Ch 9: RespirationCh 9: Respiration

The Big PictureThe Big Picture

Cellular respiration has the sole Cellular respiration has the sole purpose to produce ATP.purpose to produce ATP.

Its an exergonic reaction.Its an exergonic reaction. Can be summarized as a whole as:Can be summarized as a whole as:

Glucose + OxygenGlucose + Oxygen CO2 + Water+ ATP CO2 + Water+ ATP

Reminder on ATPReminder on ATP

ATP (adenosine triphosphate) is a ATP (adenosine triphosphate) is a nucleotide with unstable phosphate nucleotide with unstable phosphate bonds that the cell hydrolyzes for bonds that the cell hydrolyzes for energy.energy.

Cells use ATP to continue cellular Cells use ATP to continue cellular work. But they must replenish the work. But they must replenish the ATP supply to continue cellular work. ATP supply to continue cellular work. Respiration does this.Respiration does this.

Redox reactionsRedox reactions These are the energy-shuttling These are the energy-shuttling

mechansisms of metabolismmechansisms of metabolism Partial or complete gain of Partial or complete gain of

electrons=reduction electrons=reduction Partial or complete loss of Partial or complete loss of

electron=oxidationelectron=oxidation They are always coupled…so in order They are always coupled…so in order

for a material to lose an electron, for a material to lose an electron, another molecule must accept itanother molecule must accept it

The NAD+, NADH, FAD+, FADHThe NAD+, NADH, FAD+, FADH

NAD+ and FAD+ are coenzymes that NAD+ and FAD+ are coenzymes that function in the redox reactions and function in the redox reactions and are found in all cells.are found in all cells.

Traps energy-rich electrons from Traps energy-rich electrons from glucose or food.glucose or food.

NAD+= oxidized coenzymeNAD+= oxidized coenzyme NADH= reduced coenzyme NADH= reduced coenzyme

Why glucose? CWhy glucose? C66HH1212OO66

It’s the energy source used most It’s the energy source used most often by living organisms. often by living organisms.

Keep in mind that fats and proteins Keep in mind that fats and proteins could also be considered but glucose could also be considered but glucose is the “hallmark” molecule to use in is the “hallmark” molecule to use in cellular respirationcellular respiration

Glycolysis, Krebs Cycle, and Glycolysis, Krebs Cycle, and Oxidative PhosphorylationOxidative Phosphorylation

1. Glycolysis is the decomposition of 1. Glycolysis is the decomposition of glucose to pyruvate (or pyruvic glucose to pyruvate (or pyruvic

acid)acid)

2. Krebs Cycle takes pyruvate (1 2. Krebs Cycle takes pyruvate (1 pyruvate) and yields electron pyruvate) and yields electron acceptors and ATP.acceptors and ATP.

3. Oxidative phosphorylation extracts 3. Oxidative phosphorylation extracts ATP from NADH and FADH2. ATP from NADH and FADH2.

• Process that releases energy by breaking down glucose & other food molecules in the presence of oxygen

1.Glycolysis

Cellular Respiration

• Two Stages:

2. Krebs Cycle

3. Electron Transport Chain

Cellular Respiration

Glyclolysis (per glucose molecule)Glyclolysis (per glucose molecule) Takes place in cytosol.Takes place in cytosol. Mutiple steps (9 or 10 depending on Mutiple steps (9 or 10 depending on

source) in the process of source) in the process of decomposing glucose into pyruvate. decomposing glucose into pyruvate. Mg2+ ions are cofactors to help.Mg2+ ions are cofactors to help.

2 ATP go IN2 ATP go IN 4 ATP PRODUCED (so what is NET?)4 ATP PRODUCED (so what is NET?) 2 NAD+ go IN2 NAD+ go IN 2 NADH PRODUCED 2 NADH PRODUCED 2 Pyruvate (Pyrivic acid) PRODUCED2 Pyruvate (Pyrivic acid) PRODUCED

•Breaks down “Glucose” (6-carbon sugar) into 2 molecules of “Pyruvic Acid” (3-carbon compound)

•The products are:

–2 Pyruvic Acid molecules

–2 ATP molecules

–2 NADH molecules

Glycolysis

1.If Oxygen is present (Aerobic) ...“Krebs Cycle”… then to Electron Transport Chain

2.If Oxygen is absent (Anaerobic) … “Fermentation”… (directly to Electron Transport Chain)

Glycolysis has 2 pathways…

KREBS Cycle (per pyruvate)KREBS Cycle (per pyruvate) Takes place in mitochondrial matrix.Takes place in mitochondrial matrix. Pyruvate combines with CoA Pyruvate combines with CoA

(coenzyme A) to make acetyl CoA. (coenzyme A) to make acetyl CoA. This makes 1 NADH and 1 CO2.This makes 1 NADH and 1 CO2.

Acetyl CoA combines with OAA to Acetyl CoA combines with OAA to form citric acid. (7 intermediate form citric acid. (7 intermediate products). products). 3 NADH and 1 FADH2 3 NADH and 1 FADH2 are made and CO2 released. 1 are made and CO2 released. 1 ATP is made.ATP is made.

How much total ATP then for Krebs?How much total ATP then for Krebs?

