Cellular Energetics I.Energy, ATP and Enzymes A. Cell Energy 1. Introduction a. Energy is the ability to produce a change in the state or motion of matter. b. Forms of energy - electrical, chemical, radiant. c. Types of energy 1. potential - stored energy 2. kinetic - energy of motion

d. Chemical reactions and energy 1. Endergonic reaction - a reaction that absorbs energy from the surroundings. 2. Exergonic reaction - a reaction that releases energy to the surroundings. 2. Energy for biological work (examples) a. muscles to contract b. movement of ions and molecules across membranes of nerves and kidneys

3. Food and ATP energy a. The food we eat (glucose) is our main energy source b. ATP is the energy intermediate of the cell 4. Structure and function of ATP a. molecular make-up 1. Ribose sugar 2. Adenine base 3. 3 phosphate groups

b. The phosphate bonds are negatively charged, therefore they are unstable and can be easily broken by hydrolysis c. These bonds, because of their instability are considered “high-energy”. d. The breaking of the phosphate bond along with its’ transfer to another molecule will also transfer the bonds’ energy to that molecule. This movement of a phosphate is referred to as phosphorylation.

e. This reaction will change the ATP to ADP f. The molecule will eventually release the phosphate back to the ADP so that it can rejoin to make ATP again g. ATP P i energy glucose chemical energy reaction P i ADP

B. Enzymes 1. Introduction a. Enzymes are needed by living organisms as catalysts that control every chemical reaction in them b. Their purpose is the reduce the activation energy needed to start a chemical reaction c. They can only speed up a reaction that would have naturally occurred

d. They are specific for the substrate they will react with e. They are named for the substrate that they react with and then an -ase suffix is added 2. How they work a. Enzyme (w/ active site) + substrate 1 + substrate 2  enzyme-substrate complex  enzyme + product(s) b. The reaction of the enzyme with a substrate is known as the induce fit model

II. Cellular Respiration A. Introduction 1.The process by which a cell extracts energy from food to recharge ATP 2.The mirror side of these reactions are seen in the process of photosynthesis. Both energy and organelles

3. Two types a. anaerobic - does not require oxygen and is less efficient. Performed by yeast, bacteria and muscle cells b. aerobic - requires oxygen. Performed by all oxygen breathing organisms. C 6 H 12 O 6 + O 2 + H 2 O  CO 2 + H 2 O + energy

B. Aerobic Respiration 1.Glycolysis a. A sequence of reactions that convert a glucose molecule into two molecules of pyruvate with the production of ATP. Hydrogens are released during this reaction and combine with carrier molecules called NAD. NAD will carry the hydrogens to ETS. b. This reaction occurs in the cytoplasm of the cell

c. Oxygen is not required for this process to occur therefore both types of respiration will perform this reaction d. Note reaction

2. Formation of Acetyl Coenzyme A a. A reaction in which pyruvate is converted in to Acetyl-CoA. CO 2 is given off as a waste product and the hydrogens released are combined with NAD b. This reaction occurs in the mitochondria

3. The citric acid cycle a. A cyclic reaction which begins with the combining of Oxaloacetic acid with Acetyl CoA. The Acetyl-CoA will be completely degraded into the products CO 2 (waste product), hydrogen (carried off by NAD and FAD) and recharged ATP, leaving the cycle with it’s original Oxaloacetic acid

b. The cycle will turn 2 times for every one glucose molecule use in the respiration process c. This reaction occurs in the liquid matrix of the mitochondria

4. The electron transport system a. A protein transport system on the inner membrane of the mitochondria used to move and separate hydrogens given to it from NAD and FAD. The separation will setup a hydrogen concentration gradient that will recharge ADP into ATP

b. The hydrogens will eventually combine with oxygen, the final acceptor molecule, to make water c. This reaction occurs on the inner membrane of the mitochondria and liquid spaces around it. 5. Regulation of cellular respiration a. The presence of oxygen b. The amount of ADP and phosphates available

C. Anaerobic Process 1. Lactic acid fermentation a. the breakdown of glucose which yields lactic acid and recharges ATP b. this process is completed by muscle cells when the cell requires energy at a faster rate that can be supplied c. note process

2. Alcoholic fermentation a. the breakdown of glucose which yields ethanol, and CO 2 and recharges ATP b. this process is completed by yeast and bacteria cells when their oxygen supply is cut off c. note process