Name _____________________________ Class _________________ Date _________________
Chemistry of Life
Study Guide A
Answer Key
SECTION 1. ATOMS, IONS, AND
MOLECULES
SECTION 3. CARBON-BASED
MOLECULES
1. nucleus: dense center of an atom
2. neutron: particle with no electrical charge
3. proton: particle with positive electrical
charge
4. electron: particle with negative electrical
charge
5. compounds
6. elements
7. false
8. false
9. true
10. true
11. outermost
12. strong
13. electrons
14. covalent
15. compound
16. element
17. ionic bond
18. covalent bond
19. atom
20. molecule
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
SECTION 4. CHEMICAL REACTIONS
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
SECTION 2. PROPERTIES OF WATER
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
true
false
true
false
Students should sketch one of the following,
based on Figure 3.1 in the student text:
straight chain, branched chain, or ring.
Provide energy
starches, sugar
Store energy
fat, oils
source of amino acids
beans, meat, nuts
map for making proteins
DNA, RNA
polymer
false
true
true
a
b
c
evenly
solvent
nonpolar
more acidic, neutral, more basic
solute
12.
13.
14.
15.
16.
17.
reactants, products; reactants, products
chemical bonds
reactants
atoms
same rate
false
true
true
false
false
chemical reaction that absorbs more energy
than it releases
chemical reaction that releases more energy
than it absorbs
amount of energy that needs to be absorbed
for a chemical reaction to start
substances changed during a chemical
reaction
substances made by a chemical reaction
state reached when reactants and products
are made at the same rate
amount of energy that will break a bond
between two atoms
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology
Study Guide A
i
Chemistry of Life
Name _____________________________ Class _________________ Date _________________
Study Guide A continued
SECTION 5. ENZYMES
1.
2.
3.
4.
b
c
a
(starting in upper left box and moving
clockwise) in living things, temperature
and pH, by speeding them up, by binding
to the enzyme, making it possible for the
reaction to take place
5. decrease
6. enzymes
7. Enzymes
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology
Study Guide A
ii
Chemistry of Life
Name _____________________________ Class _________________ Date _________________
Section 1: Atoms, Ions, and Molecules
Study Guide A
KEY CONCEPT
All living things are based on atoms and their interactions.
VOCABULARY
atom
ion
molecule
element
ionic bond
compound
covalent bond
MAIN IDEA: Living things consist of atoms of different elements.
Draw lines to connect the parts of an atom with their descriptions.
1. nucleus
particle with a positive electrical charge
2. neutron
particle with a negative electrical charge
3. proton
particle with no electrical charge
4. electron
dense center of an atom
Circle the word or phrase that best completes the sentence.
5. Water (H2O) and carbon dioxide (CO2), are examples of
compounds / elements.
6. Elements / Compounds are made up of only one type of atom.
MAIN IDEA: Ions form when atoms gain or lose electrons.
Choose whether the statement is true or false.
7. true / false An atom becomes an ion when its number of protons changes.
8. true / false Some ions are positively charged, and some ions have no charge.
9. true / false The formation of an ion results in a full outermost energy level.
10. true / false Ions usually form when electrons are transferred from one
atom to another.
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology
Study Guide A
1
Chemistry of Life
Section 1: Atoms, Ions, and Molecules
Name _____________________________ Class _________________ Date _________________
Study Guide A continued
MAIN IDEA: Atoms share pairs of electrons in covalent bonds.
Circle the word or phrase that best completes the sentence.
11. Shared pairs of electrons fill the innermost / outermost energy levels of
bonded atoms.
12. Covalent bonds are generally very strong / weak.
13. Two atoms may form several covalent bonds to share several pairs of
protons / electrons.
14. A molecule is held together by ionic / covalent bonds.
Vocabulary Check
element
compound
ion
ionic bond
covalent bond
atom
molecule
Write each word or phrase next to its definition.
