Cellular RespirationCellular Respiration

Cellular Respiration: The Big PictureCellular Respiration: The Big Picture

We are energy beings – cellular respiration is the We are energy beings – cellular respiration is the process by which we gain energy.process by which we gain energy.

We normally run We normally run aerobic cellular respirationaerobic cellular respiration in in which we harvest energy from organic which we harvest energy from organic compounds using oxygen (Ocompounds using oxygen (O22).).

The molecule of choice for fuel is glucose.The molecule of choice for fuel is glucose.

CC66HH1212OO66 + 6O + 6O22 6CO 6CO22 + 6H + 6H22OO Glucose has an abundance of energy in its bonds. Glucose has an abundance of energy in its bonds.

We must release it in a series of small REDOX We must release it in a series of small REDOX reactions so the energy that is released does not reactions so the energy that is released does not increase cell temperature too much or the increase cell temperature too much or the proteins may freak out!proteins may freak out!

Cellular Respiration: The Big PictureCellular Respiration: The Big Picture

There are a variety of ways to carry out cellular There are a variety of ways to carry out cellular respiration and not all of them require oxygen to respiration and not all of them require oxygen to assist in the breakdown of glucose.assist in the breakdown of glucose.– Obligate AerobesObligate Aerobes – They require oxygen to – They require oxygen to

oxidize organic molecules to make energy.oxidize organic molecules to make energy.– Obligate AnaerobesObligate Anaerobes – They oxidize inorganic – They oxidize inorganic

molecules without oxygen to gain energy. (Omolecules without oxygen to gain energy. (O22 kills!)kills!)

– Facultative AnaerobesFacultative Anaerobes – They oxidize – They oxidize inorganic molecules with or without oxygen.inorganic molecules with or without oxygen.

Note the type of molecule being oxidized – Note the type of molecule being oxidized – organics give big energy boosts while inorganics organics give big energy boosts while inorganics do not yield much energy.do not yield much energy.

Cellular Respiration: The Cellular Respiration: The DetailsDetails

AKA: The Hard Part!AKA: The Hard Part!

Cellular Respiration: The DetailsCellular Respiration: The Details

Aerobic cellular respiration is as follows…Aerobic cellular respiration is as follows…

CC66HH1212OO66 + 6O + 6O22 6CO 6CO22 + 6H + 6H22OO From this, we can gather that…From this, we can gather that…

– cellular respiration involves breaking the bonds cellular respiration involves breaking the bonds in glucose to make six carbon dioxide in glucose to make six carbon dioxide molecules.molecules.

– the hydrogens get torn off of glucose to make the hydrogens get torn off of glucose to make water.water.

– the free energy released in the breakdown of the free energy released in the breakdown of glucose is harnessed to make ATP.glucose is harnessed to make ATP.

So how do we do these jobs?…So how do we do these jobs?…

The Reactions We’ll SeeThe Reactions We’ll See

There are several types of reactions that we will There are several types of reactions that we will encounter along the way.encounter along the way.

1.1. REDOXREDOX – Electrons being taken from one and – Electrons being taken from one and added to another.added to another.

2.2. Phosphorylation/DephosphorylationPhosphorylation/Dephosphorylation – The – The adding/removal of a phosphate group (POadding/removal of a phosphate group (PO44).).

3.3. Carboxylation/DecarboxylationCarboxylation/Decarboxylation – The – The adding/removal of a carbon.adding/removal of a carbon.

4.4. Hydration/DehydrationHydration/Dehydration - The adding/removal - The adding/removal of a water molecule (Hof a water molecule (H22O).O).

5.5. IsomerizationIsomerization – Making a molecule into its – Making a molecule into its isomer – same parts, different arrangement.isomer – same parts, different arrangement.

Order of OperationsOrder of Operations

Here is what we have to do…in order…Here is what we have to do…in order…1.1. GlycolysisGlycolysis – Cytosol – Glucose splitting. – Cytosol – Glucose splitting.2.2. Pyruvate OxidationPyruvate Oxidation – Matrix – Connect to – Matrix – Connect to

Kreb’s a la pyruvate Kreb’s a la pyruvate Acetyl-CoA Acetyl-CoA3.3. Kreb’s CycleKreb’s Cycle – Matrix – Energy given off – Matrix – Energy given off

mainly as NADH and FADHmainly as NADH and FADH22..4.4. Electron Transport ChainElectron Transport Chain (ETC) – (ETC) –

Mitochondrial inner membrane – NADH & Mitochondrial inner membrane – NADH & FADH2 give their energy to the ETC to create FADH2 give their energy to the ETC to create a proton problem.a proton problem.

5.5. ChemiosmosisChemiosmosis – Mitochondrial inner – Mitochondrial inner membrane – We solve the proton problem membrane – We solve the proton problem and get a big bunch of ATP while we’re at it.and get a big bunch of ATP while we’re at it.

1.1. GlycolysisGlycolysis

Glycolysis means “sugar splitting”. It occurs in Glycolysis means “sugar splitting”. It occurs in the cytoplasm.the cytoplasm.

Glucose goes through a series reactions that see Glucose goes through a series reactions that see it eventually turning into two pyruvate molecules. it eventually turning into two pyruvate molecules. These will go on to the next stage.These will go on to the next stage.

We get a net gain of 2 ATP and 2 NADH. The ATP We get a net gain of 2 ATP and 2 NADH. The ATP are ready to use and the NADH goes in our back are ready to use and the NADH goes in our back pocket for later.pocket for later.

Overall…Overall…

Glucose Glucose 2 Pyruvate 2 Pyruvate(2 ATP & 2 NADH)(2 ATP & 2 NADH)

2. Pyruvate Oxidation2. Pyruvate Oxidation

The pyruvate goes into the mitochondrion and The pyruvate goes into the mitochondrion and makes it way to the matrix.makes it way to the matrix.

