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AP Bio Exam Review: Cell Energy (Respiration & Photosynthesis)

This review covers the concepts of cell energy, including respiration and photosynthesis, and the role of enzymes in metabolic reactions. It discusses the different pathways that release and consume energy, the importance of ATP in cellular work, and the function of enzymes in speeding up reactions. The review also explains the processes of glycolysis, fermentation, and oxidative phosphorylation in respiration, as well as the light reactions and Calvin cycle in photosynthesis. Lastly, it explores the similarities and differences between respiration and photosynthesis, highlighting the importance of energy coupling and enzyme regulation.

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AP Bio Exam Review: Cell Energy (Respiration & Photosynthesis)

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  1. AP Bio Exam Review:Cell Energy(Respiration & Photosynthesis)

  2. Catabolic pathways release energy by breaking down complex molecules into simpler compounds • C6H12O6 +6O2 6H2O + 6CO2 +E • Anabolic pathways consume energy to build complex molecules from simpler ones • 6H20+6CO2 + E C6H12O6 +6O2

  3. Concept 8.3 ATP powers cellular work by coupling exergonic reactions to endergonic reactions • A cell does three main kinds of work: • Mechanical • Transport • Chemical • To do work, cells manage energy resources by energy coupling, the use of an exergonic (energy releasing) process to drive an endergonic (energy absorbing) one

  4. Concept 8.4: Enzymes speed up metabolic reactions by lowering energy barriers • A catalyst is a chemical agent that speeds up a reaction without being consumed by the reaction • An enzyme is a catalytic protein • Hydrolysis of sucrose by the enzyme sucrase is an example of an enzyme-catalyzed reaction

  5. Substrate Specificity of Enzymes • The reactant that an enzyme acts on is called the enzyme’s substrate • The enzyme binds to its substrate, forming an enzyme-substrate complex • The active site is the region on the enzyme where the substrate binds

  6. Cofactors Cofactors are nonprotein enzyme helpers such as minerals Coenzymes are organic cofactors such as vitamins Enzyme Inhibitors

  7. Allosteric Regulation • a protein’s function at one site is affected by binding of a regulatory molecule at another site • Allosteric regulation may either inhibit or stimulate an enzyme’s activity

  8. Feedback Inhibition • In feedback inhibition, the end product of a metabolic pathway shuts down the pathway

  9. Energy Harvest • Energy is released as electrons “fall” from organic molecules to O2 • Broken down into steps: Food  NADH  ETC  O2 • Coenzyme NAD+ = electron acceptor • NAD+ picks up 2e- and 2H+ NADH (stores E) • NADH carries electrons to the electron transport chain (ETC) • ETC: transfers e- to O2 to make H2O ; releases energy

  10. Cellular Respiration

  11. Mitochondrion Structure Citric Acid Cycle (matrix) ETC (inner membrane)

  12. Glycolysis Without O2 O2 present Fermentation Respiration Release E from breakdown of food with O2 Occurs in mitochondria O2 required(final electron acceptor) Produces CO2, H2O and up to 38 ATP (NADH, FADH2) • Occurs in plants and animals • Occurs in cytosol • Keep glycolysis going • No oxygenneeded • Creates alcohol [+ CO2]or lactic acid

  13. Types of Fermentation Alcohol fermentation Lactic acid fermentation Pyruvate  Lactate Ex. fungi, bacteria, human muscle cells Used to make cheese, yogurt, acetone, methanol Note: Lactate build-up does NOT causes muscle fatigue and pain (old idea) • Pyruvate  Ethanol + CO2 • Ex. bacteria, yeast • Used in brewing, winemaking, baking PURPOSE = NAD+ recycled for glycolysis

  14. Various sources of fuel • Carbohydrates, fats and proteins can ALL be used as fuel for cellular respiration • Monomers enter glycolysis or citric acid cycle at different points

  15. ENERGY aerobic (with O2) anaerobic (without O2) glycolysis (cytosol) Respiration (mitochondria) substrate-level phosphorylation Krebs cycle (citric acid cycle) fermentation electron transport chain Oxidative Phosphorylation ethanol + CO2 (yeast, some bacteria) lactic acid (animals) chemiosmosis

  16. Sites of Photosynthesis Leaf cross section Vein Mesophyll • mesophyll: chloroplasts mainly found in these cells of leaf • stomata: pores in leaf (CO2 enter/O2 exits) • chlorophyll: green pigmentin thylakoid membranes of chloroplasts Stomata O2 CO2 Mesophyll cell Chloroplast 5 µm Outer membrane Thylakoid Intermembrane space Thylakoid space Stroma Granum Innermembrane 1 µm

  17. Photosynthesis = Light Reactions + Calvin Cycle “photo” “synthesis”

  18. Light Reactions

  19. Both respiration and photosynthesis use chemiosmosis to generate ATP

  20. Calvin Cycle = produce 3C sugar (G3P)

  21. Photorespiration: low carbon-fixation when stomata closed in hot, dry climate

  22. PHOTOSYNTHESIS Comparison RESPIRATION Plants + Animals Needs O2 and food Produces CO2, H2O and ATP, NADH Occurs in mitochondria membrane & matrix Oxidative phosphorylation Proton gradient across membrane Plants Needs CO2, H2O, sunlight Produces glucose, O2 and ATP, NADPH Occurs in chloroplast thylakoid membrane & stroma Photorespiration Proton gradient across membrane

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