Cellular RespirationCellular Respiration

What is Cellular Respiration?What is Cellular Respiration?

The process of converting food energy The process of converting food energy into ATP energyinto ATP energy

CC66HH1212OO66 + 6 O + 6 O22 → → 6 CO6 CO22 + 6 H + 6 H22O + 36 ATPO + 36 ATP

Why are both Photosynthesis and Cell Why are both Photosynthesis and Cell Respiration important to Ecosystems?Respiration important to Ecosystems?

Light is the ultimate Light is the ultimate source of energy for all source of energy for all ecosystemsecosystems Chemicals cycle and Chemicals cycle and Energy flowsEnergy flowsPhotosynthesis and Photosynthesis and cellular respiration are cellular respiration are opposite reactionsopposite reactions

Why do plants need both Why do plants need both chloroplasts and mitochondria?chloroplasts and mitochondria?

Chloroplasts use Chloroplasts use energy from the energy from the sun to make sun to make glucoseglucose

Mitochondria Mitochondria convert glucose to convert glucose to ATP—the energy ATP—the energy currency of the cellcurrency of the cell

What is ATP?What is ATP?Adenosine TriphosphateAdenosine Triphosphate– 5-Carbon sugar (Ribose)5-Carbon sugar (Ribose)– Nitrogenous base (Adenine)Nitrogenous base (Adenine)– 3 Phosphate groups3 Phosphate groups

Energy currency of the Energy currency of the cellcell

The chemical bonds that The chemical bonds that link the phosphate groups link the phosphate groups together are high energy together are high energy bondsbonds

When a phosphate group When a phosphate group is removed to form ADP is removed to form ADP and P, small packets of and P, small packets of energy are releasedenergy are released

How is ATP used?How is ATP used?As ATP is broken down, it As ATP is broken down, it gives off usable energy to gives off usable energy to power chemical work and power chemical work and gives off some nonusable gives off some nonusable energy as heat.energy as heat.

Synthesizing molecules for Synthesizing molecules for growth and reproductiongrowth and reproductionTransport work – active Transport work – active transport, endocytosis, and transport, endocytosis, and exocytosisexocytosisMechanical work – muscle Mechanical work – muscle contraction, cilia and flagella contraction, cilia and flagella movement, organelle movement, organelle movementmovement

Why use ATP energy and not Why use ATP energy and not energy from glucose?energy from glucose?

Breaking down glucose yields too much energy Breaking down glucose yields too much energy for cellular reactions and most of the energy for cellular reactions and most of the energy would be wasted as heat.would be wasted as heat.

1 Glucose = 686 kcal1 Glucose = 686 kcal1 ATP = 7.3 kcal1 ATP = 7.3 kcal1 Glucose 1 Glucose → → 36 ATP36 ATP

How efficient are cells at converting glucose into How efficient are cells at converting glucose into ATP?ATP?– 38% of the energy from glucose yields ATP, 38% of the energy from glucose yields ATP,

therefore 62% wasted as heat.therefore 62% wasted as heat.

Cellular Respiration is a Redox ReactionCellular Respiration is a Redox Reaction

CC66HH1212OO66 + 6 O + 6 O22 → 6 CO→ 6 CO22 + 6 H + 6 H22OO

OxidationOxidation is the loss of electrons or H is the loss of electrons or H++

ReductionReduction is the gain of electrons or H is the gain of electrons or H++

Glucose is oxidized when electrons and HGlucose is oxidized when electrons and H++ are passed are passed to coenzymes NADto coenzymes NAD++ and FAD before reducing or and FAD before reducing or passing them to oxygen.passing them to oxygen.Glucose is oxidized by a Glucose is oxidized by a series of smaller stepsseries of smaller steps so so that smaller packets of energy are released to make that smaller packets of energy are released to make ATP, rather than one large explosion of energy.ATP, rather than one large explosion of energy.

(Oxidation)

(Reduction)

Loss of hydrogen atoms

Glucose

Gain of hydrogen atoms

Energy

Reduction and Oxidation

OILRIG

Oxidation is losing electrons

Reduction is gaining electrons

Glucose gives off energy as is is oxidized

Reduction and Oxidation

OILRIG Gain or loss of electrons is often in the form of hydrogen. The hydrogen is then passed to a coenzyme such as NAD+

Reduction and Oxidation

What are some common co-enzymes? NAD+ and FAD

NAD+ + 2 H NADH + H+

FAD + 2 H FADH2

Remember that H = 2 electrons and 2H+

Reduction and Oxidation

These co-enzymes are very important for cell respiration because they transfer high-energy electrons to electron transport systems (ETS).

Reduction and Oxidation

As the electrons move from carrier to carrier, energy is released in small quantities.

