Cellular RespirationCellular RespirationThis is the process by which animals process This is the process by which animals process food to obtain the calories needed for energy food to obtain the calories needed for energy to do the cellular processes necessary for life.to do the cellular processes necessary for life.

Watch this: Watch this: http://youtu.be/Gh2P5CmCC0M

Or this: Or this: https://www.youtube.com/watch?v=-Gb2EzF_XqA

Photosynthesis vs Cellular Photosynthesis vs Cellular RespirationRespiration

• There is an energy trail: producers (photosynthesizers) consumers (animals) decomposers (bacteria)

• A cow eating grass is an example of a consumer eating a producer

• Photosynthesis is carried out by plants inside of chloroplasts (organelle)

Plants vs AnimalsPlants vs Animals• Cellular respiration is carried out in

the mitochondria in animals and plants

• Plants carry out photosynthesis and therefore have chloroplasts and mitochondria

• Besides photosynthesis, they also must break down their products to make ATP for cellular processes

FoodFood• The ultimate source of energy in food

is “the sun”

Cellular RespirationCellular Respiration• Includes pathways that require oxygenIncludes pathways that require oxygen• Glucose directly provides energy for Glucose directly provides energy for

cellular work through cellular respiration!cellular work through cellular respiration!• Glucose is oxidized and OGlucose is oxidized and O22 is reduced is reduced• Glucose breakdown is therefore an Glucose breakdown is therefore an

oxidation-reductionoxidation-reduction reaction (redox) reaction (redox)• Breakdown of one glucose results in 36 to Breakdown of one glucose results in 36 to

38 ATP molecules38 ATP molecules • THE GOAL IS TO THE GOAL IS TO MAKE ATP MAKE ATP TO RUN THE TO RUN THE

PROCESSES OF OUR CELLS.PROCESSES OF OUR CELLS.

Cell Respiration OverviewCell Respiration OverviewGlucose: Stores energy in the molecule

Cell respiration:

• Breaks down the molecules• Extracts the contained energy

1st stage: Cytoplasm

2nd & 3rd stage:

• Transfers electrons (from glucose)

• To electron carriers (e.g., NADH, FADH)•to make ATP

Mitochondria

• Giving off waste products (CO2 & H2O)

Overall Equation for Overall Equation for Cellular RespirationCellular Respiration

6CO6CO22 + 6H + 6H220 + 36-380 + 36-38ATP’sATP’s

CC66HH1212OO6 6 + 6O+ 6O22

YIELDSYIELDS

What Type of Process is What Type of Process is Cellular Respiration?Cellular Respiration?

• An Oxidation-Reduction An Oxidation-Reduction Process or REDOX ReactionProcess or REDOX Reaction

• Oxidation of GLUCOSE --> Oxidation of GLUCOSE --> COCO22 + H + H22O O ((ee-- removed from removed from CC66HH1212OO66))

• Reduction  OReduction  O22  to  H  to  H22O O ((ee-- passed (added) to Opassed (added) to O22))

• Electrons are lost from one substance and added to another substance!Electrons are lost from one substance and added to another substance!

Other Cellular Other Cellular Respiration FactsRespiration Facts

• Metabolic Pathway that breaks Metabolic Pathway that breaks down carbohydratesdown carbohydrates

• Process is Exergonic as High-Process is Exergonic as High-energy Glucose is broken into energy Glucose is broken into COCO22 and H and H22OO

• Process is also Catabolic Process is also Catabolic because larger Glucose breaks because larger Glucose breaks into smaller moleculesinto smaller molecules

What are the Stages of What are the Stages of Cellular Respiration?Cellular Respiration?

• 1. Glycolysis1. Glycolysis• 2. The Krebs Cycle2. The Krebs Cycle• 3. The Electron Transport Chain 3. The Electron Transport Chain

(ETC)(ETC)• REMEMBER THESE STEPS!REMEMBER THESE STEPS!

What this process needs to do is to strip the electrons off of glucose and eventually use them in the electron transport chain to create a proton gradient which, when turned on, allows them to flow through an enzyme (protein) which attaches a high energy phosphate to ADP to form ATP.

So steps 1 and 2 are just electron collecting processes. It does take some work.

Cellular RespirationCellular Respiration

GlycolysisKrebs cycle

Electron transport

Where Does Cellular Where Does Cellular Respiration Take Place?Respiration Take Place?

