Cellular Respiration

Producing ATPProducing ATP

from the energyfrom the energy

in foodin food

An Overview

ATP is immediate source of energy used by ATP is immediate source of energy used by cellscells

Energy in ATP held in phosphodiester Energy in ATP held in phosphodiester bondsbonds

Most energy release in cells results from Most energy release in cells results from redox rxns. involving Glucoseredox rxns. involving Glucose

CC66HH1212OO66 + O + O22 --> 6 CO --> 6 CO22 + 6 H + 6 H22O + energyO + energy

40% of energy in Glucose is converted to 40% of energy in Glucose is converted to usable energy in ATPusable energy in ATP

Production of ATP and other organic Production of ATP and other organic molecules is endergonic and require a molecules is endergonic and require a constant input of energy to continue.constant input of energy to continue.

The source of that energy is the sun.The source of that energy is the sun. Photosynthesis is essentially the opposite of Photosynthesis is essentially the opposite of

Cellular Respiration.Cellular Respiration. Energy flows from sun to autotrophs to Energy flows from sun to autotrophs to

heterotrophs.heterotrophs. All energy is lost eventually as work or heat.All energy is lost eventually as work or heat.

Cellular Respiration

THE BEGINNINGTHE BEGINNING

**GLYCOLYSISGLYCOLYSIS

Glycolysis

Activation of GlucoseActivation of Glucose 1 ATP used to add “P” to Glucose1 ATP used to add “P” to Glucose forms Glucose Phosphateforms Glucose Phosphate

Fructose Phosphate then formedFructose Phosphate then formed 1 ATP - P = 1 ADP + P1 ATP - P = 1 ADP + P

Formation of Sugar DiphosphateFormation of Sugar Diphosphate 1 ATP used to add “P” to Fructose Phosphate1 ATP used to add “P” to Fructose Phosphate

Forms Sugar Diphosphate (sugar and two “P”’s)Forms Sugar Diphosphate (sugar and two “P”’s) 1 ATP - P = 1 ADP + P1 ATP - P = 1 ADP + P

Formation and Oxidation of G3PFormation and Oxidation of G3P Sugar Diphosphate (6 C) into two 3 C Sugar Diphosphate (6 C) into two 3 C

moleculesmolecules 1 into G3P1 into G3P Other 3 C becomes a different 3 C, but is then Other 3 C becomes a different 3 C, but is then

converted into G3Pconverted into G3P Both G3P’s lose an HBoth G3P’s lose an H

• Accepted by NAD to make 2 NADH’sAccepted by NAD to make 2 NADH’s

• High energy level eHigh energy level e--’s carried by the H’s’s carried by the H’s

• Some of the energy used to make 2 ATP’sSome of the energy used to make 2 ATP’s

Formation of PyruvateFormation of Pyruvate 3 more reactions make two Pyruvate molecules3 more reactions make two Pyruvate molecules The energy released from these reactions used The energy released from these reactions used

to make 2 ATP’sto make 2 ATP’s Two CTwo C33HH44OO33 = 6 C’s, 8 H’s, 6 O’s (just 4 H’s = 6 C’s, 8 H’s, 6 O’s (just 4 H’s

removed from Glucose, Cremoved from Glucose, C66HH1212OO6.6.

Summary of Glycolysis Glucose split into two 3 C’sGlucose split into two 3 C’s

2 ATP’s used for activation energy2 ATP’s used for activation energy 2 molecules NADH produced (+ 2 H2 molecules NADH produced (+ 2 H++)) 4 ATP’s made (net gain of 2 ATP’s)4 ATP’s made (net gain of 2 ATP’s)

Pyruvate is the 3 C madePyruvate is the 3 C made Will next enter Kreb’s Cycle if Oxygen is availableWill next enter Kreb’s Cycle if Oxygen is available Will undergo fermentation if no Oxygen is availableWill undergo fermentation if no Oxygen is available

Occurs in cytoplasmOccurs in cytoplasm No oxygen No oxygen requiredrequired (but can be present) (but can be present)

The Oxidation of Pyruvate

A necessary first step prior toA necessary first step prior to

eithereither

The Citric Acid Cycle or The Citric Acid Cycle or FermentationFermentation

Oxidation of Pyruvate

2 e2 e - - and their associated H released and their associated H released 1 e1 e - - from each Pyruvatefrom each Pyruvate Accepted by 2 NAD’s to form 2 NADH’s Accepted by 2 NAD’s to form 2 NADH’s

A C also released from each pyruvateA C also released from each pyruvate forms two COforms two CO22’s’s

Results in formation of two acetyl groupsResults in formation of two acetyl groups

The Citric Acid Cycle

Occurs in mitochondriaOccurs in mitochondria An aerobic processAn aerobic process Begins with acetyl (or Pyruvate if you Begins with acetyl (or Pyruvate if you

include the oxidation of pyruvate as part of include the oxidation of pyruvate as part of this process)this process)

Ends with COEnds with CO22 ,H ,H22O, NADH and FADHO, NADH and FADH22

and some ATP being producedand some ATP being produced

The process

Acetyl groups combine with a coenzyme Acetyl groups combine with a coenzyme the coenzyme is CoAthe coenzyme is CoA just “hanging around” in mitochondriajust “hanging around” in mitochondria forms AcetylCoAforms AcetylCoA

AcetylCoA joins a 4C compound already AcetylCoA joins a 4C compound already present present The 4 C is oxaloacetic AcidThe 4 C is oxaloacetic Acid forms Citric Acid (6C)forms Citric Acid (6C)

