Biological Science 101 – General Biology
Lecture Seven: Cellular Respiration
Ch. 9, Pgs. 163-181
- A series of processes that is involved in converting food to
- Breakdowns food (Catabolism)
- Aerobic process (O2)
- Involves enzymes.
- Conversion of food to energy
One glucose molecule -> 38 Molecules of ATP
1) Glycolysis (sugar splitting)
– Takes place in the cytoplasm.
Glucose (6-C) -> -> -> (10 Steps) -> Pyruvate + (3-C) 2H2O
2) Citric Acid Cycle
Pyruvate (3-C) -> Acetyl CO-A (2-C) -> -> -> (8 Steps) -> CO2
3) Electron transport (Oxidative Phosphorylation)
- ATP is produced. - Energy Input:
2ATP -> 2ADP (Endergonic)
- Energy Output:
- Net Output:
2ATP (Energy Molecule)
2NADH (Energy Molecule)
Citric Acid cycle - Energy Output:
3NAD -> 3NADH (x2 for Pyruvate [2X])
1FAD -> 1 FADH (x2 for Pyruvate [2X])
1 ADP -> 1 ATP (x2 for Pyruvate [2X])
Electron transport chain
- Mitochondria inner membrane (cristae).
- Electrons transferred step-by-step from NADH, FADH -> O2 (acceptor)
Electron Loss -> Oxidized
Electron Accept -> Reduced
- Energy in the form of electrons is converted into ATP.
- Enzyme involved is called ATP-Synthase.
- Hydrogen ions (H+) accumulate outside the membrane, causing a differential
charge is created (Proton-Motive-Force)
Proton-Motive-Force -> Drives the ATP-Synthase Net yield of energy (ATP)
Food -> Source of -> Glycolysis: -> Electrons -> Electron
(Glucose) Electrons (2 ATP, 2 NADH) Transport
(6NADH, 2 FADH, 2 ATP)
10 NADH = 3 ATP
2 FADH = 2 ATP
30 ATP + 4 ATP + 4 ATP = 39 ATP (+/- 10%) Efficiency:
1 Glucose -> 686 kcal/mole
1 ATP -> 7.3 kcal/mole
Efficiency in Respiration: 7.3 x 38 ATP = 686 kcal (40% Efficiency, 60% lost “as
Car -> Gasoline -> 25% Efficiency.
* Background Reading: Laboratory Week 4 Handout. Review Questions:
1. What is the role of ATP in the cell? Why is it considered a "high-energy"
Energy captured -> ATP (Adenosine triphosphate)
ATP drives transport and mechanical work.
- ATP hydrolyses causes changes in shapes and binding affinities of proteins
- ATP transports chemical energy within cells for metabolism.
- It is produced by photophosphorylation and cellular respiration and used by
enzymes and structural proteins in many cellular processes, including biosynthetic
reactions, motility, and cell division.
It is considered to be a “high-energy” molecule because it aids in intracellular energy
2. What does NAD+ do in the cell?
Another energy molecule: NAD (Nicotinamide Adenine Dinucleotide)
NAD aids Oxidation -- Electrons --> Reduction
- “High-energy foods”
3. What is an enzyme? What does it do in the cell?
- Involved in catabolism.
- Food broken down.
- Energy released.
- Catalytic proteins that speed up the rate of a reaction, without altering the end
products or change the reaction.
For chemical reactions to start, they requ