Biological Science, 6th Edition (Freeman, 2017) - 2025/2026 Study
Guide
Unit 1: The Chemical and Cellular Foundation of Life
1. What are the four major classes of biological macromolecules, and what is a
primary function of each?
ANSWER ✓ The four major classes are: 1) Carbohydrates, for energy storage and
structural support; 2) Lipids, for long-term energy storage, membrane structure, and
signaling; 3) Proteins, for catalyzing reactions (enzymes), structure, transport, and
defense; and 4) Nucleic Acids, for storing and transmitting genetic information.
2. Describe the structure of a phospholipid and explain why it is fundamental to
life.
ANSWER ✓ A phospholipid has a hydrophilic "head" (glycerol and phosphate group)
and two hydrophobic "tails" (fatty acid chains). This amphipathic nature causes them to
spontaneously form bilayers in water, creating the fundamental structure of all cellular
membranes, which separate the cell from its environment and compartmentalize
internal structures.
3. What is the endosymbiotic theory, and what evidence supports it?
ANSWER ✓ The endosymbiotic theory proposes that mitochondria and chloroplasts
evolved from free-living prokaryotic cells that were engulfed by a larger host cell.
Evidence includes: these organelles have their own DNA (circular, like bacteria), their
own ribosomes (70S, like bacteria), they double membranes, and they reproduce
independently within the cell via a process similar to binary fission.
4. How does the structure of the plasma membrane relate to its function as a
selective barrier?
ANSWER ✓ The fluid mosaic model describes the membrane as a fluid bilayer of
phospholipids with embedded proteins. This structure allows it to be selectively
permeable. Small nonpolar molecules can diffuse freely, but ions and polar molecules
require transport proteins, allowing the cell to precisely control the internal
environment.
,5. Contrast passive transport and active transport.
ANSWER ✓ Passive transport moves substances down their concentration gradient
without energy input (e.g., diffusion, facilitated diffusion). Active transport moves
substances against their concentration gradient, requiring energy (usually ATP) and
specific carrier proteins.
6. What is the primary role of ATP in cellular processes?
ANSWER ✓ ATP (Adenosine Triphosphate) is the primary energy currency of the cell.
When its third phosphate group is hydrolyzed, energy is released, which drives
endergonic cellular processes such as chemical synthesis, active transport, and
mechanical work.
7. Describe the relationship between a gene, an allele, and a chromosome.
ANSWER ✓ A gene is a specific sequence of DNA that codes for a functional product
(like a protein). An allele is a specific variant or version of a gene. Chromosomes are
long, condensed structures of DNA that contain many genes.
8. What are the key differences between prokaryotic and eukaryotic cells?
ANSWER ✓ Prokaryotic cells (Bacteria, Archaea) lack a membrane-bound nucleus and
other membrane-bound organelles, have circular DNA, and are typically smaller.
Eukaryotic cells have a true nucleus, numerous membrane-bound organelles (ER, Golgi,
mitochondria, etc.), linear DNA organized into chromosomes, and are typically larger
and more complex.
9. Explain the Central Dogma of Molecular Biology.
ANSWER ✓ The Central Dogma describes the flow of genetic information: DNA is
transcribed into RNA, and RNA is translated into a protein. This is a foundational
principle explaining how genes direct the synthesis of the proteins that determine a
cell's structure and function.
10. What is the role of the cytoskeleton?
ANSWER ✓ The cytoskeleton is a dynamic network of protein filaments (microtubules,
microfilaments, and intermediate filaments) that provides structural support, enables cell
movement (e.g., crawling, cytoplasmic streaming), facilitates intracellular transport, and
organizes organelles.
Unit 2: Energy Transformation and Metabolism
, 11. What is the overall chemical equation for cellular respiration?
ANSWER ✓ C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP (and heat). This summarizes the
process where glucose is oxidized to carbon dioxide, and oxygen is reduced to water,
releasing energy that is used to synthesize ATP.
12. Where in the eukaryotic cell do glycolysis, the Krebs cycle, and oxidative
phosphorylation occur?
ANSWER ✓ Glycolysis occurs in the cytoplasm. The Krebs (or Citric Acid) cycle occurs in
the mitochondrial matrix. Oxidative phosphorylation (the electron transport chain and
chemiosmosis) occurs across the inner mitochondrial membrane.
13. What is the primary role of oxygen in cellular respiration?
ANSWER ✓ Oxygen acts as the final electron acceptor in the electron transport chain. It
is highly electronegative and pulls electrons through the chain, facilitating the proton
gradient that drives ATP synthesis. Without oxygen, the chain backs up and stops.
14. What are the two main stages of photosynthesis, and where does each occur in
the chloroplast?
ANSWER ✓ The two stages are: 1) The light-dependent reactions, which occur in the
thylakoid membranes and convert light energy into chemical energy (ATP and NADPH);
and 2) The Calvin cycle (light-independent reactions), which occurs in the stroma and
uses that chemical energy to fix carbon dioxide into sugar.
15. How is the structure of a chloroplast adapted for its function?
ANSWER ✓ The thylakoid membranes provide a large surface area for light-absorbing
pigments and electron transport chains. The enclosed thylakoid space allows for a
proton gradient to build up. The fluid-filled stroma contains the enzymes necessary for
the Calvin cycle.
16. What is the primary function of the Calvin cycle?
ANSWER ✓ The primary function of the Calvin cycle is to fix atmospheric carbon dioxide
(CO₂) into an organic molecule and then reduce it to produce glyceraldehyde-3-
phosphate (G3P), a three-carbon sugar that can be used to make glucose and other
carbohydrates.
17. Contrast the products of the light-dependent and light-independent reactions.
ANSWER ✓ The light-dependent reactions produce ATP, NADPH, and O₂. The light-
independent reactions (Calvin cycle) use ATP and NADPH to produce G3P (sugar),
regenerating ADP and NADP⁺ in the process.
18. How do competitive and noncompetitive enzyme inhibitors differ?
ANSWER ✓ A competitive inhibitor binds to the active site of the enzyme, competing
Guide
Unit 1: The Chemical and Cellular Foundation of Life
1. What are the four major classes of biological macromolecules, and what is a
primary function of each?
ANSWER ✓ The four major classes are: 1) Carbohydrates, for energy storage and
structural support; 2) Lipids, for long-term energy storage, membrane structure, and
signaling; 3) Proteins, for catalyzing reactions (enzymes), structure, transport, and
defense; and 4) Nucleic Acids, for storing and transmitting genetic information.
2. Describe the structure of a phospholipid and explain why it is fundamental to
life.
ANSWER ✓ A phospholipid has a hydrophilic "head" (glycerol and phosphate group)
and two hydrophobic "tails" (fatty acid chains). This amphipathic nature causes them to
spontaneously form bilayers in water, creating the fundamental structure of all cellular
membranes, which separate the cell from its environment and compartmentalize
internal structures.
3. What is the endosymbiotic theory, and what evidence supports it?
ANSWER ✓ The endosymbiotic theory proposes that mitochondria and chloroplasts
evolved from free-living prokaryotic cells that were engulfed by a larger host cell.
Evidence includes: these organelles have their own DNA (circular, like bacteria), their
own ribosomes (70S, like bacteria), they double membranes, and they reproduce
independently within the cell via a process similar to binary fission.
4. How does the structure of the plasma membrane relate to its function as a
selective barrier?
ANSWER ✓ The fluid mosaic model describes the membrane as a fluid bilayer of
phospholipids with embedded proteins. This structure allows it to be selectively
permeable. Small nonpolar molecules can diffuse freely, but ions and polar molecules
require transport proteins, allowing the cell to precisely control the internal
environment.
,5. Contrast passive transport and active transport.
ANSWER ✓ Passive transport moves substances down their concentration gradient
without energy input (e.g., diffusion, facilitated diffusion). Active transport moves
substances against their concentration gradient, requiring energy (usually ATP) and
specific carrier proteins.
