bt213 lec8 cellular+respiration

8/8/2019 BT213 Lec8 Cellular+Respiration

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Cellular Respiration

Mitochondria: Structure and

Function

Metabolism of carbohydrates

Glycolysis,

Citric Acid cycleETC (Electron transport chain)

Oxidative phosphorylation


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The process by which the chemical energy of "food"

molecules is released and partially captured in the form ofATP.

Fuels:

Carbohydrates

FatsProteins

Glucose is most commonly used

Cellular respiration


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Cells use oxygen to break down the sugar glucoseand store its energy in molecules of adenosine

triphosphate (ATP).


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What Is ATP?

Energy used by all CellsEnergy used by all Cells

Adenosine TriphosphateAdenosine Triphosphate

Organic molecule containing highOrganic molecule containing high--energy Phosphate bondsenergy Phosphate bonds


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Chemical Structure of ATP

3 Phosphates Ribose Sugar

Adenine Base


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What Does ATP Do for You?

It supplies YOU withIt supplies YOU with ENERGY!ENERGY!


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How Do We Get Energy From ATP?

By breaking theBy breaking the

highhigh-- energyenergybonds betweenbonds between

thethe last twolast two

phosphates inphosphates inATPATP

Copyright Cmassengale


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What is the Process Called?

HYDROLYSIS (Adding HHYDROLYSIS (Adding H22O)O)

H2O


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How Does That Happen?

An Enzyme!An Enzyme!


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How is ATP Re-Made?

The reverse of the previous processThe reverse of the previous process

occurs.occurs.

Another Enzyme isAnother Enzyme isused!used!

ATP SynthetaseATP Synthetase


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The ADP-ATP Cycle

ATPATP--asease ATPATPSynthetaseSynthetase


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W

hen is ATP Made in the Body?

During a ProcessDuring a Process

calledcalled CellularCellularRespirationRespiration thatthattakes place intakes place in

bothboth Plants &Plants &AnimalsAnimals


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Cellular Respiration

Includes pathways that requireIncludes pathways that requireoxygenoxygen

Glucose isGlucose is oxidizedoxidized and Oand O22 isis reducedreduced Glucose breakdown is therefore anGlucose breakdown is therefore an

oxidationoxidation--reductionreduction reactionreaction

Breakdown of one glucose results inBreakdown of one glucose results in36 to 38 ATP36 to 38 ATP moleculesmolecules


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Overall Equation for Cellular

Respiration

6CO6CO22 +

6H+6H

220 + 36

0 + 36--3838ATPsATPs

CC66HH1212OO66 +

6O+6O22

YIELDSYIELDS


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What Type of Process is Cellular

Respiration?

An OxidationAn Oxidation--Reduction Process orReduction Process or

REDOX ReactionREDOX Reaction Oxidation of GLUCOSEOxidation of GLUCOSE ----> CO> CO

22+H+H

22OO (e(e--

removed from Cremoved from C66HH1212OO66))

ReductionReduction OO22 toto HH22OO (e(e--

passed to Opassed to O22))


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What Carries the Electrons?

Electron carriers

NADNAD++

((nicotinadeninenicotinadeninedinucleotidedinucleotide) acts as) acts as

the energy carrierthe energy carrier NADNAD++ is ais a coenzymecoenzyme

ItsIts ReducedReduced totoNADHNADHwhen it pickswhen it picksup two electronsup two electronsand one hydrogenand one hydrogenionion


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Are There Any Other Electron

Carriers?

YES! AnotherYES! AnotherCoenzyme!Coenzyme!

FAD+FAD+ (Flavin(Flavinadenineadeninedinucleotide)dinucleotide)

ReducedReduced totoFADHFADH

22


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Other Cellular Respiration Facts

Metabolic PathwayMetabolic Pathway that breaks downthat breaks down

carbohydratescarbohydrates Process isProcess is ExergonicExergonic as Highas High--energy Glucoseenergy Glucose

is broken into COis broken into CO22

and Hand H22OO

Process is alsoProcess is also CatabolicCatabolic because largerbecause largerGlucose breaks into smaller moleculesGlucose breaks into smaller molecules


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What are the Stages of CellularRespiration?

