Transcript Photosynthesis Notes

To Counteract the Greenhouse Effect:
Plant a Tree
Carbon Dioxide is one of the component gases of the “greenhouse” gas layer, which traps
reradiated solar radiation near the surface of our planet and increases global warming.
The more photosynthesis that takes place on our planet, the more carbon dioxide that is
consumed in the photosynthetic process and the less carbon dioxide available to the
greenhouse gas layer . PLANT A TREE TO COMBAT GLOBAL WARMING!!!
To Counteract Ozone Holes: Plant a Tree
• The ozone layer in the
stratosphere is made up of
oxygen.
• It shields the planet against the
damaging effects of ultraviolet
radiation and other forms of
solar radiation which increase
global warming.
• Holes in the ozone layer
caused by anthropogenic
pollution can be patched up
with atmospheric oxygen.
• Increasing photosynthetic
output will increase
atmospheric oxygen and help
to repair the ozone layer.
Photosynthesis and Cellular
Respiration
FOOD & ENERGY
PRODUCTION
Do We Need Plants?
• Plants as carbon sinks, removing carbon
dioxide from the atmosphere and oceans by
fixing it into organic chemicals.
• Plants also produce some carbon dioxide by
their respiration, but quickly used by
photosynthesis.
• Plants also convert energy from light into
chemical energy of C – C covalent bonds.
• Animals are carbon dioxide producers that
derive their energy from carbohydrates and
other chemicals produced by plants by the
process of photosynthesis.
Overview of photosynthesis and respiration
SUN
RADIANT
ENERGY
PHOTOSYNTHESIS
GLUCOSE
RESPIRATION
CELL
ACTIVITIES
ATP(ENERGY)
Photosynthesis vs Respiration
Photosynthesis and respiration as complementary processes in the living world.
Photosynthesis uses the energy of sunlight to produce sugars and other organic
molecules. These molecules in turn serve as food.
Respiration is a process that uses O2 and forms CO2 from the same carbon atoms that
had been taken up as CO2 and converted into sugars by photosynthesis. In respiration,
organisms obtain the energy that they need to survive.
Photosynthesis preceded respiration on the earth for probably billions of years before
enough O2 was released to create an atmosphere rich in oxygen.
(The earth's atmosphere presently contains 20% O2.)
Plant – Soil
Continuum
Obtaining raw materials
– sunlight
• leaves = solar collectors
– CO2
• stomates = gas exchange
– H2O
• uptake from roots
– nutrients
• uptake from roots
In Plants Photosynthesis Occurs In the
Chloroplasts Within the Leaves
Leaves
• Function of leaves
– photosynthesis
• energy production
• CHO production
– gas exchange
– transpiration
stoma
simple vs. compound
THE SUN: MAIN SOURCE OF
ENERGY FOR LIFE ON EARTH
Light Energy Harvested by Plants &
Other Photosynthetic Autotrophs
6 CO2 + 6 H2O + light energy → C6H12O6 + 6
O2
Light Energy Harvested by Plants & Other
Photosynthetic Autotrophs
THE FOOD WEB
Food Chain
Producers: Produce Food
• Photoautotrophs produce “food” which is
consumed directly or indirectly by organisms at
all trophic levels of a food chain/ web.
WHY ARE PLANTS GREEN?
It's not that easy being green
Having to spend each day the color of the leaves
When I think it could be nicer being red or yellow or gold
Or something much more colorful like that…
Kermit the Frog
Electromagnetic Spectrum and
Visible Light
Gamma
rays
X-rays
UV
Infrared &
Microwaves
Visible light
Wavelength (nm)
Radio waves
The Nature of Light
Photons are discreet packets of light energy made in the sun that travel
in waves of different lengths. Visible light is composed of wavelengths
ranging from 380 to 750 nanometers. Photosynthetic pigments convert
some of these visible light wavelengths into chemical energy. For
Photosynthesis, light energy from the blue and red portions of the spectrum
are converted to chemical bond energy.