Once in the matrix, the pyruvate is oxidized and Once in the matrix, the pyruvate is oxidized and turned into Acetyl-CoA (which will start the next turned into Acetyl-CoA (which will start the next stage).stage).

Along the way, a NAD becomes an NADH which Along the way, a NAD becomes an NADH which we will put in our back pocket for later.we will put in our back pocket for later.

Glucose gave us 2 pyruvate so we will end up Glucose gave us 2 pyruvate so we will end up with 2 Acetyl-CoA and 2 NADH’s.with 2 Acetyl-CoA and 2 NADH’s.

Overall…Overall…2 Pyruvate 2 Pyruvate 2 Acetyl-CoA (2 NADH) 2 Acetyl-CoA (2 NADH)

Pyruvate OxidationPyruvate Oxidation

3. Kreb’s Cycle3. Kreb’s Cycle

The two Acetyl-CoA molecules made by The two Acetyl-CoA molecules made by the previous stage now enters a cyclical the previous stage now enters a cyclical series of reactions called the Kreb’s cycle.series of reactions called the Kreb’s cycle.

For each glucose, the Kreb’s cycle turns For each glucose, the Kreb’s cycle turns twice and we will get…twice and we will get…– 2 ATP2 ATP– 6 NADH6 NADH– 2 FADH2 FADH22

The ATP are used immediately and the The ATP are used immediately and the NADH and FADHNADH and FADH22 molecules will go in our molecules will go in our back pocket for later.back pocket for later.

The Kreb’s CycleThe Kreb’s Cycle

4. The Electron Transport Chain4. The Electron Transport Chain The ETC is basically a conga line of REDOX reactions The ETC is basically a conga line of REDOX reactions

– pass the electrons to the right everybody! It all – pass the electrons to the right everybody! It all takes place on the mitochondrial inner membrane.takes place on the mitochondrial inner membrane.

Electrons from NADH and FADHElectrons from NADH and FADH22 are passed into the are passed into the chain and are handed down the line – hitting proton chain and are handed down the line – hitting proton pumps along the way.pumps along the way.

The proton pumps take protons (HThe proton pumps take protons (H++) from the matrix ) from the matrix and pump them across the membrane into the and pump them across the membrane into the intermembrane space of the mitochondrion.intermembrane space of the mitochondrion.

This is a problem as an electrostatic & pH gradient is This is a problem as an electrostatic & pH gradient is set up which is no good for the mitochondrion.set up which is no good for the mitochondrion.

NADH operates 3 proton pumps while FADHNADH operates 3 proton pumps while FADH22 operates just 2 proton pumps.operates just 2 proton pumps.

5. Chemiosmosis5. Chemiosmosis

Most texts put this step and the ETC together as Most texts put this step and the ETC together as one for good reason.one for good reason.

The proton problem created by the ETC is The proton problem created by the ETC is relieved by an enzyme, found embedded in the relieved by an enzyme, found embedded in the mitochondrial inner membrane, called mitochondrial inner membrane, called ATP ATP SynthaseSynthase..

ATP Synthase allows the protons (HATP Synthase allows the protons (H++) to come ) to come back into the mitochondrion – we’re saved!back into the mitochondrion – we’re saved!

But wait!…It gets better…ATP synthase fixes the But wait!…It gets better…ATP synthase fixes the problem and in doing so, it makes ATP!problem and in doing so, it makes ATP!

Its like a carpenter saying, “Yeah, I can fix your Its like a carpenter saying, “Yeah, I can fix your roof but you have to let me pay you for it!”.roof but you have to let me pay you for it!”.

The ETC & ATP SynthaseThe ETC & ATP Synthase

The ATP Balance SheetThe ATP Balance Sheet

Here’s how we get the 36 ATP from one Here’s how we get the 36 ATP from one molecule of glucose.molecule of glucose.– 1 ATP = 1 ATP (ATP is ATP already!)1 ATP = 1 ATP (ATP is ATP already!)– 1 NADH = 3 ATP (goes through 3 H1 NADH = 3 ATP (goes through 3 H++ pumps) pumps)– 1 FADH2 = 2 ATP (goes through 2 H1 FADH2 = 2 ATP (goes through 2 H++ pumps) pumps)

This gives us 38 ATP! What the…?!?!?This gives us 38 ATP! What the…?!?!? The trick is the 2 NADH’s made in The trick is the 2 NADH’s made in

glycolysis – in the cytosol. They have to glycolysis – in the cytosol. They have to get into the mitochondrion first and when get into the mitochondrion first and when they enter it, they are converted into they enter it, they are converted into FADHFADH22’s.’s.

So what is the bottom line?So what is the bottom line?

The Bottom Line!The Bottom Line!Stage of Stage of Cellular Cellular

RespirationRespiration

MoleculeMolecule

ProducedProduced# of ATP# of ATP

ProducedProduced

GlycolysisGlycolysis 2 ATP2 ATP 2 ATP2 ATP

2 NADH 2 NADH 2 FADH 2 FADH22 4 ATP4 ATP

Pyruvate Pyruvate OxidationOxidation

2 NADH2 NADH 6 ATP6 ATP

Kreb’s CycleKreb’s Cycle2 ATP2 ATP 2 ATP2 ATP

6 NADH6 NADH 18 ATP18 ATP

2 FADH2 FADH22 4 ATP4 ATP

THE GRAND TOTALTHE GRAND TOTAL 36 ATP36 ATP

FINFIN

(You worked hard – nice job!)(You worked hard – nice job!)