Summary of Textbook Section 5.5

Assignment:
Write a summary of 5.5

Section 5.5: Enzymes are proteins that speed up specific reactions in cells

Key Terms:

• activation energy: minimum amount of energy required to trigger a chemical reaction
• catalyst: agent that speeds up chemical reactions
• enzyme: specialized protein that catalyzes the chemical reactions of a cell
• substrate: specific reactant acted on by an enzyme
• active site: region of an enzyme into which a particular substrate fits

Chemical reactions and activation energy:

• chemical reactions require bond of reactants to weaken -> apply energy
• specific amount of energy required to trigger reaction is activation energy
• one way of applying energy is heating
• heating causes many undesired reactions in organisms, including break down cell wall

Function of enzymes:

• in cellular reactions, use catalysts to speed up reactions
• main catalyst are enzymes, which lower activation energy
• thus allow reactions without heat, at normal temperature
  
• enzymes specialized for specific reaction

Workings of enzymes:

• enzymes physically fit substrates, adjust size to fit well
• thus placing certain functional groups to react
• or physically placing closely just helps
  
• tighter grip bends substrate -> weakens bond
• enzymes can be used many times

Concept check:

1. Explain the role of activation energy in a reaction. How does an enzyme affect activation energy? The activation energy is the amount of energy needed to trigger the reaction. Without reaching the activation energy, reactions can't take place. Enzymes catalyze this process by lowering the amount of energy required to activate the reaction.
   
2. Describe how a substrate interacts with an enzyme. Substrates fit into the active sites of enzymes, areas specifically designated for placing substrates. Once there, the enzyme adjusts the size of the active site to fit the substrates tightly, weakening the original chemical bonds. After that, substrates interact with each other as usual, just at a lower temperature than usual. Substrates leave then the process is finished and the enzyme waits for other substrates.