Transcript 9.2 Photosynthesis powerpoint
Section 9.2 Photosynthesis: Trapping the Sun’s Energy
p. 225 - 230
Trapping Energy From Sunlight
• • • Plants and other
green
organisms must
trap light energy
from the sun to be able to use it.
• The
energy
must then be
stored
that can be used by the cells.
in a way
ATP
is the form!
Autotrophs
trap and make energy with photosynthesis
Trapping Energy From Sunlight
• During photosynthesis, plants use the sun’s energy to make
simple sugars
.
• These sugars are then made into
complex carbohydrates
, such as starch.
•
Starches
store energy.
Trapping Energy From Sunlight
• There are two parts to photosynthesis:
light-dependent
reactions and
light independent
reactions.
• Light-dependent reactions change
light energy
into
chemical energy
, splitting water and
releasing oxygen
.
• Light-independent reactions
produce simple sugars
.
Where Does Photosynthesis Take Place?
• Photosynthesis takes place in the
chloroplast
.
• Chloroplasts contains
pigment
.
• Pigments take in
specific wavelengths
of sunlight.
Where Does Photosynthesis Take Place?
• Wavelengths of sunlight
transfer
energy.
• The most common
pigment
chloroplast is
chlorophyll
.
in the • Chlorophyll is the main
energy-trapping
molecule in the plant.
Chlorophyll a
• Every place that doesn’t have a letter telling you the element, is a carbon.
• Hydrogens are attached to all of the empty spots on the carbons.
The red, yellow, and purple pigments are visible in the autumn.
Why can’t you see the colors during the summer?
During the summer, the plant cells manufacture chlorophyll, which hides the other pigments that are present in leaves.
Where Does Photosynthesis Take Place?
• Chlorophyll is a plant pigment that absorbs most wavelengths of sunlight except
green
.
• Since it cannot absorb green, it
reflects green
.
• This makes leaves look green!
• In fall the leaves
stop chlorophyll
so producing
other pigments
are now
visible
.
Wavelengths of light
• Light that we see and plants use for photosynthesis is a small part of the spectrum of electromagnetic radiation, from just below 400 nm to just above 700 nm. • Our peak sensitivity is in the middle of this range at about 550 nm or in the green part of the spectrum.
• Coincidentally this is the part of the spectrum which plants do not use or "see". • They absorb light in the blue and in the red.
Chlorophyll-a absorption spectrum
Wavelengths of light
• • The sunlight is absorbed by
pigments.
• Chlorophyll absorbs red and blue light and
reflects green
so it appears green.
Carotenoids
are other pigments which absorb in the blue and appear yellow.
Light-Dependent Reactions
• The first phase of photosynthesis
needs sunlight
.
• This first phase takes place in the chloroplasts, more specifically, in the
thylakoid membranes
: membranes within the chloroplast that contain enzymes.
•
Energy
from sunlight is trapped by chlorophyll in this
thylakoid membrane
.
Light-Dependent Reactions
• When sunlight strikes the
chlorophyll
the plant’s leaves the energy from the in sunlight is transferred to
electrons
in the chlorophyll.
• The
electrons
move
from the chlorophyll
to an electron transport chain.
Chlorophyll molecules absorb light energy and energize electrons for producing ATP and NADPH.
NADP is nicotinamide adenine dinucleotide phosphate The H is a hydrogen ion that gets combined with the NADP along with two excited electrons.
Light-Dependent Reactions
• *** The electrons move from the chlorophyll to an electron transport chain.
• An electron transport chain is a line of
proteins
embedded in a
membrane
along which the
electrons are passed
down.
Light-Dependent Reactions
• Each protein in the line
passes the electron
to the next protein.
• As the electrons pass along this line, they
lose some
of their energy.
Light-Dependent Reactions
• If you filled a bucket with water and passed it along a line of people very quickly, some of the water would spill.
• This is similar to how the electrons lose their energy.
Electron transport chain
What Happens to the Lost Energy?
• The energy the electrons lose can be used to form
ATP
from ADP.
• Energy that is
not used
to form ATP
can be stored
for use in the light-independent reactions.
What Happens to the Lost Energy?
• The energy is stored in an
electron carrier
called
NADPH
.
• NADPH
carries
the energy to the
light independent
reaction.
NADP
• NADP = an
electron
and proton “
carrier
” • Carries the electrons and protons to
make energy.
This is what NADP+ looks like:
Conversion of NADP + to NADPH
•
And here is a closer look at the conversion of NADP + to NADPH
Photololysis – still in phase one , light dependent In photolysis, a molecule of water is split to
replace electrons
lost from chlorophyll.
It splits water into
oxygen
and
hydrogen
.
Light-Independent Reactions
• The second phase of photosynthesis
does not
need sunlight.
• It also takes place in the chloroplasts and is called the
Calvin Cycle
.
• More specifically, it takes place in the
stroma
.
• The stroma is the
liquid-y
part of the
chloroplast
.
Light-Independent Reactions
• The Calvin Cycle uses
carbon dioxide
sugars.
to form • The sugars then become
stored energy
.
• You could say it is a series of reactions that synthesize simple sugars from carbon dioxide and hydrogen.
• It’s a big job to make sugars from
carbon dioxide
!
Light-Independent Reactions
• The ATP and NADPH produced in the
light dependent
reactions are used.
• The
chloroplasts
breaks down this large task into very small steps.
• The end result is energy
stored
in the plant as
sugar
.
Light-Independent Reactions
• Organisms that
eat plants
use these sugars to give them energy. • The energy is used in
cellular respiration
.
The stroma in chloroplast is where the Calvin Cycle takes place.
The Calvin Cycle takes the carbon in CO2, adds it to one molecule of RuBP, and forms sugars through a series of reactions in the stroma of the chloroplasts.
The NADPH and ATP produced during the earlier light-dependent reactions are important molecules for this series of reactions.
Why is the Calvin cycle in plants directly and indirectly important to animals?
The energy in the bonds of the sugars synthesized by plants is the source of energy for animals. Indirectly, Plants also provide shelter and a home to many animals
Calvin Cycle
• At the beginning, one molecule of CO 2 added to one molecule of a
five-carbon
is sugar RuBP to form a six-carbon sugar.
• After a series of reactions, the sugar breaks down to two three-carbon sugars called phosphoglyceraldehyde, or
PGAL
.
Calvin Cycle
• After 3 rounds of this cycle, 6 molecules of PGAL are produced.
• 5 PGALs are rearranged to make 3 new RuBP molecules
Calvin Cycle
• The sixth PGAL is available to make sugars elsewhere in the body.
• Calvin cycle takes 6 rounds to make one glucose molecule