KREBS CYCLE(Aerobic Pathway)

•Pyruvic Acid is broken down into CO2 in a series of energy extracting reactions

ETC (Oxidative Phosphorylation)ETC (Oxidative Phosphorylation)

Takes place in inner mitochondrial Takes place in inner mitochondrial membranemembrane

Involves a passing of electrons Involves a passing of electrons through a series of membrane through a series of membrane associated electron carriers in the associated electron carriers in the mitochondria to ultimately produce mitochondria to ultimately produce ATPATP

You shuffle electrons to pump You shuffle electrons to pump protons across the mitochondiral protons across the mitochondiral membrane against a concentration membrane against a concentration gradient to help establish a proton gradient to help establish a proton gradientgradient

The ETC transports electrons from The ETC transports electrons from NADH and FADH2 along a transport NADH and FADH2 along a transport chainchain

The respiratory chain is composed of 4 The respiratory chain is composed of 4 enzyme complexes and carriers called enzyme complexes and carriers called cytochrome c and ubiquinone (Q). The cytochrome c and ubiquinone (Q). The 11stst two complexes shuttle the electrons two complexes shuttle the electrons of NADH + H+ and FADH2 to Q. of NADH + H+ and FADH2 to Q.

The third complex moves electrons from The third complex moves electrons from Q to chytochrome c. Q to chytochrome c.

The final complex passes electrons to The final complex passes electrons to O2, an ultimate acceptorO2, an ultimate acceptor, which , which results in H20 as a by-productresults in H20 as a by-product

That chain is an energy converter That chain is an energy converter that pumped H+ across the that pumped H+ across the membrane. How? Certain members membrane. How? Certain members along the electron transport chain along the electron transport chain accept and release protons along accept and release protons along with electrons. A gradient is created with electrons. A gradient is created that is referred to as the proton-that is referred to as the proton-motive forcemotive force

Now this H+ has the capacity to do Now this H+ has the capacity to do workwork

This electron transport chain made This electron transport chain made no ATP directly, but it did ease the no ATP directly, but it did ease the fall of electrons from food to oxygenfall of electrons from food to oxygen

So now, by So now, by chemiosmosischemiosmosis, it will , it will couple this electron transport and couple this electron transport and energy release to ATP synthaseenergy release to ATP synthase

ATP synthase is an enzyme that ATP synthase is an enzyme that catalyses ATP from ADP and an catalyses ATP from ADP and an

inorganic phosphateinorganic phosphate Each NADH produces 3 ATPEach NADH produces 3 ATP Each FADH produces 2 ATPEach FADH produces 2 ATP

To summarize…To summarize… Glycolysis makes Glycolysis makes 2 NET ATP2 NET ATP and 2 and 2

NADH andNADH and

2 pyruvate2 pyruvate 2 acetyl CoA = 2 NADH 2 acetyl CoA = 2 NADH

Krebs Cycle: 6 NADH, 2 FADH2, Krebs Cycle: 6 NADH, 2 FADH2, 2 ATP2 ATP

Since Since each NADH produces 3 ATPeach NADH produces 3 ATP during oxidative phosphorylation and during oxidative phosphorylation and each FADH2 produces 2 ATP…each FADH2 produces 2 ATP…how how many ATP total?many ATP total?

Wait…but what if there is no oxygen?Wait…but what if there is no oxygen?

What will be affected? Well now What will be affected? Well now there is no electron acceptor to there is no electron acceptor to accept electrons at the end of the accept electrons at the end of the ETC. NADH will accumulate. Once all ETC. NADH will accumulate. Once all NAD+ has been made to NADH, NAD+ has been made to NADH, Krebs and glycolysis will eventually Krebs and glycolysis will eventually stop.stop.

We have to free NAD+ to allow We have to free NAD+ to allow glycolysis to continue! We must glycolysis to continue! We must release some NAD+ for use by release some NAD+ for use by glycolysisglycolysis

1.Alcoholic :

• Yeast & other microorganisms use this to produce alcohol & CO2 as wastes.

• Beer is a beverage made by alcoholic fermentation

2 TYPES: Alcoholic & Lactic Acid

FERMENTATION(Aanerobic Pathway)

Alcoholic FermentationAlcoholic Fermentation Commonly done by yeast in an anaerobic

environment. 1) Glycolysis is done as normal. And then,

to regenerate the NAD+… 2) Pyruvate 2) Pyruvate acetaldehyde acetaldehyde 3) Acetaldehyde3) Acetaldehyde ethanol…the energy in ethanol…the energy in

NADH is used to drive this reaction and NADH is used to drive this reaction and this will release NAD+. For each this will release NAD+. For each acetaldehyde, 1 ethanol is made and 1 acetaldehyde, 1 ethanol is made and 1 NAD+ is produced. NAD+ is produced.

Now we have made 2 ATP from glyocolysis Now we have made 2 ATP from glyocolysis for each 2 converted pyruvate for each 2 converted pyruvate

2.Lactic Acid:

– Exercise causes the body needs more oxygen for respiration to make more ATP

– Body resorts to lactic acid fermentation to make ATP

– Lactic Acid is also produced causing burning sensation in muscles

(Aanerobic Pathway)

Or…we can do Lactic Acid Or…we can do Lactic Acid FermentationFermentation

Lactic Acid FermentationLactic Acid Fermentation

Commonly done by: Muscle cells Commonly done by: Muscle cells during during oxygen debtoxygen debt..

Same thing as before:Same thing as before:

-do glycolysis-do glycolysis

-but then to regenerate NAD+, a -but then to regenerate NAD+, a byproduct called lactate is made byproduct called lactate is made instead of acetylaldehydeinstead of acetylaldehydeethanol.ethanol.

Diagram AssignmentDiagram Assignment

You will diagram the major pathways to You will diagram the major pathways to respiration in color in a way that is respiration in color in a way that is understandable to you. Use websites and understandable to you. Use websites and the book to help you form diagrams for the book to help you form diagrams for each section of respiration. each section of respiration.

It must be in color, complete, and have It must be in color, complete, and have words on it to describe what is happening words on it to describe what is happening in the process for full credit.in the process for full credit.

Also must have an input/output chart by Also must have an input/output chart by each stage: glycolysis, krebs, + ETCeach stage: glycolysis, krebs, + ETC