CH 2. CELLULAR CH 2. CELLULAR RESPIRATIONRESPIRATION

How are these two images related?

CH 2. CELLULAR CH 2. CELLULAR RESPIRATIONRESPIRATION

Cellular respiration is the process whereby the body converts the energy that we get from food (glucose) into an energy form that the body can use – ATP!

FOOD =

GLUCOSEATP!!!!!!

CH 2. CELLULAR CH 2. CELLULAR RESPIRATIONRESPIRATION

• There are 2 major types of cellular respiration…

» 1. AEROBIC CELLULAR RESPIRATION

» 2. ANAEROBIC CELLULAR RESPIRATION

The big difference is oxygen!!!!!

CH 2. CELLULAR CH 2. CELLULAR RESPIRATIONRESPIRATION

• There are 2 major types of cellular respiration…

» AEROBIC CELLULAR RESPIRATION

» Uses oxygen and produces MORE energy!

» ANAEROBIC CELLULAR RESPIRATION

» Does NOT use oxygen, produces LESS energy but much faster!

CH 2. CELLULAR CH 2. CELLULAR RESPIRATIONRESPIRATION

• AEROBIC CELLULAR RESPIRATION – includes anaerobic cellular

respiration plus 3 extra steps.

• Overall, there are 4 stages to cellular respiration:

– 1. GLYCOLYSIS – a 10 step process occurring in the cytoplasm

– 2. PYRUVATE OXIDATION – a one-step process in the mitochondrial matrix

– 3. THE KREBS CYCLE – an 8 step cyclical process occurring in the mitochondrial matrix

– 4. ELECTRON TRANSPORT CHAIN – a multistep process occurring in the mitochondrial membrane

CH 2. CELLULAR CH 2. CELLULAR RESPIRATIONRESPIRATION

• The overall chemical equation for cellular respiration is as follows:

C6H12O6(aq) + 6O2(g) 6CO2(g) + 6H2O(l) + 36 ATP

glucose oxygen Carbon dioxide

water ENERGY!

In other words, the combustion of one molecule of glucose yields 36 molecules of ATP along with carbon dioxide and water as by-products.

Since the activation energy needed for the combustion of glucose is quite high, each step in cellular respiration is catalyzed by specific enzymes that

lower the activation energies and allow the reactions to occur at a pace fast enough to maintain cell needs.

CH 2. CELLULAR CH 2. CELLULAR RESPIRATIONRESPIRATION

• The 3 overall goals of this process are:

• 1. to break the bonds between the six carbon atoms of glucose, resulting in 6 carbon dioxide molecules.

• 2. to move hydrogen atom electrons from glucose to oxygen, forming 6 water molecules.

• 3. to trap as much of the free energy released in the process as possible in the form of ATP.

C6H12O6(aq) + 6O2(g) 6CO2(g) + 6H2O(l) + 36 ATP

STEP ONE: GLYCOLYSISSTEP ONE: GLYCOLYSIS• Glycolysis involves 10 enzyme-

catalyzed reactions (each step has its own specialized enzyme!)

• Each reaction of glycolysis occurs in the cell's cytoplasm

C6H12O6(aq) Two 3-C molecules of pyruvate

2NADH

2ATP

STEP ONE: GLYCOLYSISSTEP ONE: GLYCOLYSIS• In glycolysis, a total of 2 ATP molecules are

USED in step one and three

• 2 ATP are produced in the 7th step, when BPG phosphorylates ADP to ATP

• 2 ATP are produced in the 10th step when PEP phosphorylates ADP to ATP

(-2ATP) + 4ATP = 2ATP

(net yield)

STEP ONE: GLYCOLYSISSTEP ONE: GLYCOLYSIS• http://www.youtube.com/watch?v

=O5eMW4b29rg

STEP TWO: PYRUVATE STEP TWO: PYRUVATE OXIDATIONOXIDATION

• TIME TO MOVE INTO THE MITOCHONDRIA!!!!

