Respiration

• Metabolism


  All the chemical reactions taking place in a cell
• Metabolic pathways


  • Biochemists arrange the thousands of chemical reactions in a cell into metabolic pathways
• Metabolites


  The intermediates in these metabolic pathways
• Catabolic reactions


  Reactions that release energy (usually breakdown reactions)
• Anabolic reactions


  Reactions that use up energy (usually synthetic reactions)
• Photosynthesis and respiration


  They are the reverse of each other, and you couldn't have one without the other
• The net result of all the photosynthesis and respiration by living organisms is the conversion of light energy to heat energy
• ATP


  The energy currency of the cell, provided by respiration
• Respiration


  Glucose + oxygen -> carbon dioxide + water (+ energy)
• ATP


  A nucleotide that stores chemical energy
• ATP synthesis


  ATP is built up from ADP and phosphate (PO4^3-)
• Processes that require energy

  • Muscle contraction, active transport, biosynthesis
• ATP breakdown


  ATP is broken down to ADP + Pi by ATPase enzymes, releasing energy
• Photosynthesis


  The reverse of respiration: carbon dioxide + water (+ light energy) -> glucose + oxygen
• Photosynthesis


  1. Light-dependent reactions

  2. Light-independent reactions
• Light-dependent reactions


  • Use light energy to split water and make ATP and energetic hydrogen atoms
• Light-independent reactions


  • Don't need light, but do need the products of the light-dependent stage (ATP and H)
• Chloroplasts


  Where photosynthesis takes place, with a double membrane and a third thylakoid membrane
• Thylakoid membrane


  • Contains the ATP synthase particles that make ATP
• Chloroplasts


  • Contain DNA, tRNA, ribosomes, and store photosynthesis products as starch and lipids
• Chlorophyll


  The green pigment in chloroplasts that absorbs light for photosynthesis
• Photosynthetic pigments


  • Chlorophyll a, chlorophyll b, carotenoids, luteins
• Different species of plants have different combinations of photosynthetic pigments, giving rise to different coloured leaves
• Plants adapted to shady conditions tend to have a higher concentration of chlorophyll and so have dark green leaves
• Plants adapted to bright conditions need less chlorophyll and have pale green leaves
• Action spectrum


  Measures the rate of photosynthesis using different wavelengths of light
• Photosystems


  • Complexes of chlorophyll and other pigments with proteins, located in the thylakoid membrane
• Photosystem I and II


  • The two kinds of photosystem in green plant chloroplasts, absorbing light at different wavelengths
• Light-dependent reactions


  Use light energy to split water, release oxygen, and produce ATP and hydrogen
• Electron transport chain


  Excited electrons passed from PSII to cytochrome complex to PSI, generating a proton gradient
• NADPH production


  Electrons from the electron transport chain are used to reduce NADP to NADPH
• ATP synthesis


  The proton gradient across the thylakoid membrane is used by ATP synthase to make ATP (photophosphorylation)
• Calvin cycle


  The light-independent reactions that fix carbon dioxide and synthesize glucose
• Carbon fixation


  CO2 binds to RuBP, catalyzed by rubisco, to form 2 molecules of 3-carbon glycerate phosphate
• Glycerate phosphate reduction


  Glycerate phosphate is reduced and activated to form triose phosphate using ATP and NADPH
• Triose phosphate metabolism


  Triose phosphate is used to regenerate RuBP and also to synthesize glucose
• Cellular respiration


  The metabolic pathway that converts glucose and oxygen into carbon dioxide, water, and energy in the form of ATP
• Stages of respiration


  • Glycolysis (anaerobic)
  • Krebs cycle (aerobic)
  • Electron transport chain (aerobic)
• Mitochondria


  • Where most of respiration takes place, with an outer membrane, inner membrane, and matrix
• Anaerobic respiration


  The breakdown of glucose to pyruvate without oxygen, taking place in the cytoplasm