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AP Biology
Photosynthesis
AP Biology
Redox Reactions
break bonds & move electrons from one
molecule to another
as electrons move they “carry energy” with them
that energy is stored in another bond,
released as heat or harvested to make ATP
e-
+ +e-
+ –loses e- gains e- oxidized reduced
oxidation reduction
redox
e-
AP Biology
How do we move electrons in biology?
Moving electrons in living systems
electrons cannot move alone in cells
electrons move as part of H atom
move H = move electronsp
e
+
H
+H
+ –loses e- gains e- oxidized reduced
oxidation reduction
AP Biology
Redox in biology
The atoms that H tends to bond with in
biology attract electrons more (more
electronegative)
Essentially moving H is moving
electrons
Oxidation is losing hydrogen atoms
Reduction is gaining hydrogen atoms
AP Biology
Energy for life
The energy captured through
photosynthesis forms the basis of the
ecological pyramid.
AP Biology
Energy needs of Life
Autotrophs (Plants)
produce their own energy (from
“self”)
convert energy of sunlight
build organic molecules (CHO)
from CO2
make energy & synthesize sugars
through photosynthesis
producers
AP Biology
Energy needs of life
All life needs a constant input of energy
Heterotrophs (Animals)
get their energy from “eating others”
eat food = other organisms =
organic molecules
make energy through respiration
consumers
AP Biology 2007-2008
AP Biology
How are they connected?
glucose + oxygen carbon + water + energydioxide
C6H12O6 6O2 6CO2 6H2O ATP+ + +
Cellular Respiration
+ water + energy glucose + oxygencarbondioxide
6CO2 6H2O C6H12O6 6O2light
energy+ ++
Photosynthesismaking energy & organic molecules from light energy
making energy & organic molecules from ingesting organic molecules
exergonic
endergonic
AP Biology
N
PK…
H2O
What does it mean to be a plant
Need to…
collect light energy transform it into chemical energy
need to get building block atomsfrom the environment C,H,O,N,P,K,S,Mg
produce all organic moleculesneeded for growth
ATP
glucose
CO2
AP Biology
Plant structure
Obtaining raw materials
sunlight
leaves = solar collectors
CO2
stomata = gas exchange
H2O
uptake from roots
nutrients
N, P, K, S, Mg, Fe…
uptake from roots
AP Biology
stomata
transpiration
gas exchange
AP Biology
Chloroplasts
chloroplastsin plant cell
cross sectionof leafleaves
chloroplast
absorb
sunlight & CO2
make
energy & sugar
chloroplastscontain
chlorophyll
CO2
AP Biology
Chloroplasts
double membrane
stroma
fluid-filled interior
thylakoid sacs
grana stacks
Thylakoid membrane
contains
chlorophyll molecules
electron transport chain
ATP synthase
H+ gradient built up within
thylakoid sac
Plant structure H+H+
H+
H+
H+H+
H+H+
H+H+
H+
outer membrane inner membrane
thylakoidgranum
stroma
thylakoid
chloroplast
ATP
AP Biology
Photosynthesis
Light reactions
light-dependent reactions
energy conversion reactions
convert solar energy to chemical energy
ATP & NADPH
Calvin cycle
light-independent reactions
sugar building reactions
uses chemical energy (ATP & NADPH) to
reduce CO2 & synthesize C6H12O6
AP Biology
Things that happen in the Light
Reaction Light absorbed by chlorophyll
This drives the transfer of H to an electron
acceptor called NADP+ which temporarily
stores energized electron.
ADP ATP (phosphorylation)
O2 is given off as a byproduct because
water is split
Two forms of compounds hold chemical
energy: NADPH and ATP
AP Biology
Calvin Cycle
CO2 gets incorporated into organic
compounds in plant (C6H12O6)
Carbon-fixation
NADPH gives H atoms to CO2 (requires
ATP)
AP Biology
I see the Light!
Light is a flow of energy called
electromagnetic energy/radiation and
travels in waves
Photons are fixed energy in light
AP Biology
Pigments of photosynthesis
Chlorophylls & other pigments
embedded in thylakoid membrane
arranged in a “photosystem” collection of molecules
AP Biology
A Look at Light The spectrum of color
ROYGBIV
AP Biology
Excitation of Chlorophyll by Light
When hit with a photon, an electron is
elevated to the next orbital. It is
“excited” and unstable.
If the electron has no where to go, it
emits light and heat when it falls back
to its original state.
AP Biology
Diagram
Using your notes and the book, draw a
detailed diagram of the light reaction
and Calvin cycle in the chloroplast.
Include what is used at each stage,
what is produced and what moves on.