Download Chapter 4 Photosynthesis PPT

Photosynthesis
Auto- & Hetero trophs Review
 Autotrophs, through the process of
photosynthesis convert sunlight into energy,
consume CO2 in that process and release
O2.(photosynthetic plants and chemosynthetic
organisms) “producers”
 Heterotrophs cannot do any of that, but must
obtain their energy by being consumers instead of
producers
Chemical Energy and ATP
 ATP (adenosine triphosphate) is the compound
used by cells to store energy
 ADP (adenosine diphosphate) will become ATP by
adding another phosphate group, thus ADP is like
a partially charged battery, ATP is like a fully
charged battery
More on ATP
 When the high energy bond between the
phosphates is broken, energy is released. (ATP is
converted to ADP)
 Web site that explains the ADP/ATP concept.
 http://www.brooklyn.cuny.edu/bc/ahp/LAD/C7/C
7_atp.html
 Cells use ATP for: active transport,intracellular
movement, and production of heat
More on ATP
 ATP in cells is in short supply and is used up
quickly
 Glucose contains about 90 times the energy of an
equal amount of ATP
 Cells generate ATP from ADP when necessary by
using the energy in carbohydrates
Van Helmont’s experiment
 1600’s
 Van Helmont found that the mass of a plant increased
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over time, but the mass of the soil it grew in did not
change.
Where did the increase in mass come from?
Addition of water accounted for most of mass gained
by plant over time
The carbon part of the increase in carbohydrate mass
had to come from the atmosphere.
Conclusion: something is going on with the stuff in the
air (CO2) and sunlight
Priestley’s Experiment
 Experiment with flame in a jar showing that O2 is
consumed by the flame
 Placed a plant in the jar which replenished the
O2, thus showing that the plant was producing O2
 Secondary conclusion: light necessary for O2
production
Ingenhousz Experiment
 Built on Priestley’s work, but showed that the
effect of the plant was impacted by the plant
being exposed to light.
 Secondary conclusion: plant being exposed to CO2
and light allowed for O2 production
 Ingenhousz NOT pictured here---
Photosynthesis Equation
Photosynthesis Equation
Light and Pigments
 “light” is composed of many different colors of
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light (due to different wavelengths)
“white” light is composed of these different
wavelengths being together.
Plants gather the light energy with pigments such
as chlorophyll a & chlorophyll b
Chlorophyll does NOT absorb the green
wavelengths of light, that is why we see
chlorophyll appears green
Carotene is another pigment (does not absorb the
red and orange wavelengths)
Each color has a different
wavelength
 Red is next to infrared
 UV is next to violet
 Wavelength is related to energy
Inside a Chloroplast
 Thylakoids are saclike photosynthetic
membranes that contain clusters of
chlorophyll and other pigments that can
capture the energy of sunlight
Photosynthesis has a light-dependent stage
which occurs within the thylakoid membrane
The light-independent stage (AKA: the Calvin
Cycle)
Occurs in the stroma, which is a region outside
the thylakoid membrane
NADP+ and NADPH
 NADP+ has the job of moving the energy
captured by photosynthesis to other places in the
cell so that it can be used
 NADP+ adds 2 high energy electrons and an H+
ion, then is changed into NADPH, which can be
used by the cell for building other molecules, such
as carbohydrates (glucose)
 NADP+ is nicotinamide adenine dinucleotide
phosphate
Light-Dependent Reactions
 Light-dependent reactions convert ADP and
NADP+ into ATP and NADPH and produce Oxygen
in the process
The Calvin Cycle
 During the Calvin Cycle, plants use the energy
that ATP and NADPH contain to build high
energy compounds that can be stored for a
longer time.
 The Calvin Cycle uses the ATP and NADPH
from light-dependent reactions to produce
high energy sugars
 The Calvin Cycle does not require light to
occur, thus is considered light-independent.
The Calvin Cycle (Light Independent
Reaction) Carbon Fixation
Calvin Cycle Details
 6 CO2 molecules enter the cycle from the atmosphere,
 The CO2 combines with six 5-Carbon molecules, resulting in
twelve 3-carbon molecules
 Using the energy of ATP and NADPH, the Twelve 3 –carbon
molecules are converted into higher energy forms
 Two of the Twelve 3-carbon molecules are converted into two
similar 3-carbon molecules. These 3-carbon molecules are used
to form various 6-carbon sugars and other compounds
 The remaining ten 3-carbon molecules are converted back into
six 5-carbon molecules. These combine with the six new CO2
molecules to begin the next cycle.
Factors that Affect Photosynthesis
 Inadequate water will slow or stop photosynthesis
 Temperatures outside of the optimal range (0C-
35 C) may destroy enzymes, slowing or stopping
photosynthesis
 Light intensity will have a direct impact on the
rate of photosynthesis. (Low intensity=less
photosynthesis, High intensity=more
photosynthesis)