This is a comprehensive list of key concepts and questions from AP Biology Unit 3: Cellular Energetics. Below are simplified answers to some of the questions for clarity and quick reference:

Enzymes and Catalysis

1. Monomer of an enzyme: Amino acids are the monomers that make up enzymes (proteins).

2. How a substrate binds: Substrates bind to an enzyme's active site, which has a specific shape complementary to the substrate.

3. After substrate binds: The enzyme changes shape slightly (induced fit), facilitating the reaction and converting the substrate into the product.

4. Function of an enzyme: Enzymes speed up biological reactions by lowering activation energy.

5. True/False (Gibbs Free Energy): False – Enzymes do not affect Gibbs Free Energy; they only lower the activation energy.

6. Enzyme's effect on reaction rate: Enzymes increase the reaction rate by providing an alternative pathway with lower activation energy.

7. Activation energy (catalyzed vs. uncatalyzed): In an enzyme-catalyzed reaction, activation energy is lower.

8. Reaction rate (catalyzed vs. uncatalyzed): Catalyzed reactions occur much faster than uncatalyzed ones.

Environmental Impacts on Enzymes

9. Conditions affecting enzyme structure: Temperature and pH.

10. Change in structure's effect: It alters the enzyme's ability to bind substrates (loss of function).

11. Outcomes of structural change:

    • Enzyme works less effectively.

    • Enzyme stops working entirely.

    • Enzyme regains function if the change is reversible.

12. Denaturation: Loss of an enzyme's functional shape due to environmental stress.

13. True/False (Reversibility): True – Some enzymes can regain their structure under the right conditions.

14. Reversible example: RNAse A.

15. Nonreversible example: Fried egg proteins.

pH and Temperature

16. Effect of hydrogen ions on pH:

    • Increase: pH decreases (more acidic).

    • Decrease: pH increases (more basic).

17. Effect of pH changes on enzyme:

    • Increase: Enzyme denatures if too basic.

    • Decrease: Enzyme denatures if too acidic.

18. Reactant concentration on rate: Higher concentrations increase reaction rate up to a saturation point.

19. Enzyme concentration on rate: Higher enzyme levels increase reaction rate, provided substrates are available.

20. Temperature effects:

    • Increase: Molecules move faster, but extreme heat denatures enzymes.

    • Decrease: Molecules move slower, reducing reaction rate.

21. Temperature on molecules: Affects kinetic energy and collision frequency.

Inhibitors

22. Competitive inhibitor: Molecule competes with the substrate for the active site.

23. Overcoming competitive inhibitor: Increase substrate concentration.

24. Noncompetitive inhibitor: Binds elsewhere on the enzyme, changing its shape.

25. Inhibitor's effect on reaction rate: Slows down the reaction rate.

Energy and Thermodynamics

26. First Law of Thermodynamics: Energy cannot be created or destroyed, only transformed.

27. Second Law of Thermodynamics: Energy transfers increase the universe's entropy.

28. Maintaining order: Requires energy input.

29. Powering cellular processes: ATP (adenosine triphosphate).

30. Endergonic reaction: Absorbs energy (e.g., photosynthesis).

31. Exergonic reaction: Releases energy (e.g., cellular respiration).

32. Energy coupling: Uses energy from exergonic reactions to power endergonic reactions.

Photosynthesis

33. Energy source: Light.

34. First photosynthetic organism: Cyanobacteria.

35. Oxygenation evidence: Banded iron formations in ancient rocks.

36. Light-dependent reactions: Convert light energy to ATP and NADPH.

37. Location: Thylakoid membranes of chloroplasts.

38. ATP synthesis: Proton gradient powers ATP synthase.

39. NADPH synthesis: Light excites electrons, which reduce NADP+ to NADPH.

40. Chlorophyll: Pigment capturing light energy.

41. Photosystem and electron transport chain: Photosystem absorbs light, exciting electrons that move through the ETC.

Cellular Respiration

42. Processes: Glycolysis, Citric Acid Cycle (Krebs), Electron Transport Chain.

43. Products: ATP, CO₂, and water.

44. Electron transport chain (ETC): Series of proteins transferring electrons to create a proton gradient.

45. ETC locations:

    • Mitochondrial inner membrane (eukaryotes).

    • Plasma membrane (prokaryotes).

46. Pathway of electrons:

    • Start: Glucose.

    • Carriers: NADH and FADH₂.

    • End: Oxygen (final acceptor).

47. Proton gradient generation: From ETC using energy from electrons.

48. Proton direction (ETC): Pumped from matrix to intermembrane space (mitochondria).

49. Chemiosmosis: Proton flow through ATP synthase drives ATP production.

50. Oxidative phosphorylation: ATP synthesis using oxygen and ETC.

51. Photophosphorylation: ATP synthesis in photosynthesis using light energy.

Organismal Fitness

52. Endotherm: Maintains body temperature through internal mechanisms (e.g., metabolism).

53. Decoupling oxidative phosphorylation: Generates heat by uncoupling proton gradient from ATP synthesis.