Download Name Date 2.4: Chemical Reactions and Enzymes Guided Reading

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2.4: Chemical Reactions and Enzymes
Guided Reading
Read pages 50-53 in your textbooks. Complete the statement or answer the questions as you read.
Chemical Reactions
1. What is a chemical reaction? Process that changes, or transforms, one set of chemical into
another, by rearranging chemical bonds.
2. Identify and describe the two parts of a reaction:
a. Reactants – elements/compounds that enter a chemical reaction
b.
Products – elements/compounds produced by a chemical reaction
Energy in Reactions
3. Energy is released or absorbed whenever chemical bonds are formed or broken
Energy Changes
4. Chemical reactions that release energy often occur on their own, or spontaneously
5. Chemical reactions that absorb energy will not occur on their own w/o a source of energy
Energy Sources
6. Where do organisms get the energy they need for chemical reactions? Some organisms, like
plants, trap energy from sunlight and produce energy-rich compounds, while animals consume
plants or other animals to obtain energy-rich compounds
Activation Energy
7. What is activation energy? The energy needed to get a chemical reaction started
Enzymes
8. What is a catalyst? A substance used to speed up the rate of a chemical reaction
9. How do they work? They lower the activation energy needed for the chemical reaction
Nature’s Catalyst
10. What are enzymes? Biological catalysts (usually proteins)
11. Give an example of one way that enzymes allow our body to function? The enzyme, carbonic
anhydrase, speeds up the reaction needed to convert carbon dioxide (and water) to carbonic
acid, so that carbon dioxide doesn’t build up in the bloodstream. Carbonic acid is then removed
The Enzyme-Substrate Complex
12. How does an enzyme help reactants react? They bond to the reactants, providing a site where
the reactants can be brought together, and reduce the activation energy
13. The reactants of enzyme-catalyzed reactions are called substrates.
14. Where do the substrates bond? Active site.
15.
Compare an enzyme-substrate complex to a lock and key?
Each enzyme only works with
specific substrates. The enzyme is the lock, and only specific substrates (keys) will fit into the
active site, allowing it to work (or the lock to unlock)
Regulation of Enzyme Activity
16. What conditions can affect the activity of an enzyme?
Temperature, pH, regulatory molecules
Complete the graph below by labeling each line and each arrow.
Answer ‘Assessment’ questions on a separate sheet of paper: 1 (a+b), 2 (a+b), 3 (a+b)
1.a. the bonds change – often they formed or broken.
b. because new chemical are not formed.
2. a. the energy that is needed to get a reaction started.
b. A reaction that occurs spontaneously releases energy. A reaction that does not occur
spontaneously absorbs energy.
3. a. proteins that act as biological catalysts
b. enzymes provide a site where reactants, called substrates, can be brought together to react.
The substrates bind to a site on the enzyme called the active site, forming an enzymesubstrate complex. This reduces the activation energy needed for the reaction.