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Energy
• Ability to do work,
moves or changes
matter.
• Comes in many
different forms
(chemical energy,
potential energy, solar
energy, electricity, heat).
• Never created or
destroyed only
transformed.
Autotrophs - Organisms which make their own food,
directly utilize the sun’s energy (i.e trees).
Heterotrophs - Organisms
who obtain energy from
the food they consume,
cannot directly utilize the
sun’s energy (i.e. bears)
ATP - Adenosine Triphosphate
• Cells’ energy molecule. Energy is stored
within the bonds of the phosphates.
• ATP is used to run all cellular activity
(protein synthesis, membrane pumps, DNA
regulation).
• ADP (2P) would be a dead battery while
ATP (3P) would be a charged battery.
Photosynthesis: Using light to make food
The gift of a green world.
• Life on Earth is solar
powered.
• By converting the energy
in sunlight into chemical
energy, photosynthesis
produces 160 billion
metric tons of
carbohydrates each year.
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
THE BASICS OF PHOTOSYNTHESIS
• Almost all plants are photosynthetic autotrophs, as
are some bacteria and protists.
– They generate their own organic matter through
photosynthesis.
(c) Euglena
(d) Cyanobacteria
(b) Kelp
(a) Mosses, ferns, and
flowering plants
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 7.2
Kingdom Plantae
Simple Plants: (a) Mosses
Simple Plants: (a) Mosses, (b) Hornworts, (c) Liverworts
Ferns
Cone Trees
Flowering Plants
• With flowers for
reproduction
• Seeds are
produced inside
the fruit
(matured ovary)
Water Lily Leaf
Victoria regia
Succulent cacti
Cacti
Carnivorous plants obtain some of their nutrients
from animal tissues.
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Photosynthesis
• Plant process whereby the energy in the sun is used
to convert H2O and CO2 into high energy sugars and
O2 waste.
• 6CO2 + 6H2O + sun energy  C6H12O6 + 6O2
Light
• Sun: white light (energy) is composed of a
range of wavelengths (colors)
Gamma
rays
X-rays
UV
Infrared
Visible light
Wavelength (nm)
Microwaves
Radio
waves
• Chloroplasts absorb
light energy and
convert it to
chemical energy
Light
Reflected
light
Absorbed
light
Transmitted
light
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
Chloroplast
The location and structure of chloroplasts
Chloroplast
LEAF CROSS SECTION
MESOPHYLL CELL
LEAF
Mesophyll
Stoma
(pl. stomata)
Intermembrane space
CHLOROPLAST
Outer
membrane
Granum
Grana
Figure 7.2
Stroma
Inner
membrane
Stroma
Thylakoid
Thylakoid
compartment
Chloroplast Pigments
• Chloroplasts contain several pigments
– Chlorophyll a
– Chlorophyll b
– Carotenoids
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
Pigments – The Rainbow Catchers
• Light-absorbing
molecules
• Absorb some
wavelengths and
reflect others
• Color you see are
the wavelengths
NOT absorbed
chlorophyll a
chlorophyll b
Wavelength (nanometers)
An Overview of Photosynthesis
H2O
Chloroplast
CO2
Light
NADP+
ADP
+ P
LIGHT
REACTIONS
(in grana)
CALVIN
CYCLE
(in stroma)
ATP
NADPH
O2
Sugar
Chloroplast
Organelle found inside plant cell where photosynthesis occurs.
• Thylakoids - sac-like
photosynthetic membranes
found inside the chloroplasts,
contain chlorophyll and other
light absorbing pigments. Site
of the Light-Dependent
reactions.
• Stroma - region outside the
thylakoid membrane, but still
inside the chloroplast. Site of
the Calvin Cycle reactions.
Photosynthesis is comprised of two
reactions
1) Light Dependent Reactions
2) Calvin Cycle (Dark Cycle) Reactions
Light-Dependent Reactions
•
•
•
•
Requires light.
Occurs in the thylakoid membranes.
Breaks H2O molecule and produces O2.
Converts ADP into ATP and NADP+ into NADPH.
Light Reactions (Photolysis)
• Light energy is used to split water and give
– Oxygen and hydrogen
– 2 H2O + light  4 H+ + O2
• Light energy is used to make ATP
Electron Carrier
• Molecule which carries sunlight excited
electrons from chlorophyll to other
chemical reactions in the cell.
• Hot Coals / Fire / Tongs analogy
Chlorophyll is the main
synthetic pigment
Plants produce O2 gas
• The O2 liberated by photosynthesis is a
byproduct made by splitting water (H2O)
Calvin Cycle Reactions
• Does not require
light.
• Occurs in the
stroma.
• Uses energy in
NADPH and ATP to
convert CO2 into
high energy sugars.
Dark Reactions (Carbon Fixation)
• ATP and Hydrogen (H) are used to “fix” CO2
– To make organic molecules C6H12O6 (glucose)
Variables effecting Photosynthesis
•
•
•
•
Light Intensity
CO2 Concentration
Temperature
Graphs Shape required
MEASURE PHOTOSYNTHESIS
• Production of Oxygen
• Uptake of CO2
• Increase in Biomass (glucose, plant growth)
Carbon
dioxide
Water
Glucose
PHOTOSYNTHESIS
Oxygen
gas
Photosynthesis & Cellular Respiration
Linked Processes
Aerobic Respiration
Photosynthesis
• Energy-releasing pathway
• Energy-storing pathway
• Requires oxygen
• Releases oxygen
• Releases carbon dioxide
• Requires carbon dioxide
• Predominant producers on land are plants such
as oak trees and cacti
• In aquatic environments, algae and
photosynthetic bacteria are the main food
producers
How Photosynthesis Moderates the Greenhouse Effect
• Old-growth forests:
– Are important for
lumber
– Are important for
moderating world
climates
– Are homes to
many species of
plants and
wildlife that exist
nowhere else
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
• The Greenhouse effect:
– Warms the atmosphere
– Is caused by atmospheric CO2
Sunlight
Atmosphere
Radiant heat
trapped by CO2
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings