This document is a study guide for a biology class that covers cells and energy. It includes review questions and key concepts about photosynthesis, cellular respiration, ATP, and fermentation. The study guide has sections on chemical energy and ATP, an overview of photosynthesis, photosynthesis in detail, an overview of cellular respiration, cellular respiration in detail, and fermentation. It provides the student with questions to test their understanding of these topics as well as diagrams and equations to label.

1. Name ______________________________ Class___________________Date__________________
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology i Cells and Energy
Study Guide A
Cells and Energy
Study Guide A
Answer Key
SECTION 1. CHEMICAL ENERGY
AND ATP
1. molecule; food molecules
2. high-energy; lower-energy
3. phosphate group
4. a; d; b; c
5. b; e
6. c; d
7. a; f
8. chemical energy; light energy
9. three; two
10. chemical; molecules
SECTION 2. OVERVIEW OF
PHOTOSYNTHESIS
1. chemical energy
2. light energy; chemical energy
3. visible light
4. photosynthesis
5. stroma; grana
6. grana
7. Equation: 6CO2 + 6H2O C6H12O6 + 6O2
8. 6CO2 and 6H2O
9. 6O2 and C6H12O6
10. b
11. require light; energy
12. do not require light; sugars
13. Refer to Figure 2.2 for a visual answer.
The four steps are: d, a, b, c
14. energy; sugars
15. green
16. independent
SECTION 3. PHOTOSYNTHESIS
IN DETAIL
1. capture; transfer
2. molecules
3. ATP; NADPH
4. b, g, d, f, c, e, a
5. carbon dioxide
6. 1 b; 2 d; A a; 3 e; 4 c
7. proteins
8. synthesizes
9. with no beginning or end.
SECTION 4. OVERVIEW OF
CELLULAR RESPIRATION
1. energy; oxygen
2. oxygen
3. mitochondria
4. glucose; ATP
5. b; c
6. a; c
7. Equation: C6H12O6 + 6O2  6CO2 + 6H2O
8. 6O2 and C6H12O6
9. 6CO2 and 6H2O
10. d
11. Refer to Figure 4.2 for a visual answer.
The four steps are: d, b, a, c
12. sugar
13. oxygen
14. break down
SECTION 5. CELLULAR
RESPIRATION IN DETAIL
1. glucose
2. Pyruvate and NADH; ATP
3. two; four
4. c
5. c, b, a, d, e
6. inner
7. electrons; hydrogen ions
8. c, d, b, a
9. electrons
SECTION 6. FERMENTATION
1. ATP
2. electrons
3. hard exercise
4. oxygen
5. two
6. For a visual answer, refer to the lactic acid
fermentation diagram in Section 6. The
order of the four steps is: d, b, c, a
7. For a visual answer, refer to the alcoholic
fermentation diagram in Section 6. The
order of the four steps is: c, a, d, b

2. Name ______________________________ Class___________________Date__________________
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology ii Cells and Energy
Study Guide A
Study Guide A continued
8. Uses pyruvate and NADH = Both; Recycles
NAD+ to glycolysis = Both; Produces
Lactic Acid = Lactic acid fermentation;
Produces alcohol and carbon dioxide =
Alcoholic Fermentation.
9. cheese, yogurt
10. bread
11. carbon dioxide
12. waste product; muscles

3. Name ______________________________ Class___________________Date__________________
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology 1 Cells and Energy
Study Guide A Section 1: Chemical Energy and ATP
Section 1: Chemical Energy and ATP
Study Guide A
KEY CONCEPT
All cells need chemical energy.
VOCABULARY
MAIN IDEA: The chemical energy used for most cell processes is carried
by ATP.
Circle the word or phrase that best completes the statement.
1. All cells use adenosine triphosphate (ATP) for energy. ATP is a molecule /
organelle that transfers energy from the breakdown of ADP / food molecules
to cell processes.
2. ATP is a high-energy / low-energy molecule that is converted into
higher-energy / lower-energy ADP when a phosphate group is removed
and energy is released.
3. ADP is converted back into ATP by the addition of a phosphate group /
food molecule.
4. Put the letter of the appropriate statement into each box of the cycle diagram
below to show the relationship between ATP and ADP.
a. High-energy adenosine triphosphate (ATP)
b. Lower-energy adenosine diphosphate (ADP)
c. Energy added from breakdown of carbon-based molecules, phosphate
added
d. Phosphate removed, energy released
ATP ADP chemosynthesis

