Lehninger-Principles-of-Biochemistry-8th-Edition-part-1-The-
Foundations-of-Biochemistry
,Lehninger-Principles-of-Biochemistry-8th-Edition-part-1-The-
Foundations-of-Biochemistry
CHAPTER-1:-Foundations-of-Biochemistry
1. Q:-What-are-the-four-major-classes-of-biomolecules?
A:-Proteins,-nucleic-acids,-carbohydrates,-and-lipids.
2. Q:-Why-is-carbon-uniquely-suited-as-the-backbone-element-for-biological-
molecules?
A:-Carbon-forms-four-stable-covalent-bonds,-can-create-single/double/triple-
bonds,-and-readily-forms-chains-and-rings-with-itself-and-other-elements.
3. Q:-Define-the-first-law-of-thermodynamics-as-it-applies-to-living-systems.
A:-Energy-can-be-neither-created-nor-destroyed—only-converted-from-one-
form-to-another.-Living-organisms-transform-energy-but-cannot-create-it-de-
novo.
4. Q:-What-is-ΔG°'-and-why-is-the-prime-symbol-important-in-biochemistry?
A:-ΔG°'-is-the-standard-free-energy-change-at-pH-7.0-(physiological-pH).-The-
prime-distinguishes-biochemical-standard-state-(pH-7)-from-chemical-standard-
state-(pH-0).
5. Q:-When-ΔG-is-negative,-is-a-reaction-spontaneous-or-nonspontaneous?
A:-Spontaneous-(exergonic).
6. Q:-What-three-general-strategies-do-cells-use-to-accomplish-
thermodynamically-unfavorable-reactions?
A:-(1)-Coupling-to-favorable-reactions,-(2)-Maintaining-reactant/product-
concentrations-far-from-equilibrium,-(3)-Using-energy-carriers-(ATP,-NADH).
7. Q:-What-is-the-primary-energy-currency-molecule-in-cells?
A:-ATP-(adenosine-triphosphate).
8. Q:-Name-three-characteristics-that-distinguish-living-organisms-from-
nonliving-matter.
A:-Highly-organized-structure,-ability-to-extract/transform-energy,-capacity-
for-self-replication-with-inheritance.
9. Q:-What-is-the-relationship-between-ΔG,-ΔH,-and-ΔS?
A:-ΔG-=-ΔH-–-TΔS-(Gibbs-free-energy-equation).
10. Q:-Why-can't-living-systems-be-at-equilibrium?
A:-Equilibrium-represents-maximum-entropy-(disorder)-and-no-net-energy-
flow—conditions-incompatible-with-life's-organized,-energy-requiring-
processes.
CHAPTER-2:-Water
11. Q:-What-molecular-property-gives-water-its-high-dielectric-constant?
A:-Its-bent-molecular-geometry-and-polar-O–H-bonds-create-a-permanent-
dipole-moment.
,Lehninger-Principles-of-Biochemistry-8th-Edition-part-1-The-
Foundations-of-Biochemistry
12. Q:-How-does-water's-high-specific-heat-benefit-living-organisms?
A:-It-buffers-cells-and-organisms-against-rapid-temperature-changes,-
maintaining-thermal-stability.
13. Q:-Define-hydrophobic-effect.
A:-The-tendency-of-nonpolar-substances-to-aggregate-in-aqueous-solution,-
driven-by-water-molecules-maximizing-their-own-entropy-by-minimizing-
ordered-cages-around-hydrophobic-surfaces.
14. Q:-What-is-the-concentration-of-H⁺-in-pure-water-at-25°C?
A:-1.0-×-10⁻⁷-M.
15. Q:-Calculate-the-pH-of-a-solution-with-[H⁺]-=-2.5-×-10⁻⁴-M.
A:-pH-=-–log(2.5-×-10⁻⁴)-=-3.60.
16. Q:-What-is-the-pKₐ-of-water?
A:-14.0-(at-25°C).
17. Q:-Why-does-ice-float-on-liquid-water?
A:-Ice-has-an-open,-hexagonal-crystal-lattice-with-greater-volume-(lower-
density)-than-liquid-water-due-to-maximized-hydrogen-bonding.
18. Q:-How-many-hydrogen-bonds-can-a-single-water-molecule-form?
A:-Up-to-four-(two-as-donor-via-H-atoms,-two-as-acceptor-via-lone-pairs-on-
oxygen).
19. Q:-What-is-the-hydrophobic-effect's-thermodynamic-basis?
A:-Increase-in-entropy-of-water-molecules-when-hydrophobic-groups-
aggregate,-releasing-ordered-water-molecules-into-the-bulk-solvent.
