5.5 Enzymes are proteins that speed up specific reactions in cells

Enzymes and Activation Energy

• molecules absorb energy
• the "start-up' energy is called activation energy(ex: burn candle with match)
• heat up the mixture of molecules can provide activation energy
• catalysts, which cellular reactions depend on, are compounds that speed up chemical reactions
• enzymes are specialized proteins which are the main catalysts of chemical reactions in organisms
• enzymes can provide reactions to occur at the cell's normal temperature
• enzyme lowers the energy requirement barrier
• every enzyme catalyzes a specific kind of chemical reation

How Enzymes Work

• the shape of each enzyme fits the shape of only particular reactant molecules
• a specific reactant acted upon by an enzyme is called the enzyme's substrate
• the substrate fits into a particular region of the enzyme, called the active site
• the fit between substrated and enzyme isn't rigid
• an znzyme can lower activation energy by accepting two substrates into adjacent sites
• enzymes can catalyze larger molecules from smaller molecules
• an enzyme's structure and shape are essential to its function
• an enzyme's shape is able to change it's surrounding environment

Concept Check:

1.Explain the role of activation energy in a reaction. How does an enzyme affect activation energy?

Activation energy activates the reatants and triggers a chemical reaction. An enzyme can keep a cell at its normal temperature, but you need to heat up molecules to provide activation energy.

2.Describe how a substrate interacts with an enzyme.

A substrate is a specific reactant acted upon by an enzyme, and substrate can help enzyme to lower its activatoin energy.