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