• Pigments absorb certain
wavelengths of light and
convert their energy into
chemical energy.
• Pigments reflect or
transmit wavelengths of
light energy that they do
not convert to chemical
energy, therefore, they
appear this color.
• Chlorophyll is green,
therefore, it absorbs
blue and red
wavelengths of light
Chloroplasts Have the
Green Pigment
Chlorophyll
Chloroplast Pigments
• Chloroplasts contain several pigments
– Chlorophyll a
– Chlorophyll b
– Carotenoids
The feathers of male cardinals
are loaded with carotenoid
pigments. These pigments
absorb some wavelengths of
light and reflect others.
Sunlight minus absorbed
wavelengths or colors
equals the apparent color
of an object.
Why are plants green?
Transmitted light
WHY ARE PLANTS GREEN?
Plant Cells
have Green
Chloroplasts
The thylakoid
membrane of the
chloroplast is
impregnated with
photosynthetic
pigments (i.e.,
chlorophylls,
carotenoids).
THE COLOR OF LIGHT SEEN IS THE
COLOR NOT ABSORBED
• Chloroplasts
absorb light
energy and
convert it to
chemical energy
Light
Reflected
light
Transmitted
light
Chloroplast
Absorbed
light
Pigments
• Visible color is from wavelengths not
absorbed
• Pigments capture light energy from
absorbed wavelengths
Photo = Light
Synthesis = To Make
• Light energy is converted to chemical bond
energy. With this energy the chemical bonds of
carbon dioxide and water are broken and
reassembled into carbohydrates. In this
process oxygen is also produced.
PHOTOSYNTHESIS
• Photosynthesis is the process by which
autotrophic organisms use light energy to
make sugar (glucose) and oxygen gas from
carbon dioxide and water
Carbon
dioxide
Water
Glucose
PHOTOSYNTHESIS
Oxygen
gas
Six molecules of water + six molecules of
carbon dioxide
produce
one molecule of sugar (glucose) + six
molecules of oxygen
THE BASICS OF PHOTOSYNTHESIS
• Almost all plants are photosynthetic autotrophs, as
are some bacteria and protists
– Autotrophs generate their own organic matter through
photosynthesis
– Sunlight energy is transformed to energy stored in the
form of chemical bonds
(c) Euglena
(a) Mosses, ferns, and
flowering plants
(b) Kelp
(d) Cyanobacteria
Photosynthesis
• Method of converting sun energy into
chemical energy usable by cells
• Autotrophs: self feeders, organisms
capable of making their own food
– Photoautotrophs: use sun energy e.g.
plants photosynthesis - makes organic
compounds (glucose) from light
– Chemoautotrophs: use chemical energy
e.g. bacteria that use sulfide or methane
chemosynthesis-makes organic compounds
from chemical energy contained in sulfide or
methane
Photosynthesis
• Photosynthesis takes place in
specialized structures inside plant cells
called chloroplasts
– Light absorbing pigment molecules e.g.
