Transcript Photosynthesis in Detail

Photosynthesis is…
…the process through which plants
convert light energy to chemical energy
in order to produce food
 The energy involved in photosynthesis
is eventually stored in the chemical
bonds of molecules like glucose.

Question
A.
B.
C.
D.
Which of the following are necessary
in order for photosynthesis to occur?
Water, carbon dioxide, and light
water
Energy are all needed in order for
light energy
photosynthesis to occur.
carbon dioxide
all of the above
Why are Plants Green?
Objects appear a certain
color because they
reflect that color.
 Plants are filled with
chlorophyll, a pigment
that reflects green light.
 Plants absorb mostly red
and blue light and reflect
green light.

Question
A.
B.
C.
D.
In the simulation on the previous slide, the oxygen
meter displays a negative number when the light is
off. This is because the plant is
undergoing photosynthesis.
undergoing the Calvin cycle.
undergoing cellular respiration.
undergoing combustion reactions.
Like all organisms that undergo aerobic cellular
respiration, plants use oxygen to release the
chemical energy stored in glucose and make ATP.
Leaves contain chloroplasts.

Chloroplasts are:
– capsule-shaped organelles
– contained by two membranes
– located inside the mesophyll cells of leaves
Question
A.
B.
C.
D.
Where in a plant would you expect to find
the greatest number of chloroplasts?
root cells
Within a leaf, the chloroplasts are
concentrated in the inner layer of tissue,
stomata cells
which is known as the mesophyll.
leaf vein cells
mesophyll cells
Question
A.
B.
C.
D.
How do the mesophyll cells exchange gases with
the outside environment?
through simple diffusion
through active transport
through endocytosis and exocytosis
through openings in the leaf called “stomata”
Stomata allow carbon dioxide to be
taken in and oxygen and water vapor
to exit. For this reason, most plants
keep their stomata closed for most
of the day, when evaporation is
more likely.
Chloroplast Parts
Thylakoids: disk-shaped vesicles
stacked inside the chloroplast
 Granum: a stack of thylakoids
 Stroma: liquid material inside the
chloroplast
 Chlorophyll: pigment located inside
the thylakoid that absorbs light energy;
gives plants their green color

Chlorophyll
Question
Complete the following analogy.
mitochondrion : matrix :: chloroplast : _______
A. stroma
Both the matrix and the stroma are
B. granum
metabolically-active, fluid-filled areas
inside the innermost membranes of the
C. thylakoid
organelle of which they are a part.
D. inner membrane
Light-Dependent Reactions
 In
this set of reactions, the energy in
sunlight is captured and used to
make energy-storing compounds.
(ATP & NADPH)
 These reactions take place inside the
thylakoid membranes.
 Also known as the “Light Reactions.”
Four Processes of the
Light-Dependent Reactions
1.
2.
3.
4.
Light Absorption
Electron Transport
Oxygen Production
ATP Formation
Question
A.
B.
C.
D.
What is the first step in the light-dependent
reactions?
formation of ATP
Light initiates the process of
photosynthesis by energizing the
absorption of light
electrons in the reaction-centers
production of oxygen of photosystems I & II.
transport of electrons
The Light-Independent Reactions
 Includes
the Calvin cycle.
 Light does not play a role in these
reactions; they can take place in the
light or the dark.
 Sometimes misleadingly called the
“dark reactions.”
Question
A.
B.
C.
D.
Why is it misleading to call the Calvin cycle
reactions the “dark reactions?”
They cannot happen in the dark.
They can only happen in the light.
They can only happen in the dark.
They can happen any time—light or dark.
These reactions are not dependent on
light energy. They can occur as long as
CO2, ATP, and NADPH are present.
The Calvin Cycle
 The
light independent
reactions form a cycle, or
circular series of
reactions.
– This
cycle is called the
“Calvin Cycle” after the
person who first described
it, Melvin Calvin.
This is as detailed as we’ll get!
 The
Calvin Cycle uses
CO2 along with ATP and
NADPH from the light
reactions to form the
building blocks for
glucose.