GlycolysisGlycolysis

The Krebs CycleThe Krebs Cycle

The Electron Transport Chain +The Electron Transport Chain +OxidativeOxidative phosphorylationphosphorylation


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Where Does Cellular Respiration

Take Place?

It actually takesIt actually takesplace in twoplace in two

parts of the cell:parts of the cell:

Glycolysis occursGlycolysis occurs

in the Cytoplasmin the CytoplasmKrebs Cycle &Krebs Cycle &ETC TakeETC Takeplace inplace inthe Mitochondriathe Mitochondria



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Review of Mitochondria Structure

SmoothSmooth outerouterMembraneMembrane

FoldedFolded innerinnermembranemembrane

Folds calledFolds called CristaeCristae

Space inside cristaeSpace inside cristaecalled thecalled the MatrixMatrix



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intermembranespace inner

membrane

outer

membrane

matrix

cristae

Mitochondria Structure Double membrane energy harvesting organelle

smooth outer membrane

highly folded inner membrane

cristae

intermembrane space fluid-filled space between membranes

matrix

inner fluid-filled space

DNA, ribosomes

enzymes

mitochondrialDNA

What cells would have alot of mitochondria?


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Mitochondria Function

What does this tell us about the

evolution of eukaryotes?

Endosymbiosis!

Dividing mitochondria

Who else divides like that?

Advantage of highly folded inner

membrane?

More surface area for membrane-

bound enzymes

Membrane-bound proteins

Enzymes

Oooooh!Form fitsfunction!


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Diagram of the Process

Occurs in

Cytoplasm

Occurs in Matrix

Occurs across

Cristae



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1 Glycolysis

2 Oxidative decarboxylation of pyruvate

3 Citric Acid cycle

4 Electron Transport Chain (ETC) and Oxidative

phosphorylation

Cellular respiration

Four steps


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1 Glycolysis: occurs in cytosol outside mitochondria

2 Oxidative decarboxylation of pyruvate

(grooming phase/migration from cytosol to matrix)

3 Citric Acid cycle (Krebs cycle)Occurs in matrix of mitochondria

4 Electron Transport Chain and Oxidative

Phosphorylation (chemiosmosis)

(inner mitochondrial membrane)

Break down of Cellular respiration


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Glucose +2NAD+ +2Pi +2ADP 2 Pyruvate +2NADH+2ATP +2H2O

C6 C3


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Glucose

Glucose-6-phosphate = C6

Fructose-6-phosphate = C6+P

Fructose-1,6-bisphosphate = C6+PP

Glyceraldehyde 3-phosphate = 2xC3+P

1,3-bisphosphoglycerate = 2xC3+PP

3-phosphoglycerate = 2xC3+P

Phosphoenolpyruvate = 2xC3+P

Pyruvate = 2xC3

ATP

ADP

ATP

ADP

2NAD+

2NADH

2ADP

2ATP

-2ATP

+4 ATP

+2 NADP

For each Glucose MoleculeTotal: 2ATP +2NADH+2 Pyruvate

1. Glycolysis

2ADP

2ATP

2H2O


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(Nicotinamide adenine dinucleotide)


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2. Oxidative Decarboxylation of Pyruvate(Grooming phase)


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2. Pyruvate decarboxylation

Pyruvate + CoA + NAD+ Acetyl-CoA + CO2 + NADH

Occurs in Matrix of MitochondriaMatrix contains Pyruvate Dehydrogenase,

2C3C

NADH


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Acetyl-CoA enters the Kerbs cycle

Krebs cycle:

Aerobic process

Complete oxidation of glucose derivatives

To CO2

and H2O


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Krebs (citric acid) cycle / TCA (tricarboxylic acid) cycle


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Total 8 steps:

All steps reversible

Only three irreversible

Step 1, Step 3, Step 4

TCA cycle

1. Citratesynthase

2. Aconitase

2. Aconitase

3. Isocitratedehydrogenase

4. E-ketoglutaratedehydogenase

5. Succinyl-CoAsynthase

6. Succinatedehydrogenase

7. Fumarase

8. Malatedehydrogenase


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Krebs cycleproduces large

quantities of

electron carriers NADH

FADH2

go to Electron

Transport Chain

Electron Carriers = Hydrogen Carriers

Whats soimportant aboutelectron carriers?