4. Name ______________________________ Class___________________Date__________________
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology 2 Cells and Energy
Study Guide A Section 1: Chemical Energy and ATP
Study Guide A continued
MAIN IDEA: Organisms break down carbon-based molecules to produce ATP.
Put the letter for each of the following six statements into the appropriate list to
identify the roles of different types of molecules when they are broken down to
make ATP.
a. molecules least likely to be broken down
b. molecules most commonly broken down
c. molecules that store most of the energy in a person’s body
d. triglyceride yields about 146 ATP
e. glucose yields about 36 ATP
f. store about the same amount of energy as carbohydrates
MAIN IDEA: A few types of organisms do not need sunlight and photosynthesis
as a source of energy.
Circle the word or phrase that best completes the statement.
8. Chemosynthesis is a process by which some organisms use chemical energy /
light energy instead of chemical energy / light energy to make energy-storing
carbon-based molecules.
Type of Molecule Role in ATP Production
5. Carbohydrates
4 calories per mg (4 Calories per gram)
6. Lipids
9 calories per mg (9 Calories per gram)
7. Proteins
9 calories 4 calories per mg
(4 Calories per gram)

5. Name ______________________________ Class___________________Date__________________
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology 3 Cells and Energy
Study Guide A Section 1: Chemical Energy and ATP
Study Guide A continued
Vocabulary Check
Fill in each blank with the word or phrase that best completes the sentence.
9. The prefix tri- means “three,” and the prefix di- means “two.” Therefore,
adenosine triphosphate (ATP) has ___________ phosphate groups, and
adenosine diphosphate (ADP) has __________________ phosphate groups.
10. The prefix chemo- means “chemical,” and synthesis comes from a Greek word
that means “to put together.” Therefore, chemosynthesis means “to put
together with chemicals.” In chemosynthesis, ______________ energy is used
to produce carbon-based ____________ that store energy.

6. Name ______________________________ Class___________________Date__________________
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology 4 Cells and Energy
Study Guide A Section 3: Photosynthesis in Detail
Section 2: Overview of Photosynthesis
Study Guide A
KEY CONCEPT
The overall process of photosynthesis produces sugars that store chemical energy.
VOCABULARY
MAIN IDEA: Photosynthetic organisms are producers.
Circle the word or phrase that best completes the statement.
1. Some organisms are called producers because they produce the source of
chemical energy / light energy for themselves and for other organisms.
2. Photosynthesis captures chemical energy / light energy to make sugars that
store chemical energy / light energy.
3. Chlorophyll is a molecule in chloroplasts that absorbs some of the energy in
visible light / ultraviolet light.
MAIN IDEA: Photosynthesis in plants occurs in chloroplasts.
4. Chloroplasts are membrane-bound organelles where _________ takes place
in plants.
5. Photosynthesis takes place in two parts of a chloroplast: the _________
and the _________.
6. Thylakoids are coin-shaped, membrane-enclosed compartments
inside the _________.
7. The overall process of photosynthesis can be written as a chemical equation.
Fill in the blanks in the equation below using the appropriate compound from
the box.
_________ + __________  ________ + ________
8. The two reactants in the photosynthesis equation are _________ and
_________.
9. The two products in the photosynthesis equation are _________ and
_________.
photosynthesis light-dependent reactions
chlorophyll light-independent reactions
thylakoid
6O2 6CO2 6H2O C6H12O6

7. Name ______________________________ Class___________________Date__________________
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology 5 Cells and Energy
Study Guide A Section 3: Photosynthesis in Detail
Photosynthesis
Study Guide A continued
10. Why is the photosynthesis equation often written with several arrows?
a. Because many enzymes are added to the reactants to make the products.
b. Because many chemical reactions occur with the help of many enzymes.
c Because many reactants can enter into the photosynthesis reaction.
d. Because many products can be made from the photosynthesis reaction.
Circle the word or phrase that best completes the statement.
11. The light-dependent reactions require light / do not require light, and they
absorb and transfer sugars / energy.
12. The light-independent reactions require light / do not require light, and they
build sugars / energy.
13. Use the space below to sketch a chloroplast. Label the grana, thylakoids,
and stroma. Indicate where each of the following steps of the photosynthetic
process occurs.
a. Energy carried along the thylakoid membrane is transferred to molecules
that carry energy to the light-independent reactions.
b. Carbon dioxide is added to a cycle of chemical reactions to build larger
molecules.
c. A six-carbon simple sugar (usually glucose; C6H12O6) is formed.
d. Energy from sunlight is absorbed and transferred along the thylakoid
membrane. Water molecules are broken down and oxygen is released.