20. Q:-Define-amphipathic-molecule-and-give-one-biological-example.
A:-A-molecule-with-both-hydrophilic-and-hydrophobic-regions.-Example:-
phospholipids,-fatty-acids,-or-detergents.
21. Q:-What-is-the-ion-product-of-water-(K_w)-at-25°C?
A:-1.0-×-10⁻¹⁴-M².
22. Q:-Why-is-water-an-excellent-solvent-for-ionic-compounds?
A:-Its-high-dielectric-constant-(ε-≈-78.5)-weakens-electrostatic-attractions-
between-ions,-allowing-dissociation.
23. Q:-What-is-the-heat-of-vaporization-of-water-and-why-is-it-biologically-
significant?
A:-~40.7-kJ/mol-at-100°C;-enables-evaporative-cooling-(sweating)-as-an-
effective-thermoregulatory-mechanism.
24. Q:-How-does-water-participate-directly-in-biochemical-reactions?
A:-As-reactant-(hydrolysis)-or-product-(condensation/dehydration-synthesis).
CHAPTER-3:-Amino-Acids,-Peptides,-and-Proteins
25. Q:-How-many-standard-proteinogenic-amino-acids-exist?
A:-20.
26. Q:-At-physiological-pH-(~7.4),-what-is-the-predominant-ionic-form-of-a-typical-
amino-acid?
, Lehninger-Principles-of-Biochemistry-8th-Edition-part-1-The-
Foundations-of-Biochemistry
A:-Zwitterion-(α-carboxylate-deprotonated-[–COO⁻],-α-amino-protonated-[–
NH₃⁺]).
27. Q:-Which-amino-acid-lacks-a-chiral-α-carbon?
A:-Glycine-(its-R-group-is-H,-so-α-carbon-has-two-identical-H-substituents).
28. Q:-Name-the-three-aromatic-amino-acids.
A:-Phenylalanine,-tyrosine,-tryptophan.
29. Q:-Which-amino-acid-contains-a-sulfhydryl-group?
A:-Cysteine.
30. Q:-What-covalent-bond-forms-between-two-cysteine-residues?
A:-Disulfide-bond-(–S–S–).
31. Q:-Which-amino-acid-is-technically-an-imino-acid?
A:-Proline-(its-side-chain-cyclizes-back-to-the-α-amino-group,-forming-a-
secondary-amine).
32. Q:-What-is-the-pKₐ-range-for-the-α-carboxyl-group-of-amino-acids?
A:-~1.8–2.5.
33. Q:-What-is-the-pKₐ-range-for-the-α-amino-group-of-amino-acids?
A:-~8.7–10.7.
34. Q:-Calculate-the-isoelectric-point-(pI)-for-alanine-(pKₐ₁-=-2.34,-pKₐ₂-=-9.69).
A:-pI-=-(2.34-+-9.69)/2-=-6.02.
35. Q:-Which-amino-acids-have-ionizable-side-chains?
A:-Asp,-Glu-(acidic);-His,-Cys,-Tyr-(weakly-acidic);-Lys,-Arg-(basic).
36. Q:-What-is-the-pKₐ-of-the-histidine-imidazole-side-chain-and-why-is-it-
biologically-important?
A:-~6.0;-near-physiological-pH,-allowing-histidine-to-act-as-proton-
donor/acceptor-in-enzyme-active-sites.
37. Q:-What-type-of-bond-links-amino-acids-in-proteins?
A:-Peptide-(amide)-bond.
38. Q:-What-is-the-directionality-of-polypeptide-chains?
A:-N-terminus-(free-α-amino)-→-C-terminus-(free-α-carboxyl).
39. Q:-Why-is-the-peptide-bond-planar-and-relatively-rigid?
A:-Partial-double-bond-character-due-to-resonance-between-carbonyl-oxygen-
and-amide-nitrogen-restricts-rotation.
40. Q:-What-is-the-trans-configuration-preference-for-peptide-bonds-and-why?
A:->99.9%-are-trans-(except-preceding-Pro);-minimizes-steric-clash-between-
adjacent-α-carbons.
41. Q:-Name-three-methods-for-determining-amino-acid-composition-of-a-protein.
A:-Acid-hydrolysis-followed-by-ion-exchange-chromatography,-HPLC,-or-mass-
spectrometry.
42. Q:-What-reagent-specifically-reacts-with-N-terminal-amino-acids-for-
sequencing?
