Cellular RespirationCellular RespirationVocabulary:Vocabulary:

-Glycolysis-Glycolysis

-Kreb’s Cycle-Kreb’s Cycle

-Pyruvic acid-Pyruvic acid

-Fermentation-Fermentation

-Aerobic Reaction-Aerobic Reaction

-Anaerobic Reaction-Anaerobic Reaction

ReviewReview

• What is photosynthesis?What is photosynthesis?• Where does this occur?Where does this occur?• What is the difference between ATP What is the difference between ATP

and ADP?and ADP?• What is the difference between What is the difference between

NADPH and NADP+?NADPH and NADP+?• Light vs. Dark reactionsLight vs. Dark reactions

• After glucose is made in After glucose is made in photosynthesis, how is the energy in photosynthesis, how is the energy in the sugar molecules released so it the sugar molecules released so it can be can be usedused by the organism? by the organism? – cellular respiration!cellular respiration!

• Cellular Respiration occurs in Cellular Respiration occurs in bothboth plant & animal cells plant & animal cells – WHERE????WHERE????

– CYTOPLASMCYTOPLASM & &

MITOCHONDRIAMITOCHONDRIA!!!!!!

The The Power HousePower House of the Cell!! of the Cell!!

Cellular Respiration…Cellular Respiration…A Controlled ProcessA Controlled Process

• Food (glucose), like fuel, is Food (glucose), like fuel, is "burned" by our cells for energy"burned" by our cells for energy– if it's burned all at once, too much if it's burned all at once, too much

energy is releasedenergy is released

• therefore, the reaction is broken therefore, the reaction is broken down into many small steps down into many small steps controlled by controlled by ENZYMESENZYMES– Cells Cells graduallygradually release the energy release the energy

from glucose and other compoundsfrom glucose and other compounds

• the energy is transferred to the the energy is transferred to the bondsbonds of ATP which stores and of ATP which stores and releases the energy in usable releases the energy in usable amounts to be used by the cellamounts to be used by the cell

• energy is energy is stored in bondsstored in bonds between between phosphate groupsphosphate groups

AMP ADP ATP

P

P

Cellular RespirationCellular Respiration

• Process that releases Process that releases ENERGYENERGY by by breaking down food molecules in the breaking down food molecules in the presence of oxygenpresence of oxygen

• Occurs in Occurs in bothboth plants and animals plants and animals

Cell respiration occurs in 3 Cell respiration occurs in 3 stages:stages:

• GlycolysisGlycolysis• Citric (Krebs) cycleCitric (Krebs) cycle• Electron transport chainElectron transport chain

GlycolysisGlycolysis(glyco= sugar, lysis = breaks (glyco= sugar, lysis = breaks

down)down)• Process occurs in the Process occurs in the cytoplasmcytoplasm• Breaks glucose down from 6-carbon Breaks glucose down from 6-carbon

compound into two 3-carbon compound into two 3-carbon compounds (called pyruvate)compounds (called pyruvate)

Equation:Equation:

enzymes in enzymes in

CC66HH1212OO66 2 pyruvates + 2 2 pyruvates + 2 ATPATP

cytoplasmcytoplasm

• Glycolysis can occur if oxygen is Glycolysis can occur if oxygen is present (present (aerobicaerobic) or absent ) or absent ((anaerobicanaerobic))– Glycolysis is ALWAYS the first step Glycolysis is ALWAYS the first step

in breaking down glucosein breaking down glucose• If oxygen IS present, then cells If oxygen IS present, then cells

proceed with Respiration/Krebsproceed with Respiration/Krebs• If oxygen is NOT present, then cells If oxygen is NOT present, then cells

fermentferment

Cellular Respiration can Cellular Respiration can be broken down into be broken down into 22

processes:processes:1)1) Glycolysis: Glycolysis: breaking down breaking down

glucoseglucose

2)2) Respiration (Krebs Cycle & Electron Respiration (Krebs Cycle & Electron Transport Chain): Transport Chain): uses oxygen to uses oxygen to finish breaking down products finish breaking down products from Glycolysis & release from Glycolysis & release energyenergy

GLUCOSE

O2

CO2

H2O & heat energy

Glucose + Oxygen Carbon Dioxide + Water

 

C6H12O6 + 6O2 6CO2 + 6H2O

Look familiar???

Respiration/Krebs Respiration/Krebs

• Occurs in the Mitochondria of cellOccurs in the Mitochondria of cell• Only if oxygen is PRESENT Only if oxygen is PRESENT (aerobic)(aerobic)

• UsesUses the pyruvic acid from glycolysis to the pyruvic acid from glycolysis to

produce carbon dioxide, water, and produce carbon dioxide, water, and ATPATP• Products: Products:

– 34 ATP per molecule of glucose34 ATP per molecule of glucose– carbon dioxidecarbon dioxide– waterwater

So how does this So how does this happen?happen?