8. Name ______________________________ Class___________________Date__________________
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology 6 Cells and Energy
Study Guide A Section 3: Photosynthesis in Detail
Study Guide A continued
Vocabulary Check
Fill in each blank with the word or phrase that best completes the sentence.
14. The prefix photo- means “light,” and synthesis means “to put together.”
During photosynthesis, __________ from light is used to put together
_________.
15. The prefix chloro- means “green,” and the suffix -phyll means “leaf.”
Therefore, chlorophyll is the light-absorbing molecule that makes leaves
look _________.
16. The prefix in- means “not.” Therefore, the reactions in photosynthesis that do
not require light are called light-_________.
Main idea: THE SECOND STAGE OF PHOTOSYNTHESIS USES ENERGY
FROM THE FIRST STAGE TO MAKE SUGARS.
5. The Calvin cycle uses energy from the light-dependent reactions to convert
_________________ into sugars.
6. Using the diagram on the next page, put the letter from each of the following
statements into the appropriate box to show the four steps of the Calvin cycle.
a. A three-carbon molecule exits the cycle. Other three-carbon molecules stay
in the cycle.
b. Carbon dioxide is added to the Calvin cycle.
c. Energy is used to convert the remaining three-carbon molecules into five-
carbon molecules.
d. Energy is used to split six-carbon molecules. Three-carbon molecules are
formed and rearranged.
e. When two three-carbon molecules have left the cycle they bond to form a
six-carbon sugar (glucose).

9. Name ______________________________ Class___________________Date__________________
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology 7 Cells and Energy
Study Guide A Section 3: Photosynthesis in Detail
3.
A.
4.
2.
1.
Study Guide A continued
Vocabulary Check
Circle the word or phrase that best completes the statement.
7. The electron transport chain is a series of proteins / carbohydrates in the
thylakoid membrane along which energized electrons travel.
8. The first part of an enzyme’s name tells you about its function. All enzymes
end with the suffix -ase. Therefore, ATP synthase is an enzyme that
synthesizes / synchronizes ATP.
9. The word cycle tells you that the chemical reactions of the Calvin cycle go
from one to another with a beginning and an end / with no beginning or end.

10. Name ______________________________ Class___________________Date__________________
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology 8 Cells and Energy
Study Guide A Section 4: Overview of Cellular Respiration
Section 4: Overview of Cellular Respiration
Study Guide A
KEY CONCEPT
The overall process of cellular respiration converts sugar into ATP using oxygen.
VOCABULARY
MAIN IDEA: Cellular respiration makes ATP by breaking down sugars.
Circle the word or phrase that best completes the statement.
1. Cellular respiration is a process that releases glucose / energy from sugars
and other carbon-based molecules to make ATP when oxygen / carbon dioxide
is present.
2. Cellular respiration is called an aerobic process, because it needs oxygen /
carbon dioxide to take place.
3. Cellular respiration takes place in the chloroplasts / mitochondria.
4. During glycolysis, one molecule of glucose / protein is split into two three-
carbon molecules and two ADP / ATP are formed.
MAIN IDEA: Cellular respiration makes ATP by breaking down sugars.
5. Circle the two ways in which cellular respiration seems to be the opposite
of photosynthesis.
a. The reactions occur at either end of the chloroplast.
b. The overall chemical equations are the reverse of each other.
c. Cellular respiration breaks down sugars to make ATP, and photosynthesis
uses ATP to make sugars.
d. Cellular respiration produces oxygen, and photosynthesis produces carbon
dioxide.
6. Circle the two parts of a mitochondrion where cellular respiration takes place.
a. matrix
b stroma
c. inner mitochondrial membrane
d. outer mitochondrial membrane
cellular respiration anaerobic
aerobic Krebs cycle
glycolysis

