2-4 Chemical Reactions and Enzymes

• Chemical Reaction – a process that changes one set of chemicals into another.

• Products – elements & compounds that are produced by a reaction

• Reactants – elements & compounds that enter into a reaction.

Reactants Products

Energy in Reactions

• Exergonic Reactions - some chemical reactions release energy– Happen spontaneously– Ex: HCl + Zn H + ZnCl

• Endergonic Reactions - some chemical reactions absorb energy– Will not occur without a source of energy– H2 + O H2O– Activation Energy: the energy needed to start a

chemical reaction.

Exergonic vs. Endergonic

• “Downhill” reaction

• Spontaneous

• Releases Energy

• “Uphill” reaction

• Requires Energy (Activation Energy)

• Absorbs Energy

Enzymes

• Catalyst – a substance that speeds up a chemical reaction by lowering the activation energy.

• Enzymes – are proteins that act as a biological catalyst.

Enzyme Action

Substrate – the reactants of an enzyme catalyzed reaction

Active Site – where the substrate and enzyme join.– Have complimentary shapes– Can only bind with a specific molecule – “induced fit”

Substrate

Enzyme Active Site

Animation

Regulation of Enzyme Activity

• Enzymes work best at certain pH levels and temperatures.– Most enzymes in humans work best at 37 C

• Denaturation – a change in the enzymes shape. – Enzyme becomes nonfunctional– Heat and pH can cause denaturation

• Some enzymes can be turned on and off– Lactose intolerance

Animation

Graphic Organizer Assignment

Use the large sheet of paper provided to create graphic organizers as follows:

1. T-Chart – Use Functional groups and list structure vs. what the group makes (e.g. alcohol, acid, ketone etc.)

2. Spider Map – Use “enzyme” for the center circle and elaborate on information related to enzymes from there.

3. Venn Diagram – Compare and contrast endergonic and exergonic reactions, include a graph of each type

4. Vocabulary Word Map – Use “organic molecules” to start, then list carbohydrates, lipids, proteins and nucleic acids. Add vocab related to these four classes of organic molecules. Draw at least one structure for each of the four classes.

X axis

Y axisB

A

D

C

1. What letter represents the product?2. What letter represents the reactant?3. What letter represents the activation energy?4. How should the x and y axis be labeled?5. Is the reaction exergonic or endergonic?

Explain

Vocab for 2nd constructed response:Enzyme – a protein that is a catalyst (speeds up a chemical reaction)Reactants – compounds that enter a reactionProducts – compound produced by a reactionSubstrate – reactant(s) that join with enzyme Active site – where enzyme and substrate joinDenatured – a change in the enzyme’s shapeStructure (shape) and function - enzymes must have the right shape

to work properly

Othe Factors that affect enzyme function:TemperaturepHConcentration of enzyme