A:-Phenylisothiocyanate-(Edman-degradation).
Foundations-of-Biochemistry
,Lehninger-Principles-of-Biochemistry-8th-Edition-part-1-The-
Foundations-of-Biochemistry
CHAPTER-1:-Foundations-of-Biochemistry
1. Q:-What-are-the-four-major-classes-of-biomolecules?
A:-Proteins,-nucleic-acids,-carbohydrates,-and-lipids.
2. Q:-Why-is-carbon-uniquely-suited-as-the-backbone-element-for-biological-
molecules?
A:-Carbon-forms-four-stable-covalent-bonds,-can-create-single/double/triple-
bonds,-and-readily-forms-chains-and-rings-with-itself-and-other-elements.
3. Q:-Define-the-first-law-of-thermodynamics-as-it-applies-to-living-systems.
A:-Energy-can-be-neither-created-nor-destroyed—only-converted-from-one-
form-to-another.-Living-organisms-transform-energy-but-cannot-create-it-de-
novo.
4. Q:-What-is-ΔG°'-and-why-is-the-prime-symbol-important-in-biochemistry?
A:-ΔG°'-is-the-standard-free-energy-change-at-pH-7.0-(physiological-pH).-The-
prime-distinguishes-biochemical-standard-state-(pH-7)-from-chemical-standard-
state-(pH-0).
5. Q:-When-ΔG-is-negative,-is-a-reaction-spontaneous-or-nonspontaneous?
A:-Spontaneous-(exergonic).
6. Q:-What-three-general-strategies-do-cells-use-to-accomplish-
thermodynamically-unfavorable-reactions?
A:-(1)-Coupling-to-favorable-reactions,-(2)-Maintaining-reactant/product-
concentrations-far-from-equilibrium,-(3)-Using-energy-carriers-(ATP,-NADH).
7. Q:-What-is-the-primary-energy-currency-molecule-in-cells?
A:-ATP-(adenosine-triphosphate).
8. Q:-Name-three-characteristics-that-distinguish-living-organisms-from-
nonliving-matter.
A:-Highly-organized-structure,-ability-to-extract/transform-energy,-capacity-
for-self-replication-with-inheritance.
9. Q:-What-is-the-relationship-between-ΔG,-ΔH,-and-ΔS?
A:-ΔG-=-ΔH-–-TΔS-(Gibbs-free-energy-equation).
10. Q:-Why-can't-living-systems-be-at-equilibrium?
A:-Equilibrium-represents-maximum-entropy-(disorder)-and-no-net-energy-
flow—conditions-incompatible-with-life's-organized,-energy-requiring-
processes.
CHAPTER-2:-Water
11. Q:-What-molecular-property-gives-water-its-high-dielectric-constant?
A:-Its-bent-molecular-geometry-and-polar-O–H-bonds-create-a-permanent-
dipole-moment.
,Lehninger-Principles-of-Biochemistry-8th-Edition-part-1-The-
Foundations-of-Biochemistry
12. Q:-How-does-water's-high-specific-heat-benefit-living-organisms?
A:-It-buffers-cells-and-organisms-against-rapid-temperature-changes,-
maintaining-thermal-stability.
13. Q:-Define-hydrophobic-effect.
A:-The-tendency-of-nonpolar-substances-to-aggregate-in-aqueous-solution,-
driven-by-water-molecules-maximizing-their-own-entropy-by-minimizing-
ordered-cages-around-hydrophobic-surfaces.
14. Q:-What-is-the-concentration-of-H⁺-in-pure-water-at-25°C?
A:-1.0-×-10⁻⁷-M.
15. Q:-Calculate-the-pH-of-a-solution-with-[H⁺]-=-2.5-×-10⁻⁴-M.
A:-pH-=-–log(2.5-×-10⁻⁴)-=-3.60.
16. Q:-What-is-the-pKₐ-of-water?
A:-14.0-(at-25°C).
17. Q:-Why-does-ice-float-on-liquid-water?
A:-Ice-has-an-open,-hexagonal-crystal-lattice-with-greater-volume-(lower-
density)-than-liquid-water-due-to-maximized-hydrogen-bonding.
18. Q:-How-many-hydrogen-bonds-can-a-single-water-molecule-form?
A:-Up-to-four-(two-as-donor-via-H-atoms,-two-as-acceptor-via-lone-pairs-on-
oxygen).
19. Q:-What-is-the-hydrophobic-effect's-thermodynamic-basis?
A:-Increase-in-entropy-of-water-molecules-when-hydrophobic-groups-
aggregate,-releasing-ordered-water-molecules-into-the-bulk-solvent.
