3.7 CELLULAR RESPIRATION - Weebly · 2018. 10. 14. · CELLULAR RESPIRATION How are these two images related? Wednesday, April 10, 2013. CELLULAR RESPIRATION Cellular respiration

3.7 CELLULAR RESPIRATION

How are these two images related?

Wednesday, April 10, 2013

CELLULAR RESPIRATIONCellular 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

ATP!!!!!! Wednesday, April 10, 2013

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

C6H12O6(aq) + 6O2(g) 6CO2(g) + 6H2O(l) + 36 ATPglucose oxygen Carbon

dioxidewater 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



• 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



STEP 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: 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)



• There are 2 major types of cellular respiration…

» 1. AEROBIC CELLULAR RESPIRATION

» 2. ANAEROBIC CELLULAR RESPIRATION

The big difference is oxygen!!!!!


• 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!



STEP TWO: PYRUVATE OXIDATION

• 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!!!!



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



2. NAD+ is reduced by two H atoms



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

a molecule called acetyl-CoAWednesday, April 10, 2013


• 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!!!!!!Acetyl-CoA is a CENTRAL

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.


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.


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

moleculesThe 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 TRANSPORT CHAIN

• each NADH molecule results in 3 ATP molecules

• each FADH2 molecule results in 2 ATP molecules


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3.7 CELLULAR RESPIRATION - Weebly · 2018. 10. 14. · CELLULAR RESPIRATION How are these two images related? Wednesday, April 10, 2013. CELLULAR RESPIRATION Cellular respiration