Electron transport system (ETS)

Generation of ATP

There are two ways to generate ATP

Chemiosmosis

Substrate-Level Phosphorylation

All Types of Molecules can be used All Types of Molecules can be used to form ATP by Cell Respiration: to form ATP by Cell Respiration:

Proteins, Carbohydrates, Proteins, Carbohydrates, and Lipids must first be and Lipids must first be broken down into their broken down into their monomers and absorbed monomers and absorbed in the small intestine.in the small intestine.

Monomers may be Monomers may be further broken down into further broken down into intermediate molecules intermediate molecules before entering different before entering different parts of Cell respiration parts of Cell respiration to ultimately form ATP.to ultimately form ATP.

CarbohydratesCarbohydratesMonosaccharides Monosaccharides

(CH(CH22O)O)

– Major cell nutrient, Major cell nutrient,

produced during PSN, produced during PSN,

raw material for raw material for

other molecules. other molecules.

– 6 Carbon sugars 6 Carbon sugars [Hexoses][Hexoses]

Glucose, Fructose, Glucose, Fructose,

GalactoseGalactose

– 5 Carbon sugars 5 Carbon sugars [Pentose][Pentose]

Deoxyribose, Deoxyribose,

RiboseRibose

Fatty Acids Fatty Acids

Carbon backbone (4 – 24 Carbon backbone (4 – 24

carbon atoms)carbon atoms)

Carboxyl group (- COOH)Carboxyl group (- COOH)

UnsaturatedUnsaturated– One or more double bonds One or more double bonds

in backbone in backbone

SaturatedSaturated– All single bonds in All single bonds in

backbonebackbone

DehydrogenasesDehydrogenasesThey are enzymes that remove a pair of They are enzymes that remove a pair of hydrogen atoms (2 protons + 2 electrons) hydrogen atoms (2 protons + 2 electrons) from the substrate (glucose) oxidizing it. from the substrate (glucose) oxidizing it. The enzyme delivers the 2 electrons along The enzyme delivers the 2 electrons along with one proton to its coenzyme NAD+. with one proton to its coenzyme NAD+. The other proton is released as a hydrogen The other proton is released as a hydrogen ion to the surrounding solution.ion to the surrounding solution.

H-C-OH+NADH-C-OH+NAD++ C=O+NADH+ H C=O+NADH+ H++

Cell Respiration can be divided into 4 Parts:Cell Respiration can be divided into 4 Parts:

1) Glycolysis1) Glycolysis2) Oxidation of Pyruvate / Transition Reaction2) Oxidation of Pyruvate / Transition Reaction3) The Krebs Cycle3) The Krebs Cycle4) The Electron Transport Chain and 4) The Electron Transport Chain and Chemiosmotic PhosphorylationChemiosmotic Phosphorylation

Where do the 4 parts of Cellular Where do the 4 parts of Cellular Respiration take place?Respiration take place?

Glycolysis: Glycolysis: – CytosolCytosol

Oxidation of Oxidation of Pyruvate:Pyruvate:– MatrixMatrix

The Krebs Cycled:The Krebs Cycled:– MatrixMatrix

Electron Transport Electron Transport Chain and Chain and Cheimiosmotic Cheimiosmotic Phosphorylation:Phosphorylation:– CristaeCristae

Parts of the MitochondriaParts of the Mitochondria

Anaerobic Respiration (no oxygen required, cytoplasm)Anaerobic Respiration (no oxygen required, cytoplasm)

1. Glycolysis(substrate level)

Glucose 2 Pyruvate2 ATP 4 ATP (Net 2 ATP)

2 NADH

Aerobic Respiration (oxygen required, mitochondria)Aerobic Respiration (oxygen required, mitochondria)

2. OxidationofPyruvate

2 Pyruvate 2 CO2

2 NADH2 Acetyl CoA

3. Krebs Cycle(substrate level)

2 Acetyl CoA 4 CO2

2 ATP6 NADH2 FADH2

4. ElectronTransportChain

(chemiosmotic)

10 NADH 32 ATP2 FADH2 H2OOxygen

Total: 36 ATP produced

ATP is made in two ways:ATP is made in two ways:1) 1) Substrate Level Substrate Level

PhosphorylationPhosphorylation (glycolysis (glycolysis & Krebs cycle)& Krebs cycle)

2) 2) Chemiosmotic Chemiosmotic PhosphorylationPhosphorylation (electron (electron transport chain)transport chain)

Substrate-Level Substrate-Level Phosphorylation:Phosphorylation:Energy and phosphate are Energy and phosphate are transferred to ADP using an transferred to ADP using an enzyme, to form ATP. enzyme, to form ATP. Phosphate comes from one Phosphate comes from one of the intermediate of the intermediate molecules produced from molecules produced from the breakdown of glucose.the breakdown of glucose.