____________________ 15. a substance made of atoms of different elements
bonded together in a certain ratio
____________________ 16. a particular type of atom
____________________ 17. a bond formed by the electrical force between two
ions of opposite charge
____________________ 18. a bond formed when two atoms share a pair
of electrons
____________________ 19. the smallest basic unit of matter
____________________ 20. two or more atoms held together by covalent bonds
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology
Study Guide A
2
Chemistry of Life
Section 1: Atoms, Ions, and Molecules
Name _____________________________ Class _________________ Date _________________
Section 2: Properties of Water
Study Guide A
KEY CONCEPT
Water’s unique properties allow life to exist on Earth.
VOCABULARY
hydrogen bond
solution
acid
cohesion
solvent
base
adhesion
solute
pH
MAIN IDEA: Life depends on hydrogen bonds in water.
Choose whether the statement is true or false.
1. true / false Polar molecules have two regions with a slight positive charge.
2. true / false Water is a polar molecule.
3. true / false Slightly charged regions of water molecules form hydrogen bonds.
Choose the best answer for the question.
4. Which property allows water to resist changes in temperature?
a. high specific heat
b. cohesion
c. adhesion
d. polarity
5. Which property causes water to form beads?
a. high specific heat
b. cohesion
c. adhesion
d. polarity
6. Which property of water helps plants to transport water from their roots to
their leaves?
a. high specific heat
b. cohesion
c. adhesion
d. polarity
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology
Study Guide A
3
Chemistry of Life
Section 2: Properties of Water
Name _____________________________ Class _________________ Date _________________
Study Guide A continued
MAIN IDEA: Many compounds dissolve in water.
Circle the word or phrase that best completes the sentence.
7. A solution is a mixture of substances that is evenly / unevenly distributed
throughout the entire mixture.
8. Blood plasma is an example of a solvent / solute.
9. “Oil and water don’t mix” because a polar / nonpolar molecule can’t easily
dissolve in a polar solvent.
MAIN IDEA: Some compounds form acids or bases.
10. In the pH table below, add labels to show which side of the table shows pHs
that are more acidic, and which side shows pHs that are more basic. Then add
a label to show which pH is neutral.
1
2
3
4
5
6
7
8
9
10 11
12
13
14
_________________________________________________________
Vocabulary Check
Fill in the blank with either solvent or solute.
11. A __________ dissolves in a solution.
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology
Study Guide A
4
Chemistry of Life
Section 2: Properties of Water
Name _____________________________ Class _________________ Date _________________
Section 3: Carbon-Based Molecules
Study Guide A
KEY CONCEPT
Carbon-based molecules are the foundation of life.
VOCABULARY
monomer
lipid
amino acid
polymer
fatty acid
nucleic acid
carbohydrate
protein
MAIN IDEA: Carbon atoms have unique bonding properties.
Choose whether the statement is true or false.
1. true / false Carbon atoms form the building blocks of most living things.
2. true / false Carbon’s outer energy level is full.
3. true / false Carbon atoms can form covalent bonds with up to four other atoms.
4. true / false The three basic structures of carbon-based molecules are straight
chain, bent chain, and ring.
5. Choose one of the three basic structures of carbon-based molecules to sketch
in the space below. Label your sketch with the name of the basic structure.
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology
Study Guide A
5
Chemistry of Life
Section 3: Carbon-Based Molecules
Name _____________________________ Class _________________ Date _________________
Study Guide A continued
MAIN IDEA: Four main types of carbon-based molecules are found in living
things.
Complete the table with the functions and examples provided for each type of
carbon-based molecule.
Functions
Examples
Provide energy
meat
fat
oils
Building blocks of proteins sugar
beans
DNA
Map for making proteins
starches
nuts
RNA
Store energy
Molecule Type
Functions
Examples
Carbohydrate
6.
7.
Lipid
8.
9.
Protein
10.
11.
Nucleic acid
12.
13.
Vocabulary Check
14. The prefix mono- means “one,” and the prefix poly- means “many.”
Which contains more molecules, a monomer or a polymer?
