LEC 1

• Major classes of photosynthetic pigments found in plants and algae

  • Chlorophyll
  • Carotenoids
• Major chlorophylls


  • Chlorophyll a
  • Chlorophyll b
  • Chlorophyll c
  • Chlorophyll d
  • Bacteriochlorophyll
• Chlorophyll a and chlorophyll b

  Found in higher plant chloroplasts
• Examples of carotenoids

  • Lycopene (red tomato)
  • Zeaxanthin (yellow corn seeds)
  • B-carotene (orange peel)
• Carotenoids


  • Function as photosynthetic pigments that are very efficient molecules for the disposal of excess energy
  • Reside in the thylakoid membrane, absorb excess energy, and safely dissipate that energy as heat
• Absorption spectrum


  The specific pattern of wavelength a pigment absorbs from the visible light
• Chlorophyll a absorbs wavelengths from either end of the visible spectrum (blue and red), but not green
• Chlorophyll appears green because green is reflected or transmitted
• Carotenoids absorb in the short-wavelength blue region, and reflect the long yellow, red, and orange wavelengths
• Many photosynthetic organisms have a mixture of pigments to absorb energy from a wider range of wavelengths
• Spectrophotometer


  An instrument that can differentiate which wavelengths of light a substance can absorb
• Using a spectrophotometer


  1. Extract pigments from leaves

  2. Place samples in spectrophotometer

  3. Identify which wavelengths of light the organism can absorb
• A living cell cannot store significant amounts of free energy. Excess free energy would result in an increase of heat in the cell, which would result in excessive thermal motion that could damage and then destroy the cell.
• Living cells accomplish storing and releasing energy as needed by using the compound adenosine triphosphate (ATP) which is known as the "energy currency" of the cell due to its versatility to fill any energy need of the cell.
• Coupled Reaction Processes


  1. Oxidation (stripping an electron from a compound)

  2. Reduction (addition of an electron to another compound)

  3. Redox reactions (oxidation and reduction occurring together)
• Endergonic reactions


  Require an input of energy (e.g. photosynthesis)
• Exergonic reactions


  Release energy (e.g. cellular respiration)
• Hydrolysis of ATP


  Breaking down ATP to produce ADP, inorganic phosphate, and release of free energy
• Dehydration of ATP


  Regenerating ATP from ADP and inorganic phosphate, requires an input of free energy
• Adenosine triphosphate (ATP)


  Comprised of adenosine bound to three phosphate groups

  
• ATP


  • At the heart is a molecule of adenosine monophosphate (AMP)
  • ADP is formed by the addition of a second phosphate group
  • ATP is formed by the addition of a third phosphate group

  
• High-energy bonds in ATP


  Bonds between the second and third (beta and gamma) phosphate groups, and between the first and second phosphate groups

  
• ATP consists of three parts: 1 adenine molecule, 1 ribose sugar molecule and 3 phosphate molecules.

  
• Energy is stored in the bond that is found between the 2nd and 3rd phosphate groups of ATP.

  
• ATP Decomposition


  Cell breaks off the last (3rd) phosphate group from the ATP molecule to release energy, leaving adenosine diphosphate (ADP) with two phosphate groups
• ATP Synthesis


  ATP molecules are constantly being rebuilt from ADP and lone phosphate groups, using energy from glucose
• Glucose is a monosaccharide or simple sugar that plants produce during photosynthesis, and this energy is used to synthesize ATP from ADP and phosphate.
• Photosynthesis


  The process by which green plants harness light energy from the sun to convert it to the chemical energy of sugar

  
• The use of carbon dioxide and water during photosynthesis results in the manufacture of glucose and oxygen gas (as by-product)

  
• Light reaction events


  1. Light energy or photon is absorbed by a pigment molecule

  2. Electron in chlorophyll a pair is raised to an excited state and transferred to primary electron acceptor

  3. Splitting of water molecule into electrons, hydrogen ions, and oxygen

  4. Excited electrons passed through electron transport chain to Photosystem I

  5. Chemiosmosis drives ATP synthesis

  6. Photon absorbed by Photosystem I, electron excited and transferred to ferredoxin

  7. NADP+ reductase transfers electron to NADP+ to form NADPH

  
• Cyclic electron flow


  1. Ferredoxin passes electron back to cytochrome complex instead of NADP+ reductase

  2. No NADPH produced but ATP still synthesized
• Carbon, hydrogen, oxygen, nitrogen and magnesium are the major essential nutrients needed by plants
• An instrument called spectrophotometer can differentiate which wavelengths of light a substance can absorb.  
• Chlorophyll a and chlorophyll b are found in higher plant chloroplasts
• These carotenoids reside in the thylakoid membrane, absorb excess energy, and safely dissipate that energy as heat.  
• Carotenoids absorb in the short-wavelength blue region, and reflect the long yellow, red, and orange wavelengths.  
• Chlorophyll a absorbs wavelengths from either end of the visible spectrum (blue and red), but not green.
• Part 1. The Structure of ATP ATP consists of three parts: 1 adenine molecule, 1 ribose sugar molecule and 3 phosphate molecules. Energy is stored in the bond that is found between the 2nd and 3rd phosphate groups.
• Part 2. ATP Decomposition When a cell requires energy, it breaks off the last(3rd) phosphate groupfrom the ATP molecule, which release energy. The molecule that is left over is called adenosine diphosphate which consists of adenine, ribose sugar and TWO phosphate groups. ADP contains less energy than ATP. 
• Part 3: ATP synthesis ATP molecules are constantly being rebuilt from ADP and lone phosphate groups. This ensures that cells always have a source of energy. However, it takes energy to make ATP. The energy to make ATP comes from a carbohydrate called GLUCOSE. Glucose is a monosaccharide or simple sugar. Plants produce glucose during photosynthesis.