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 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 in Cytoplasm
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 highenergy 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