Biology 1225 Chapter Notes - Chapter 5: Pyruvic Acid, Glycolysis, Phosphorylation
5 Jun 2018
School
Department
Course
Professor
5: Capturing and releasing Energy
Tuesday, May 22, 2018
2:11 PM
• Photosynthesis: Process by which green plans capture sunlight and use energy to make sugars
o Photosynthesis is also performed by many bacteria using chlorophyll (these are
cyanobacteria)
o Early earths atmosphere had very little oxygen, the activity of billions of cyanobacteria
accumulated oxygen into the atmosphere that allowed aerobic life to evolve
o Glucose was one of the first sugars to form
o Light energy is converted to chemical bond energy that holds together the various atoms
making up the Glucose molecule
o The rate at which photosynthesis occurs depends on a number of facts: wavelength light
impinging the leaf, temp, etc.
o From glucose, the plant cell is then able to construct all the other molecules that are
required for survival/growth, including starch (the main way plant cells store energy)
o Summary formula for photosynthesis: 6CO2 + 6H20 + LIGHT ENERGY = C6H12O6+ 6O2
o CO2 is key requirement for formation of glucose in photosynthesis (rate of photosynthesis
depends on availability of CO2)
o CO2 enters the plant mainly through the stomata (openings found mainly on the
undersides of the leaves) and diffuses directly into cells within the interior of the leaf
o Water enters via the roots and Is carried through out the plant in the veins therefore
water availability Is also an influential factor in photosynthesis
o Oxygen is a waste product of photosynthesis but is essential for respiration
o Plants remove CO2 (counteract global warming) and renew the supply of oxygen
Photosynthesis consists of "light dependent reactions" and "light independent reactions"
• Light-Dependent Reactions:
o Light energy is absorbed by chlorophyll and other pigments in the thylakoid membranes of
the chloroplast
o Only chlorophyll A: a certain molecule can absorb specific wavelengths of light and use
this light energy to perform photosynthesis
o These special chlorophyll molecules re called reaction centers (other kinds of chlorophyll
absorb other wavelengths and pass the energy over the reaction centers)
o Reaction centers release light-energized electrons to nearby electron acceptors, some of
the electrons bring about the synthesis of ATP, and some are incorporated into the bonds
of another energy transport molecule called NADPH
find more resources at oneclass.com
find more resources at oneclass.com
