Cellular RespirationCellular Respiration

Textbook Chapter 8Textbook Chapter 8

Review Book Topic 2Review Book Topic 2

Cellular RespirationCellular Respiration

Living things rely on the chemical Living things rely on the chemical energy stored in the food they digestenergy stored in the food they digest

– Energy (eEnergy (e--) released from the breakdown ) released from the breakdown of glucose is used to combine ADP + Pof glucose is used to combine ADP + Pii to to form ATPform ATP

Occurs in autotrophs and heterotrophs Occurs in autotrophs and heterotrophs in the mitochondriain the mitochondria

There are two types of cellular There are two types of cellular respirationrespiration

– AerobicAerobic

– AnaerobicAnaerobic

First step is the same for all organismsFirst step is the same for all organisms

– GlycolysisGlycolysis

Anaerobic RespirationAnaerobic Respiration

Does not require oxygen (ODoes not require oxygen (O22))

Cell receives very little of the chemical Cell receives very little of the chemical energy in glucoseenergy in glucose

Ex. Yeast, bacteriaEx. Yeast, bacteria

Only carries on glycolysis and Only carries on glycolysis and fermentation steps of cellular respirationfermentation steps of cellular respiration

Aerobic RespirationAerobic Respiration

Requires oxygen (ORequires oxygen (O22) from the atmosphere ) from the atmosphere or from the water in which it is dissolvedor from the water in which it is dissolved

Glucose is completely broken down into Glucose is completely broken down into carbon dioxide and watercarbon dioxide and water

Allows the maximum amount of energy to Allows the maximum amount of energy to be removed from glucosebe removed from glucose

Ex. Eukaryotic organisms (humans, plants, Ex. Eukaryotic organisms (humans, plants, etc.)etc.)

GlycolysisGlycolysis

Splitting of glucose (6-carbons) into Splitting of glucose (6-carbons) into two pyruvic acid molecules (3-carbons)two pyruvic acid molecules (3-carbons)

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

Begins with phosphorylationBegins with phosphorylation

– Two phosphates bond to one glucose Two phosphates bond to one glucose molecule using energy from the molecule using energy from the breakdown of ATPbreakdown of ATP

– Glucose is split in half to form PGAL Glucose is split in half to form PGAL (phosphoglyceraldehyde)(phosphoglyceraldehyde)

– PGAL loses electrons to become PGAL loses electrons to become pyruvic acidpyruvic acid

For each pyruvic acid molecule producedFor each pyruvic acid molecule produced

– 2 ATP molecules are formed2 ATP molecules are formed

– NADNAD++ is converted to NADH is converted to NADH

Net energy output of glycolysisNet energy output of glycolysis

– 4 ATP molecules produced for every glucose 4 ATP molecules produced for every glucose moleculemolecule

– 2 NADH (used later when O2 NADH (used later when O22 is present to form is present to form additional energy)additional energy)

FermentationFermentation (Anaerobic)(Anaerobic)

In anaerobic respiration, all energy In anaerobic respiration, all energy obtained by the cell is from the process obtained by the cell is from the process of glycolysis of glycolysis

No additional ATP is produced by any No additional ATP is produced by any other reactions carried out by the cellother reactions carried out by the cell

Pyruvic acid is changed into other Pyruvic acid is changed into other compoundscompounds

– Ex. Yeast - ethyl alcohol and carbon Ex. Yeast - ethyl alcohol and carbon dioxidedioxide

COCO22 causes bread to rise causes bread to rise

Ethyl alcohol is used to make wine, Ethyl alcohol is used to make wine, beer, liquorbeer, liquor

– Ex. Bacteria – lactic acidEx. Bacteria – lactic acid

Occurs within the mitochondria of Occurs within the mitochondria of the cellthe cell

– Reactions occur Reactions occur on the inside or on the inside or the surface of the the surface of the inner membraneinner membrane

Pyruvic Acid BreakdownPyruvic Acid Breakdown (Aerobic)(Aerobic)

Pyruvic acid breaks down into Pyruvic acid breaks down into

– Carbon dioxideCarbon dioxide

– NADHNADH

– Acetyl CoA Acetyl CoA

2-carbon compound combined 2-carbon compound combined with coenzyme A (CoA)with coenzyme A (CoA)

Acetyl CoA enters the Krebs cycleAcetyl CoA enters the Krebs cycle

Krebs CycleKrebs Cycle (Aerobic)(Aerobic)

Each turn of the Krebs cycle:Each turn of the Krebs cycle:

– Requires 1 molecule of acetyl CoARequires 1 molecule of acetyl CoA

– Yields 2 molecules of carbon dioxide, Yields 2 molecules of carbon dioxide, 3 molecules of NADH, 1 molecule of 3 molecules of NADH, 1 molecule of FADHFADH22

