Cellular Respiration and Fermentation

Review The purpose of photosynthesis is to take

kinetic light energy and convert it into potential chemical energy in the form of GLUCOSE

In order to build glucose, low energy CO2 and H20 molecules are built up using light energy.

Chloroplasts fix carbon

which requires energy input

Mitochondria release energy from organic

molecules

Cellular Respiration Goal – To BREAK DOWN glucose and use energy to produce ATP

Can happen WITH oxygen present Aerobic 

Can happen WITHOUT oxygen present Anaerobic

Two Routes an organism can release energy Fermentation (aka anaerobic respiration)

Takes place entirely in the cytoplasm (no mitochondria necessary)

Only nets 2 ATP (inefficient) per glucose No oxygen necessary!

Aerobic Cellular Respiration Takes place mostly in mitochondria Nets 36 ATP per glucose Oxygen necessary!

Either way, both start with the same process, Glycolysis, which means “glucose splitting”

Overview of Cell Respiration and Fermentation

Glucose

Glycolysis Krebs cycle

Electrontransport

Fermentation (without oxygen)

Alcohol or lactic acid

IT ALL STARTS WITH GLYCOLYSIS!!!!

Glycolysis

Glucose

To the electron transport chain

Glycolysis Summary

• One molecule of glucose split in half two molecules of pyruvic acid

• Uses 2 ATP to start the process but gets 4 ATP back in the end. (Net 2 ATP!)

• 4 high energy electrons are removed from the carbon compounds and passed to an electron carrier– 2 NAD+ 2 NADH– Electrons carriers will take high energy electrons to

the electron transport chain for later use!

What happens after glycolysis?• Depends on who you are and what your oxygen

availability is.• In order to move forward with cell respiration, you

must have the following;– Mitochondria– Available Oxygen

• If an organism does not have one or more of these, big problem as all available NAD+ molecules will be used-up. Without available NAD+, glycolysis shuts down and now not even 2 ATP generated from glucose via glycolysis

• Enter fermentation AKA anaerobic respiration.

Fermentation

• Release of energy from food molecules in the absence of oxygen

• AKA: Anaerobic respiration– Two forms:

• Alcoholic fermentation• Lactic acid fermentation

– NADH reverts back to NAD+ in both types by dropping back off their electrons and H ions.

– With NAD+ freed up again, ATP production can continue via glycolysis

•  

Lactic Acid Fermentation Occurs in many cells

Both eukaryotic and prokaryotic

Pyruvic acid + NADH lactic acid + NAD+

In foods, production of acid results in characteristic flavors of cheeses and yogurt

This is what happens in our muscles when we exercise heavily “feel the burn”

Lactic Acid Fermentation Point of this happening is so the NADH can

go back to NAD+ and keep glycolysis going!

Glucose Pyruvic acid Lactic acid

Alcoholic Fermentation Occurs in yeast and a few other

microorganisms

Pyruvic acid + NADH alcohol + CO2 + NAD+ Bread dough rising Wine and Beer fermentation

Alcohol Fermentation

(same as pyruvate)

Uses – producing alcohol

Uses – producing CO2 Bubbles

3 Possible Pathways

Fermentation Aerobic Cellular Respiration

Aerobic Cellular RespirationTHE PROCESS BY WHICH CELLS UTILIZE

OXYGEN TO BREAK DOWN ORGANIC MOLECULES INTO WASTE PRODUCTS, WITH THE RELEASE OF ENERGY THAT CAN BE USED FOR BIOLOGICAL WORK.

Using energy from glucose into ATP!

Equation

6O2 + C6H1206 6CO2 + 6H20 + Energy (ATP)

Cellular Respiration - 3 Main Steps 1.Glycolysis (same process as in fermentation)

Occurs in cytoplasm of cell Net 2 ATP per glucose

2. Krebs Cycle Occurs in mitochondria Net 2 ATP per glucose

3. Electron Transport Chain Occurs in mitochondria Net 32 ATP per glucose

Glucose(C6H1206)

+Oxygen

(02)

GlycolysisKrebsCycle

ElectronTransport

Chain

Carbon Dioxide

(CO2)+

Water(H2O)

Cellular Respiration

Cellular Respiration

GlucoseGlycolysis

Cytoplasm

Pyruvic acid

Electrons carried in NADH

Krebs Cycle

Electrons carried in

NADH and FADH2 Electron

Transport Chain

Mitochondrion

Overview of Aerobic Respiration

Glucose

Glycolysis Krebs cycle

Electrontransport

Fermentation (without oxygen)

