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 This
powerpoint presentation has
been adapted from Life 4e-Lewis,
Gaffin, Hoefnagels and Parker.
Publishers-McGraw-Hill 1998 and
Principles of Anatomy and
Physiology,Tortora and
Grabowski.
Publishers- John Wiley & sons,
Inc. 2000
AUTOTROPHY
Obtaining energy from a
non-living world
photoautotroph
chemoautotroph
Two types of Autotrophs
 Photoautotrophs
 Convert
CO2 and H2O to sugars
utilizing light E (blue and red)
 Examples: plants, algae, some
bacteria
 Chemoautotrophs
 Some convert CO2 and H2S to
sugars utilizing chemicals(energy)
such as H2S.
 Examples: some bacteria
(hydrothermal vents)
 Autotrophy
is the energy basis
for all life on this planet.
Directly keeps the autotroph
alive (can make its own sugar)
Indirectly keeps all of the
heterotrophs alive(get eaten!)
 Autotrophy
produces glucose
 Glucose will be used for:
Cellular respiration
Modified with minerals/other
molecules to become:
Nucleotides, amino acids,
lipids, other carbohydrates
Energy Flow
Energy flows in one direction through an
ecosystem.
Route of energy flow is determined by an
ecosystem’s trophic structure.
animals that eat
carnivores(tertiary consumers)
animals that eat herbivores
(Secondary
consumers)
animals that eat producers
(primary
consumers)
photo- or chemoautotrophs
Food web - several
species function at more
than one trophic level.
I strongly suggest you view and
use what is appropriate from the
following link:
http://photoscience.la.asu.edu/photosyn/education/learn.html
PHOTOSYNTHESIS
 6CO2
+ 12H2O  C6H12O6 + 6O2 + 6H2O
 Several consequences to this evolutionary
advance/mutation.
 Oxygen gas (O2 ) slowly built up in
atmosphereAerobic respiration now a possibility
UV
Ozone forms (3 O2
2 O3)
Life can now leave the safety of the water and
colonize land
Light (see page 103)
Visible light makes up only a small
portion of the electromagnetic
spectrum.
Characteristics of Visible Light:
 is
a spectrum of
colors/wavelengths ranging from
violet to red
 consists of packets of energy
called photons
 photons travel in waves, having a
measurable wavelength ()
measured in nanometers (nm)10-9
A photon’s energy is inversely related to
its wavelength ()...
...the shorter the ()..., the greater
the energy it possesses.
Which of the following photons possess
the greatest amount of energy?
Green photons
Red photons
Blue photons
 = 530nm
 = 660nm
 = 450nm
What happens to light when it strikes an
object?
 reflected
(bounces off)
 transmitted
(passes through)
 absorbed
Only absorbed wavelengths of light
function in photosynthesis.
Photosynthetic Pigments
Molecules that capture photon
energy by absorbing certain
wavelengths of light.
Primary pigments
Chlorophylls
a & b - bluish green
pigments found in plants, green
algae & some bacteria.
See page 105
Chlorophyll a is the
dominant pigment
in plant
photosynthesis.
Accessory Pigments
Carotenoids
- orange, yellow
pigments found in plants, algae,
bacteria.
Anthocyanins - reds and purples
Each pigment absorbs a
particular range of
wavelengths.
See page 105
Leaf- See page 728
Chloroplasts- See page 104
Sites of photosynthesis in plants & algae.
Concentrated in the palisade mesophyll
cells of most plants.
Chloroplast structure: See page 104
 Stroma - gelatinous matrix; contains
ribosomes, DNA & various enzymes.
 Thylakoid - flattened membranous sac;
embedded with photosynthetic pigments.
Chloroplast
Photosynthesis.
CO2 from atmosphere, H2O from soil
Requires correct enzymes and
pigments plus sunlight (red
and blue,) ATP, NADPH to
convert the reactants into the
products
6CO2 + 12H2O  C6H12O6 + 6O2 + 6H2O
Stomata/Stoma
- pores extending
through the leaf epidermis
Stomata regulate gas (CO2,O2 and
H2O) exchange with the
environment.
Usually based on their different
concentration gradients, CO2 will
diffuse into the leaf; H2O and O2
will diffuse out of the leaf.
Photosynthesis occurs in two
biochemical pathways:
 Light reactions - harvest photon
energy to synthesize ATP & NADPH.
Splits H20
 Calvin cycle reactions - use ATP and
NADPH from light reactions to
reduce (add hydrogen/electrons) to
CO2 forming carbohydrates.
Overview of Photosynthesis
Light Reactions
 require
light
 occur in thylakoids of chloroplasts
 involve photosystems II & I (light
harvesting systems).
