Transcript Plant Science

Identifying the Properties of
Photosynthesis
Photosynthesis is:
• This conversion of the Sun’s energy into
chemical energy is the single most
important reaction on earth, and could be
called
• THE REACTION OF LIFE.
Photosynthesis
One of the main differences
between plants and animals is the
ability of plants to manufacture
their own food.
Photosynthesis - Respiration
Comparison
• Photosynthesis
• Respiration
• Occurs only in green plants
• Occurs only in green plant cells
• Proceeds only in light
• Food is made
• Increases dry weight
• CO2, H2O are used
• Produces sugars and O2
• Stores energy in sugar
• ATP & NADPH produced
• ATP and NADPH used in sugar
synthesis
• Occurs in all plants and animals
• Occurs in all living cells
• Proceeds in light and darkness
• Food is used
• Decreases dry weight
• Sugar and O2 are used
• Produces CO2 and H2O
• Releases energy
• ATP produced
• ATP and NADPH used for many
reactions
Photosynthesis
• In Photosynthesis Light energy is
captured by chlorophyll contained in
green tissue of plants, mainly the leaves,
• And is used to convert carbon dioxide
CO2 from the air and water H2O from the
soil & atmosphere into carbohydrates
C6H12O6 which are stored in the plant for
future use.
Photosynthesis
occurs in the
chlorophyll
molecule of the
chloroplasts in
the leaves of
green plants
and
photosynthetic
bacteria
Plant Cell with Chloroplast
Algae Cell
with
Chloroplasts.
Photosynthesis
• The carbohydrate is stored inside cell
vacuoles until use in several metabolic
processes:
• Glycolysis - glucose to pyruvic acid
• Respiratory metabolism
• Metabolic maintenance - growth of
plant cells and tissues
Photosynthesis
• Photosynthesis takes place in the CHLOROPLAST
of the cells.
The Structure of the Chloroplasts
Plant Cell
The Leaf & Photosynthesis
Green Plant
Carbon Dioxide + Water
Glucose + Oxygen +
Light Energy Water
Requirements for Photosynthesis
• 1. Healthy, living, green plant
• 2. Light
• 3. Carbon Dioxide (CO2)
• 4. Water (H2O)
Factors Affecting Photosynthesis
Factors Affecting Photosynthesis
• 1. Light Quality
• 2. Light Intensity
• 3. Light Duration
• 4. Carbon Dioxide Concentration
• 5. Temperature
• 6. Water Availability
Factors Affecting Photosynthesis
• 1.
Light Quality
• Light is required for the process of
photosynthesis
• Chloroplasts contain chlorophyll capable of
intercepting light and converting
electromagnetic energy to chemical energy.
• Chlorophyll molecules absorb mostly red
(700 nm) and blue (450 nm) light and reflect
green light (that is why plants look green to
the human eye).
Light Waves & Photosynthesis
Light Spectrum
Factors Affecting Photosynthesis
• 2.
Light Intensity
• Influences the rate of photosynthesis.
• Some species require high light intensity
• “Sun-loving plants”
• Corn, turf
• Some species do not require high light intensity
• “Shade-loving plants”
• Forest floors, house ornamentals
Factors affecting Photosynthesis
• 3.
Light Duration
• A plants photosynthetic production is directly
proportional to the length of day.
• The longer the leaves receive light, the
longer they photosynthesize and the faster
the plant grows.
Factors Affecting Photosynthesis
• 4.
CO2 Carbon Dioxide Concentration
• Concentration of Carbon Dioxide in the air
surrounding the leaves affects photosynthesis.
• Normal atmospheric concentrations of CO2 are
0.03% and O2 are 21% .
• Experiments have shown increases in
atmospheric CO2 can increase photosynthesis
rates.
• Increasing CO2 to 0.1% will double the photosynthesis
rate in wheat, rice, and some vegetables.
The exchange of
oxygen & carbon
dioxide in the leaf
occurs through
pores called stoma
Factors Affecting Photosynthesis
• 5.
Temperature
• As a general rule, if light is not limiting,
photosynthesis rates will double for each
18oF increase in temperature
• Excessively high temperatures (>100o ) will
reduce photosynthesis by causing stoma
closure (no uptake of CO2)
• 65-85oF is optimum
Factors Affecting Photosynthesis
• 6.
Water Availability
• Excessive soil moisture reduces root
respiration and limits photosynthesis in leaves
• Water stress conditions (low soil moisture;
hot, drying winds)
• Plants transpire water faster than it can be
absorbed through roots
• Leaves wilt and gas exchange (CO2 and O2) is
restricted thus decreasing photosynthesis rates
Photosynthesis - Equation
General Reaction
Green Plant
Glucose + Water +
Light EnergyOxygen
Carbon Dioxide + Water
Green Plant
6 CO2 + 12 H2O
Light Energy
C6H12O6 + 6H2O + 6 O2
Discussing the Equation
• Six molecules of carbon dioxide react with
• twelve molecules of water
• in the presence of light and a green plant
• to produce:
• one molecule of glucose (carbohydrate)
• six molecules of water and
• six molecule of oxygen
Green Plant
6 CO2 + 12 H2O
Light Energy
C6H12O6 + 6 H2O + 6 O2
Products of Photosynthesis
• Carbohydrates
• Water
• Oxygen
Green Plant
6 CO2 + 12 H2O
Light Energy
C6H12O6 + 6 H2O + 6 O2
Photosynthesis
in a Plant
The Chemistry of Photosynthesis
• The process of photosynthesis is stated in
simple equations, but the total process is
extremely complex.
