CHEMICAL REACTIONS & ENZYMES CHAPTER 2 SECTION 4 SC-B-2.8-EXPLAIN THE FACTORS THAT AFFECT THE RATES OF BIOCHEMICAL REACTIONS (INCLUDING pH, TEMPERATURE, & THE ROLE OF ENZYMES AS CATALYSTS).

ESSENTIAL QUESTION WHY ARE ENZYMES IMPORTANT TO LIVING THINGS?

A chemical reaction is a process that changes one set of chemicals into another set of chemicals.

Chemical Reactions ReactantsProducts elements or cpds that enter into a chemical reacti on elements or cpds that are produced in a chemical reaction

Chemical Reactions The chemical bonds of the reactants are broken & the chemical bonds of the products are formed.

Reversible Reactions Some chemical reactions in living things are reversible. example:

ENERGY IN REACTIONS Whenever chemical bonds are formed or broken energy is released or absorbed. Chemical reactions that release energy often occur spontaneously. Chemical reactions that absorb energy will not occur without a source of energy.

Exergonic reactions (release energy) in form of: ◦ heat ◦ light ◦ sound

In living organisms exergonic reactions often coupled with endergonic reactions

Activation Energy is the energy necessary to get the reaction started required whether reaction is exergonic or endergonic

What does the Law of Conservation of Energy tell you?

Exergonic Reaction Curve

Endergonic Reaction Curve

Enzymes Enzymes are biological catalysts ◦ very specific ◦ substance(s) it reacts with called a substrate ◦ speed up chemical reactions ◦ lower activation energy ◦ without enzymes chemical reactions would take so long to occur there would be no life. ◦ name often tells you what it acts on ◦ name ends in -ase

Effect of Enzyme on Reaction Curve

Enzymes: Active Site Active Site: location on enzyme molecule where substrate fits in (like key into a lock)

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Factors that Affect Enzyme Activity 1. pH ◦ enzymes in stomach pH 2, stop working when get to small intestine where pH is higher 2. temperature ◦ in humans: enzymes work 37 ◦ C 3. cell regulators ◦ most enzymes not active 24/7 but have a “switch” cells use as needed