Citric Acid undergoes two rxns to form Citric Acid undergoes two rxns to form isocitric acid isocitric acid

Isocitric Acid is oxidizedIsocitric Acid is oxidized The H’s released are accepted by NAD and The H’s released are accepted by NAD and

FADFAD forms 4 NADH and two FADHforms 4 NADH and two FADH22

some of the energhy used to form two more ATP some of the energhy used to form two more ATP moleculesmolecules

Forms Fumaric AcidForms Fumaric Acid Fumaric Acid undergoes 2 rxnsFumaric Acid undergoes 2 rxns

Forms Oxaloacetic AcidForms Oxaloacetic Acid Combines with AcetylCoA to form Citric AcidCombines with AcetylCoA to form Citric Acid The whole darn thing happens again!The whole darn thing happens again! Two more NADH’s producedTwo more NADH’s produced

2NADH produce in the Oxidation of 2NADH produce in the Oxidation of PyruvatePyruvate

2ATP’s produced in Citric Acid Cycle2ATP’s produced in Citric Acid Cycle 6 NADH and 2 FADH6 NADH and 2 FADH22 also produced in also produced in

Citric Acid CycleCitric Acid Cycle Add that to the net gain of 2 ATP and 4 Add that to the net gain of 2 ATP and 4

NADH produced in glycolysisNADH produced in glycolysis 4ATP4ATP 10 NADH10 NADH 2 FADH2 FADH22

Electron Transport Chain

Utilizing the energy held in NADH and Utilizing the energy held in NADH and FADHFADH22 previously produced to make ATP previously produced to make ATP

Produced by chemiosmosis Produced by chemiosmosis Gradient produced b/w the area within the Gradient produced b/w the area within the

inner and outer mitochondrial membrane and inner and outer mitochondrial membrane and inside the mitochondriainside the mitochondria

2 NADH from glycolysis were actively 2 NADH from glycolysis were actively transported in (required 1 ATP each)transported in (required 1 ATP each)

The ETC

High energy e High energy e - - ’s carried by NADH and FADH’s carried by NADH and FADH22

transported out of inner mitochondrial membrane transported out of inner mitochondrial membrane into area b/w inner and outer membrane by into area b/w inner and outer membrane by cytochromes embedded in the membrane.cytochromes embedded in the membrane. protons followprotons follow ee - - accepted by Oxygen to form H accepted by Oxygen to form H22OO

creates proton conc. gradientcreates proton conc. gradient Protons move back across membrane in response Protons move back across membrane in response

to gradientto gradient Movement coupled to production of ATPMovement coupled to production of ATP

The Balance Sheet from ETC Each NADH drives synthesis of 3 ATPEach NADH drives synthesis of 3 ATP

10 NADH from glycolysis, oxidation of pyruvate and 10 NADH from glycolysis, oxidation of pyruvate and the citric acid cyclethe citric acid cycle

30 ATP30 ATP but the NADH’s from glycolysis cost 1 ATP each to but the NADH’s from glycolysis cost 1 ATP each to

transport (- 2 ATP)transport (- 2 ATP)

Each FADHEach FADH22 drives synthesis of 2 ATP drives synthesis of 2 ATP 2 FADH2 FADH22 ‘s from Citric acid cycle ‘s from Citric acid cycle

4 ATP4 ATP Net gain from ETC = 32 ATPNet gain from ETC = 32 ATP

Overview of Oxidative Metabolism GlycolysisGlycolysis

2ATP (net gain), 2 NADH2ATP (net gain), 2 NADH anaerobic, in cytoplasmanaerobic, in cytoplasm

Oxidation of PyruvateOxidation of Pyruvate 2 NADH2 NADH

Citric Acid CycleCitric Acid Cycle 2ATP, 6 NADH, 2 FADH2ATP, 6 NADH, 2 FADH22

aerobic, in mitochondriaaerobic, in mitochondria ETCETC

32 ATP (net gain), H32 ATP (net gain), H22O O

in christae of mitochondriain christae of mitochondria

Fermentation

Anaerobic Respiration:Anaerobic Respiration:

allowing Glycolysis toallowing Glycolysis to

continue without Ocontinue without O22

Alcoholic Fermentation Pyruvate from glycolysis is oxidizedPyruvate from glycolysis is oxidized

forms acetylforms acetyl COCO22 also formed also formed

Acetyl combines with H from NADH (from gly)Acetyl combines with H from NADH (from gly) forms ethyl alcoholforms ethyl alcohol also forms NAD to be used in glycolysisalso forms NAD to be used in glycolysis

Alcohol becomes toxic @ 12 %Alcohol becomes toxic @ 12 % ceases fermentationceases fermentation thats why fermented drinks have max alcohol of 12%thats why fermented drinks have max alcohol of 12%

Uses: wine, brewing, bakingUses: wine, brewing, baking

Lactic Acid Fermentation

Pyruvate from glycolysis doesnt get oxidizedPyruvate from glycolysis doesnt get oxidized an enzyme helps to bond H from NADH to an enzyme helps to bond H from NADH to

pyruvatepyruvate forms Lactic Acid - “Ooooh feel the burn!”forms Lactic Acid - “Ooooh feel the burn!” makes NAD available for glycolysis to continuemakes NAD available for glycolysis to continue

Occurs in aerobic cells under OOccurs in aerobic cells under O22 stress - muscle stress - muscle

Also occurs in certain other microorganismsAlso occurs in certain other microorganisms sour cream, yogurtsour cream, yogurt vinegarvinegar