• The overall process is separated into two
parts:
• Light Reactions (Hill Reaction)
• Dark Reactions (Calvin Cycle)
The Light and Dark Reactions of
Photosynthesis.
Light Reaction (Hill Reaction)
• In the Light Reaction, energy in the form of
light received by chlorophyll is used to:
• 1.)
• 2.)
Reduce (NADP+) to NADPH.
Provide chemical energy through the
production of adenosine triphosphate (ATP) from
adenosine diphosphate (ADP).
• 3.) The water molecule is split to produce O2
and H+
Green Plant
6 CO2 + 12 H2O
Light Energy
C6H12O6 + 6 H2O + 6 O2
The Z-Scheme of Photosynthesis
• A chlorophyll photo-active center (PSII)
in the granum is activated by light and
splits the water molecule into O2 and H+.
• As the Energy is passed downhill, ATP is
formed. ATP is energy.
• A second photo-active center (PSI)
receives light, and releases energy,
delivering electrons to form NADPH.
Light Reaction (Z-Scheme)
Increasing Energy Level
Electron
Acceptors
Electron
Transport
System
Electron
Transport
System
H+
2 e-
2 e-
Light
Light
P 680
P 700
Photosystem I
Photosystem II
2H2O  4H+ + O2 + 2e- (Photolysis)
NADP+
NADPH
Z-Scheme - Light Reaction
Z-Scheme of the Light Reaction
• 1.
Light Reaction - Hill Reaction
Notes:
Light energy is received by chlorophyll
and used to reduce NADP to NADPH..
• 2.
Production of ATP
• 3.
The water molecule is split to produce
Oxygen.
Green Plant
6 CO2 + 12 H2O
Light Energy
C6H12O6 + 6 H2O + 6 O2
Light Reaction - Hill Reaction
Notes:
• The Hill Reaction occurs in the Granum of the
Chloroplast.
• Requires Light
Light Reaction
Hill Reaction
Dark Reaction
Calvin Cycle
The Light
Reactions of
Photosynthesis
stop when the sun
goes down.
The Dark Reaction
is known as the Calvin Cycle
Dark Reacton - Calvin Cycle
• The Calvin Cycle is the Carbon-Fixing
Cycle of Photosynthesis. It does not
require light.
• It may proceed in light or dark.
Dark Reaction - Calvin Cycle
• The Calvin Cycle takes place in the stroma of
the chloroplast.
Dark Reaction - Calvin Cycle
• The Calvin Cycle uses NADPH and ATP from
the Light Reaction to convert Carbon Dioxide
to a six Carbon Sugar Molecule.
Dark Reaction - Calvin Cycle
• Carbon dioxide molecules from the air enter
the cycle one cycle at a time, making six turns
of the cycle necessary to produce one
molecule of (sugar) glucose, C6H12O6.
Calvin
Cycle
Dark Reaction (Calvin Cycle)
• In the Dark Reaction of Photosynthesis,
• 1.
Carbon taken into the plant as CO2 from
the air accepts the energy, ATP & NADPH
from light reaction.
• 2.This energy is used to convert carbon
dioxide into carbohydrates, (Glucose).
Green Plant
6 CO2 + 12 H2O
Light Energy
C6H12O6 + 6 H2O + 6 O2
Calvin Cycle Notes
• Does not require light.
• May proceed in light or dark.
• Occurs in the Stroma of the Chloroplast.
• Uses NADPH & ATP from the light reaction
to convert CO2 to a 6 carbon sugar.
Green Plant
6 CO2 + 12 H2O
Light Energy
C6H12O6 + 6 H2O + 6 O2
Review of Photosynthesis
Photosynthesis -
• Photosynthesis
• Occurs only in green plants
• Occurs only in green plant cells
• Proceeds only in light
• Food is made
• Increases dry weight
• CO2, H2O are used
• Produces sugars and O2
• Stores energy in sugar
• ATP and NADPH are produced
Photosynthesis is:
• The Transformation of sun’s energy
(light) into useable chemical energy
• The Reaction of Life
Requirements for Photosynthesis
• 1. Healthy, living, green plant
• 2. Light
• 3. Carbon Dioxide (CO2)
• 4. Water (H2O)
Factors Affecting Photosynthesis
• Light Quality
• Light Intensity
• Light Duration
• Carbon Dioxide
• Temperature
• Water
Availability
Photosynthesis - Equation
General Reaction
Green Plant
6 CO2 + 12 H2O
Light Energy
C6H12O6 + 6 H2O + 6 O2
The Chemistry of Photosynthesis
• The process of photosynthesis is stated in
simple equations, but the total process is
extremely complex. The overall process
is separated into two parts:
• Light Reactions (Hill Reaction)
• Dark Reactions (Calvin Cycle)
Hill Reaction Notes:
• Light energy is received by chlorophyll
and used to synthesize ATP and NADPH
• Requires Light
• Creates Oxygen
• Occurs in the Granum
Calvin Cycle Notes
• Does not require light
• May proceed in light or dark
• Occurs in the Stroma
• Uses NADPH & ATP from the light
reaction to convert CO2 to a 6 carbon
sugar.