• It actually It actually takes place takes place in two parts in two parts of the cell:of the cell:

GlycolysisGlycolysis occurs in the occurs in the CytoplasmCytoplasmKrebs Cycle & Krebs Cycle & ETCETC Take Take place place in the in the MitochondriaMitochondria

Review of Mitochondria Review of Mitochondria StructureStructure

• SmoothSmooth outer outer MembraneMembrane

• FoldedFolded inner inner membranemembrane

• Folds called Folds called CristaeCristae

• Space inside Space inside cristae called cristae called the the MatrixMatrix

Copyright Cmassengale

In A Nutshell…In A Nutshell…

Diagram of the Diagram of the ProcessProcess

Occurs in

Cytoplasm Occurs

in Matrix

Occurs across Cristae

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1st stage:

Glycolysis

2nd stage:

Krebs cycle (or citric acid)

3rd stage:

Electron transport

Electrons are the stars!• If we track the transfer of hydrogen

from sugar to oxygen, we also follow the transfer of electrons. During cellular respiration, hydrogen and its bonding electrons change partners from sugar to oxygen, forming water as a product. Energy is also released.

Glycolysis, Glycolysis, occursoccurs in the cytoplasmin the cytoplasm Series of steps (but 2 phases)

Glucose 2 pyruvic acid molecules

As bonds in glucose are broken

Electrons (and H+ ions) NAD+

NADH

Glucose Is oxidized

NAD+ Is reduced

Net output is 2 ATP for each glucose molecule

But, most of the released energy carried by NADH

1.

2.

Steps of Glycolysis• 1. glucose (6 carbon sugar) is broken into

two 3 carbon molecules which requires 2 ATP

• 2. The 3 carbon molecules donate high energy electrons to NAD+ forming NADH (reduction)

• 3. 4 ATP are produced. Net, 2 ATP• The two 3 carbon molecules are pyruvate

and still hold a lot of energy which will be harvested in step 2. the Kreb’s cycle (citric acid cycle)

With or Without OxygenWith or Without Oxygenaerobic means with oxygenaerobic means with oxygen

Glucose 2 pyruvic acidsGlucose 2 pyruvic acidsPhase one

6 carbon

3 carbon

3 carbon

Glycolysis, Glycolysis, phase 1phase 1Some ATP is used to start the ‘breakdown’ of glucose

Cytoplasm

Mitochondria

Glycolysis, phase 2

High energy electrons are donated To

NAD+Forming NADH

Glycolysis, phase 2

And, phosphate groups are transferredATP is made

Overall Review of GlycolysisOverall Review of Glycolysis

Notice that two ATPs are used and Four are yielded, resulting in net 2 ATPs produced.

Glycolysis Glycolysis DiagramDiagram

Glycolysis Glycolysis SummarySummary

• Also produces 2 NADH and 4 Also produces 2 NADH and 4 ATPATP

• Pyruvate is oxidized to Acetyl Pyruvate is oxidized to Acetyl CoA and COCoA and CO22 is removed is removed

In-between glycolysis & KrebsIn-between glycolysis & Krebs

1. Pyruvic acid molecules are modified. It loses one carbon

Just before (or as) they enter the mitochondria

And CO2 is released

The altered molecule is acetic acid(…vinegar!)

Acetic acid is attached to a carrier molecule

Called coenzyme A one NADH is producedAnd forms acetyl CoA

To the mitochondrion

Prep for Citric Acid Cycle

Krebs cycle, Krebs cycle, in the mitochondriain the mitochondria

Net output is 2 ATP for each glucose molecule

But again, most of the released energy carried by NADH

Series of reactions

And more CO2 is released – the first electron acceptor of cellular respiration is NAD+

Continues to break down the sugar

Captures more energy

As NADH & FADH2

Present as acetic acid

A Little Krebs Cycle HistoryA Little Krebs Cycle History

• Discovered by Discovered by Hans KrebsHans Krebs in in 19371937

• He received the He received the Nobel PrizeNobel Prize in in physiology or physiology or medicine in medicine in 1953 for his 1953 for his discoverydiscovery

• Forced to leave Forced to leave Germany prior Germany prior to WWII because to WWII because he was Jewishhe was Jewish

Krebs Cycle Krebs Cycle SummarySummary

• Requires Oxygen (Aerobic)Requires Oxygen (Aerobic)• Cyclical series of oxidation Cyclical series of oxidation

reactions that give off COreactions that give off CO22 and and produce one ATP per cycleproduce one ATP per cycle

• Turns twice per glucose moleculeTurns twice per glucose molecule• Produces two ATP Produces two ATP • Takes place in matrix of Takes place in matrix of

mitochondriamitochondria

Krebs Cycle Krebs Cycle SummarySummary

• Each turn of the Krebs Cycle Each turn of the Krebs Cycle also produces 3NADH, also produces 3NADH, 1FADH1FADH22, and 2CO, and 2CO22

• Therefore, For each Glucose Therefore, For each Glucose molecule, the Krebs Cycle molecule, the Krebs Cycle produces 6NADH, 2FADHproduces 6NADH, 2FADH22, , 4CO4CO22, and 2ATP, and 2ATP

Krebs CycleKrebs Cycle

ATP

NETS: 3NADH, 1ATP, 1FADHNETS: 3NADH, 1ATP, 1FADH22, & 2CO, & 2CO22

What Carries the What Carries the Electrons?Electrons?

