Notes on Photosynthesis

1
Notes on Photosynthesis

• Uses CO2 to create glucose
• Uses sunlight to capture energy in the form of
  chemical bonds in glucose
• Uses H2O to provide electrons for these bonds
• Releases O2 as the result breaking apart the water

2
More photosynthesis

• What happens to the glucose?
• Turns to plant structure, such as cellulose in
  the cell wall
• Get stored for later use as energy - such as
  starch
• Gets used in cellular respiration to make ATP for
  cell processes - this creates waste heat

3
Cellular respiration

• Refers to any time organisms break up organic
  molecuels to get out energy int eh form of atp
  that also involves O2 - mitochondria does this.
• Because it is an energy conversion - heat is a
  waste product, as are CO2 and H2O
• Happens in producers as well as in consumers

4
Where consumers put their food

• 1) Undigested - passes through (cellulose)
• 2) Respiration
• 3) Becomes part of the organism growth, repair,
  maintenance (weight gain is one form of growth)

5
Fermentation

• Fermentation is the anaerobic breakdown of
  organic compounds.
• Performed mostly by bacteria and other
  micro-organisms
• Products are different than in respiration
  alcohol, methane, acetic acid.

6
Carbon Cycle (1)

• A reasonable starting place is the atmosphere
  where carbon exists as CO2
• Leaves atmosphere in 2 ways
• 1) Photosynthesis
• 2) dissolution (dissolving) into water,
  especially the ocean, and rainwater

7
Carbon Cycle (2)

• After photosynthesis
• 1) Plant can use in respiration - releasing CO2
• 2) carbon can flow up food chain, either being
  stored or used for respiration
• 3) eventually decomposed either because of plant
  detritues or animal death - this releases CO2 (in
  soil)
• 4) can become fossil fuels

8
Carbon cycle (3)

• From water
• Can be used for photosynthesis by aquatic plants
• Can interact with soil to become CaCO2, this can
  be incorporated in shells and become limestone

9
Phosphorous cycle (1)

• A cycle of mineral nutrients
• 1) these do not have a gas phase (cycle slower)
• 2) in soil it is mainly phosphate ion in
  compounds (PO4 3-)
• 3) enters biota from soil in to roots, then
  through food chain or exits in waste
• 4) a common limiting factor

10
Nitrogen cycle (1)

• Lots in the atmosphere - 78 of air is N2 gas.
• Biota cannot interact with nitrogen directly from
  the air (no enzymes to break triple bond)
• Bacteria in the soil (or roots of some plants) do
  nitrogen fixation to remove it from atm.

11
Nitrogen cycle (2)

• Once nitrogen is fixed (as NO3- or other nitrogen
  ions)
• 1) intake by roots of plant
• 2) denitrification by bacteria to re-release NO2
  to the atmosphere
• Other types of fixation lightning, industrial,
  combustion of fossil fuels

12
Nitrogen cycle (3)

• Once nitrogen is in biota it can
• 1) be returned to soil by decomposers
• 2) be excreted as waste (and returned to soil)
• 3) released by combustion (from detritus, forest
  fires, garbage incineration, burning of fossil
  fuels)