_____________________
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology
Study Guide A
6
Chemistry of Life
Section 3: Carbon-Based Molecules
Name _____________________________ Class _________________ Date _________________
Section 4: Chemical Reactions
Study Guide A
KEY CONCEPT
Life depends on chemical reactions.
VOCABULARY
chemical reaction
bond energy
exothermic
reactant
equilibrium
endothermic
product
activation energy
MAIN IDEA: Bonds break and form during chemical reactions.
1. Label the reactants and products in the chemical reactions shown below.
____________________________
CH4 + 2O2
CO2 + 2H2O
_______________________________
____________________________
6CO2 + 6H2O
6O2 + C6H12O6
_______________________________
Circle the word or phrase that best completes the sentence.
2. During a chemical reaction, chemical bonds / solutes break and reform.
3. Reactants / products are the substances changed during a chemical reaction.
4. Bond energy is the amount of energy it takes to break a bond between two
atoms / ions.
5. Equilibrium occurs when reactants and products are made at the same rate /
different rates.
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology
Study Guide A
7
Chemistry of Life
Section 4: Chemical Reactions
Name _____________________________ Class _________________ Date _________________
Study Guide A continued
MAIN IDEA: Chemical reactions release or absorb energy.
Choose whether the statement is true or false.
6. true / false Not all chemical reactions involve changes in energy.
7. true / false Activation energy is required for a chemical reaction to start.
8. true / false Some chemical reactions release more energy than they absorb,
while others absorb more energy than they release.
9. true / false Chemical reactions can occur whether or not energy is added to the
reactants.
10. true / false An exothermic chemical reaction absorbs more energy than it
releases.
Vocabulary Check
Draw lines to connect the words or phrases that mean the same thing.
11. endothermic reaction
substances changed during a
chemical reaction
12. exothermic reaction
substances made by a chemical reaction
13. activation energy
chemical reaction that releases more
energy than it absorbs
14. reactants
chemical reaction that absorbs more
energy than it releases
15. products
amount of energy that needs to be
absorbed for a chemical reaction to start
16. equilibrium
amount of energy that will break a bond
between two atoms
17. bond energy
state reached when reactants and
products are made at the same rate
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology
Study Guide A
8
Chemistry of Life
Section 4: Chemical Reactions
Name _____________________________ Class _________________ Date _________________
Section 5: Enzymes
Study Guide A
KEY CONCEPT
Enzymes are catalysts for chemical reactions in living things.
VOCABULARY
catalyst
substrate
enzyme
MAIN IDEA: A catalyst lowers activation energy.
Choose the best answer to the question.
1. Activation energy is the energy required to
a. complete a chemical reaction.
b. start a chemical reaction.
c. produce a catalyst.
d. produce the reactants.
2. Which of the following can reduce the amount of energy needed for a
chemical reaction to take place?
a. reactant
b. product
c. catalyst
d. hydrogen bond
3. What happens to the speed of a chemical reaction when a catalyst is present?
a. It speeds up.
b. It slows down.
c. It stays the same.
d. It becomes erratic.
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology
Study Guide A
9
Chemistry of Life
Section 5: Enzymes
Name _____________________________ Class _________________ Date _________________
Study Guide A continued
MAIN IDEA: Enzymes allow chemical reactions to occur under tightly controlled
conditions.
4. Take notes about enzymes by filling in the Main Idea Web below.
What physical factors affect the
action of enzymes?
Where do enzymes act as catalysts?
Enzymes
How do enzymes affect the
speed of chemical reactions in
the body?
How does a substrate affect an
enzyme?
Vocabulary Check
Circle the word or phrase that best completes the sentence.
5. A catalyst can increase / decrease the amount of energy needed to start a
chemical reaction.
6. Substrates are to catalysts / enzymes as keys are to locks.
7. Enzymes / substrates are catalysts for chemical reactions in living things.
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology
Study Guide A
10
Chemistry of Life
Section 5: Enzymes