GlycolysisGlycolysis

Glucose (CGlucose (C66) is split to make ) is split to make 2 Pyruvates (C2 Pyruvates (C33))– 11stst: ATP energy used to phosphorylate : ATP energy used to phosphorylate

glucose (stored energy)glucose (stored energy)– 22ndnd: phosphorylated glucose broken : phosphorylated glucose broken

down into two Cdown into two C33 sugar phosphates sugar phosphates– 33rdrd: the sugar phosphates are oxidized : the sugar phosphates are oxidized

to yield electrons and Hto yield electrons and H++ ions which are ions which are donated to 2 NADdonated to 2 NAD++ → → 2 NADH (stored 2 NADH (stored electron and hydrogen for the Electron electron and hydrogen for the Electron Transport Chain)Transport Chain)

– 44thth: The energy from oxidation is used to : The energy from oxidation is used to make 4 ATP molecules (net 2 ATP)make 4 ATP molecules (net 2 ATP)

This is substrate level phosphorylation This is substrate level phosphorylation because an enzyme transfers because an enzyme transfers phosphate to ADP making ATPphosphate to ADP making ATP

Glycolysis produces very little ATP Glycolysis produces very little ATP energy, most energy is still stored in energy, most energy is still stored in Pyruvate molecules.Pyruvate molecules.

Glucose 2 Pyruvate2 ATP 4 ATP (Net 2 ATP)

2 NADH

Pyruvate Pyruvate DehydrogenaseDehydrogenase catalyzes oxidative catalyzes oxidative decarboxylation of decarboxylation of pyruvate, to form pyruvate, to form acetyl-CoA. The acetyl-CoA. The overall reaction is overall reaction is shown at right. shown at right.

Oxidation of Pyruvate /Transition ReactionOxidation of Pyruvate /Transition Reaction

When Oxygen is present, 2 Pyruvates go to the matrix where they are converted into 2 Acetyl CoA (C2).Multienzyme complex: – 1st: each Pyruvate releases

CO2 to form Acetate. – 2nd: Acetate is oxidized and

gives electrons and H+ ions to 2 NAD+ → 2 NADH.

– 3rd Acetate is combined with Coenzyme A to produce 2 Acetyl CoA molecules.

2 NADH’s carry electrons and hydrogens to the Electron Transport Chain.

2 Pyruvate 2 CO2

2 NADH2 Acetyl CoA

The Krebs Cycle / Citric Acid CycleThe Krebs Cycle / Citric Acid Cycle

8 Enzymatic Steps in Matrix of Mitochondria: Break down and Oxidize each Acetyl CoA (2-C’s) to release 2 CO2 and yield electrons and H+ ions to 3 NAD+ + 1 FAD → 3 NADH + FADH2. This yields energy to produce ATP by substrate level phosphorylation.

The first step of the Krebs cycle combines Oxaloacetate (4 C’s) with Acetyl CoA to form Citric Acid, then the remaining 7 steps ultimately recycle oxalacetate.

Two Turns of the Krebs Cycle are required to break down both Acetyl Coenzyme A molecules.

The Krebs cycle produces some chemical energy in the form of ATP but most of the chemical energy is in the form of NADH and FADH2 which then go on to the Electron Transport Chain.

2 Acetyl CoA 4 CO2

2 ATP6 NADH2 FADH2

NAD vs FADNAD vs FAD

FADFAD ( (FFlavinlavin A Adeninedenine D Dinucleotide) is inucleotide) is a derivative of the B-vitamin a derivative of the B-vitamin riboflavin (dimethylisoalloxazine-riboflavin (dimethylisoalloxazine-ribitol). The flavin ring system ribitol). The flavin ring system undergoes undergoes oxidation/reduction.oxidation/reduction. Whereas NAD+ is a coenzyme that Whereas NAD+ is a coenzyme that reversibly binds to enzymes, FAD is a reversibly binds to enzymes, FAD is a prosthetic groupprosthetic group, that is , that is permanently part of the complex. permanently part of the complex. 

The Electron Transport ChainThe Electron Transport Chain

NADH and FADHNADH and FADH22 produced produced earlier, go to the Electron earlier, go to the Electron Transport Chain.Transport Chain.NADH and FADHNADH and FADH22 release release electrons to carriers/proteins electrons to carriers/proteins embedded in the membrane embedded in the membrane of the cristae. As the of the cristae. As the electrons are transferred, Helectrons are transferred, H++ ions are pumped from the ions are pumped from the matrix to the intermembrane matrix to the intermembrane space up the concentration space up the concentration gradient. Electrons are gradient. Electrons are passed along a series of 9 passed along a series of 9 carriers until they are carriers until they are ultimately donated to an ultimately donated to an Oxygen molecule. Oxygen molecule. ½ O½ O22 + 2 electrons + 2 H + 2 electrons + 2 H++ (from NADH and FADH(from NADH and FADH22) ) → → HH22O. O.