– Produces only 1 ATP moleculeProduces only 1 ATP molecule

For each glucose molecule the For each glucose molecule the Krebs cycle turns twiceKrebs cycle turns twice

– Overall net output of 2 ATPOverall net output of 2 ATP

Almost all the chemical energy Almost all the chemical energy removed from the pyruvic acid is removed from the pyruvic acid is carried by the electrons producedcarried by the electrons produced

All remaining energy released by the All remaining energy released by the breakdown of glucose is carried by the breakdown of glucose is carried by the electrons in NADH and FADHelectrons in NADH and FADH22

– Carried out by the electron transport chain Carried out by the electron transport chain to release energy from NADH and FADHto release energy from NADH and FADH22

– Energy (eEnergy (e--) is used to pump H) is used to pump H++ ions across ions across the mitochondrial membrane (just like in the mitochondrial membrane (just like in photosynthesis)photosynthesis)

– Most of the energy in aerobic Most of the energy in aerobic respiration is produced by respiration is produced by chemiosmosischemiosmosis

HH++ go from high to low concentration by go from high to low concentration by passing through ATP synthase in passing through ATP synthase in mitochondrial membranemitochondrial membrane

Energy produced from the movement of HEnergy produced from the movement of H++ allows ADP + P allows ADP + P ATP ATP

– Oxygen atom combines with each Oxygen atom combines with each pair of Hpair of H++ to form water to form water

Water is used by the cell or excretedWater is used by the cell or excreted

– 32 ATP molecules are produced by 32 ATP molecules are produced by the electron transport chain for each the electron transport chain for each molecule of glucosemolecule of glucose

Aerobic Respiration Aerobic Respiration SummarySummary

Produces a total of 36 ATP molecules from each Produces a total of 36 ATP molecules from each molecule of glucosemolecule of glucose

– 2 ATP – glycolysis2 ATP – glycolysis

– 2 ATP – Krebs cycle2 ATP – Krebs cycle

– 32 ATP – electron transport chain32 ATP – electron transport chain

Net reaction:Net reaction:

CC66HH1212OO66 + 6 H + 6 H22O + 6 OO + 6 O22 6 CO 6 CO22 + 12 H + 12 H22O + 36 O + 36 ATPATP

Efficiency of Cellular Efficiency of Cellular RespirationRespiration

Anaerobic respiration only produces 2 Anaerobic respiration only produces 2 ATPATP

– Very inefficientVery inefficient

– Leaves most of the potential energy Leaves most of the potential energy of the glucose in the end products of of the glucose in the end products of fermentationfermentation

– Meets the needs of many simple Meets the needs of many simple organisms (ex. yeast, bacteria)organisms (ex. yeast, bacteria)

Aerobic respiration yields almost 20 times as Aerobic respiration yields almost 20 times as much energy per glucose molecule as much energy per glucose molecule as fermentation doesfermentation does

– Efficient Efficient About 45% of the total energy obtainable About 45% of the total energy obtainable

from the breakdown of glucose is stored from the breakdown of glucose is stored as ATP moleculesas ATP molecules

Ex. automobile engines only convert 25% Ex. automobile engines only convert 25% of the chemical energy of its fuel into of the chemical energy of its fuel into useful energyuseful energy

Muscle FatigueMuscle Fatigue

Some organisms that have the Some organisms that have the capacity for aerobic respiration can capacity for aerobic respiration can function by anaerobic respiration alone function by anaerobic respiration alone when free oxygen is not availablewhen free oxygen is not available

Ex. Muscle cells can function for a short amount Ex. Muscle cells can function for a short amount of time without oxygen by using the energy of time without oxygen by using the energy obtained from glycolysis aloneobtained from glycolysis alone

– During prolonged periods of physical activity, During prolonged periods of physical activity, the muscle cells use oxygen faster than it the muscle cells use oxygen faster than it can be supplied (shuts down Krebs cycle)can be supplied (shuts down Krebs cycle)

– Muscles then continue to release energy by Muscles then continue to release energy by glycolysisglycolysis

– Pyruvic acid is converted to lactic acid which Pyruvic acid is converted to lactic acid which can build up causing muscle fatiguecan build up causing muscle fatigue

Respiration of Fats and Respiration of Fats and ProteinsProteins

Other organic compounds can be broken down Other organic compounds can be broken down using aerobic respiration to extract energy from using aerobic respiration to extract energy from proteins and fatsproteins and fats

Broken down and converted to compounds that Broken down and converted to compounds that can enter the respiratory pathway at an can enter the respiratory pathway at an intermediate point in the glucose breakdown intermediate point in the glucose breakdown pathwaypathway

When fats are used for energy, twice as much When fats are used for energy, twice as much ATP is produced as when glucose is usedATP is produced as when glucose is used

When proteins are used for energy, the same When proteins are used for energy, the same amount of energy is produced as a carbohydrate amount of energy is produced as a carbohydrate (not preferred by the cell)(not preferred by the cell)