of Cellular Respiration § One molecule of glucose is broken down and 36 ATP are generated.

§ Oxygen is used by the electron transport chain – it accepts electrons from the end of the ETC.

§ Carbon dioxide is produced by the Transition Reaction and the Citric Acid Cycle.

Summary of Cellular Respiration Summary of Cellular Respiration

§ Glycolysis: Starts the process by taking in § Electron transport chain glucose. § Takes electrons from NADH and FADH2 § Produces 2 ATP & 2 NADH. and uses them to produce ATP using the § The Transition Reaction: ATP Synthase protein. § Requires oxygen: Oxygen is the final § Produces 2 CO2 and 2 NADH. electron acceptor on the electron § The Citric Acid Cycle: transport chain. § Produces 2 ATP but also produces 6 NADH

and 2 FADH2. § One glucose can produce a total of 36 ATP

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Sources of Energy Complex Carbohydrates must first be broken down into glucose before entering glycolysis

O Fats and proteins enter H2N CH C OH the process at different R steps

Animation Oxygen

§ Respiration Movie § Cellular respiration that requires oxygen is Aerobic Cellular Respiration.

§ Sometimes organisms, including humans, need to produce energy without using oxygen.

§ When you need energy quick, or if there is

not enough O2 then the cell will use Anaerobic Fermentation.

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Anaerobic Fermentation Anaerobic Fermentation

§ Anaerobic Fermentation: § Breakdown of glucose without oxygen. § Use the anaerobic pathway to produce § Takes place entirely in the cytoplasm. ATP from glycolysis without the Transition Reaction, Citric Acid Cycle or § It is very inefficient - results in only two ATP. the ETC

Fermentation in Animals

§ When cells need energy quick they will use this pathway for a short time. § Glycolysis → 2 pyruvic acid + 2 NADH→ → 2 lactate (lactic acid) and 2 NAD+. § End result = lactate and 2 ATP produced (from glycolysis) and NAD+ is regenerated

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What is the starting molecule of glycolysis? What is the starting molecule of glycolysis?

1. Acetyl CoA 1. Acetyl CoA 25% 25% 25% 25% 25% 25% 25% 25% 2. Protein 2. Protein 3. Glucose 3. Glucose 4. Pyruvate (pyruvic 4. Pyruvate (pyruvic acid) acid)

Protein Glucose Protein Glucose Acetyl CoA Acetyl CoA

Pyruvate (pyruvic acid) Pyruvate (pyruvic acid)

Which stage produces CO2 Which stage produces CO2

1. Glycolysis 1. Glycolysis 20% 20% 20% 20% 20% 20% 20% 20% 20% 20% 2. Electron 2. Electron Transport Chain Transport Chain 3. Transition 3. Transition 4. Citric acid Cycle 4. Citric acid Cycle 5. Both 3 and 4 5. Both 3 and 4

Glycolysis Transition Glycolysis Transition Both 3 and 4 Both 3 and 4 Citric acid Cycle Citric acid Cycle

Electron Transport ... Electron Transport ...

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Which stage uses O2 Which stage uses O2

1. Glycolysis 1. Glycolysis 2. Citric Acid (Krebs) 33% 33% 33% 2. Citric Acid (Krebs) 33% 33% 33% Cycle Cycle 3. Electron 3. Electron Transport Chain Transport Chain

Glycolysis Glycolysis Krebs Cycle Krebs Cycle

Electron Transport ... Electron Transport ...

Which stage produces the most NADHs Which stage produces the most NADHs

1. Glycolysis 1. Glycolysis 2. Citric Acid (Krebs) 33% 33% 33% 2. Citric Acid (Krebs) 33% 33% 33% Cycle Cycle 3. Electron 3. Electron Transport Chain Transport Chain

Glycolysis Glycolysis Krebs Cycle Krebs Cycle

Electron Transport ... Electron Transport ...

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Which stage produces the most ATP Which stage produces the most ATP

1. Glycolysis 1. Glycolysis 2. Krebs Cycle 33% 33% 33% 2. Krebs Cycle 33% 33% 33% 3. Electron 3. Electron Transport Chain Transport Chain

Glycolysis Glycolysis Krebs Cycle Krebs Cycle

Electron Transport ... Electron Transport ...

Important Concepts Important Concepts

§ Read Ch 4 § Describe in detail how is ATP made using the electron transport chain § What is Cellular respiration and Anaerobic Fermentation and what are the differences + § What is the role of ATPsynthase, H , O2, NADH between them. and FADH2 and the electron transport chain in ATP production? § What are the four steps of aerobic cellular respiration, what happens in each step, what § Know the overall picture of cellular respiration are the starting molecules, what comes out of (summary slides) each step, where in the cell does each step

occur, how many ATP and NADH/FADH2 are produced in each step.

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Important Concepts Definitions § What is the role of oxygen in cellular respiration, what steps produce carbon dioxide § Aerobic cellular respiration, anaerobic fermentation , ATP synthase, metabolism § What is anaerobic fermentation, what steps are involved in fermentation, what end products are produced in humans, is oxygen required? when is it used.