NOTES: CH 10, part 1: Photosynthesis in Nature
10.1 – Photosynthesis converts light energy to the chemical energy of food.
● PHOTOSYNTHESIS =
& the conversion of this energy to
(in the form of sugar)
-AUTOTROPHS: “
”;
 PHOTOAUTOTROPHS:
to synthesize food (e.g. plants)
● Photosynthesis occurs in
,
, certain other
, and some
● These organisms feed not only themselves but also the entire living world…thank you plants! 
● HETEROTROPHS: “
”;
-animals that eat plants or other animals
● Almost all heterotrophs, including humans, depend on photoautotrophs
**some heterotrophs are:
-decomposers:
Chloroplasts: The Sites of Photosynthesis in Plants
●
● Their green color is from CHLOROPHYLL, the
● Light energy absorbed by chlorophyll drives the synthesis of organic molecules in the chloroplast
● Through microscopic pores called STOMATA,
CHLOROPLASTS:
●
● found primarily in leaves (
)
● contain green pigment
(absorbs light energy)
● found mainly in mesophyll (
)
● a typical mesophyll cell has
● CO2 enters and O2 leaves through
● water is delivered to leaves
CHLOROPLAST:
(sketch a chloroplast):
● enclosed by 2 membranes
● STROMA =
● THYLAKOID MEMBRANES are interconnected & contain the thylakoid space, or lumen (are usually in stacked
columns called
)
● chlorophyll is stored in the thylakoid membranes
 STROMA =
 THYLAKOID MEMBRANES are interconnected & contain the thylakoid space, or lumen (are usually in stacked
columns called
)
 chlorophyll is stored in the thylakoid membranes
PATHWAYS OF PHOTOSYNTHESIS
 TOTAL equation for photosynthesis:
6CO2
+
12H2O + light

energy
C6H12O6
+
6O2
+
6H2O
 NET EQUATION:
The Splitting of Water
● Chloroplasts
hydrogen into sugar molecules
, incorporating the electrons of
Tracking Atoms Through Photosynthesis: (draw in arrows to track the atoms)
Reactants:
6CO2 + 12H2O
Products:
C6H12O6 + 6H2O + 6O2
Photosynthesis as a Redox Process
● Photosynthesis is a redox process in which
and
*like respiration, photosynthesis is a series of redox reactions…BUT, the electron flow is reversed!…the electrons
increase in potential energy as they move from water  sugar …an uphill process!
(the required energy boost comes from light energy)
Two Stages of Photosynthesis:
1)
(a.k.a. the “dark reactions” or light-independent reactions)
2)
● Photosynthesis consists of the light reactions (the photo part) and the Calvin cycle (the synthesis part)
LIGHT REACTIONS:
●

● light is absorbed by chlorophyll and drives a transfer of electrons and H from water to an acceptor called:
● water is split and
●
NADP+
as a “waste product”
is reduced to NADPH…ALSO, ATP is generated via phosphorylation of ADP (
CALVIN CYCLE:
● CO2 from air is incorporated into organic molecules by
● NADPH and ATP from the light reactions power the production of sugar
● also called:
“
”
Locations of the Photosynthesis Reactions:
● Light reactions occur in the
● Calvin cycle occurs in the
or
!)