6. What is the primary role of ATP in cellular processes?
ANSWER ✓ ATP (Adenosine Triphosphate) is the primary energy currency of the cell.
When its third phosphate group is hydrolyzed, energy is released, which drives
endergonic cellular processes such as chemical synthesis, active transport, and
mechanical work.
7. Describe the relationship between a gene, an allele, and a chromosome.
ANSWER ✓ A gene is a specific sequence of DNA that codes for a functional product
(like a protein). An allele is a specific variant or version of a gene. Chromosomes are
long, condensed structures of DNA that contain many genes.
8. What are the key differences between prokaryotic and eukaryotic cells?
ANSWER ✓ Prokaryotic cells (Bacteria, Archaea) lack a membrane-bound nucleus and
other membrane-bound organelles, have circular DNA, and are typically smaller.
Eukaryotic cells have a true nucleus, numerous membrane-bound organelles (ER, Golgi,
mitochondria, etc.), linear DNA organized into chromosomes, and are typically larger
and more complex.
9. Explain the Central Dogma of Molecular Biology.
ANSWER ✓ The Central Dogma describes the flow of genetic information: DNA is
transcribed into RNA, and RNA is translated into a protein. This is a foundational
principle explaining how genes direct the synthesis of the proteins that determine a
cell's structure and function.
10. What is the role of the cytoskeleton?
ANSWER ✓ The cytoskeleton is a dynamic network of protein filaments (microtubules,
microfilaments, and intermediate filaments) that provides structural support, enables cell
movement (e.g., crawling, cytoplasmic streaming), facilitates intracellular transport, and
organizes organelles.
Unit 2: Energy Transformation and Metabolism
, 11. What is the overall chemical equation for cellular respiration?
ANSWER ✓ C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP (and heat). This summarizes the
process where glucose is oxidized to carbon dioxide, and oxygen is reduced to water,
releasing energy that is used to synthesize ATP.
12. Where in the eukaryotic cell do glycolysis, the Krebs cycle, and oxidative
phosphorylation occur?
ANSWER ✓ Glycolysis occurs in the cytoplasm. The Krebs (or Citric Acid) cycle occurs in
the mitochondrial matrix. Oxidative phosphorylation (the electron transport chain and
chemiosmosis) occurs across the inner mitochondrial membrane.
13. What is the primary role of oxygen in cellular respiration?
ANSWER ✓ Oxygen acts as the final electron acceptor in the electron transport chain. It
is highly electronegative and pulls electrons through the chain, facilitating the proton
gradient that drives ATP synthesis. Without oxygen, the chain backs up and stops.
14. What are the two main stages of photosynthesis, and where does each occur in
the chloroplast?
ANSWER ✓ The two stages are: 1) The light-dependent reactions, which occur in the
thylakoid membranes and convert light energy into chemical energy (ATP and NADPH);
and 2) The Calvin cycle (light-independent reactions), which occurs in the stroma and
uses that chemical energy to fix carbon dioxide into sugar.
15. How is the structure of a chloroplast adapted for its function?
ANSWER ✓ The thylakoid membranes provide a large surface area for light-absorbing
pigments and electron transport chains. The enclosed thylakoid space allows for a
proton gradient to build up. The fluid-filled stroma contains the enzymes necessary for
the Calvin cycle.
16. What is the primary function of the Calvin cycle?
ANSWER ✓ The primary function of the Calvin cycle is to fix atmospheric carbon dioxide
(CO₂) into an organic molecule and then reduce it to produce glyceraldehyde-3-
phosphate (G3P), a three-carbon sugar that can be used to make glucose and other
carbohydrates.
17. Contrast the products of the light-dependent and light-independent reactions.
ANSWER ✓ The light-dependent reactions produce ATP, NADPH, and O₂. The light-
independent reactions (Calvin cycle) use ATP and NADPH to produce G3P (sugar),
regenerating ADP and NADP⁺ in the process.
18. How do competitive and noncompetitive enzyme inhibitors differ?
ANSWER ✓ A competitive inhibitor binds to the active site of the enzyme, competing
