Name______________________________ Class __________________ Date ______________

 

Reading Guide

Section 2–3 Carbon Compounds (pages 45–49)

This section explains how the element carbon is able to form millions of carbon, or organic, compounds. It also describes the four groups of organic compounds found in living things.

The Chemistry of Carbon

1. How many valence electrons does each carbon atom have?

 

 

2. What gives carbon the ability to form chains that are almost unlimited in length?

 

tom can bond to other carbon atoms.

Macromolecules

3. Many of the molecules in living cells are so large that they are known as_________________.

 

 

4. What is the process called by which macromolecules are formed?

 

 

5. When monomers join together, what do they form?

 

 

6. What are four groups of organic compounds found in living things?

a.

b.

c.

d.

 

Carbohydrates

7. What atoms make up carbohydrates?

 

 

drates.

8. Circle the letter of each sentence that is true about carbohydrates.

a. Starches and sugars are examples of carbohydrates.

b. Living things use them as their main source of energy.

c. The monomers in sugar polymers are starch molecules.

d. Plants and some animals use them for strength and rigidity.

 

9. Single sugar molecules are also called ____________________________________________ .

 

10. Circle the letter of each monosaccharide.

a. galactose     b. glycogen     c. glucose       d. fructose

 

11. What are polysaccharides?

 

 

 

12. How do plants and animals store excess sugar?

 

 

 

Lipids

13. What kinds of atoms are lipids mostly made of?

 

 

ms.

14. What are three common categories of lipids?

 

a. ____________________________ b.________________________ c.____________________

 

15. Many lipids are formed when a glycerol molecule combines with compounds

called _______________________________________________________________________ .

 

16. Circle the letter of each way that fats are used in living things.

a. As parts of biological membranes

b. To store energy

c. To give plants rigidity

d. As chemical messengers

 

17. Complete the table about lipids.

LIPIDS

 

Kind of Lipid

Description

 

 

Each carbon atom in a lipid’s fatty acid chain is joined to another

carbon atom by a single bond.

 

Unsaturated

 

 

 

 

 A lipid’s fatty acids contain more than one double bond.

 

 

 

 

Nucleic Acids

18. Nucleic acids contain what kinds of atoms?

 

 

19. The monomers that make up nucleic acids are known as_____________________________ .

 

20. A nucleotide consists of what three parts?

 

21. What is the function of nucleic acids in living things?

 

 

22. What are two kinds of nucleic acids?

a.

 

b.

 

Proteins

23. Proteins contain what kinds of atoms?

 

 

24. Proteins are polymers of molecules called ________________________________________ .

 

25. What are four roles that proteins play in living things?

a.

 

b.

 

c.

 

d.

 

 

Section 2–4 Chemical Reactions and Enzymes (pages 50–53)

This section describes what happens to chemical bonds during chemical reactions. It also

explains how energy changes affect chemical reactions and describes the importance of enzymes.

Chemical Reactions

1. What is a chemical reaction?

 

 

2. Complete the table about chemicals in a chemical reaction.

CHEMICALS IN A CHEMICAL REACTION

 

Chemicals

Definition

 

Reactants

 

 

Products

 

 

reactio

 

n

3. Chemical reactions always involve changes in chemical______________________________ .

 

Energy in Reactions

4. What is released or absorbed whenever chemical bonds form or are broken?

 

5. What do chemical reactions that absorb energy need to occur?

 

 

6. Chemists call the energy needed to get a reaction started the ___________________________.

 

7. Complete the graph of an energy-releasing reaction by adding labels to show the energy

of the reactants, the energy of the products, and the activation energy.

a

Enzymes

8. What is a catalyst?

 

 

9. Proteins that act as biological catalysts are called ___________________________________.

 

10. What do enzymes do?

 

 

11. From what is part of an enzyme’s name usually derived?

 

12. The reactants of enzyme-catalyzed reactions are known as ___________________________.

 

13. Why are the active site and the substrates in an enzyme-catalyzed reaction often compared to a lock and key?

 

14. Look at figure 2-22. The binding together of an enzyme and a substrate forms a(an) _________________________________________________.

 

15. How do most cells regulate the activity of enzymes?