Alcohol or lactic acid

Acetyl

CoA

2 2 32

6 NADH2 NADH

2 FADH22 NADH

After Glycolysis……. With free 02 and mitochondria, a cell can

release even more energy from pyruvic acid. Only 10% of total energy of glucose released in

glycolysis! We already know how glycolysis “splits” a

glucose molecule into 2 pyruvic acid, so lets pick up with what happens AFTER glycolysis

Structure of the Mitochondria

• Outer membrane• Inner membrane• Inter-membrane space• Cristae

– Projections of the inner membrane– Contain the enzymes of the ETS, ATP synthase

• Matrix– Inside area of the mitochondria

• Cells can contain 10 – 1000s of Mitochondria

Kreb’s Cycle Big Picture

Further break-down of pyruvic acid molecules into CO2 via series of energy releasing reactions.

Energy which is released is used to generate ATP (one per pyruvic acid molecule)

Electrons released during cycles used to make; NAD+ NADH FAD FADH2 Will be used later in electron transport (check to be

cashed!)

Before Pyruvic Acid enters the Kreb’s cycle, it get modified;

• Carbon removed C02• Electrons removed NADH• Coenzyme A joins the remaining 2-carbon

molecule acetyl-CoA• Acetyl-CoA joins up with a 4-carbon compound

already in the cycle and forms………… Citric Acid (6 carbon molecule)!

• Equation:– Pyruvic acid Acetyl Co A + CO2 + NADH

• Entry into Krebs Cycle– Acetyl CoA + 4-C (oxaloacetate) Citric Acid (6-C)

Kreb’s Cycle (aka Citric Acid Cycle

Citric Acid Production

Mitochondrion

IMPORTANT!

This cycle is repeated twice for

each glucose molecule!

Results of Krebs Cycle

• Per Glucose molecule (2 cycles)– 2 ATP– 6 NADH To electron transport chain– 2 FADH2 To electron transport chain– 6 CO2 (waste product) (4 in Krebs 2 in shuttle

step)– Also, 2 NADH were generated just before

Kreb’s Cyles started when pyruvic acid was converted to Acetyl-CoA!

Electron Transport Big Idea

All those high energy electrons which have been saved-up until now can be “cashed-in” for some big ATP gains!

Electron transport links the movement of these high-energy electrons with the formation of ATP!

Electron Transport Electrons passes along an “electron transport

chain” Prokaryotes

Chain is a series of carrier proteins on cell membrane

Eukaryotes (one we really care about) Chain is a series of carrier proteins located on

inner membrane of mitochondria.

Electron Transport High Energy electrons passed along transport

chain At end of chain, electrons passed to H+ and

Oxygen to form H20. Oxygen is final electron acceptor

Oxygen is important for the main reason that it accepts the low energy electrons and hydrogen ions which are wastes of cellular respiration!

Electron Transport and ATP production The movement of electrons down transport chain is

coupled to the movement of hydrogen ions across inner membrane into the intermembrane space

Hydrogen ion gradient established Special transport proteins along inner membrane

called ATP synthases. As hydrogen moves through ATP synthase, ADP and

P joined to form ATP! CALLED CHEMIOSMOSIS

Electron Transport ChainElectron Transport

Hydrogen Ion Movement

ATP Production

ATP synthase

Channel

The importance of oxygen• Must be present to accept electrons and protons

of hydrogen. Becomes WATER!

• Krebs and ETS cannot function without O2

• Photosynthesis and respiration– Products of Photosynth. are the raw materials for

cellular respiration and vice versa– Both utilize ETS– Krebs and Calvin are similar, both involve

rearrangements of carbon compounds– Krebs forms ATP, NADH and FADH2 while Calvin

uses ATP and NADPH

Grand Totals Net 36 ATP per glucose

38% efficiencyExceeds efficiency of gas combustion in a car.

Totals:Step ATP NADH FADH2 Total ATP

(net)Glycolysis 2 (net) 2* 0 6

Prep Step 0 2 6Krebs Cycle 2 6 2 24

*energy is expended to get NADH (glycolysis) to ETSOnly 2 ATP per NADH from glycolysis

3 ATP per NADH (prep and Krebs); 2 ATP per FADH2

Energy and Exercise Quick energy

ATP contained in muscles used in a few seconds After that:

Anaerobic (weight lifting, sprinting – high ATP demands short term) Most ATP through lactic acid fermentation (90

seconds) Lots of oxygen required to get rid of buildup (oxygen

dept) Sore muscles – caused by tissue damage

(cont.) Aerobic (jogging, light weights, - med ATP

demands long term) First use ATP/glucose in blood

Glycogen Lasts for 15-20 minutes

Body breaks down fats after that