 CEB Textbook Chapter 4, page 68; Chapter 6 pages 92 and
93; and Chapter 7, pages 107-110
 Mastering Biology, Chapters 4, 6, and 7
After studying this topic you should be able to:





Identify and describe the structure and function
of chloroplasts.
Explain why the process of photosynthesis is
important to humans and ecosystems.
Define and compare autotrophs and
heterotrophs, producers and consumers.
Write the overall equation for photosynthesis.
Draw and describe the road map for
photosynthesis.
X You do not need to study sections: The Light Reactions:
Converting Solar Energy to Chemical Energy and The
Calvin Cycle: Making Sugar from Carbon Dioxide (pages
110-116).


All energy on earth comes from the sun.
We depend on:
› Plants
› Algae (underwater plants/protists)
› Cyanobacteria (photosynthetic bacteria)
 To provide this energy to us!

Heterotrophs or Consumers
Organisms that must eat
organic material (food) to get
nutrients and energy

Heterotrophs consume
Autotrophs (herbivores),
other heterotrophs
(carnivores) or both
(omnivores) for their energy
needs

Complex biological molecules
are broken down and
reassembled into molecules
needed by organisms
(e.g.Respiration)
4

Autotrophs - Organisms that make
their own organic matter (e.g. glucose)
from inorganic material

Phototrophs – use solar energy
(photosynthesis) to get energy

Chemotrophs – use different chemical
processes to get energy
5


Carbon dioxide and water
are taken in by plants
Plants absorb light energy
and convert it to a usable
form.
› ATP

Energy is used to “fix”
carbon dioxide into sugar
molecules
› Chemical potential energy

Sugar is converted to
starch and stored for use
by the plant, and by
animals when they eat
plants.
Plant Photosynthesis
internal leaf structure
outer membrane
inner membrane
thylakoid
chloroplasts
Importance of Photosynthesis!
• The source (indirectly or directly)
of all our food
• The source of all fossil fuels and
Biomass
• The Starting point for food chains
in almost all ecosystems. It is a
means by which energy enters
them
• It is a source of O2 used for
cellular respiration and absorbs
some of the CO2 produced by
respiration and combustion
(reduces global warming)
Jan Van Helmont
(1580 – 1644)
 Found the mass of a
pot of soil and a
seedling. Watered
the seedling for five
years. Found the
mass again
 Concluded that the
increase in mass
came from water
Joseph Priestly
(1733-1804)
 Found that a candle
goes out when
placed in a jar.
However, the candle
keeps burning if a
sprig of mint is also
placed in the jar.
 Concluded that
plants produce
[Oxygen]
Jan Ingenhousz
(1730-1799)
 Showed that
Priestley’s
experiment only
works in the light.
 Concludes that
light is necessary
for plants to
produce oxygen
Photosynthesis The process by which
plants, algae, and some bacteria
transform light energy to chemical
energy stored in the bonds of sugars.
13
‘synthesis’ = BUILD
‘photo’ = LIGHT
Photosynthesis means building with Light
carbon dioxide + water
CO2
H2O
chlorophyll
glucose
oxygen
+
C6H12O6
O2
 Green plants can make their own food from ……..… and ………..…
 using energy in the form of ………………….
 which is absorbed by chlorophyll in the ………………...
 The end products of photosynthesis are ………. and ………….
The glucose is very useful for the plant
Can be converted
into fats and oils
for the seeds
Can be converted
to fructose for
the fruit
Can be used
in respiration
to release
energy
glucose
Can be joined
together to
make cellulose
for the cell
walls
Can be combined with
nutrients from the
soil to make proteins
for the new growth
can be joined
together to make
starch for
storage

Have TWO
membranes
› A “bi-bilayer!”
The inner
membrane is called
the thylakoid.
 The thylakoid is
folded and looks
like stacks of coins
called granum
(grana singular).
 The stroma is the
space surrounding
the granum


A false-color
transmission
electron
micrograph of a
chloroplast from
a tobacco leaf.
Chloroplasts

Chlorophyll molecules
are green pigments
that are embedded in
the thylakoid
membrane

Act like a light
“antenna”

These molecules can
absorb sunlight energy.
Image from Biology 11: College Preparation. Pg 73. Nelson,
Toronto. 2003.
Photosynthetic pigments
Chlorophylls a –
the “main”
photosynthetic
pigment
Accessory pigments..
Chlorophyll b
Carotenoids
Substances that absorb certain wavelengths
of light and reflect other wavelengths
Thus they are colored
Examples:
Chlorophyll (a and b) – green
Carotene – red/orange
Xanthophylls - yellow
What
wavelengths of
light do you
think plants use
the least in
photosynthesis?
GREEN!! CORRECT
1) Light dependent reactions –
they require light and
therefore occur in the
thylakoid membrane
2) Light independent
reactions(Calvin Cycle) –
these don’t require light and
occur in the stroma

Happens ONLY in
sunlight (Hence they
depend on light!)
1.
Image from: Biology 11: College Preparation. Pg 74. Nelson, Toronto. 2003.
Light is absorbed by
chlorophyll molecules
within thylakoid
membrane. This
excites electrons in
the molecule.
Energy from sunlight is
trapped by
chlorophyll
water molecules are
split into H+ and 02
NADPH and ATP are
formed,
O2 is given off as a
waste gas
Masteringbiology.com
Products from the light reactions (ATP
and NADPH) and CO2 from the
atmosphere are used to produce
carbohydrates
Light Independent Reactions
(also called Calvin Cycle, after man who discovered them)
Are a cyclical set of reactions that use the CO2 from the
atmosphere to make the high energy sugar glucose

Happen in sunlight, and
in the dark.
›
›
1.
2.
3.
4.
Image from: Biology 11: College Preparation. Pg 74. Nelson, Toronto. 2003.
Hence “independent of
light”
Occurs in the stroma of
the chloroplast.
ATP generated by
sunlight drives the Calvin
Cycle.
CO2 is “fixed” into sugars!
Monosaccarides (eg.
glucose) are
manufactured in the
cycle.
Monosaccarides are
used to “build”
polysaccharides (eg.
Starch).
NADPH converts back to
NADP+
Masteringbiology.com
Concept Map
Photosynthesis
includes
Light
independent
reactions
Light
dependent
reactions
uses
Light
Energy
Thylakoid
membranes
to produce
ATP
NADPH
occurs in
occur in
Stroma
of
O2
Chloroplasts
uses
ATP
NADPH
to produce
Glucose
Mastering Biology Activities
 The Sites of Photosynthesis (Chapter 7)
 Overview of Photosynthesis (Chapter 7)
 The Light Reactions and Calvin Cycle
 Complete Bioflix study sheet:
Photosynthesis.
 Build a Chemical Cycling System
(Chapter 6)
 Chapter 4 activity Review Animal and
Plant Cell Structure and Function
Chloroplast
 Photosynthesis
 NADPH/NADP+
 ATP/ADP
 Light Reaction
 Calvin Cycle
 Thylakoid membrane
 Autotrophs (Producers)
 Heterotrophs (Consumers)
