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Cellular Respiration

1. Series of chemical reactions to produce energy for the cell.
2. Stages: glycolysis, PDC, Krebs cycle, electron transport



Molecule that contains energy. When energy is needed, the cell will hydrolyze the bond between the second and third triphosphate molecule. This leaves a molecule of adenosine diphosphate and a molecule of phosphate.


How does the cell get ATP?

1. Takes a glucose molecule from glycogen for respiration
2. Respiration requires glucose and oxygen, and produces water, carbon dioxide, and ATP.


Electron Carriers

1. Store energy released during respiration as electrons
2. An electron is reduced when it accepts electrons and oxidized when it gives them up.



Electron carriers, act as coenzymes.



1. Occurs in cytoplasm
2. Glucose is split into 2 pyruvate molecules (3C). 2 molecules of each product.
3. Occurs without oxygen
4. Uses 2 ATP, but produces 2 net ATP
5. NAD carries electrons for later use



Group of enzymes that prepares pyruvate for the next step of respiration (Krebs Cycle).


What occurs during PDC?

1. Krebs cycle only accepts 2 carbon atoms, yet pyruvate has 3.
2. PDC removes one carbon and attaches the remaining two to coenzyme A (acetyl coA)
3. Gives off carbon dioxide and produces another molecule of NADH
4. Found in the matrix of the mitochondria
5. Requires oxygen (CO2)


Krebs Cycle

1. Coenzyme A combines with oxaloacetic acid to form citric acid
2. 3 molecules of NADH, 1 of FADH, and 1 of ATP are produced, and CO2 is released
3. Cycle runs twice for each glucose molecule and requires oxygen
4. Oxaloacetic acid is a substrate and a product, and is regenerated each time the cycle is completed.
5. Gives energy to NADH and FADH


Electron Transport

1. Goal is to return electron carriers to their empty state (oxidation) and use energy from the electrons to make ATP.
2. NADH and FADH hand down electrons to a chain of carrier molecules, and pass them down until they get to oxygen, forming water.
3. Carrier molecules use the energy of the electrons they're transporting to pump H ions out of matrix and into the intermembrane space.
4. Occurs in inner membrane of mitochondria


Why are electron carriers oxidized?

Must be oxidized for glycolysis, PDC, and Krebs Cycle


Is electron transport an aerobic or anaerobic process?

Aerobic process. Oxygen is the last molecule in the chain to accept electrons (final electron acceptor). If oxygen is unavailable, the chain is backed up and processes can't be conducted.


ATP Synthase

1. Protein that allows H ions to cross membrane into the matrix.
2. Relies on facilitated diffusion of the ions down their gradient to produce ATP
3. Uses energy to combine ADP and a phosphate to produce ATP


How is a carrier oxidized?

1. Something else is reduced (given electrons)
2. In animals, electrons are taken from NADH and given to pyruvate. NADH becomes NAD, and pyruvate is reduced to lactic acid



1. Regenerating empty electron carriers in the absence of oxygen.
2. Products (ethanol or lactic acid) are toxic. If levels of lactic acid are too high, muscle won't contract.
3. Only produces 2 net ATP, so oxygen is necessary because 2 ATP can't keep cells functioning for long.