Photosystems
contain antenna
complex that
captures photon
energy & passes
it to a reaction
center.
Light Reactions of Photosynthesis
Light Reactions
1. Light drives both
photosystems (PS).
2. Water splits, O2
formed & electron to
PS II
3. excited electron enters
ETC. ATP is made,
similar to respiration.
4. electron replaces the
one lost in PS I.
5. electron from PS I
enters ETC.
6. This ETC produces
NADPH
Fig. 10.13
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 10.17
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
ATP Production: See page 108
Go to Light Reaction animation
Go to Calvin Cycle animation
Overview of Photosynthesis
Carbon Reactions(Calvin cycle; C3
cycle)
 occurs in stroma of chloroplasts
requires ATP & NADPH (from light
reactions), and CO2 from
atmosphere.
Produces- H2O and 2 PGALs
(glucose)
Calvin Cycle;
see pg.111
Fig. 10.18
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Overview of Photosynthesis
 Calvin
Cycle Steps
 CO2 combines with the 5-carbon sugar
RuBP
 This reaction is catalyzed by the enzyme
RUBISCO
 The resulting unstable 6-carbon compound
breaks down into 2 molecules of 3-carbon
PGA
 The PGA molecules get energy from ATP
and a H from NADPH to form PGAL.
 The PGAL gets rearranged and another
ATP is used to recycle into RuBP.
Calvin Cycle
 It
takes 3 “turns” of the cycle to release
one PGAL.
 It takes 2 PGALs to make a glucose.
 So… it takes 6 turns of the cycle to make
a glucose.
 Each turn of the cycle is started by the
entrance of one CO2.
 So look back at the overall equation. It
takes 6CO2 to make one C6H12O6.
Calvin Cycle;
see pg.111
Plants that use only the
Calvin cycle to fix carbon
are called C3 plants.
Ex. cereals, peanuts,
tobacco, spinach, sugar
beets, soybeans, most
trees & lawn grasses.
Calvin Cycle;
see pg.111
Photorespiration and Special Adaptations
Photorespiration: See page 118
Process that counters photosynthesis.
Occurs when stomata close under hot,
dry conditions:
 O2 levels in plant leaf increase
 CO2 levels in plant leaf decrease
Under these conditions, rubisco attaches
to O2 (rather than to CO2).
Thus,less PGAL is produced (up to
50%).
No
known function of
photorespiration
Photosynthesis has produced
all atmospheric O2. So when
photosynthesis and Rubisco
are thought to have evolved
there was little to no O2
therefore photorespiration
was not a problem.
C3 because first
stable molecule is
a 3 Carbon sugar
C4 and CAM Photosynthesis: See
pages 119-120
Adaptations that allow certain plants
to conserve water and reduce
photorespiration when exposed to
higher temperatures.
C4 Photosynthesis
C4 plants reduce photorespiration by
physically separating the light
reactions and Calvin cycle.
Leaf anatomy of a
C4 plant
vs.
C3 plant
C4 Photosynthesis:
 Light reactions
occur in
chloroplasts of
mesophyll cells.
 Calvin cycle occurs
in chloroplasts of
bundle sheath cells.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
CAM Photosynthesis
CAM plants reduce photorespiration by acquiring
CO2 at night. Therefore don’t have to open
stomata and dehydrate during hot days.
Night:
mesophyll cells fix
CO2 as malic acid
 malic acid is stored in
vacuoles.

Malic
acid
Day:

malic acid releases
CO2 which enters
Calvin cycle.
Fig. 10.19
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Rate of photosynthesis
Rate= activity per unit of time
Light intensity,water conc.,
temperature, conc. of oxygen
and carbon dioxide
All affect the rate of
photosynthesis
Light- see page 115
increasing light= increasing rate
of photosynthesis until light
saturation point, then declines.
Why?
CO2increasing CO2 similar curve
except no decline (reaches
saturation)
See
page 116
Temperature
As temperature increases
so does rate of
photosynthesis, then it
declines to zero.
Why?
See
page 116
Limiting factors
Light, temperature etc. all
interact with each other.
Factors in shortest supply have
the greatest effect on the rate
of photosynthesis. These are
called limiting factors..
 Sugar
made in the chloroplasts supplies
the entire plant with chemical energy
and carbon skeletons to synthesize all
the major organic molecules of cells.
 About 50% of the organic material is
consumed as fuel for cellular
respiration in plant mitochondria.
 Carbohydrate in the form of the
disaccharide sucrose travels via the
veins to nonphotosynthetic cells.
 There, it provides fuel for respiration
and the raw materials for anabolic
pathways including synthesis of
proteins and lipids and building the
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings