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2.2: Biochemical Reactions

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Lesson 2.2: True or False

Name___________________ Class______________ Date________

Write true if the statement is true or false if the statement is false.

_____ 1. A substance that forms as a result of a chemical reaction is called a reactant.

_____ 2. Only some chemical reactions need energy to get started.

_____ 3. Biochemical reactions take place inside the cells.

_____ 4. A chemical reaction that releases heat is an exothermic reaction.

_____ 5. Most biochemical reactions need help to get started.

_____ 6. Anabolic reactions give off energy.

_____ 7. Metabolism is the sum of all the biochemical reactions in an organism.

_____ 8. In a chemical reaction, the quantity of an element may change.

_____ 9. During a chemical reaction, some bonds break and new bonds form.

_____ 10. Activation energy is the energy needed to start a chemical reaction.

_____ 11. An enzyme speeds up the reaction by lowering the activation energy.

_____ 12. In a chemical reaction, the number of atoms on one side of the arrow may differ from the number of atoms on the other side.

_____ 13. Matter is always conserved.

_____ 14. Understanding chemistry is needed to understand fully the processes within the cell.

_____ 15. In a chemical reaction, the quantity of each element does not change.

Lesson 2.2: Critical Reading

Name___________________ Class______________ Date________

Read these passages from the text and answer the questions that follow.

Biochemical Reactions and Enzymes

Biochemical reactions are chemical reactions that take place inside the cells of living things. Biochemistry is a relatively new field that emerged at the interface of biology and chemistry. Its emergence shows that knowledge of chemistry as well as biology is needed to understand fully the life processes of organisms at the level of the cell. The sum of all the biochemical reactions in an organism is called metabolism. It includes both exothermic and endothermic reactions.

Types of Biochemical Reactions

Exothermic reactions in organisms are called catabolic reactions. These reactions break down molecules into smaller units and release energy. An example of a catabolic reaction is the breakdown of glucose, which releases energy that cells need to carry out life processes. Endothermic reactions in organisms are called anabolic reactions. These reactions build up bigger molecules from smaller ones. An example of an anabolic reaction is the joining of amino acids to form a protein. Which type of reactions — catabolic or anabolic — do you think occur when your body digests food?

Enzymes

Most biochemical reactions in organisms need help in order to take place. Why is this the case? For one thing, temperatures are usually too low inside living things for biochemical reactions to occur quickly enough to maintain life. The concentrations of reactants may also be too low for them to come together and react. Where do the biochemical reactions get the help they need to proceed? The help comes from enzymes.

An enzyme is a protein that speeds up a biochemical reaction. An enzyme works by reducing the amount of activation energy needed to start the reaction. Less activation energy is needed when the correct enzyme is present than when it is not present.

Enzymes are involved in most biochemical reactions, and they do their job extremely well. A typical biochemical reaction could take several days to occur without an enzyme. With the proper enzyme, the same reaction can occur in just a split second! Without enzymes to speed up biochemical reactions, most organisms could not survive. The activities of enzymes depend on the temperature, ionic conditions, and the pH of the surroundings. Some enzymes work best at an acidic pH, while others work best in neutral environments.

Questions

1. What is an enzyme?

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2. How are biochemistry and metabolism related?

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3. Which type of reactions — catabolic or anabolic — do you think occur when your body digests food?

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4. How do enzymes work?

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5. What is activation energy?

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Lesson 2.2: Multiple Choice

Name___________________ Class______________ Date________

Circle the letter of the correct choice.

  1. Reactants in the burning of methane include
    1. CH4 and 2O2.
    2. CO2 and 2H2O.
    3. CH4 and CO2.
    4. CO2 and 2O2.
  2. Activities of enzymes depend on
    1. pH.
    2. temperature.
    3. ionic conditions.
    4. all of the above
  3. An enzyme is a ____________.
    1. carbohydrate
    2. lipid
    3. protein
    4. nucleic acid
  4. Reactions that take place inside cells are
    1. cellular reactions.
    2. enzyme reactions.
    3. metabolic reactions.
    4. biochemical reactions.
  5. What is the main difference between an endothermic reaction and an exothermic reaction?
    1. An endothermic reaction gives off energy and an exothermic reaction absorbs energy.
    2. An exothermic reaction gives off energy and an endothermic reaction absorbs energy.
    3. An endothermic reaction does not need activation energy.
    4. Only endothermic reactions involve enzymes.
  6. Another name for a “biological catalyst” could be a(n)
    1. enzyme.
    2. reactant.
    3. activator.
    4. metabolism.
  7. The joining of amino acids to form a protein is a(n)
    1. anabolic reaction.
    2. catabolic reaction.
    3. amino acid reaction.
    4. polypeptide reaction.
  8. The “push” needed to start a chemical reaction is the
    1. enzymatic energy.
    2. endothermic energy.
    3. activation energy.
    4. reactant energy.

Lesson 2.2: Vocabulary I

Name___________________ Class______________ Date________

Match the vocabulary word with the proper definition.

Definitions

_____ 1. represents a chemical reaction

_____ 2. a protein that speeds up a biochemical reaction

_____ 3. a substance that forms as a result of a chemical reaction

_____ 4. a substance that starts a chemical reaction

_____ 5. sum of all the biochemical reactions in an organism

_____ 6. a process that changes some chemical substances into others

_____ 7. exothermic reactions in organisms

_____ 8. endothermic reactions in organisms

_____ 9. chemical reactions that take place inside the cells of living things

_____ 10. a chemical reaction that releases energy

_____ 11. a chemical reaction that absorbs energy

_____ 12. the energy needed to start a chemical reaction

Terms

a. activation energy

b. anabolic reaction

c. biochemical reaction

d. catabolic reaction

e. chemical equation

f. chemical reaction

g. enzyme

h. endothermic

i. exothermic

j. metabolism

k. product

l. reactant

Lesson 2.2: Vocabulary II

Name___________________ Class______________ Date________

Fill in the blank with the appropriate term.

1. Biochemical reactions are chemical reactions that take place inside the ____________ of living things.

2. During a chemical reaction, the ____________ are used up to create the products.

3. All chemical reactions need ____________ to get started.

4. ____________ reactions in organisms are called catabolic reactions.

5. ____________ energy provides the push needed to start a chemical reaction.

6. Your ____________ includes both exothermic and endothermic reactions.

7. A chemical reaction involves the breaking and forming of ___________.

8. In a chemical reaction, all matter is ____________.

9. Energy can be released during a chemical reaction in the form of ____________ and light.

10. In a chemical reaction, there is the same amount of each ____________ in the products as there was in the reactants.

11. An ____________ reaction builds up bigger molecules from smaller ones.

12. An ____________ works by reducing the amount of activation energy needed to start the reaction.

Lesson 2.2: Critical Writing

Name___________________ Class______________ Date________

Thoroughly answer the question below. Use appropriate academic vocabulary and clear and complete sentences.

Describe the roles of enzymes in biochemical reactions. Use specifics in discussing how enzymes work. Provide an example of a biochemical reaction involving an enzyme.

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