cellular respiration

Advanced BiologyAdvanced Biology

Cellular RespirationCellular Respiration

Energy FlowEnergy Flow

Energy flows into Energy flows into an ecosystem as an ecosystem as sunlight and sunlight and leaves as heatleaves as heat

Light energy

ECOSYSTEM

CO2 + H2O

Photosynthesisin chloroplasts

Cellular respirationin mitochondria

Organicmolecules

+ O2

ATP

powers most cellular work

Heatenergy

Cellular RespirationCellular Respiration

C6H12O6 + 6O2 6CO2 + 6H2O + Energy

Stored in ATP

In cellular respiration the mitochondria break In cellular respiration the mitochondria break down (reduce) glucose releasing its stored energy down (reduce) glucose releasing its stored energy and producing and producing CO2 and and H2O as wastes

The energy is then stored in ATP molecules

Monosaccharide produced

by plants

Oxygen produced by plants during photosynthes

is

Waste CO2 is used by plants to

make more sugars 6.1

Redox ReactionsRedox Reactions

Redox reactionsRedox reactions– Transfer electrons from one reactant to Transfer electrons from one reactant to

another by oxidation and reductionanother by oxidation and reduction In In oxidationoxidation

– A substance A substance loses electronsloses electrons, or is , or is oxidizedoxidized

In In reductionreduction– A substance A substance gains electronsgains electrons, or is , or is

reducedreduced6.2

Redox ReactionsRedox Reactions Examples of redox reactions:Examples of redox reactions:

C6H12O6 + 6O2 6CO2 + 6H2O + Energy

becomes oxidized

becomes reduced

Na + Cl Na+ + Cl–

becomes oxidized(loses electron)

becomes reduced(gains electron)

#1

#2

6.2

Cellular RespirationCellular Respiration

Cellular respiration Cellular respiration oxidizes glucose in a oxidizes glucose in a series of stepsseries of steps

NADNAD+ + accepts accepts electrons from the electrons from the oxidation of glucoseoxidation of glucose

NADH is the reduced NADH is the reduced form of NADform of NAD+ +

NAD+

H

O

O

O O–

O

O O–

O

O

O

P

P

CH2

CH2

HO OHH

HHO OH

HO

H

H

N+

C NH2

HN

H

NH2

N

N

Nicotinamide(oxidized form)

N

6.3

Electron Transport ChainsElectron Transport Chains

From food via NADH

Uncontrolled Reaction Cellular Respiration6.4

Making ATPMaking ATP

Oxidative phosphorylationOxidative phosphorylation – – ATP is ATP is made as the result of an electron transport made as the result of an electron transport chainchain

Substrate-level phosphorylationSubstrate-level phosphorylation – ATP – ATP is made directly when an enzyme transfers is made directly when an enzyme transfers a P (phosphate) to ADPa P (phosphate) to ADP

6.5

ReviewReview

What particles store the energy in What particles store the energy in glucose?glucose?

What molecule carries electrons?What molecule carries electrons? What molecule gains and stores the What molecule gains and stores the

energy from the electrons?energy from the electrons?

The CellThe Cell

Cell Membrane

Cytoplasm

Golgi Apparatus

EndoplasmicReticulum

Nucleus

Mitochondria

3 Phases of Cellular 3 Phases of Cellular RespirationRespiration

GlycolysisGlycolysis– Breaks down glucose into two molecules Breaks down glucose into two molecules

of pyruvateof pyruvate The citric acid cycleThe citric acid cycle

– Completes the breakdown of glucoseCompletes the breakdown of glucose Oxidative phosphorylationOxidative phosphorylation

– Is driven by the electron transport chainIs driven by the electron transport chain– Generates ATPGenerates ATP

6.6

3 Phases of Cellular 3 Phases of Cellular RespirationRespiration

Electronscarried

via NADH

Glycolysis

Glucose Pyruvate

ATP

Electrons carried via NADH and

FADH2

Citric acid cycle

Oxidativephosphorylation:electron transport

andchemiosmosis

ATPATP

Mitochondrion

6.6

GlycolysisGlycolysis

Occurs in the cytoplasm of the cell Occurs in the cytoplasm of the cell

Means “splitting of sugar”Means “splitting of sugar”

Breaks down glucose into pyruvateBreaks down glucose into pyruvate1 6-Carbon glucose 1 6-Carbon glucose

2 3-Carbon sugar 2 3-Carbon 2 3-Carbon sugar 2 3-Carbon pyruvatespyruvates

6.7

ATP is required as activation energy to begin the reactions of glucolysis

ATP is then produced in the payoff phase along with 2NADH

Investment and Payoff

6.8

#1 – Two ATP are added to glucose to produce fructose 1,6-bisphosphate

#2 – Fructose 1,6-bisphosphate is split into two molecules of Glyceraldehyde 3-Phosphate

