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Energy in a Cell

Chapter 9 explores how cells acquire and utilize energy through two fundamental processes: photosynthesis and cellular respiration. Photosynthesis in plants converts sunlight into chemical energy stored as glucose, while cellular respiration in mitochondria breaks down food molecules to produce ATP, the main energy currency of the cell. This chapter covers the structure of ATP, its energy-releasing mechanisms, and the roles of electron transport chains in both processes, highlighting the intricate balance of energy transformation essential for life.

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Energy in a Cell

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  1. Energy in a Cell Chapter 9

  2. Goals • How cells get energy • Photosynthesis • Cellular Respiration

  3. ATP • Adenosine Triphosphate • Energy = ATP • Made up of: • Adenosine • Ribose – sugar • 3 – phosphates – positively charged particles

  4. ATP • Energy of ATP is stored in the bonds between the phosphates • Phosphate bonds break = energy is released • ADP

  5. ADP • Adenosine Diphosphate • Made of • Adenosine • Ribose • 2 phosphates

  6. Forming & breaking down ATP • Adenosine – P = little energy • Adenosine – P – P = more energy • Adenosine – P – P – P = Tremendous Energy

  7. Cells need energy for: • Making new molecules = Enzymes • Maintain Homeostasis • Break down food molecules • Send Nerve Impulses • Reproduction • Movement = Cilia & Flagella

  8. 9.2 Photosynthesis • Plants trapping sunlight energy to make sugar/glucose • Converting sunlight energy to chemical energy

  9. Photosynthesis • 6CO2 + 6H2O + Sun → C6H12O6 + 6O2 • Takes place in Chloroplast

  10. Chloroplast

  11. Chloroplast • Chlorophyll – Pigment that absorbs specific wavelengths of sunlight • Chlorophyll a & b absorb all wavelengths of sunlight except • Pigments – molecules that absorb specific wavelengths

  12. 2 phases of Photosynthesis • Light – dependent rxn - Energy to make glucose 2. Light – independent rxn - Make glucose

  13. Light – Dependent Rxn • Converts sunlight energy into chemical energy

  14. Light – Dependent Rxn • How does it work? • Sunlight energy excites electrons in the chlorophyll • Excited electrons pass from chlorophyll to Electron Transport Chain (ETC)

  15. Electron Transport Chain (ETC) • Series of proteins in the thylakoid membrane • Each step of ETC small amounts of energy are lost • Energy lost used to make ATP from ADP & pump H+ ions back to thylakoid membrane

  16. ETC • Electrons move down ETC then transferred to Stroma where NADP+ accepts the electron • NADP+ - Nicatinamide adenine dinucleotide phosphate

  17. NADP+ • Electron carrier molecule • Becomes NADPH when it accepts electrons (end of ETC)

  18. NADPH • Provides energy to form carbohydrates or glucose • Photolysis – Splitting of water to replace electrons = oxygen we breathe

  19. ETC

  20. Chloroplast

  21. Light Independent RXN • Also known as Calvin Cycle • Does not require sunlight

  22. Calvin Cycle • Series of rxns that use CO2 to build carbohydrates or glucose • Takes place in stroma of chloroplasts

  23. Calvin Cycle • Carbon fixation – 1 carbon atom from CO2 is added to a 5 carbon sugar • 6 carbon sugar from #1 splits in two molecules of PGA (phosphoglyceric acid) • Several rxns take place = 2 molecules PGAL form by using ATP & NADPH from light rxn

  24. Calvin Cycle • Several cycles = 2 PGAL leave to form Glucose • Some PGAL reform 5 carbon sugar that we started with - Ready for a new Calvin Cycle to start

  25. 9.3 Cellular Respiration • Process which mitochondria breaks down food to produce ATP • C6H12O6 + 6O2→ 6CO2 + 6H2O + Energy • Takes place in Mitochondria

  26. 3 Stages of Cellular Respiration • Anaerobic – without O2 • Glycolysis – series of rxns that breakdown glucose (6 carbon) into 2 molecules of Pyruvic acid (3 carbon)

  27. Glycolysis • Takes place in cytoplasm of cell • 2 ATP used to start • 4 ATP produces • Net gain = 2 ATP • NAD+ electron carrier molecule

  28. 3 Stages of Cellular Respiration • Aerobic – with O2 • Citric acid cycle – (Krebs cycle) • Series of rxns breakdown carbohydrates or glucose • Opposite of Calvin cycle • 2 ATP produced • 3 NADH + H+ produced = 1 NADH = 3 ATP • 2FADH produced = 1 FADH = 2 ATP • 2 CO2 produced

  29. 3 Stages of Cellular Respiration • Aerobic • ETC • Takes place in Mitochondria • NADH & FADH pass electrons along releasing small amounts of energy • Pump H+ back to center of mitochondria • Final electron acceptor = O2 • Without O2 chain becomes blocked • 32 ATP produced

  30. ETC – cellular respiration

  31. Fermentation • Without O2 • Allows our cells to continue to make ATP w/o O2 after glycolysis for a short period of time

  32. Fermentation • Lactic acid – 2 lactic acid molecules are byproducts of producing just 2 ATP • Occurs in muscle cells

  33. Fermentation • Alcoholic – ethyl alcohol is formed as a byproduct to produce 2 ATP • Occurs in yeast cells and bacteria

  34. Comparing ATP production

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