20. Q:-Define-amphipathic-molecule-and-give-one-biological-example.
A:-A-molecule-with-both-hydrophilic-and-hydrophobic-regions.-Example:-
phospholipids,-fatty-acids,-or-detergents.
21. Q:-What-is-the-ion-product-of-water-(K_w)-at-25°C?
A:-1.0-×-10⁻¹⁴-M².
22. Q:-Why-is-water-an-excellent-solvent-for-ionic-compounds?
A:-Its-high-dielectric-constant-(ε-≈-78.5)-weakens-electrostatic-attractions-
between-ions,-allowing-dissociation.
23. Q:-What-is-the-heat-of-vaporization-of-water-and-why-is-it-biologically-
significant?
A:-~40.7-kJ/mol-at-100°C;-enables-evaporative-cooling-(sweating)-as-an-
effective-thermoregulatory-mechanism.
24. Q:-How-does-water-participate-directly-in-biochemical-reactions?
A:-As-reactant-(hydrolysis)-or-product-(condensation/dehydration-synthesis).
CHAPTER-3:-Amino-Acids,-Peptides,-and-Proteins
25. Q:-How-many-standard-proteinogenic-amino-acids-exist?
A:-20.
26. Q:-At-physiological-pH-(~7.4),-what-is-the-predominant-ionic-form-of-a-typical-
amino-acid?
, Lehninger-Principles-of-Biochemistry-8th-Edition-part-1-The-
Foundations-of-Biochemistry
A:-Zwitterion-(α-carboxylate-deprotonated-[–COO⁻],-α-amino-protonated-[–
NH₃⁺]).
27. Q:-Which-amino-acid-lacks-a-chiral-α-carbon?
A:-Glycine-(its-R-group-is-H,-so-α-carbon-has-two-identical-H-substituents).
28. Q:-Name-the-three-aromatic-amino-acids.
A:-Phenylalanine,-tyrosine,-tryptophan.
29. Q:-Which-amino-acid-contains-a-sulfhydryl-group?
A:-Cysteine.
30. Q:-What-covalent-bond-forms-between-two-cysteine-residues?
A:-Disulfide-bond-(–S–S–).
31. Q:-Which-amino-acid-is-technically-an-imino-acid?
A:-Proline-(its-side-chain-cyclizes-back-to-the-α-amino-group,-forming-a-
secondary-amine).
32. Q:-What-is-the-pKₐ-range-for-the-α-carboxyl-group-of-amino-acids?
A:-~1.8–2.5.
33. Q:-What-is-the-pKₐ-range-for-the-α-amino-group-of-amino-acids?
A:-~8.7–10.7.
34. Q:-Calculate-the-isoelectric-point-(pI)-for-alanine-(pKₐ₁-=-2.34,-pKₐ₂-=-9.69).
A:-pI-=-(2.34-+-9.69)/2-=-6.02.
35. Q:-Which-amino-acids-have-ionizable-side-chains?
A:-Asp,-Glu-(acidic);-His,-Cys,-Tyr-(weakly-acidic);-Lys,-Arg-(basic).
36. Q:-What-is-the-pKₐ-of-the-histidine-imidazole-side-chain-and-why-is-it-
biologically-important?
A:-~6.0;-near-physiological-pH,-allowing-histidine-to-act-as-proton-
donor/acceptor-in-enzyme-active-sites.
37. Q:-What-type-of-bond-links-amino-acids-in-proteins?
A:-Peptide-(amide)-bond.
38. Q:-What-is-the-directionality-of-polypeptide-chains?
A:-N-terminus-(free-α-amino)-→-C-terminus-(free-α-carboxyl).
39. Q:-Why-is-the-peptide-bond-planar-and-relatively-rigid?
A:-Partial-double-bond-character-due-to-resonance-between-carbonyl-oxygen-
and-amide-nitrogen-restricts-rotation.
40. Q:-What-is-the-trans-configuration-preference-for-peptide-bonds-and-why?
A:->99.9%-are-trans-(except-preceding-Pro);-minimizes-steric-clash-between-
adjacent-α-carbons.
41. Q:-Name-three-methods-for-determining-amino-acid-composition-of-a-protein.
A:-Acid-hydrolysis-followed-by-ion-exchange-chromatography,-HPLC,-or-mass-
spectrometry.
42. Q:-What-reagent-specifically-reacts-with-N-terminal-amino-acids-for-
sequencing?
A:-Phenylisothiocyanate-(Edman-degradation).