#3 – The two G3P’s are further oxidized producing 4 ATP (2 Net) and 2 NADH

#4 – G3P has now been completely oxidized to pyruvate

Glycolysis – In Detail

6.9

Before the citric acid cycle can begin Before the citric acid cycle can begin pyruvate must first be converted to acetyl pyruvate must first be converted to acetyl CoACoA

CYTOSOL MITOCHONDRION

NADH+ H+NAD+

2

31

CO2 Coenzyme A

PyruvateAcetyl CoA

S CoA

C

CH3

O

Transport protein

O–

O

O

C

C

CH3

3C 2C

CO2 NADH6.10

= ATP

The Citric Acid CycleThe Citric Acid Cycle Products Products

from one from one acetyl acetyl CoACoA– 3 NADH3 NADH– 1 ATP1 ATP– 1 FADH1 FADH– 2 CO2 CO

6.11

2

2

ReviewReview

How many carbons are left from 1 How many carbons are left from 1 glucose at the beginning of the citric glucose at the beginning of the citric acid cycle?acid cycle?

Electron TransportElectron Transport

NADH and FADH NADH and FADH provide electrons provide electrons for the chainfor the chain

The electrons The electrons transfer is transfer is exergonic because exergonic because they lose energy at they lose energy at each stepeach step

Where does this Where does this energy go?energy go?

2

Electronslide

6.12

Electrons from NADH and FADH are Electrons from NADH and FADH are passed to oxygen, forming waterpassed to oxygen, forming water

Electron transfer causes protein Electron transfer causes protein complexes to pump Hcomplexes to pump H++ from the from the mitochondrial matrix to the mitochondrial matrix to the intermembrane spaceintermembrane space

The resulting HThe resulting H++ gradient gradient– Stores energyStores energy– Drives chemiosmosis in ATP synthaseDrives chemiosmosis in ATP synthase– Is referred to as a proton-motive forceIs referred to as a proton-motive force

Electron TransportElectron Transport 6.12/6.13

The YieldThe Yield

There are three main processes in this metabolic enterpriseThere are three main processes in this metabolic enterprise

Electron shuttlesspan membrane

CYTOSOL 2 NADH

2 FADH2

2 NADH 6 NADH 2 FADH22 NADH

Glycolysis

Glucose

2Pyruvate

2AcetylCoA

Citricacidcycle

Oxidativephosphorylation:electron transport

andchemiosmosis

MITOCHONDRION

by substrate-levelphosphorylation

by substrate-levelphosphorylation

by oxidative phosphorylation, dependingon which shuttle transports electronsfrom NADH in cytosol

Maximum per glucose:About

36 or 38 ATP

+ 2 ATP + 2 ATP + about 32 or 34 ATP

or

6.14

Making ATP without OxygenMaking ATP without Oxygen

Cellular respirationCellular respiration– Relies on oxygen to produce ATP using Relies on oxygen to produce ATP using

the electron transport chainthe electron transport chain FermentationFermentation

– Allows cells to produce ATP in the Allows cells to produce ATP in the absence of oxygenabsence of oxygen

6.15

Fermentation or Fermentation or Respiration?Respiration?

Pyruvate is a key juncture in catabolismPyruvate is a key juncture in catabolismGlucose

CYTOSOL

Pyruvate

No O2 presentFermentation

O2 present Cellular respiration

Ethanolor

lactate

Acetyl CoA

MITOCHONDRION

Citricacidcycle

Alcohol Fermentation

Lactic Acid Fermentation

aerobicanaerobic

2 ADP + 2 P1 2 ATP

GlycolysisGlucose

2 NAD+ 2 NADH

2 Pyruvate

2 Acetaldehyde 2 Ethanol

H

H OH

CH3

C

O –

OC

C O

CH3

H

C O

CH3

CO22

2 ADP + 2 P1 2 ATP

GlycolysisGlucose

2 NAD+ 2 NADH

2 Lactate

O–

C O

C O

CH3O

C O

C OHH

CH3

2 Pyruvate

Alcohol fermentation– Pyruvate is converted Pyruvate is converted

to ethanol in two steps, to ethanol in two steps, one of which releases one of which releases COCO22

Lactic acid fermentationLactic acid fermentation– Pyruvate is reduced, using Pyruvate is reduced, using

NADH, to form lactate as a NADH, to form lactate as a waste productwaste product

6.16

Amino acids

Sugars Glycerol Fattyacids

GlycolysisGlucose

Glyceraldehyde-3- P

Pyruvate

Acetyl CoA

NH3

Citricacidcycle

Oxidativephosphorylation

FatsProteins Carbohydrates Glycolysis and the Glycolysis and the citric acid cycle citric acid cycle connect to many connect to many other metabolic other metabolic pathwayspathways

These pathways These pathways funnel electrons from funnel electrons from many kinds of organic many kinds of organic molecules into molecules into cellular respirationcellular respiration

Organisms use these Organisms use these organic molecules to organic molecules to build other build other substances or to substances or to make ATPmake ATP

6.17