• The Citric (Krebs) cycle and the The Citric (Krebs) cycle and the electron transport chain turn the electron transport chain turn the pyruvate into COpyruvate into CO22, H, H22O, and ATPO, and ATP

• To do this, pyurvate loses a carbon To do this, pyurvate loses a carbon atom to make Acetyl CoAatom to make Acetyl CoA

• Acetyl CoA enters the Krebs Cycle to Acetyl CoA enters the Krebs Cycle to produce COproduce CO22, NADH, and FADH, NADH, and FADH22

• The NADH and FADHThe NADH and FADH22 carry energy to carry energy to the electron transport chain to make the electron transport chain to make more ATP (this requires more ATP (this requires oxygenoxygen))

CC66HH1212OO6 6 + 6O+ 6O22 6 CO 6 CO22 + 6 H + 6 H22O + 36 O + 36 ATPATP

Summary of Cellular RespirationSummary of Cellular Respiration

GLYCOLYSISGLYCOLYSIS

““break sweetness”break sweetness”

RESPIRATIONRESPIRATION/ / Kreb’s CycleKreb’s Cycle

Location in the Location in the cell:cell:

CytoplasmCytoplasm MitochondriaMitochondria

It starts with:It starts with: CC66HH1212OO66 (glucose)(glucose)

2 pyruvic acid2 pyruvic acid

It ends with:It ends with: 2 (C2 (C33HH66OO33) ) pyruvic acidpyruvic acid

HH22O, O, COCO22, ATP, ATP

Is Oxygen Is Oxygen required?required?

NONO YES! YES! AEROBICAEROBIC

# of ATP’s # of ATP’s Produced:Produced:

2 (tiny)2 (tiny) 34 (lots!) 34 (lots!)

GRAND TOTAL= 36 GRAND TOTAL= 36 ATP!!ATP!!

• 22 are produced in are produced in GlycolysisGlycolysis and and 3434 in in Respiration/ Kreb’s CycleRespiration/ Kreb’s Cycle– 18 times more ATP are produced in the 18 times more ATP are produced in the

presence of Oxygen!!presence of Oxygen!!

How efficient is this??How efficient is this??• The 36 ATP molecules The 36 ATP molecules

the cell makes per 1 the cell makes per 1 glucose represents glucose represents about 38% of the total about 38% of the total energy in glucoseenergy in glucose

• Even though it doesn’t Even though it doesn’t seem like much, this is seem like much, this is more efficient than your more efficient than your car’s gas burning car’s gas burning engineengine

• What happens to the What happens to the remaining 62%??? remaining 62%??? – It is released as heat.It is released as heat.

What happens if your cells What happens if your cells aren’t getting enough aren’t getting enough

oxygen?oxygen?

• Respiration/Kreb’s Respiration/Kreb’s CANNOTCANNOT proceed proceed• Fermentation occursFermentation occurs

– Pyruvic Acid builds up in Pyruvic Acid builds up in animal muscle cellsanimal muscle cells as as LACTIC ACIDLACTIC ACID… feel the burn!… feel the burn!

– In In other organismsother organisms, the pyruvic acid builds up, , the pyruvic acid builds up, ferments, and becomes ferments, and becomes alcoholalcohol

• Fermentation: release of energy from Fermentation: release of energy from food molecules in absence of oxygen food molecules in absence of oxygen (anaerobic)(anaerobic)

• Enables cells to carry out energy Enables cells to carry out energy production in the production in the absence of Oxygenabsence of Oxygen

• result of glycolysis + fermentation yields result of glycolysis + fermentation yields 2 ATP2 ATP molecules per 1 molecule of molecules per 1 molecule of glucose (not nearly as much energy!!!!)glucose (not nearly as much energy!!!!)

2 Fermentation Pathways:2 Fermentation Pathways:1.1.Lactic Acid Lactic Acid

Fermentation:Fermentation:• pyruvic acid from pyruvic acid from

glycolysis is converted glycolysis is converted to lactic acidto lactic acid

• lactic acid is produced in lactic acid is produced in muscles during rapid muscles during rapid exercise exercise (body can't (body can't supply enough Osupply enough O22 to the to the tissues)tissues)

• the build-up of lactic the build-up of lactic acid causes a burning, acid causes a burning, painful sensation in your painful sensation in your musclesmuscles

Energy & Exercise: Quick Energy & Exercise: Quick EnergyEnergy

• Muscle cells only contain enough ATP Muscle cells only contain enough ATP for a few seconds of “burst” energy for a few seconds of “burst” energy – emergency, starting gun of raceemergency, starting gun of race

• When this is gone, cells resort to lactic When this is gone, cells resort to lactic acid fermentation which can provide acid fermentation which can provide enough ATP for about 90 secondsenough ATP for about 90 seconds

Long Term EnergyLong Term Energy• If a race or energy need is longer, If a race or energy need is longer,

your body your body mustmust go through cellular go through cellular respiration to get enough ATP to respiration to get enough ATP to continuecontinue– Even well-conditioned athletes have to Even well-conditioned athletes have to

pace themselvespace themselves– Your body stores energy in muscleYour body stores energy in muscle

• glycogen glycogen

– these stores are enough to last for 15-these stores are enough to last for 15-20 minutes of activity when broken 20 minutes of activity when broken down through cellular respirationdown through cellular respiration

– After this, your body begins to break After this, your body begins to break down fats and other stored moleculesdown fats and other stored molecules

2.2. Alcoholic Alcoholic Fermentation:Fermentation:

• Occurs in yeast cells & Occurs in yeast cells & some other some other microorganismsmicroorganisms

• Pyruvic acid is broken Pyruvic acid is broken down into a 2-Carbon down into a 2-Carbon alcoholalcohol plus plus carbon carbon dioxidedioxide

Alcoholic FermentationAlcoholic Fermentation

• Important to brewers & bakers! Important to brewers & bakers! – When yeast in dough runs out of When yeast in dough runs out of

oxygen it ferments, giving off bubbles oxygen it ferments, giving off bubbles of carbon dioxide gas—which forms of carbon dioxide gas—which forms air space in breadair space in bread

– Alcohol produced in the dough Alcohol produced in the dough evaporates when bread is bakedevaporates when bread is baked

*(when the level of alcohol reaches *(when the level of alcohol reaches 12%, yeast cells die)12%, yeast cells die)