How Cells Harvest Chemical Energy – Cellular Respiration

Cellular Respiration C6H12O6 + 602  6CO2 + 6H20 Glycolysis 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 Triphosphate Energy used by all Cells Organic molecule containing high-energy Phosphate bonds

Chemical Structure of ATP

What Does ATP Do for You? It supplies YOU with ENERGY!

How Do We Get Energy From ATP? By breaking the high- energy bonds between the last two phosphates in ATP

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 parts of the cell: Glycolysis occurs in the Cytoplasm Krebs Cycle & ETC Take place in the Mitochondria

Review of Mitochondria Structure Smooth outer Membrane Folded inner membrane Folds called Cristae Space inside cristae called the Matrix

Diagram of the Process Occurs in Matrix Occurs across Cristae Occurs in Cytoplasm

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 Cytoplasm Anaerobic (Doesn’t Use Oxygen) Requires input of 2 ATP Glucose split into two molecules of Pyruvate Also produces 2 NADH and 4 ATP

Formation of Acetyl CoA 1. 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) Cyclical series of oxidation reactions that give off CO2 and produce one ATP per cycle Turns twice per glucose molecule Produces two ATP Takes place in matrix of mitochondria

Krebs Cycle Summary Each turn of the Krebs Cycle also produces 3NADH, 1FADH2, and 2CO2 Therefore, For each Glucose molecule, the Krebs Cycle produces 6NADH, 2FADH2, 4CO2, 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 Chain 4. 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