Cellular Energetics

1. Cellular Energetics How do cells acquire and use Energy?

2. Why is energy essential to life? • cell division • movement of flagella or cilia • the production and storage of proteins • muscle contractions during exercise • your heart pumping • your brain controlling your entire body

3. What is energy? • The capacity to do work • ie. change or move something • chemical energy= changes structure • mechanical energy= move objects • light energy= boosts electrons to an outer shell • thermal energy (heat)= increases the motion of molecules

4. Potential vs. Kinetic energy • A.K.A.-- stored vs. expended energy • glycogen is potential energy that when broken down and metabolized is kinetic energy that is used by muscles • Chemical bonds store energy that can be released when the bond is broken. • Just as some springs are tighter than others, some chemical bonds store more energy than others.

5. The Laws of Thermodynamics • # 1: The law of Energy Conservation- • “Energy is neither created nor destroyed” • Examples: • Electrical energy is converted to mechanical energy when we plug in a clock or turn on a blender • Green plants convert solar energy into chemical energy that is stored as starch or cellulose and used by the plant

6. #2: With each energy transfer, some energy is lost • Every time energy changes or moves, some of it, or all of it, becomes less useful • Examples: • Remember Food Chains? As you move further and further up the food chain, there is less available energy. • When you exercise, some of the food energy gets converted into muscle work, but most of it gets converted to thermal energy. That's why you get all hot and sweaty.. • Cars convert chemical energy (gasoline) into mechanical energy in order to turn the wheels. • Heat is generated and must be removed by a radiator and only about 5% of the chemical energy is converted into the mechanical energy which moves the car.

7. ENTROPY • a natural tendency towards disorder. It requires energy to fight disorder. Think of your bedroom, for example! • Cells spend energy to fight this tendency so they use ATP

8. Adenosine triphosphate • a.k.a ATP • is the energy molecule that transports chemical energy within cells! • It is made up of an adenine and a ribose molecule (a.k.a. adenosine)+ three phosphate groups

9. Things to know about ATP: • The phosphate groups are charged molecules • molecules with the same charge do not like being too close to each other. • Bonding phosphate groups to the adenosine requires CONSIDERABLE energy. • So much energy is required to force the third charged phosphate close to the other two, that when the bond is broken, a great amount of energy is released. • When the chemical bonds between phosphate groups in ATP are broken, energy is released and ADP is formed. • ADP can reform ATP by bonding with another phosphate group.

10. animation Another animation

11. A few more tid-bits about ATP: • No storage is necessary– • This cycle or formation/breakdown is important so a cell doesn’t have to store all of the ATP it needs. As long as phosphate molecules are available, the cell has an unlimited supply of energy. • Use it or lose it! • ATP is broken down and the released energy must be captured and used efficiently—otherwise it will be wasted. • Think of a rechargeable battery— • it’s of little use sitting on a table, but if you snap it into the holder on the radio, the radio then has access to the stored energy and can use it. Then, when the energy has been used up, the batteries can be taken out, recharged, and replaced into the radio.

12. Different types of reactions • The energy-related reactions within cells generally involve the synthesis or the breakdown of complex organic molecules. Here’s the difference: • Anabolic reactions • are those that synthesize compounds • Energy is required for these reactions. • Also called endergonic • Catabolic reactions • Reactions that break down molecules • Energy is released when molecules are broken down. • Also called exergonic

13. Activation Energy • Energy required to cause even spontaneous reactions to begin Is this an example of an Endergonic or Exergonic Reaction?

14. What are enzymes? • catalysts • most are proteins • speed up chemical reactions Enzymes bind temporarily to one or more of the reactants of the reaction they catalyze. In doing so, they lower the amount of activation energy needed and thus speed up the reaction Overview

15. Real World Examples: • Catalase- catalyzes the decomposition of hydrogen peroxide into water and oxygen. • 2H2O2 -> 2H2O + O2 • One molecule of catalase can break 40 million molecules of hydrogen peroxide each second. • Carbonic anhydrase- is found in red blood cells where it catalyzes the reaction • CO2 + H2O <-> H2CO3 • It enables red blood cells to transport carbon dioxide from the tissues to the lungs.

16. The Lock & Key Analogy • In order to do its work, an enzyme must unite — even if ever so briefly — with at least one of the reactants. Successful binding of enzyme and substrate requires that the two molecules be able to approach each other closely over a fairly broad surface.

17. Vocab to Know: • Substrate(s)- • The reactants which bind to enzymes and are subsequently converted to a product or products • Active Site- • the area on the enzyme that binds the substrate(s) • The active site and the substrate(s) have complementary shape – like pieces in a jig-saw puzzle.

18. Factors that Effect Enzyme Activity • Heat • first it boosts enzyme activity by increasing molecular motion. • Above a critical temperature, the rate of reaction rapidly decreases because enzymes change shape and get denatured.   • Cold- • slows reaction time down

19. pH • a rise or fall in H+ conc. can change the charge of amino acid and affect the structure of the active site.

20. Concentration • Increased concentration of enzyme does not increase the rate of reaction once a critical conc. is reached. • This is because enzymes are recycled.

21. Competitive inhibitors- • an inhibitor has a similar structure as the substrate and clogs the active site so enzymes cannot work (ex. sulfa drugs)

22. Heavy Metals • can bind nonspecifically to an enzyme and alter their shape so that they cannot function properly • ex. lead, mercury, & arsenic

23. Bigger Picture • Metabolic Pathways- • A set of enzymatic reactions involved in either building or dismantling complex molecules • Feedback Inhibition- • when a key enzyme in a metabolic pathway is temporarily inactivated when the conc. of the end product of the pathway becomes elevated. One final animation