CH 2. CELLULAR RESPIRATIONWednesday, April 10, 2013
CELLULAR RESPIRATION 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 = GLUCOSE
• 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.
CELLULAR RESPIRATION
• 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
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
CELLULAR RESPIRATION
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
Wednesday, April 10, 2013
STEP 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)
Wednesday, April 10, 2013
» 1. AEROBIC CELLULAR RESPIRATION
» 2. ANAEROBIC CELLULAR RESPIRATION
Wednesday, April 10, 2013
» AEROBIC CELLULAR RESPIRATION » Uses oxygen and produces MORE energy!
» ANAEROBIC CELLULAR RESPIRATION
» Does NOT use oxygen, produces LESS energy but much faster!
CELLULAR RESPIRATION
• 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!!!!
Wednesday, April 10, 2013
STEP TWO: PYRUVATE OXIDATION
Wednesday, April 10, 2013
STEP TWO: PYRUVATE OXIDATION
Wednesday, April 10, 2013
STEP TWO: PYRUVATE OXIDATION
3. A sulfur-containing compound called coenzyme A (CoA) is attached to the remaining acetic acid portion – forming
a molecule called acetyl-CoA Wednesday, April 10, 2013
STEP TWO: 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!
Wednesday, April 10, 2013
MOLECULE IN ENERGY METABOLISM!!!!!
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.
Wednesday, April 10, 2013
STEP THREE: KREBS CYCLE • 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.
Wednesday, April 10, 2013
STEP THREE: KREBS CYCLE • 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 2 Because there are 2 acetyl-CoA molecules that go through
Wednesday, April 10, 2013
The Krebs Cycle produces:
- 4 molecules of CO2
- 6 NADH - 2 ATP
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
• each NADH molecule results in 3 ATP molecules
• each FADH2 molecule results in 2 ATP molecules
Wednesday, April 10, 2013