chlorophyll
The location and structure of chloroplasts
Chloroplast
LEAF CROSS SECTION
MESOPHYLL CELL
LEAF
Mesophyll
CHLOROPLAST
Intermembrane space
Outer
membrane
Granum
Grana
Stroma
Inner
membrane
Stroma
Thylakoid
Thylakoid
compartment
Photosynthesis occurs in chloroplasts
• In most plants, photosynthesis occurs
primarily in the leaves, in the chloroplasts
• The leaves have the most chloroplasts
• The green color comes from chlorophyll in the
chloroplasts
• The pigments absorb light energy
• A chloroplast contains:
– stroma, a fluid
– grana, stacks of thylakoids
• The thylakoids contain chlorophyll
– Chlorophyll is the green pigment that captures
light for photosynthesis
Chloroplast
two outer
membranes
thylakoid
membrane
system
Organelle of
photosynthesis in
plants and algae
stroma
thylakoid compartment
Location of Photosynthetic
Reactions
• The two chemical reactions of
photosynthesis are localized:
1. The conversion of sunlight energy to
chemical energy (light-dependent reactions)
occurs on the thylakoid membranes
2. The synthesis of glucose and other
molecules (light-independent reactions)
occurs in the surrounding stroma
Two Groups of Reactions
1. Light-dependent reactions
– Chlorophyll and other molecules of the
thylakoids capture sunlight energy
– Sunlight energy is converted to the energy
carrier molecules ATP and NADPH
– Oxygen gas is released as a by-product
Two Groups of Reactions
2. Light-independent reactions
– Enzymes in the stroma synthesize
glucose and other organic molecules
using the chemical energy stored in
ATP and NADPH
Light-dependent Reactions
• Photosystem: light capturing unit, contains
chlorophyll, the light capturing pigment
• Electron transport system: sequence of
electron carrier molecules that shuttle electrons,
energy released to make ATP
• Electrons in chlorophyll must be replaced so that
cycle may continue - these electrons come from
water molecules, oxygen is liberated from the
light reactions
• Light reactions yield ATP and NADPH used to
fuel the reactions of the Calvin cycle (light
independent or dark reactions)
How the Light Reactions Generate ATP and NADPH
Primary
electron
acceptor
Primary
electron
acceptor
Energy
to make
NADP
3
2
Light
Light
Primary
electron
acceptor
1
Reactioncenter
chlorophyll
Water-splitting
photosystem
2 H + 1/2
NADPH-producing
photosystem
Calvin Cycle (light independent or
“dark” reactions)
• ATP and NADPH generated in light
reactions used to fuel the reactions which
take CO2 and break it apart, then
reassemble the carbons into glucose.
• Called carbon fixation: taking carbon
from an inorganic molecule (atmospheric
CO2) and making an organic molecule out
of it (glucose)
• Simplified version of how carbon and
energy enter the food chain
PHOTOSYNTHESIS
• The light reactions
convert solar
energy to
chemical energy
Light
Chloroplast
NADP
– Produce ATP & NADPH
• The Calvin cycle makes
sugar from carbon
dioxide
– ATP generated by the light
reactions provides the energy
for sugar synthesis
– The NADPH produced by the
light reactions provides the
electrons for the reduction of
carbon dioxide to glucose
ADP
+P
Light
reactions
Calvin
cycle
Review: Photosynthesis uses
light energy to make food molecules
A Summary of the Chemical Processes of Photosynthesis
Chloroplast
Light
Photosystem II
Electron
transport
chains
Photosystem I
CALVIN
CYCLE
Stroma
Cellular
respiration
Cellulose
Starch
LIGHT REACTIONS
CALVIN CYCLE
Other
organic
compounds
The Importance of Photosynthesis
• The energy entering chloroplasts as sunlight gets
stored as chemical energy in organic compounds
• Sugar made in the chloroplasts supplies chemical
energy & carbon skeletons to synthesize the organic
molecules of cells
• Plants store excess sugar as starch in structures
such as roots, tubers, seeds, & fruits
• In addition to food production, photosynthesis
produces the O2 in our atmosphere
Summary
• Light Dependent Reaction
– Light + chlorophyll --> ATP + NADPH + (O2 as
waste)
• Light Independent Reaction (Calvin Cycle)
– CO2 + ATP + NADPH --> glucose
Starch
What happens to the glucose
produced by photosynthesis?
CH2OH
O H
H
O
CH2OH
H
OH
H
H
OH
Glucose
subunit
O H
H
O
CH2OH
H
OH
H
H
OH
Glucose
subunit
O H
H
O
H
OH
H
H
OH
Glucose
subunit
O
Up to 1000
or more
monomers
What happens to the glucose
produced by photosynthesis?
Sucrose
CH2OH
O
H
O
HOCH2
H
H
H
OH
H
O
H
HO
CH2OH
HO
H
OH
Glucose
subunit
HO
H
Fructose
subunit
It's not that
easy being
green… but it
is essential for
life on earth!