Lecture Notes-16 Biology 1004

North Arkansas College

Topic: Energy and Enzymes

1. It is the constant input of energy that maintains the structure, intricate patterns and activities of the organism.
2. Nature is basically disorganized (e.g. Your room, house, etc., become messy if not regularly cleaned.). Requires a constant input of energy to clean, organize, etc.
3. There are several types of energy and transformation.
4. It is often difficult to be able to understand the need for energy as we observe large organisms.
5. Energy input is essential to maintain order and function.
6. There are 2 important energy laws.

1. The first law of energy - Energy cannot be created or destroyed; it can only change forms.
2. The second law of energy - Energy cannot re recycled: It is transferred and some is lost as heat.

7. There are several forms of energy that can be transferred from one type to another:

1. Mechanical
2. Chemical
3. Heat
4. Electrical
5. Solar

8. Nature is randomly disordered - Water runs downhill, bodies decay when they die, and a house becomes messier without constant energy input. The same is required to maintain living system. We do not store energy as ATP, but we use 100 lbs of ATP daily.
9. There are 2 general classes of energy:

1. Kinetic - energy in motion.
2. Potential - stored energy.

10. The definition of energy: The ability to do work or move an object a specific distance. We measure this energy in calories or joules. Calorie is the heat required to raise the temperature of 1 gram of water 1°C. Kcal = 1000 calorie. Joule = 4.184 calories.
11. In living systems, energy is derived from chemical bond energy storied in various nutrients. This chemical bond energy is transformed to useable energy as ATP (adenosine triphosphate).

A – O – P ~ O – P ~ O – P

~ P = high energy bond (6,000-12,000 cal.)

12. The source of all energy is the sun (solar energy). We obtain only 2% of sun’s energy.
13. Stored energy is converted into useable energy in living systems via enzyme reactions or process of metabolism.

1. Metabolism - the sum total of all cellular reactions in the cell.
2. Catabolism - the break down of nutrients with release of energy.
3. Anabolism - the build up of nutrients with the use of energy.

14. Enzymes - the biological catalyst that speeds up reactions, but is not used up in the reaction. Enzymes lower the activation energy that is required for molecules to combine together.
15. Enzyme reactions are specific due to active sites on the surface that can only recognize particular substrates.
16. Enzymes are specific for their substrate due to active sites on their surface. Active sites recognize a particular substrate (lock and key theory). Enzymes combine with the substrates to produce a product or products to regenerate the enzyme.

17. Some everyday uses of enzymes:

1. Meat tenderizer (Papain, Protease) breaks down muscle protein.
2. Contact lens cleaner breaks down proteins on lens surface.
3. Laundry detergent breaks down grease, grass stains, bloodstains, and other proteins.
4. Nature’s Miracle breaks down animal waste, etc.
5. Insecticides such as Malathion, Paratheon, inhibit enzymes essential for insect metabolism.
6. Spider’s (and other insects) inject enzymes into prey to solubilize the tissue.
7. Enzymes that are temperature sensitive control cat coat color in Siamese cats (darker close to body due to warmth). Hair on extremities is lighter due to enzyme sensitivity. In seals, etc., babies are light colored, while older seals are darker colored due to enzyme activity.

1. Temperature - Enzyme reactions are chemical reactions. Chemical reactions are accelerated with increasing temperature up to the point where the enzyme becomes inactivated. Too cold a temperature - will slow down and stop reaction. Too high a temperature - will inactivate enzyme.
2. pH - All enzymes have an ideal (optimum) pH for activity. Pepsin in stomach works best at pH 2. Most enzymes are active over a range of pH 4-9 with optimum activity near neutral pH 6.5-7.5.
3. Concentration of Enzyme - If the substrate concentration remains constant, increased amounts of enzyme increases the rate of the reaction up to the point where all of the substrate is used up.
4. Substrate Concentration - If the enzyme concentration is kept constant, the rate of the reaction increases with increasing concentrations of the substrate (more substrate to fill active sites). Eventually all of the active sites are filled and reaction levels off.

Enzymes tend to work in tandem as part of the enzyme pathway.

E₁ E₂ E₃ E₄ E₅ E₆

A - B - C - D - E - F - G

All 20 amino acids are synthesized in this way.

Enzymes and their activity can be inhibited by either of 2 types of inhibition:

1. Competitive Inhibition - an inhibitor whose structure is similar to an enzyme substrate. It replaces that substrate in the active sites. It competes with substrate for active site on the enzyme. An example would be Sulfa drug - sulfanilamide which resembles para amino benzoic acid (PABA). PABA is required for synthesis of vitamins and nucleotides. Sulfanilamide fills up active sites on the enzyme that converts PABA - folic acid. It is used to treat bacterial infections.
2. Non-Competitive Inhibition - an inhibitor attaches to a site other than active sites (e.g. allostearic site) to block the enzyme activity.
3. Feedback Inhibition - end product of enzyme pathway feeds back and blocks enzyme(s) leading to its production.

1. Enzymes are very important in energy production (in conversion of nutrients). There are 2 major pathways in most living organisms for energy production.

1. Respiration - Carbohydrates in the form of glucose are converted into C0₂ & H₂0 & energy
2. Photosynthesis - CO₂ & H₂0 are converted through solar energy to carbohydrates and H₂0.

2. The two are interactive. Energy reactions may be either:

1. Exothermic or exergonic
2. Endothermic or endergonic

Interrelationships between these maintain the order of living systems.

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