sections 2.4 & 2.5 chemical reactions & enzymes. 2.4 chemical reactions key concept: life...

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Sections 2.4 & 2.5 CHEMICAL REACTIONS & ENZYMES

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Page 1: Sections 2.4 & 2.5 CHEMICAL REACTIONS & ENZYMES. 2.4 Chemical Reactions Key Concept: Life depends on chemical reactions

Sections 2.4 & 2.5

CHEMICAL REACTIONS &

ENZYMES

Page 2: Sections 2.4 & 2.5 CHEMICAL REACTIONS & ENZYMES. 2.4 Chemical Reactions Key Concept: Life depends on chemical reactions

2.4 Chemical Reactions•Key Concept:•Life depends on chemical reactions.

Page 3: Sections 2.4 & 2.5 CHEMICAL REACTIONS & ENZYMES. 2.4 Chemical Reactions Key Concept: Life depends on chemical reactions

Bonds break and form during chemical reactions.

•Chemical reactions change substances into different ones by breaking and forming chemical bonds.• Reactants are changed during a chemical reaction.• Products are made by a chemical reaction.

• Endothermic and Exothermic Reactions

Page 4: Sections 2.4 & 2.5 CHEMICAL REACTIONS & ENZYMES. 2.4 Chemical Reactions Key Concept: Life depends on chemical reactions

Chemical reactions release or absorb energy.

•Activation energy is the amount of energy that needs to be absorbed to start a chemical reaction

Page 5: Sections 2.4 & 2.5 CHEMICAL REACTIONS & ENZYMES. 2.4 Chemical Reactions Key Concept: Life depends on chemical reactions

Exothermic reactions release more energy than they absorb.

• Reactants have higher bond energies than products.• Excess energy is released by the reaction.• Energy “exits” the reaction. (Exo = exit) Ex: Cellular

Respiration, making ice cubes

Page 6: Sections 2.4 & 2.5 CHEMICAL REACTIONS & ENZYMES. 2.4 Chemical Reactions Key Concept: Life depends on chemical reactions

Endothermic reactions absorb more energy than they release.•Reactants have lower bond energies than products.•Energy is absorbed by the reaction to make up the difference.•Energy goes into the reaction. (Endo = “into”) Ex: Photosynthesis, melting ice cubes

Page 7: Sections 2.4 & 2.5 CHEMICAL REACTIONS & ENZYMES. 2.4 Chemical Reactions Key Concept: Life depends on chemical reactions

STOP & REVIEW• _________ __________change substances into different ones by breaking and forming chemical bonds.• Chemical Reactions• _____________ are changed during a chemical reaction.• Reactants• __________ are made by a chemical reaction.• Products• ___________ ____________ is the amount of energy that needs to be absorbed to start a chemical reaction.• Activation Energy• ______________ reactions release more energy than they absorb.• Exothermic• ___________ reactions absorb more energy than they release.• Endothermic

Page 8: Sections 2.4 & 2.5 CHEMICAL REACTIONS & ENZYMES. 2.4 Chemical Reactions Key Concept: Life depends on chemical reactions

2.5 Enzymes•Key Concept:•Enzymes are catalysts for chemical reactions in living things.

Page 9: Sections 2.4 & 2.5 CHEMICAL REACTIONS & ENZYMES. 2.4 Chemical Reactions Key Concept: Life depends on chemical reactions

A catalyst lowers activation energy.•Catalysts are substances that speed up chemical reactions•Decrease activation energy• Increase reaction rate

Page 10: Sections 2.4 & 2.5 CHEMICAL REACTIONS & ENZYMES. 2.4 Chemical Reactions Key Concept: Life depends on chemical reactions

Enzymes allow chemical reactions to occur under tightly controlled

conditions.•Enzymes are catalysts in living things.•Enzymes are needed for almost all processes.•Most enzymes are proteins.

Page 11: Sections 2.4 & 2.5 CHEMICAL REACTIONS & ENZYMES. 2.4 Chemical Reactions Key Concept: Life depends on chemical reactions

Disruptions in homeostasis can prevent enzymes from

functioning.•Enzymes function best in a small range of conditions.•Changes in temperature or pH can break hydrogen bonds.•An enzyme’s function depends on its structure.

Page 12: Sections 2.4 & 2.5 CHEMICAL REACTIONS & ENZYMES. 2.4 Chemical Reactions Key Concept: Life depends on chemical reactions

An enzyme’s structure allows only certain reactants to bind to the

enzyme.•Substrates: reactants that bind to an enzyme•Active site: area on the enzyme where substrates bind

Page 13: Sections 2.4 & 2.5 CHEMICAL REACTIONS & ENZYMES. 2.4 Chemical Reactions Key Concept: Life depends on chemical reactions

Lock and key model shows how enzymes function

•Substrates are brought together at the active site of the enzyme•Enzyme weakens the bonds between the substrates.•Reaction forms a product that is released from the enzyme.

Page 14: Sections 2.4 & 2.5 CHEMICAL REACTIONS & ENZYMES. 2.4 Chemical Reactions Key Concept: Life depends on chemical reactions

STOP & REVIEW• _________ are catalysts for chemical reactions in living things.• Enzymes• ________ are substances that speed up chemical reactions by• Catalysts

• Decreasing __________ ______• Activation energy• Increasing ___________ _______• Reaction rate• Most enzymes are _______________• proteins• Changes in __________ or _____ can break hydrogen bonds.• Temperature or pH• An enzyme’s function depends on its _________• Structure

• __________: reactants that bind to an enzyme• Substrates• ________ _____: area on the enzyme where substrates bind• Active Site