Campbell Biology in Focus, 3rd Edition - 2026/2027 Study Guide
Unit 1: The Chemistry and Energy of Life
1. Explain the theme of evolution in the context of molecular unity and diversity.
ANSWER ✓ All living organisms share a common genetic language (DNA/RNA),
universal metabolic pathways, and use the same core set of biochemical building blocks
(e.g., amino acids, nucleotides). This molecular unity strongly supports common
ancestry. Diversity arises from evolutionary modifications of these shared foundations
through processes like mutation, gene duplication, and natural selection, leading to the
vast array of forms and functions.
2. Describe the emergent properties of water that make it essential for life.
ANSWER ✓ Water's properties emerge from hydrogen bonding. These include: high
specific heat (moderates temperature), high heat of vaporization (cooling by
evaporation), cohesion/adhesion (water transport in plants), expansion upon freezing
(ice floats), and versatility as a solvent (dissolves polar/ionic substances). These
collectively create a stable environment for biochemical reactions.
3. Contrast the structure and function of the four major classes of biological
macromolecules.
ANSWER ✓ Carbohydrates: Polymers of sugars (e.g., starch, cellulose, glycogen).
Functions: energy storage (starch, glycogen) and structural support
(cellulose). Lipids: Diverse hydrophobic molecules (e.g., fats, phospholipids, steroids).
Functions: long-term energy storage, membrane structure (phospholipids), signaling
(steroids). Proteins: Polymers of amino acids linked by peptide bonds. Functions:
enzymatic catalysis, defense, transport, structural support, movement,
regulation. Nucleic Acids: Polymers of nucleotides (DNA, RNA). Functions: hereditary
information storage (DNA), transfer and expression of information (RNA).
4. Explain how the structure of an enzyme determines its function and regulation.
ANSWER ✓ An enzyme's unique 3D shape, particularly its active site, allows specific
substrate binding (lock-and-key or induced fit model). Its function (catalysis) depends
on this precise orientation of substrates. Regulation occurs via allosteric sites (non-
competitive inhibition/activation), competitive inhibition at the active site, and feedback
inhibition from downstream products.
5. Define the First and Second Laws of Thermodynamics in a biological context.
ANSWER ✓ First Law: Energy cannot be created or destroyed, only transferred or
transformed. In cells, chemical energy in glucose is transformed into ATP energy and
,heat. Second Law: Every energy transfer increases the entropy (disorder) of the universe.
Cells maintain order by using energy (ATP) to power work, releasing heat and increasing
surroundings' entropy.
6. How does ATP serve as the primary energy currency of the cell?
ANSWER ✓ ATP (adenosine triphosphate) stores energy in the high-energy phosphate
bonds between its phosphate groups. Hydrolysis of the terminal phosphate (ATP → ADP
+ Pi) releases energy that can be coupled to endergonic cellular work (e.g., synthesis,
transport, movement). ATP is regenerated by adding a phosphate to ADP using energy
from catabolic reactions.
Unit 2: Cell Biology & Communication
7. Compare and contrast the structure and function of prokaryotic and eukaryotic
cells.
ANSWER ✓ Prokaryotes: Simple, no membrane-bound organelles, DNA in nucleoid,
generally smaller. Eukaryotes: Complex, compartmentalized with organelles (nucleus,
mitochondria, ER, etc.), DNA within a double-membrane nucleus, generally larger. Key
functional difference: compartmentalization in eukaryotes allows separation and
specialization of metabolic processes.
8. Trace the pathway of synthesis, modification, and export of a secretory protein.
ANSWER ✓ 1. Synthesis: Ribosome on rough ER synthesizes the protein, threading it
into the ER lumen. 2. Modification: Protein folds and may undergo glycosylation in the
ER. 3. Transport: Vesicles bud from ER, fuse with the cis face of the Golgi apparatus.
4. Further Modification: Protein is modified, sorted, and tagged in Golgi cisternae.
5. Export: Vesicles from trans Golgi fuse with the plasma membrane, releasing the
protein via exocytosis.
9. Explain how the endomembrane system is functionally integrated.
ANSWER ✓ The endomembrane system (ER, Golgi, lysosomes, vesicles, plasma
membrane) is integrated through vesicular transport. The rough ER synthesizes proteins
and lipids. Transport vesicles shuttle these products to the Golgi for processing. The
Golgi then dispatches vesicles to the plasma membrane for secretion or to lysosomes
for digestion. This flow creates interconnected, dynamic compartments.
10. Describe the Fluid Mosaic Model of the plasma membrane.
ANSWER ✓ The model describes the membrane as a fluid bilayer of phospholipids,
where proteins are embedded or attached, creating a mosaic pattern. Membrane
components can move laterally (fluid), but asymmetric distribution is maintained.
Cholesterol modulates fluidity. Proteins perform functions like transport, signal
transduction, and cell-cell recognition.
, 11. Contrast passive and active transport across membranes.
ANSWER ✓ Passive Transport: Movement down a concentration gradient (high → low);
does not require energy. Includes simple diffusion, facilitated diffusion via
channel/carrier proteins. Active Transport: Movement against a gradient (low → high);
requires energy (usually ATP hydrolysis). Includes protein pumps (e.g., Na+/K+ pump)
and co-transport (secondary active transport).
12. Explain how cell signaling leads to a cellular response, using a G-protein-
coupled receptor (GPCR) pathway as an example.
ANSWER ✓ 1. Reception: Signaling molecule (ligand) binds to GPCR, activating it.
2. Transduction: Activated GPCR activates a G protein, which then activates an enzyme
(e.g., adenylyl cyclase). Adenylyl cyclase produces cAMP (second messenger), which
activates protein kinase A (PKA). 3. Response: PKA phosphorylates specific target
proteins, altering their activity and leading to the final cellular response (e.g., glycogen
breakdown).
Unit 3: Cellular Energetics
13. Describe how the proton motive force links electron transport to ATP
synthesis.
ANSWER ✓ During electron transport, protons (H+) are pumped across the inner
mitochondrial membrane (or thylakoid membrane) from the matrix (stroma) to the
intermembrane space (thylakoid lumen), creating both a concentration gradient and an
electrical gradient (together, the proton motive force). This stored potential energy
drives protons back through ATP synthase, powering the phosphorylation of ADP to ATP
(chemiosmosis).
14. Compare the inputs, outputs, and locations of glycolysis, the citric acid cycle,
and oxidative phosphorylation.
ANSWER ✓ Glycolysis: Inputs: 1 glucose, 2 ATP, 2 NAD+. Outputs: 2 pyruvate, 4 ATP (net
2), 2 NADH. Location: Cytosol. Citric Acid Cycle: Inputs: Acetyl CoA (from pyruvate).
Outputs per acetyl CoA: 3 NADH, 1 FADH2, 1 ATP (GTP), CO2. Location: Mitochondrial
matrix. Oxidative Phosphorylation: Inputs: NADH, FADH2, O2. Outputs: H2O, ~28-34
ATP. Location: Inner mitochondrial membrane.
15. Explain why ATP yield from glucose is approximate and variable.
ANSWER ✓ The theoretical maximum is ~36-38 ATP per glucose, but the actual yield is
lower (~30-32) due to: 1) Variable shuttles for moving cytosolic NADH into
mitochondria (malate-aspartate vs. glycerol-3-P shuttle yields different ATP). 2) The
proton motive force is also used for other work (e.g., pyruvate import, heat). 3)
Membranes are somewhat permeable to protons (leakage).
Unit 1: The Chemistry and Energy of Life
1. Explain the theme of evolution in the context of molecular unity and diversity.
ANSWER ✓ All living organisms share a common genetic language (DNA/RNA),
universal metabolic pathways, and use the same core set of biochemical building blocks
(e.g., amino acids, nucleotides). This molecular unity strongly supports common
ancestry. Diversity arises from evolutionary modifications of these shared foundations
through processes like mutation, gene duplication, and natural selection, leading to the
vast array of forms and functions.
2. Describe the emergent properties of water that make it essential for life.
ANSWER ✓ Water's properties emerge from hydrogen bonding. These include: high
specific heat (moderates temperature), high heat of vaporization (cooling by
evaporation), cohesion/adhesion (water transport in plants), expansion upon freezing
(ice floats), and versatility as a solvent (dissolves polar/ionic substances). These
collectively create a stable environment for biochemical reactions.
3. Contrast the structure and function of the four major classes of biological
macromolecules.
ANSWER ✓ Carbohydrates: Polymers of sugars (e.g., starch, cellulose, glycogen).
Functions: energy storage (starch, glycogen) and structural support
(cellulose). Lipids: Diverse hydrophobic molecules (e.g., fats, phospholipids, steroids).
Functions: long-term energy storage, membrane structure (phospholipids), signaling
(steroids). Proteins: Polymers of amino acids linked by peptide bonds. Functions:
enzymatic catalysis, defense, transport, structural support, movement,
regulation. Nucleic Acids: Polymers of nucleotides (DNA, RNA). Functions: hereditary
information storage (DNA), transfer and expression of information (RNA).
4. Explain how the structure of an enzyme determines its function and regulation.
ANSWER ✓ An enzyme's unique 3D shape, particularly its active site, allows specific
substrate binding (lock-and-key or induced fit model). Its function (catalysis) depends
on this precise orientation of substrates. Regulation occurs via allosteric sites (non-
competitive inhibition/activation), competitive inhibition at the active site, and feedback
inhibition from downstream products.
5. Define the First and Second Laws of Thermodynamics in a biological context.
ANSWER ✓ First Law: Energy cannot be created or destroyed, only transferred or
transformed. In cells, chemical energy in glucose is transformed into ATP energy and
,heat. Second Law: Every energy transfer increases the entropy (disorder) of the universe.
Cells maintain order by using energy (ATP) to power work, releasing heat and increasing
surroundings' entropy.
6. How does ATP serve as the primary energy currency of the cell?
ANSWER ✓ ATP (adenosine triphosphate) stores energy in the high-energy phosphate
bonds between its phosphate groups. Hydrolysis of the terminal phosphate (ATP → ADP
+ Pi) releases energy that can be coupled to endergonic cellular work (e.g., synthesis,
transport, movement). ATP is regenerated by adding a phosphate to ADP using energy
from catabolic reactions.
Unit 2: Cell Biology & Communication
7. Compare and contrast the structure and function of prokaryotic and eukaryotic
cells.
ANSWER ✓ Prokaryotes: Simple, no membrane-bound organelles, DNA in nucleoid,
generally smaller. Eukaryotes: Complex, compartmentalized with organelles (nucleus,
mitochondria, ER, etc.), DNA within a double-membrane nucleus, generally larger. Key
functional difference: compartmentalization in eukaryotes allows separation and
specialization of metabolic processes.
8. Trace the pathway of synthesis, modification, and export of a secretory protein.
ANSWER ✓ 1. Synthesis: Ribosome on rough ER synthesizes the protein, threading it
into the ER lumen. 2. Modification: Protein folds and may undergo glycosylation in the
ER. 3. Transport: Vesicles bud from ER, fuse with the cis face of the Golgi apparatus.
4. Further Modification: Protein is modified, sorted, and tagged in Golgi cisternae.
5. Export: Vesicles from trans Golgi fuse with the plasma membrane, releasing the
protein via exocytosis.
9. Explain how the endomembrane system is functionally integrated.
ANSWER ✓ The endomembrane system (ER, Golgi, lysosomes, vesicles, plasma
membrane) is integrated through vesicular transport. The rough ER synthesizes proteins
and lipids. Transport vesicles shuttle these products to the Golgi for processing. The
Golgi then dispatches vesicles to the plasma membrane for secretion or to lysosomes
for digestion. This flow creates interconnected, dynamic compartments.
10. Describe the Fluid Mosaic Model of the plasma membrane.
ANSWER ✓ The model describes the membrane as a fluid bilayer of phospholipids,
where proteins are embedded or attached, creating a mosaic pattern. Membrane
components can move laterally (fluid), but asymmetric distribution is maintained.
Cholesterol modulates fluidity. Proteins perform functions like transport, signal
transduction, and cell-cell recognition.
, 11. Contrast passive and active transport across membranes.
ANSWER ✓ Passive Transport: Movement down a concentration gradient (high → low);
does not require energy. Includes simple diffusion, facilitated diffusion via
channel/carrier proteins. Active Transport: Movement against a gradient (low → high);
requires energy (usually ATP hydrolysis). Includes protein pumps (e.g., Na+/K+ pump)
and co-transport (secondary active transport).
12. Explain how cell signaling leads to a cellular response, using a G-protein-
coupled receptor (GPCR) pathway as an example.
ANSWER ✓ 1. Reception: Signaling molecule (ligand) binds to GPCR, activating it.
2. Transduction: Activated GPCR activates a G protein, which then activates an enzyme
(e.g., adenylyl cyclase). Adenylyl cyclase produces cAMP (second messenger), which
activates protein kinase A (PKA). 3. Response: PKA phosphorylates specific target
proteins, altering their activity and leading to the final cellular response (e.g., glycogen
breakdown).
Unit 3: Cellular Energetics
13. Describe how the proton motive force links electron transport to ATP
synthesis.
ANSWER ✓ During electron transport, protons (H+) are pumped across the inner
mitochondrial membrane (or thylakoid membrane) from the matrix (stroma) to the
intermembrane space (thylakoid lumen), creating both a concentration gradient and an
electrical gradient (together, the proton motive force). This stored potential energy
drives protons back through ATP synthase, powering the phosphorylation of ADP to ATP
(chemiosmosis).
14. Compare the inputs, outputs, and locations of glycolysis, the citric acid cycle,
and oxidative phosphorylation.
ANSWER ✓ Glycolysis: Inputs: 1 glucose, 2 ATP, 2 NAD+. Outputs: 2 pyruvate, 4 ATP (net
2), 2 NADH. Location: Cytosol. Citric Acid Cycle: Inputs: Acetyl CoA (from pyruvate).
Outputs per acetyl CoA: 3 NADH, 1 FADH2, 1 ATP (GTP), CO2. Location: Mitochondrial
matrix. Oxidative Phosphorylation: Inputs: NADH, FADH2, O2. Outputs: H2O, ~28-34
ATP. Location: Inner mitochondrial membrane.
15. Explain why ATP yield from glucose is approximate and variable.
ANSWER ✓ The theoretical maximum is ~36-38 ATP per glucose, but the actual yield is
lower (~30-32) due to: 1) Variable shuttles for moving cytosolic NADH into
mitochondria (malate-aspartate vs. glycerol-3-P shuttle yields different ATP). 2) The
proton motive force is also used for other work (e.g., pyruvate import, heat). 3)
Membranes are somewhat permeable to protons (leakage).
