CHEMISTRY - Part Deux Reactions, Energy and Water

Reactions Reactions: Form: Synthesis, Anabolic A+B => AB Break: Decomposition, Catabolic AB => A + B Exchange: Synthesis + Decomposition AB + CD => AC + BD Dissociation: Breaking IONIC bonds to form independent ions

Chemical Reactions: Terms Reactants: Atoms and Molecules present before the reaction Products: Atoms or Molecules present after reaction

Chemical Energy Energy is neither created nor destroyed Energy changes form: Heat, Kinetic (mechanical), Potential Chemical (potential) Chemical Energy is stored in bonds Releasing that energy = FREE Energy

Chemical Reactions do two things: 1. Produce new products 2. Transform Energy

Chemistry and Energy Bonds: Stored Energy Synthesis requires FREE energy Decomposition releases FREE energy Free = Available!

Take “2” to Review Energy: Be able to describe the four basic forms of energy What kind of energy is STORED in chemical bonds? (2 kinds) What kind of Energy is “available” What kind of reaction releases FREE Energy?

Energy “Homeostasis” Familiar Phrases: I’m all out of energy… “What a bundle of energy!” “Energy in = Energy out” ENERGY CURRENCY OF LIFE “Free Energy” makes things happen ATP is a special molecule – delivering “Free Energy” to get the job done ATP cannot be stockpiled….

ATP Turnover… Synthesis: Restoring the free energy of ATP by adding P: ADP + P ATP Decomposition: Releasing free energy for work by losing P: ATP ADP + P Energy Homeostasis is the balance of ATP Supply and Demand

FACT: When Chemical Bonds are broken, MOST OF THE ENERGY IS RELEASED AS HEAT! In Human metabolism ~ 80% is released as heat That leaves ~ 20% available for work or synthesis of other molecules = FREE ENERGY

Energy Molecule ATP: Adenosine TriPhosphate Glucose can be “decomposed” to release its “bond” energy ~20% of the FREE energy is trapped and stored in ATP when ONE GLUCOSE MOLECULE IS totally oxidized

QUESTION? Why does body temperature Increase during Exercise?

Reaction Rates Nature of Reactants: Opposites attract We share common interests (electrons) Concentration of Reactants and Products At parties, there are more people, more chances of meeting someone with the “right chemistry” “Uh-oh, my girlfriend is here too…”

Reaction Rates Nature of Reactants Concentration of Reactants and Products Temperature Enzymes

Reaction Rates Nature of Reactants Concentration of Reactants and Products Temperature Enzymes

Enzymes: “Matchmakers” in Chemistry Proteins: Unique shapes Unchanged in reaction “catalysts”

Take “2” to Review: Review Reaction Rates: Why don’t we vary body temperature to speed up or slow down reaction rates? What affect would “warming up” have on the ability to increase ATP synthesis for exercise demands?

Water: The “stuff” of life! Absorbs lots of heat without changing temperature Lubricant Reactant in many biological reactions: CO 2 + H 2 O => H 2 CO 3

...and Water also: Is a “solvent” for polar molecules and ions Because of its polar nature, and the ability to dissolve ions, is a good medium to “conduct” currents!

Water and pH Neutral = 7.0 Body Fluids: Saliva = 6.5 Blood = 7.4 Stomach = 1.0!

Acids, Bases and Buffers Acid: Substance which donates H+ Base: Substance which donates OH- which can accept H+ Buffer: Substance which absorbs either H+ or OH-: Acids and Bases can buffer one another

Salts: When Acids and Bases Buffer Each Other A molecule made of the +ion and -ion remaining when an acid and base buffer one another: HCl => H+ + Cl- NaOH => OH- + Na+ => H 2 O + NaCl (Salt!)

BUFFERS Resist Changes in pH when acids or bases are added.

Assignment: Read: Pages Write about Energy Homeostasis: Since ATP cannot be stockpiled what happens to ATP demand during exercise? What happens to ATP supply during exercise? During Exercise, will there be more ATP synthesis or more ATP decomposition reactions occurring?

CHALLENGE! (For extra- credit) Verify this statement: “Strong acids are strong because they are substances which donate many H + to a solution.” True or False? Explain. First student to me the explanation gets 5 points!