• NADNAD++ (nicotinadenin(nicotinadenine dinucleotide) e dinucleotide) acts as the acts as the energy carrierenergy carrier

• NADNAD++ is a is a coenzymecoenzyme

• It’s It’s ReducedReduced to to NADHNADH when it when it picks up two picks up two electrons and electrons and one hydrogen one hydrogen ionion

Are There Any Other Are There Any Other Electron Carriers?Electron Carriers?

• YES! YES! Another Another Coenzyme!Coenzyme!

• FAD+FAD+ (Flavin (Flavin adenine adenine dinucleotide)dinucleotide)

• ReducedReduced to to FADHFADH22

Electron Transport, Electron Transport, in the mitochondriain the mitochondria

Most of the ATP is produced in the ETC

And, NADH & FADH donate their electrons to the ETC

Which produces ~ 34 ATP

O2 exerts a strong pull on electrons

At the end of the chain of steps

And combines electrons & H+ ions to form H2O

The ‘downhill’ flow of electrons powers an enzymeATP synthase

Electron TransportElectron TransportAn array of molecules (…proteins)

In the inner membrane of the mitochondrion

Electrons move from one member to the next

The energy given up pumps H+ to inner space

Matrix Oxygen captures

electronsHydrogens are added, water forms

Matrix

The buildup of H+ ions give up energy

When they diffuse through a special protein

ATP synthase

ATP synthase captures their energyTo make ATP

ATP Synthase

ATP Synthase – actual protein

Electron Transport Chain Electron Transport Chain SummarySummary

• 34 ATP Produced34 ATP Produced• HH22O ProducedO Produced• Occurs Across Inner Occurs Across Inner

Mitochondrial membraneMitochondrial membrane• Uses coenzymes NAD+ and FAD+ Uses coenzymes NAD+ and FAD+

to accept e- from glucoseto accept e- from glucose• NADH = 3 ATP’sNADH = 3 ATP’s• FADHFADH22 = 2 ATP’s = 2 ATP’s• Oxygen is eventually reduced by Oxygen is eventually reduced by

the electrons to form water!the electrons to form water!

What would happen to the flow of electrons if oxygen were not present?

a. The flow of electrons would continue but at a slower rate.

b. The flow would cease and ATP production would stop.

c. The presence of oxygen would have no effect.

Cyanide binds strongly with the last electron carrier in the chain.

How would this affect the flow of electrons?

a. The flow of electrons would continue but at a slower rate.

b. The flow would cease and ATP production would stop.

c. The presence of cyanide would have no effect.

Learning checkLearning check1. Of the 3 stages of cell respiration, which

produces the most ATP per glucose?

2. In glycolysis, _______ is oxidized and _______ is reduced.

3. The final electron acceptor of the electron transport chains in mitochondria is _______.

Learning checkLearning check

4. Cells can harvest the most chemical energy from which of the following?

a. An NADH moleculeb. A glucose moleculec. Six carbon dioxide moleculesd. Two pyruvic acid molecules

FermentationFermentation

Occurs when OOccurs when O22 NOT present NOT present (anaerobic)(anaerobic)

Called Lactic Acid Called Lactic Acid fermentation in muscle cells fermentation in muscle cells (makes muscles tired)(makes muscles tired)

Called Alcoholic fermentation Called Alcoholic fermentation in yeast (produces ethanol)in yeast (produces ethanol)

Nets only 2 ATPNets only 2 ATP

Learning checkLearning checkThis figure represents an overview of the different processes of cellular respiration.

a) 1. Glycolysis; 2. Electron transport chain; 3. Krebs cycle

b) 1. Glycolysis; 2. Krebs cycle; 3. Electron transport chain

c) 1. Krebs cycle; 2. Electron transport chain; 3. Glycolysis

d) 1. Electron transport chain; 2. Glycolysis; 3. Krebs cycle

Which of the following correctly identifies the different processes?