CHAPTER 7: CELLULAR RESPIRATIONCHAPTER 7: CELLULAR RESPIRATION

7-1: 7-1: GlycolysisGlycolysis + + FermentationFermentation 7-2: 7-2: Aerobic RespirationAerobic Respiration

Cellular RespirationCellular Respiration Most foods contain usable Most foods contain usable energyenergy, stored , stored

in complex organic compounds such as:in complex organic compounds such as: ProteinsProteins CarbohydratesCarbohydrates FatsFats

All cells break down organic compounds All cells break down organic compounds into simpler molecules, a process that into simpler molecules, a process that releases releases energyenergy to power cellular to power cellular activitiesactivities

Harvesting Chemical EnergyHarvesting Chemical Energy Cellular RespirationCellular Respiration

Complex process in which cells make Complex process in which cells make ATPATP by by breaking down organic compoundsbreaking down organic compounds• Both Both autotrophsautotrophs + + heterotrophsheterotrophs undergo cell undergo cell

respirationrespiration• Some of the energy is used to make Some of the energy is used to make ATPATP; then ; then

energy used by cells to do energy used by cells to do workwork

Overview of Cellular RespirationOverview of Cellular Respiration Biochemical pathway with PhotosynthesisBiochemical pathway with Photosynthesis

Products + ReactantsProducts + Reactants Redox reactions (‘Redox reactions (‘OILRIGOILRIG’: ’: ee-- = = energyenergy))

EquationEquation CC66HH1212OO66 + + 66 O O22 66 CO CO22 + + 66 H H22O + O + NRGNRG

Two Stages:Two Stages: GlycolysisGlycolysis Aerobic RespirationAerobic Respiration

Glycolysis Glycolysis

Biochemical pathway in which Biochemical pathway in which oneone 6- 6-C molecule of C molecule of glucoseglucose is oxidized to is oxidized to produce produce twotwo 3-C molecules of 3-C molecules of pyruvic pyruvic acidacid Catalyzed by specific enzymesCatalyzed by specific enzymes Reactions occur within Reactions occur within cytosolcytosol of cells of cells AnaerobicAnaerobic process process

4 Major Steps of 4 Major Steps of GlycolysisGlycolysis

1.1. Two phosphate groups are attached to Two phosphate groups are attached to one molecule of one molecule of glucoseglucose, forming a new , forming a new 6-C compound. 6-C compound. ATPATP supplies the supplies the phosphate groupsphosphate groups

2.2. The 6-C compound splits into 2 3-C The 6-C compound splits into 2 3-C compounds called compounds called G3PG3P

GlycolysisGlycolysis (cont.)(cont.)3.3. The 2 The 2 G3PG3P molecules are oxidized and each molecules are oxidized and each

receives a phosphate group creating two new receives a phosphate group creating two new 3-C compounds. During the oxidation, 3-C compounds. During the oxidation, NADNAD++ picks up electrons lost by the oxidation of each picks up electrons lost by the oxidation of each G3PG3P compound ( compound (redoxredox) - ) - NADHNADH

4.4. All phosphate groups are removed which All phosphate groups are removed which makes 2 new 3-C compounds calledmakes 2 new 3-C compounds called pyruvic pyruvic acidacid. Each phosphate groups is added to ADP . Each phosphate groups is added to ADP to make four molecules of to make four molecules of ATPATP

Net Yield of NRG?Net Yield of NRG? GlycolysisGlycolysis only produces 2 only produces 2 ATPATP molecules molecules

to be used by the cell from one molecule to be used by the cell from one molecule of of glucoseglucose

*Even though 4 ATP are produced at Step *Even though 4 ATP are produced at Step 4, 2 ATP were used in Step 1*4, 2 ATP were used in Step 1*

Recap of Recap of GlycolysisGlycolysis

Video Recap…Video Recap…

Glycolysis

FermentationFermentation If oxygen is present after If oxygen is present after glycolysisglycolysis, , pyruvic acid pyruvic acid

enters enters Aerobic RespirationAerobic Respiration In anaerobic conditions, some cells can convert In anaerobic conditions, some cells can convert

pyruvic acid pyruvic acid into other compounds through into other compounds through additional biochemical pathwaysadditional biochemical pathways