11. Name ______________________________ Class___________________Date__________________
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology 9 Cells and Energy
Study Guide A Section 4: Overview of Cellular Respiration
Cellular Respiration
Study Guide A continued
7. The overall process of cellular respiration can be written as a chemical
equation. Fill in the blanks in the equation below using the appropriate
compound from the box.
__________ + __________  ________ + ________
8. The two reactants in the cellular respiration equation are ________ and
_________.
9. The two products in the cellular respiration equation are ________ and
_________.
10. Why is the cellular respiration equation written with several arrows?
a. Because a series of products result from the reaction.
b. Because a series of reactants enter into the reaction.
c. Because a series of chemicals is added to the process.
d. Because a series of chemical reactions occurs.
11. Use the space below to sketch a mitochondrion. Label the matrix and
inner membrane. Indicate where each of the following steps of the cellular
respiration process occurs.
a. Energized electrons are passed along the electron transport chain in the
inner mitochondrial membrane.
b. Energy is transferred to the second stage of cellular respiration (the electron
transport chain).
c. A large number of ATP are formed. Oxygen picks up electrons, and water is
released as a waste product.
d. Three-carbon molecules enter the Krebs cycle and are broken down. ATP
and other energy-carrying molecules are formed. Carbon dioxide is released
as a waste product.
6O2 6CO2 6H2O C6H12O6

12. Name ______________________________ Class___________________Date__________________
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology 10 Cells and Energy
Study Guide A Section 4: Overview of Cellular Respiration
Study Guide A continued
Vocabulary Check
Fill in the blank with the word or phrase that best completes the sentence.
12. The prefix glyco- comes from a Greek word that means “sweet.” The suffix
-lysis comes from a Greek word that means “to loosen.” Therefore, during
glycolysis, a _________ is broken down (or “loosened”).
13. Glycolysis is an anaerobic process, because it takes place without
__________________.
14. During the Krebs cycle, chemical reactions _____________________ carbon-
based molecules.

13. Name ______________________________ Class___________________Date__________________
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology 11 Cells and Energy
Study Guide A Section 6: Fermentation
Lactic Acid Fermentation
Section 6: Fermentation
Study Guide A
KEY CONCEPT
Fermentation allows the production of a small amount of ATP without oxygen.
VOCABULARY
MAIN IDEA: Fermentation allows glycolysis to continue.
1. Fermentation is important, because it allows glycolysis to continue making
_________ when oxygen is unavailable for cellular respiration.
2. Fermentation removes ____________ from NADH and recycles NAD+ to
glycolysis.
3. Fermentation takes place in your muscle cells during
_____________________________, when not enough oxygen is available.
4. Fermentation is an anaerobic process, because it occurs without
_______________.
5. Fermentation is involved in the production of ATP by allowing glycolysis to
take place. Glycolysis yields _______________ net ATP.
6. In the space below, draw the process of lactic acid fermentation and label it
with the statements listed.
a. NAD+
is recycled to glycolysis.
b. NADH is used to convert pyruvate into lactic acid.
c. NADH is changed into NAD+
.
d. Pyruvate and glycolysis enter fermentation.
fermentation
lactic acid

14. Name ______________________________ Class___________________Date__________________
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology 12 Cells and Energy
Study Guide A Section 6: Fermentation
Alcoholic Fermentation
Study Guide A continued
MAIN IDEA: Fermentation and its products are important in several ways.
7. In the space below, draw the process of alcoholic fermentation and label it
with the statements listed.
a. NADH is used to convert pyruvate into alcohol and carbon dioxide.
b. NAD+ is recycled to glycolysis.
c. Pyruvate and glycolysis enter fermentation.
d. NADH is changed into NAD+ .
8. Place a check mark in the appropriate boxes below to show how lactic acid
fermentation and alcoholic fermentation are similar and how they are different.
Lactic Acid
Fermentation
Alcoholic
Fermentation Both
Uses pyruvate and NADH
Recycles NAD+ to
glycolysis
Produces lactic acid
Produces alcohol and
carbon dioxide

15. Name ______________________________ Class___________________Date__________________
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology 13 Cells and Energy
Study Guide A Section 6: Fermentation
Study Guide A continued
9. Name one commercial use of lactic acid fermentation. ________________
10. Name one commercial use of alcoholic fermentation. ________________
Vocabulary Check
Circle the word or phrase that best completes the statement.
11. The term fermentation is based on a word that means “to bubble.” This
meaning is related to the fermentation process, because bubbles of carbon
dioxide / oxygen are produced during alcoholic fermentation.
12. Lactic acid is the three-carbon reactant / waste product of lactic acid
fermentation. It causes a burning feeling in your muscles / blood vessels during
exercise