H+

H+ H+

H+

H+ H+H

+

H+

H+

ATP

ADP

+ Pi


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H+

H+ H+

H+

H+H+

H+H+H+And how do we do that?

ATP

ADP P+

Set up a H+ gradient

allow H+ to flow

through ATP synthase

powers bonding

of Pi to ADP

ADP + Pi p ATP


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4. Oxidative phosphorylation

Oxidative phosphorylation is the process in which

ATP is formed as a result of transfer of electrons

from NADH or FADH2 to O2 by a series of electron

carriers.

What happens during oxidative phosphorylation?


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What happens during oxidative phosphorylation?

1. Electrons are transferred from NADH/FADH2 (e-donor) to O2 (e

-

acceptor).2. Carried out by a series of protein complexes.

3. Protein complexes are present on the inner membrane of

mitochondria.

4. These linked sets of enzymes are called electron transport chains

(ETC).

5. Energy is released during flow of electrons in ETC.

6. This energy is used to transport H+ from matrix to intermembrane

space

7. As a result of this potential energy is generated in the form of H+

gradient.

8. A large enzyme called ATP synthase present on the inner membrane ofmitochondria

9. ATPase uses this potential energy to generate ATP/ Synthesis ATP

10. O2 in the end accepts electron and H+ and forms H2O


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The respiratory chain

Mitochondrial electron transport chain

Four protein complex

Three are proton pumps

Proton from matrix to intermembrane space1.NADH-coenzyme Q oxidoreductase (complex I)

2.Succinate-Q oxidoreductase (complex II) (not a proton pump)

3.Q-cytochrome c oxidoreductase (complex III)

4. Cytochrome c oxidase (complex IV)

Electron flow within these complexes leads tothe transport of protons across the the inner

mitrochondrial membrane


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The respiratory chain

Mitochondrial electron transport chain


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Succinate-Q oxidoreductase (complex II)

Succinate dehydrogenase

Only enzyme that is part of both the citric acid cycle and the electron

transport chain

Succinate

dehydrogenase

Oxidative phosphorylation


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Complex I = NADH dehydrogenase

Complex III = succinate-

ubiquinone

oxidoreductase

Complex IV = cytochrome c

oxidoreductase

Coenzyme Q/

ubiquinone

Cytochrome cOxidative phosphorylation


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Respiration-linked H+ pumping out of the matrix conserves some of the freeenergy of spontaneous e transfers as potential energy of an electrochemicalH+

gradient.

matrix

innermembrane

outermembrane

inter-membrane

space

mitochondrion

cristae

Conventional view ofmitochondrial structure isat right.

Respiratory chain is incristae of the inner

membrane. Spontaneous electron

transferthrough

respiratory chain complexes I, III & IV is coupled to H+ ejection from thematrix to the intermembrane space.


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A total of10H+ are ejected from the mitochondrial matrix per 2 e

transferred from NADH to oxygen via the respiratory chain.

Matrix

H+

+NADHNAD++2H+ 2H++O2 H2O

2e

I Q III IV

+ +

4H+ 4H+ 2H+

Intermembrane Space

cytc

Spontaneouselectron flow

through each ofcomplexes I, III,& IV is coupledto H+ ejectionfrom the

matrix.


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Net Energy Yield from the Oxidation of glucose molecule

From Glycolysis: 2 2 TP

From Pyruvate ecarb. 2

From TC : 2FADH +6NADH +2GTP

ETC:

3ATP/NADH

2ATP/FADH

+4ATP +30ATP

+38ATP T TAL


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Pyruvate Kinase


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1,3-bisphosphoglycerate 3-phosphoglycerate

ADP ATP

Phosphoglycerate

Kinase


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Production of ATP in cells

Two Processes

A.Substrate level Phosphorylation

B.Chemiosmosis:

Production of ATP is coupled to the diffusion of

H+ ions across a selectively-permeable

membrane.

Chloroplast (Photophosphorylation) Mitochondria (Oxidative phosphorylation)


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cellular respiration


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Thus, glycolysis and the Krebs are catabolic

pathways that funnel high-energy electrons

from allkinds of food molecules into theelectron transport chain, which powers ATP

syntesis.

bt213 lec8 cellular+respiration

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