Chemical Reactions & Enzymes

I. Chemistry• A. We already know that all living things are made up of

chemical compounds.• B. Chemistry is not only what life is made up of- chemistry is

also what life does.• 1. growth, interaction with environment, reproduction & movement are

all based on chemical reactions

II. Chemical Reactions• A. Chemical reactions: is a process that changes, or transforms one set

of chemicals into another by changing bonds between atoms• 1. Can occur quickly or slowly

• B. Chemical reactions have two parts:• 1. Reactants: elements or compounds that enter the reaction (what you start

with)• 2. Products: elements or compounds that are produced (what you end up with)

II. Chemical Reactions• Examples

2H₂ + O₂ 2H₂O_______ _______

C₆H₁₂O₆ + 6O₂ 6CO₂ + 6H₂O __________ __________

III. Energy in Reactions • A. Whenever chemical bonds form or are broken energy is released or

absorbed. • Think about after you ingest a meal

• B. Energy changes is a good indicator if a chemical reaction will occur.• C. Chemical reactions that release energy (exothermic)often occur

spontaneously• D. Chemical reactions that absorb energy (endothermic) will not occur

without a source of energy

III. Energy in Reactions• Examples

– Reactions that release energy

Pure Sodium + Water

– Reactions the absorb energy

(Take the energy of stirring)

Cold Packs

IV. Activation Energy

• A. The energy needed for a chemical reaction to start is known as activation energy.

• B. Examples

V. Enzymes• A. Some chemical reactions that make life possible are to slow or have

very high activation energies therefore our cells compensate by making catalysts

• B. Catalysts are substances that speed up reactions by lowering the activation energy.

• C. Enzymes are proteins that act as catalyst inside a cell.

Soil Chemistry• During your lab you were testing various amounts of soil

for the amount cations they contained.• The higher the amount of cations the better the quality of

soil. ( Due to more H+ ions being present ).• Please use the samples of tubes on your desk to help

better analyaze your sample of soil.• All samples are labeled A,B,C,D.• Be sure not to mix them up!

pH of Soil

• Alkaline: 8.0• Neutral: 7.0• Acid: 6.0• Very Acidic: 5.0• The natural cause is the presence of soil minerals producing sodium carbonate (Na2CO3) and sodium bicarbonate (NaHCO3) upon weathering.

pH of Soil

pH actually tells you how many H+ ions are found in your solution.

Most plants like a soil pH close to neutral or just a little on the acid side. A very high or very low pH can be toxic to the plants.

For acidic soil: Baking soda mixed with wet soil sample will froth. For alkaline soil: A few drops of cider vinegar on a soil sample will fizz.

Nitrogen Levels

• when N inputs to the soil system exceed crop needs, there is a possibility that excessive amounts of nitrate

• (NO 3 - ) may enter

either ground or surface water.

Nitrogen Levels• N should be fairly high, it is necessary for plants to grow.• N is oftentimes added to soils in the form of fertilizer if

there is a deficiency.

Phosphorous levels• One of the main roles of P in living organisms is in the

transfer of energy. Organic compounds that contain P are used to transfer energy from one reaction to drive another reaction within cells. ( think enzymes)

• The concentration of P is usually sufficiently low in fresh water so that algae growth is limited. When lakes and rivers are polluted with P, excessive growth of algae often results. High levels of algae reduce water clarity and can lead to decreases in available dissolved oxygen as the algae decays, conditions that can be very detrimental to game fish populations.

Potash Levels

• K levels are necessary, however high levels are unwanted.

• Lower levels will cause yellowing.