Bioenergetics

• Types of autotrophs


  • Organisms that get energy from the sun - harness solar energy
  • Organisms that use energy from chemicals - without light energy
• Organisms that get energy from the sun


  • Best-known autotrophs that harness solar energy through the process of photosynthesis
  • Use light energy to power chemical reactions that convert carbon dioxide and water into oxygen and energy-rich carbohydrates such as sugars and starches

  
• Organisms that use energy from chemicals


  • Produce energy without light
  • Rely on energy within the chemical bonds of inorganic molecules such as hydrogen sulfide
  • Chemosynthesis is the process where organisms use chemical energy to produce carbohydrates
  • Performed by several types of bacteria
  • Some live in very remote places on Earth, such as volcanic vents on the deep ocean floor and hot springs
  • Others live in more common places, such as tidal marshes along the coast
• Types of heterotrophs


  • Herbivores
  • Carnivores
  • Omnivores
  • Detritivores
  • Decomposers
• Chloroplasts


  • Organelles found in plant cells and some other eukaryotic organisms
  • Conduct photosynthesis
  • Carry out almost all fatty acid synthesis in plants
  • Involved in a plant's immune response
  • A type of plastid that specializes in photosynthesis
• Thylakoids


  • Saclike photosynthetic membranes found in chloroplasts
  • Arranged in stacks called grana
  • Contain clusters of chlorophyll and other pigments and protein called photosystems that are able to capture the energy from the sunlight

  
• Photosynthesis


  • The process by which several living organisms utilize solar energy (that is, sunlight) for growth and metabolism
  • The process of converting light energy into chemical energy by living organisms

  
• Photosynthesis


  Uses carbon dioxide, water, and solar energy to produce oxygen and carbohydrates

  
• Photosynthesis usually produces 6-carbon sugars (C6H12O6) as its final products

  
• NADP+ and NADPH


  • NADP+ is a compound that accepts and holds two high energy electrons along with the hydrogen ion (H+), converting it to NADPH
  • NADPH can carry high-energy electrons produced by light absorption in chlorophyll to chemical reactions elsewhere in the cell
  • The high-energy electrons are used to build variety of molecules the cell needs, including carbohydrates like glucose
• Light-dependent reactions


  1. Use energy from the sunlight to produce oxygen gas and convert ADP and NADP+ into the energy carriers ATP and NADPH

  2. Take place within the thylakoid membranes of the chloroplasts

  
• Steps in light-dependent reactions


  • Photosystem II
  • Electron Transport Chain
  • Photosystem I
  • Hydrogen Ion Movement
  • ATP Formation

  
• Light-independent reactions or Calvin Cycle


  1. Use ATP and NADPH from the light reactions to form high-energy sugars that can be stored for a long time

  2. Occur in the stroma

  
• Steps in Calvin Cycle


  • CO2 Enters the Cycle
  • Energy Input
  • 6-Carbon Sugar Produced
  • 5-Carbon Molecules Regenerated

  
• The Calvin cycle uses six (6) molecules of carbon dioxide to produce a single 6-carbon sugar molecule
• Cellular respiration


  The process that releases energy by breaking down food molecules in the presence of oxygen

  
• Cellular respiration


  1. Glycolysis

  2. Citric Acid Cycle

  3. Electron Transport Chain

  
• Glycolysis


  • Literally means "splitting sugars"
  • Glucose, a six-carbon sugar, is split into two molecules of a three-carbon sugar
  • In the process, two molecules of ATP, two molecules of pyruvic acid, and two "high energy" electron carrying molecules of NADH are produced
  • Can occur with or without oxygen

  
• Cellular respiration


  1. Glycolysis

  2. Citric Acid Cycle

  3. Electron Transport

  
• Glycolysis


  Literally means "splitting sugars". Glucose, a six-carbon sugar, is split into two (2) molecules of a three-carbon sugar. In the process, two (2) molecules of ATP, two (2) molecules of pyruvic acid, and two (2) "high energy" electron carrying molecules of NADH are produced.

  
• Fermentation


  The combined process of glycolysis and a different pathway when oxygen is not present. It is also referred to as anaerobic respiration.

  
• Types of fermentation


  • Alcoholic Fermentation
  • Lactic Acid Fermentation
• Citric Acid Cycle


  Also referred as Krebs cycle, is the series of energy extracting reactions where pyruvic acid is broken down into carbon dioxide in the presence of oxygen.

  
• Electron Transport


  The process that uses high energy electrons from the Krebs cycle to convert ADP into ATP.
• In the presence of oxygen, the Krebs cycle and electron transport enable the cell to produce 34 more ATP molecules per glucose molecule in addition to the two (2) ATP molecules obtained from glycolysis.

  
• The 36 ATP molecules the cell makes per glucose represent 38% of the total energy of glucose. The 62% is released as heat, which is one (1) of the reasons your body feels warmer during vigorous exercise.
• Photosynthesis


  The process that stores energy by converting carbon dioxide and water into glucose and oxygen using sunlight.

  
• Photosynthesis and cellular respiration


  Almost opposite processes
• Differences between photosynthesis and cellular respiration


  • Photosynthesis stores energy, cellular respiration withdraws energy
  • Photosynthesis removes carbon dioxide from the environment, cellular respiration puts it back
  • Photosynthesis releases oxygen into the atmosphere, cellular respiration uses that oxygen to release energy from food
  • Products of photosynthesis are similar to the reactants of cellular respiration and vice versa
  • Cellular respiration takes place in all eukaryotes and some prokaryotes, photosynthesis only occurs in plants, algae and some bacteria

  
• Food Chain


  Illustrates that energy stored by producers can be passed through an ecosystem. This is a series of steps in which organisms transfer energy by eating and being eaten.
• Food Web


  Shows feeding relationships among various organisms in an ecosystem form a network of interactions. A food web links together all the food chains in an ecosystem.

  
• Trophic Level


  Refers to each step in a food chain or food web. Producers make up the first level. Consumers make up the second. Each consumer depends on the trophic level below it for energy.
• Only about 10% of the energy available within a trophic level is transferred to organisms at the next trophic level.
• Photosynthesis

  6CO2 (carbon dioxide) + 6H2O (water)

  -> C6H12O6 (glucose) + 6O2 (oxygen)

  Cell Respiration

  6O2 (oxygen) + C6H12O6 (glucose)

  -> 6CO2 (carbon dioxide) + 6H2O (water)