» the 2 molecules of pyruvate from glycolysis are transported through the two mitochondrial membranes into the matrix

» In the matrix, a multi-enzyme complex catalyzes 3 MAJOR CHANGES!!!!

STEP TWO: PYRUVATE STEP TWO: PYRUVATE OXIDATIONOXIDATION

1. A low-energy carboxyl group is removed as CO2.

STEP TWO: PYRUVATE STEP TWO: PYRUVATE OXIDATIONOXIDATION

2. NAD+ is reduced by two H atoms

STEP TWO: PYRUVATE STEP TWO: PYRUVATE OXIDATIONOXIDATION

3. A sulfur-containing compound called coenzyme A (CoA) is attached to the remaining acetic acid portion – forming

a molecule called acetyl-CoA

STEP TWO: PYRUVATE STEP TWO: PYRUVATE OXIDATIONOXIDATION

• The following is the overall equation for pyruvate oxidation:

2 pyruvate + 2NAD+ + 2CoA 2acetyl-CoA + 2NADH + 2H+ + 2CO2

Acetyl-CoA moves on the third step! = Krebs Cycle!

NADH skips step three and moves on to stage four! = electron transport chain!

WARNING!!!!!!WARNING!!!!!!Acetyl-CoA is a CENTRAL

MOLECULE IN ENERGY MOTABOLISM!!!!!ALL molecules that are catabolized for energy are converted into acetyl-CoA – including proteins, lipids and carbohydrates!

acetyl-CoA is MULTIFUNCTIONAL – it can be used to produce fat or ATP

if the body needs energy, acetyl-CoA will enter the KREBS CYCLE and transfer its free energy into ATP

if the body does not need energy, acetyl-CoA is channelled into an anabolic pathway that synthesizes lipids.

STEP THREE: KREBS STEP THREE: KREBS CYCLECYCLE

• The Krebs Cycle is an 8-step process!!!!» each step is catalyzed by its own enzyme

• It is a cyclic process!• the product of step 8 (oxaloacetate) is the

reactant in step 1!!!!!

The Krebs Cycle is a cyclic series of reactions that transfers energy from organic molecules to ATP, NADH, and FADH2 and removes carbon atoms as CO2.

STEP THREE: KREBS STEP THREE: KREBS CYCLECYCLE

• http://www.youtube.com/watch?v=WcRm3MB3OKw

STEP THREE: KREBS STEP THREE: KREBS CYCLECYCLE

• By the end of the Krebs cycle, the original glucose molecule is entirely consumed!

» the 6 carbon atoms leave as low energy CO2 molecules

The Krebs Cycle produces:

- 2 molecules of CO2

- 3 NADH

- 1 ATP

- 1 FADH2

X 2Because there are 2 acetyl-CoA molecules that go through

The Krebs Cycle produces:

- 4 molecules of CO2

- 6 NADH

- 2 ATP

- 2 FADH2

Energy is harvested in steps 3,4,5,6 & 8 :

-In steps 3, 4 and 8 NAD+ is reduced to NADH

- In step 5 ATP is formed by phosphorylation

- In step 6 FAD is reduced to FADH2

The reduced coenzymes now go on to stage 4 ELECTRON TRANSPORT CHAIN

STEP FOUR: ELECTRON STEP FOUR: ELECTRON TRANSPORT CHAINTRANSPORT CHAIN

• http://www.youtube.com/watch?v=_PgjsfY71AM

• http://www.youtube.com/watch?v=xbJ0nbzt5Kw&feature=related

• http://www.youtube.com/watch?v=3y1dO4nNaKY&feature=related

• http://www.youtube.com/watch?v=RpL6ws-ixZ4

• http://www.youtube.com/watch?v=kN5MtqAB_Yc&NR=1

STEP FOUR: ELECTRON STEP FOUR: ELECTRON TRANSPORT CHAINTRANSPORT CHAIN

• each NADH molecule results in 3 ATP molecules

• each FADH2 molecule results in 2 ATP molecules

ENERGY TOTALS!!!ENERGY TOTALS!!!

• review pg. 110 – figure 25

• Review pg. 114 – table 3