1. Professor Collier Spring Semester 2012
Bioenergics
Professor Collier
Spring Semester 2012

2. Learning Objectives The Laws of Thermodynamics
How is energy transformed in the biosphere?
What is metabolism?
What is ATP?
What is cellular respiration?

3. The Laws of Thermodynamics
The First Law or Law of Conservation basically says that energy or matter can neither be created nor destroyed.
In bio-terms, the change in the internal energy of a closed system ( human body) is equal to the heat added to the system minus the work the done by the system.

4. The Laws of Thermodynamics
Since the system operates in the real world, some energy always escapes into the outside world, thus leading to both inefficiency and the Second Law…
The Second Law states that it is impossible to obtain a process where the unique effect is the subtraction of a positive heat from a reservoir and the production of a positive work.

5. The Laws of Thermodynamics
Energy exhibits entropy. In bio-terms, energy or heat cannot flow from a colder body to a hotter body. You cannot keep a continual flow of heat to work to heat to work without adding energy to the system (human body).

6. How is energy transformed in the Biosphere?
Kinetic energy is the energy of action, that is, energy that is doing work.
Potential energy is energy that stored or inactive.
The molecules in food we eat contain potential energy. That energy is converted to kinetic energy and used to do biological work when those molecules are oxidized in metabolism.

7. What is metabolism?
Metabolism includes all of the chemical rxns that occur in cells.
Efficiency and specificity are achieved by enzymes, a class of proteins that catalyze, or speed up, the steps of metabolism
Enzymes increase the rate at which chemical rxns occur in cells, but it can not force a rxn to go in another direction against the Laws of Thermodynamics.
Note: Rxn means reaction.

8. Metabolic Efficiency
Cellular rxns require an amount of energy in order for the reactant molecules to start a rxn which is called the activation energy.
Enzymes affect the activation energy which facilitates the organization and distribution of molecular energy.

9. Enzyme and Substrate Complex
How efficient are enzymes? They are very selective and reactant. Enzymes and substrates (the substances acted upon) must bind tightly together at the active site like a lock and key

10. What is ATP?
ATP stands adenosine triphosphate. It’s a ribonucleotide containing three phosphates.
The unique feature is the last phosphate. If it detaches a packet of energy is released that the cell is designed to capture and use.

11. What is ATP? Dephosphorylation
ATP is separated from its terminal (last) phosphate to make ADP + P(inorganic).
Phosphorylation
ATP is synthesized in the pathways that release energy, an ADP is joined to a phosphate.

12. What is Cellular Respiration?
Cellular respiration is the process of breaking down food molecules and capturing their energy in ATP molecules.
This breakdown process releases high-energy electrons that travel to the mitochondria where they are combined with oxygen. All steps controlled by enzymes.
Cellular respiration occurs in three steps:
Step 1: Glycolysis
Step 2: the Krebs Cycle,
Step 3: Electron Transport Chain.

13. Glycolysis

14. Glycolysis It takes place in the cytoplasm of all cells.
There are two phases:
Energy in the form of ATP. The main compound formed in this rxn is glyceraldehyde-3-phopshate, which is then broken down into pyruvate and 2 ATP are formed at the SAME time.
In addition, two molecules of an energy-carrying molecule named nicotinamide adenine dinucleotide (NADH) are formed.

15. Glycolysis
The low energy form of NADH is NAD+, an electron acceptor that carries electrons and hydrogens from glycolysis to the mitochondria.
The majority of the energy harnessed in glycolysis is conserved in the high enengy electrons of NADH and in the bonds of ATP.
The fate of pyruvate is dependent on the presence or absence of oxygen.

16. Glycolysis
If oxygen is present, pryruvate is converted into one molecule named acetyl CoA and then goes to the Krebs Cycle.
If no oxygen is present, the pyruvate is converted into lactic acid, which builds up until the oxygen supply is restored.

17. The Krebs Cycle
The Krebs Cycle (citric acid cycle) takes place in the mitochondrial matrix.

18. The Krebs Cycle

19. The Krebs Cycle
The cycle is a series of enzymatic rxns that breakdown the original carbons from pyruvate into carbon dioxide with the parallel synthesis of two molecules of ATP, 6 molecules of FADH2 (another high energy carrier).
It takes TWO turns of the Krebs Cycle to completely oxidize glucose. At the end of the cycle, oxaloacetate is regenerated.

20. The Electron Transport Chain

21. The Electron Transport Chain
The Electron Transport Chain does not produce ATP directly. It generates a proton (H+) gradient across the inner mitochondrial membrane, which stores the potential energy used to phosphorylate ADP to yield ATP (chemiosmosis).
Most of the electron carriers of the ETC are proteins embedded in the inner mitochondrial membrane (cristae). A notable exception is ubiquinone, which is a lipid.

22. The Electron Transport Chain
Each successive carrier molecule is more electronegative than the previous one.
Oxygen (greatest electronegativity) is the final acceptor.
Multiple copies of the ATP synthase which is a protein complex can be found in the cristae.
The ATP synthase makes the majority of cellular ATP.
It used the proton gradient across the inner mitochondrial membrane to power ATP synthesis.

23. The Electron Transport Chain
The ETC and chemiosmosis generate about ninety percent of the cell’s ATP (34 molecules).

24. Summation
Glucose is not the only cellular fuel. All simple sugars are catabolized and enters at its own point in cellular respiration.
Glycerol enters at the last step in the first phase of glycolysis, while fatty acids enter the transition stage between glycolysis and the Krebs Cycle.
Some amino acids are converted to pyruvate and others at the level of the Krebs cycle.
All complex metabolic pathways are under enzymatic control.

25. Summation
Cellular respiration is inhibited by large amounts of ATP and citrate ( an early product of the Krebs Cycle).
It is stimulated by high amounts of adenosine monophosphate.
In this way, the energy balance of the cell can be carefully monitored and regulated.