GlycolysisGlycolysis + additional pathways = + additional pathways = FermentationFermentation Takes place in the Takes place in the cytosolcytosol of cells of cells Does not produce any Does not produce any ATPATP Helps regenerate Helps regenerate NADNAD++, which is used throughout , which is used throughout

cellular respirationcellular respiration Differs in enzymes used and compounds madeDiffers in enzymes used and compounds made Two most common: Two most common: Lactic Acid Lactic Acid + + AlcoholicAlcoholic

Lactic Acid FermentationLactic Acid Fermentation

Pyruvic acid Pyruvic acid converted into converted into lactic acidlactic acid L.A.F. L.A.F. involves the transfer of one involves the transfer of one HH atom atom

and one free and one free protonproton (H(H++)) In the process, In the process, NADNAD++ is regenerated and can is regenerated and can

be used again in be used again in glycolysisglycolysis

Lactic Acid FermentationLactic Acid Fermentation

L.A.F. (cont.)L.A.F. (cont.) L.A.F.L.A.F. used by microorganisms in used by microorganisms in

manufacturing dairy products such as manufacturing dairy products such as yogurt and cheeseyogurt and cheese

L.A.F. (cont.)L.A.F. (cont.) L.A.F.L.A.F. also occurs in your muscle during also occurs in your muscle during

strenuous exercisestrenuous exercise During this type of exercise, muscle cells use During this type of exercise, muscle cells use

up Oup O22 much more quickly than it can be much more quickly than it can be

delivered to themdelivered to them As OAs O22 depletes, depletes, aerobic respiration aerobic respiration is changed is changed

to to L.A.F.L.A.F. The cytosol more acidic and muscles become The cytosol more acidic and muscles become

fatigued or sorefatigued or sore EventuallyEventually lactic acid lactic acid gets converted back togets converted back to

pyruvic acid pyruvic acid by the by the liverliver

Alcoholic FermentationAlcoholic Fermentation

Pyruvic acid Pyruvic acid converted into converted into ethyl alcohol ethyl alcohol ++ COCO22

Alc. Fermentation (cont.)Alc. Fermentation (cont.)1.1. A COA CO22 molecule is removed from molecule is removed from pyruvic pyruvic

acidacid, leaving a 2-C compound, leaving a 2-C compound

2.2. Two Hydrogen atoms are added to the 2-Two Hydrogen atoms are added to the 2-C compound to form C compound to form ethyl alcohol ethyl alcohol (ethanol)(ethanol)

H atoms transferred from NADH and HH atoms transferred from NADH and H++, , regenerating regenerating NADNAD++ for use in for use in glycolysisglycolysis

Alc. Fermentation (cont.)Alc. Fermentation (cont.)

Alc. Fermentation (cont.)Alc. Fermentation (cont.) AFAF by yeast cells to make beer + by yeast cells to make beer +

winewine These microorganisms eat the These microorganisms eat the

SUGARSUGAR in fruit or grains which in fruit or grains which cause fermentation to take placecause fermentation to take place

AFAF also used in making bread. also used in making bread. Rises due to loss of CORises due to loss of CO22

Fermentation (anaerobic pathways)Fermentation (anaerobic pathways)

Efficiency of GlycolysisEfficiency of Glycolysis GlycolysisGlycolysis alone is only alone is only 2%2% efficient at efficient at

extracting energy from extracting energy from glucoseglucose So where is the rest of the energy?So where is the rest of the energy?

PYRUVIC ACID!!!!!!!PYRUVIC ACID!!!!!!! Early Earth + Early Earth + GlycolysisGlycolysis??

Some early unicellular organisms, such as bacteria, Some early unicellular organisms, such as bacteria, might have been able to survive on using might have been able to survive on using glycolysisglycolysis for energy productionfor energy production

Most organisms Most organisms needneed moremore energyenergy (>(>22 ATPATP), so ), so they needed to find a better energy-producing they needed to find a better energy-producing mechanismmechanism

• AEROBIC RESPIRATION!!!AEROBIC RESPIRATION!!!