Cellular Energy - AP Biology

1. Which two processes are linked by the electron transport chain?

   Glycolysis/Krebs cycle and oxidative phosphorylation. Electrons from metabolism power ATP synthesis.

2. What is photorespiration?

   Process where Rubisco adds O$_2$ instead of CO$_2$ to RuBP. Wasteful process that reduces photosynthetic efficiency.

3. Which organelle is primarily involved in energy production?

   Mitochondrion. Known as the powerhouse of the cell.

4. Which molecule acts as the main electron carrier in photosynthesis?

   NADP+. Similar to NADH but used in photosynthetic reactions.

5. Which molecule is regenerated at the end of the Calvin cycle?

   RuBP (Ribulose bisphosphate). Five-carbon sugar that accepts $CO_2$ in carbon fixation.

6. Which type of plant minimizes photorespiration by fixing CO$_2$ into four-carbon compounds?

   C4 plants. Spatial separation prevents photorespiration in hot climates.

7. Which photosystem is involved in the splitting of water?

   Photosystem II. First photosystem that oxidizes water molecules.

8. What is substrate-level phosphorylation?

   Direct transfer of a phosphate group to ADP to form ATP. ATP formed directly from substrate without electron transport.

9. Which enzyme synthesizes ATP in the electron transport chain?

   ATP synthase. Uses proton gradient to drive ATP production.

10. How many ATP are produced from one molecule of glucose in cellular respiration?

    Approximately 30-32 ATP. Complete oxidation yields maximum ATP from glucose.

11. State the formula for cellular respiration.

    $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{Energy (ATP)}$. Glucose and oxygen react to produce carbon dioxide, water, and ATP.

12. Identify the wavelengths of light most effectively absorbed by chlorophyll.

    Blue and red wavelengths. Green light is reflected, not absorbed.

13. State the main product of alcohol fermentation.

    Ethanol. Produced by yeast during anaerobic fermentation.

14. State the equation for photosynthesis.

    $6CO_2 + 6H_2O + \text{light energy} \rightarrow C_6H_{12}O_6 + 6O_2$. Overall equation showing reactants and products of photosynthesis.

15. Identify the final electron acceptor in the electron transport chain.

    Oxygen. Accepts electrons at the end of the transport chain.

16. In which part of the chloroplast do the light-dependent reactions occur?

    Thylakoid membranes. Contains chlorophyll and photosystems for light capture.

17. Identify the process that generates ATP using a proton gradient.

    Chemiosmosis. Uses proton gradient to drive ATP formation.

18. What is chemiosmosis?

    Movement of ions across a semipermeable membrane, down their electrochemical gradient. Drives ATP synthesis using proton concentration differences.

19. Which phase of cellular respiration occurs in the cytoplasm?

    Glycolysis. First stage breaks down glucose without oxygen.

20. What is the role of NADH in cellular respiration?

    Electron carrier. Transfers high-energy electrons to the electron transport chain.

21. What is the net gain of ATP from glycolysis?

    2 ATP. Four ATP produced minus two ATP invested equals net gain.

22. What is the main adaptation of CAM plants?

    Stomata open at night to minimize water loss. Temporal separation conserves water in dry environments.

23. What molecule is glucose converted into during glycolysis?

    Pyruvate. Three-carbon molecule produced when glucose splits in half.

24. Identify the location of the Krebs cycle in the cell.

    Mitochondrial matrix. Innermost compartment of mitochondria where citric acid cycle occurs.

25. What is the function of the electron transport chain?

    Transfer electrons to create a proton gradient for ATP synthesis. Creates proton gradient that powers ATP synthase.

26. Where does the Calvin cycle take place?

    Stroma of the chloroplast. Fluid-filled space surrounding thylakoid membranes.

27. What is the purpose of fermentation in cells?

    Regenerate NAD+ for glycolysis. Allows glycolysis to continue when oxygen is unavailable.

28. What is the primary function of the light-dependent reactions?

    To produce ATP and NADPH. Energy carriers needed for the Calvin cycle.

29. What are the end products of the light-dependent reactions?

    ATP, NADPH, and O$_2$. Light reactions produce energy carriers and release oxygen.

30. Which molecule provides electrons for the light-dependent reactions?

    Water (H$_2$O). Split by light to provide electrons and protons.

31. What is the primary pigment involved in photosynthesis?

    Chlorophyll. Green pigment that absorbs light energy.

32. What is the role of Rubisco in the Calvin cycle?

    Catalyzes the fixation of CO$_2$. Key enzyme that combines $CO_2$ with RuBP.

33. Identify the process that converts light energy into chemical energy.

    Photosynthesis. Plants capture sunlight to make glucose.

34. What is the role of coenzyme A in cellular respiration?

    Transfers acetyl group to Krebs cycle. Carries acetyl groups from pyruvate to Krebs cycle.

35. What is the main purpose of the Calvin cycle?

    To convert CO$_2$ into glucose. Light-independent reactions that fix carbon dioxide.

36. Which process produces the most ATP: glycolysis, Krebs cycle, or oxidative phosphorylation?

    Oxidative phosphorylation. Generates about 28-30 ATP molecules through electron transport.

37. Which type of fermentation occurs in muscle cells?

    Lactic acid fermentation. Occurs during intense exercise when oxygen is limited.

38. What is the main energy currency of the cell?

    ATP (Adenosine Triphosphate). Stores and releases energy through phosphate bonds.

39. During which process is carbon dioxide released in cellular respiration?

    Krebs cycle. Carbon atoms are removed as $CO_2$ during this cycle.

40. What is the initial reactant in the Krebs cycle?

    Acetyl-CoA. Two-carbon unit that enters the citric acid cycle.

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