Download photosynthesis - Shore Regional High School

PHOTOSYNTHESIS
Energy and Life
Living things depend on Energy
We need energy to play soccer, go fishing
and even sleep. On a cellular level, we also
need energy for active transport, growth
and repair, and reproduction of cells.
AUTOTROPHS & HETEROTROPHS
• Autotrophs: organisms that are able to produce their own
food
• What are some examples?
• Heterotrophs: organisms that are Not able to produce their
own food
• Most autotrophs use PHOTOSYSTHESIS to produce their own
food
WHAT IS PHOTOSYNTHESIS
PHOTOSYSTHESIS- THE BIG PICTURE
inputs
outputs
inpu
ENERGY IN THE CELL
• Energy comes in many forms
• Biochemical energy is stored
in
• CARBS AND LIPIDS
Cells metabolize these compounds in a form it can use called ATP
ATP is the energy currency of the cell the only energy the cell
recognizes
1 MOLECULE OF C6H12O6= 90x the chemical energy of ATP
ATP AND ADP
Adenosine---p-----p +energy from glucose+ p
ADP
Adenosine diphosphate
ADP adenosine + ribose sugar+2
phosphate groups
Adenosine----p----p------p
ATP
Adenosine triphosphate
Lots of energy (originally
from glucose is stored in
this bond
ATP adenosine+ ribose
sugar +3 phosphate
groups
Energy stored in ATP is released when ATP is converted to ADP
and a phosphate group. When the bond is broken energy is
released ATP is like a fully charged battery------ ADP like a
battery not fully charged
SITE OF PHOTOSYNTHESIS
In addition to O2 and H2O photosynthesis also requires a pigment
What is the PIGMENT found in chloroplasts that is responsible for trapping
light energy? ANSWER chlorophyll
There are two types of chlorophyll a (light green) and b (dark green)
Plants also contain other light-absorbing pigments, such as xanthophylls,
anthocyanins, and carotenoids (these are referred to as accessory
pigments) we know that leaves contain these pigments because of the color
of the leaves in the fall
These pigments do not absorb light well in the green region of the light
spectrum which is why most plants are green
SITE OF PHOTOSYNTHESIS
sun
energy
chloroplast
•
•
•
Co2 +
water
Sugar and oxygen
•
When chlorophyll absorbs light, the
following occurs
Energy(light)is directly transferred to
the electrons in the chlorophyll
molecule
When transferred the energy level in
the electron is raised (electrons get
excited)
Excited electrons have HIGH ENERGY
and must have a special chemical
carrier called “NADPH”
Electron chauffeur
STRUCTURE OF A CHLOROPLAST
• Draw a chloroplast
• Thylakoid: bag-like
photosynthetic membranes
• Grana: stacked thylakoids
(grannum) single stack
• Stroma: fluid inside the
chloroplast but OUTSIDE the
thylakoid membrane
PHOTOSYNTHESIS AS A BIOCHEMICAL PATHWAY
PHOTOSYNTHESIS IS A BIOCHEMICAL PATHWAY
Photosynthesis is broken down into 2 stages
1. Light dependent reactions
2 Light independent reactions (Calvin Cycle)
Light dependent
reactions
Take place in the thylakoid
membranes
Occurs only in light
light independent
reactions
Take place in the stroma
Occurs only in the
absence of light
PHOTOSYNTHESIS AS A BIOCHEMICAL PATHWAY
LIGHT DEPENDENT REACTIONS
LIGHT DEPENDENT REACTIONS
TAKE PLACE WHERE? Chloroplast in the
thykaloid
REQUIRE WHAT? Sunlight, and water H2O
inputs
•H2O
•Light energy
outputs
•ATP
•- NADPH
•O2
LIGHT DEPENDENT REACTIONS PH II
•
•
•
•
Photosystem II (PH II) Inside the thykaloid
Discovered AFTER PH I, but in the photosynthetic process
Pigments absorb light
Energy from the light “excite” electrons, increasing their
energy
• Excited electrons passed through the electron transport chain
• The electron is passed from one molecule to another as it
decreases an energy level or step, the energy given off from
the electron decreasing an energy level is used to form ATP
• This is the ETC
LIGHT DEPENDENT REACTIONS- PH II
• Photosystem II (PH II)
• One major problem with PH II is that the electrons are lost
–
–
–
–
How does PH II replenish the electrons?
By splitting the H2O molecule
Into H+ H+ ions
These ions will then be pumped back into the thylakoid reenergized by light and be carried by NADPH back to the
electron transfer chain
A by-product of this reaction is O2 which is then released into the
atmosphere by the plants for organisms to breathe
LIGHT DEPENDENT REACTIONS– PH I
• Photosystem l (PH I)
• High energy electrons move through the PH II to photosystem I
• Energy from these electrons transports H+ ions from the stroma to the
inner thylakoid
Pigments in PH I use energy from light to reenergize the electrons. These reenergized electrons are picked up by NADP+ to form NADPH (the high
energy chauffeur) REMEMBER?
So what is NADPH’s role in photosynthesis?
IT IS THE HIGH ENERGY ELECTRON CARRIER
LIGHT DEPENDENT REACTIONS– PH I
• Hydrogen ion movement
• As a result of the H+ ions released during the splitting of H2O
and electron transport, the inside of the thylakoid membrane
becomes (+) changed while the outside is (-) charged
• This difference in charges provides the energy to make ATP
• ATP synthase:
LIGHT INDEPENDENT REACTIONS
• Light independent reactions
• Take place where?
• Require what?
• Also called the Calvin Cycle of “Dark Reactions”
inputs
--
outputs
Products of
light
dependent
rxn’s
--
LIGHT INDEPENDENT REACTIONS
• Calvin cycle
• 6 CO2 molecules enter the cycle from the atmosphere