Cellular Respiration How Cells Harvest Chemical Energy – Cellular Respiration

Cellular Respiration

How Cells Harvest Chemical Energy – Cellular

Respiration

Cellular Respiration

• C6H12O6 + 602 6CO2 + 6H20

• A catabolic pathway

• Oxygen is consumed as a reactant along with organic compounds.

• Involves three stages:

• Glycolysis• Krebs Cycle• Electron Transport Chain

What Is ATP?• Adenosine TriphosphateAdenosine Triphosphate

• Energy used by all CellsEnergy used by all Cells

• Organic molecule containing high-energy Phosphate bondsOrganic molecule containing high-energy Phosphate bonds

Chemical Structure of ATP

What Does ATP Do for You?

It supplies YOU withIt supplies YOU with ENERGY!ENERGY!

How Do We Get Energy From ATP?

By breaking the By breaking the high- energy high- energy bonds between bonds between the last two the last two phosphatesphosphates in in ATPATP

NADH and FADH2

NAD+ traps electrons from glucose to make NADH (energy stored)

Similarly, FAD+ stores energy as FADH2

Where Does Cellular Respiration Take Place?

It actually takes place in two It actually takes place in two parts of the cell:parts of the cell:

• Glycolysis occurs in the Glycolysis occurs in the CytoplasmCytoplasm

• Krebs Cycle & ETC TakeKrebs Cycle & ETC Take place in the place in the MitochondriaMitochondria

Review of Mitochondria Structure

Smooth outer Smooth outer MembraneMembrane

Folded inner Folded inner membranemembrane

Folds called Folds called CristaeCristae

Space inside Space inside cristae called the cristae called the MatrixMatrix

Diagram of the Process

Occurs in Cytoplasm

Occurs in Matrix

Occurs across Cristae

Glycolysis 1. Means “splitting of sugar”

2. Occurs in the cytosol of the cell

3. Partially oxidizes glucose (6C) into two pyruvate (3C) molecules.

4. Occurs whether or not oxygen is present.

5. An exergonic process, (meaning energy is released) most of the energy harnessed is conserved in the high-energy electrons of NADH and in the phosphate bonds of ATP

Glycolysis Summary• Takes place in the CytoplasmTakes place in the Cytoplasm

• Anaerobic (Doesn’t Use Oxygen)Anaerobic (Doesn’t Use Oxygen)

• Requires input of 2 ATPRequires input of 2 ATP

• Glucose split into two molecules of PyruvateGlucose split into two molecules of Pyruvate

• Also produces 2 NADH and 4 ATPAlso produces 2 NADH and 4 ATP

Formation of Acetyl CoA1. Junction between glycolysis and Krebs cycle

2. Oxidation of pyruvate to acetyl CoA

3. Pyruvate molecules are translocated from the cytosol into the mitochondrion by a carrier protein in the mitochondrial membrane.

4. A CO2 is removed from pyruvate – making a 2C compound.

5. Coenzyme A is attached to the acetyl group.

Formation of Acetyl CoA

Formation of Acetyl CoA

Krebs Cycle Requires Oxygen (Aerobic)Requires Oxygen (Aerobic) Cyclical series of oxidation reactions that Cyclical series of oxidation reactions that

give off COgive off CO22 and produce one ATP per cycle and produce one ATP per cycle Turns Turns twicetwice per glucose molecule per glucose molecule Produces two ATP Produces two ATP Takes place in matrix of mitochondriaTakes place in matrix of mitochondria

Krebs Cycle Summary

Each turn of the Krebs Cycle also produces Each turn of the Krebs Cycle also produces 3NADH, 1FADH3NADH, 1FADH22, and 2CO, and 2CO22

Therefore, For each Glucose molecule, the Therefore, For each Glucose molecule, the Krebs Cycle producesKrebs Cycle produces 6NADH, 2FADH 6NADH, 2FADH22, ,

4CO4CO22, and 2ATP, and 2ATP

Electron Transport Chain 1. Located in the inner membrane of the

mitochondria.

2. Oxygen pulls the electrons from NADH and FADH2 down the electron transport chain to a lower energy state

. 3. Process produces 34 ATP or 90% of the ATP in

the body.

Electron Transport Chain4. Requires oxygen, the final electron acceptor.

5. For every FADH2 molecule – 2 ATP’s are produced.

6. For every NADH molecule – 3 ATP’s are produced.

7. Chemiosmosis – the production of ATP using the energy of H+ gradients across membranes to phosphorylate ADP.

ATP Synthase A protein in the inner membrane in the mitochondria.

Uses energy of the ion gradient to power ATP synthesis.

For every H+ ion that flows through ATP synthase, one ATP can be formed from ADP

Cellular Respiration in Summary

Glycolysis• 2 ATP

• 2 NADH 4-6 ATP (Depends on how this NADH molecule gets to the ETC. To make things simple we will say that these two NADH’s make 4 ATP )

Formation of Acetyl CoA• 2 NADH 6 ATP

Cellular Respiration in Summary

Krebs Cycle• 2 ATP

• 6 NADH 18 ATP

• 2 FADH2 4 ATP

Grand Total = 36 ATP

Fermentation Occurs when O2 NOT present (anaerobic) Called Lactic Acid fermentation in muscle

cells (makes muscles tired) Called Alcoholic fermentation in yeast

(produces ethanol) Nets only 2 ATP