10 NADH 32 ATP2 FADH2 H2OOxygen

http://vcell.ndsu.nodak.edu/animations/etc/movie.htm

Chemiosmotic PhosphorylationChemiosmotic Phosphorylation

Hydrogen ions travel down their concentration gradient through a Hydrogen ions travel down their concentration gradient through a channel protein coupled with an enzyme called channel protein coupled with an enzyme called ATP SynthaseATP Synthase..As HAs H++ ions move into the matrix, energy is released and used to ions move into the matrix, energy is released and used to combine ADP + P combine ADP + P → → ATP.ATP.Hydrogens are recycled and pumped back across the cristae using Hydrogens are recycled and pumped back across the cristae using the Electron Transport Chain.the Electron Transport Chain.ATP diffuses out of the mitochondria through channel proteins to ATP diffuses out of the mitochondria through channel proteins to be used by the cell.be used by the cell.

http://vcell.ndsu.nodak.edu/animations/atpgradient/movie.htm

ATP SynthaseATP SynthaseMultisubunit complex Multisubunit complex with 4 parts:with 4 parts:– RotorRotor – spins as H – spins as H++ ions flow ions flow– StatorStator – holds the rotor and – holds the rotor and

knob complex together in the knob complex together in the cristaecristae

– Internal RodInternal Rod – extends – extends between rotor and knob, spins between rotor and knob, spins when rotor spins which then when rotor spins which then turns the knobturns the knob

– KnobKnob – contains 3 catalytic – contains 3 catalytic sites that when turned change sites that when turned change shape and activate the enzyme shape and activate the enzyme used to make ATPused to make ATP

Review ATP Production:Review ATP Production:

1) Glycolysis 1) Glycolysis → → 2 ATP2 ATP2) Oxidation of Pyruvate 2) Oxidation of Pyruvate → → No No

ATPATP3) The Krebs Cycle 3) The Krebs Cycle → → 2 ATP2 ATP4) The Electron Transport 4) The Electron Transport

Chain and Chemiosmotic Chain and Chemiosmotic Phosphorylation: Phosphorylation: – Each NADH produces 2-Each NADH produces 2-

3 ATP so 10 NADH 3 ATP so 10 NADH →→ 28 ATP28 ATP

– Each FADHEach FADH22 produces 2 produces 2 ATP so 2 FADHATP so 2 FADH22 → → 4 4 ATPATP

Total = 36 ATPTotal = 36 ATP

1 Glucose = 686 kcal1 Glucose = 686 kcal1 ATP = 7.3 kcal1 ATP = 7.3 kcal1 Glucose 1 Glucose → → 36 ATP36 ATPHow efficient are cells at How efficient are cells at converting glucose into converting glucose into ATP?ATP?– 38% of the energy from 38% of the energy from

glucose yields ATP, glucose yields ATP, therefore 62% wasted as therefore 62% wasted as heat (used to maintain heat (used to maintain body temperature or is body temperature or is dissipated)dissipated)

– Ex. Most efficient Cars: Ex. Most efficient Cars: only 25% of the energy only 25% of the energy from gasoline is used to from gasoline is used to move the car, 75% heat.move the car, 75% heat.

Anaerobic Respiration: FermentationAnaerobic Respiration: FermentationIf there is NO oxygen, then cells can make ATP by If there is NO oxygen, then cells can make ATP by FermentationFermentationWithout oxygen, Oxidation of Pyruvate and the Electron Transport Without oxygen, Oxidation of Pyruvate and the Electron Transport Chain do not operate.Chain do not operate.

Glucose Glucose →→ Pyruvate Pyruvate →→ Lactate Lactate NADNAD++ GlycolysisGlycolysis 2 NADH 2 NADH Reduction RxnReduction Rxn or or

2 ATP 2 ATP Alcohol + COAlcohol + CO22

Fermentation yields a net gain of 2 ATP by substrate level Fermentation yields a net gain of 2 ATP by substrate level phosphorylation for every 1 Glucose. (Inefficient)phosphorylation for every 1 Glucose. (Inefficient)

Two Forms of FermentationTwo Forms of Fermentation: : Lactic Acid Fermentation (animals)Lactic Acid Fermentation (animals)Alcohol Fermentation (yeast)Alcohol Fermentation (yeast)