Chapter 6: Photosynthesis
Mrs. Stewart
Honors Biology
Central Magnet
Standards
 CLE
3210.3.3 - Investigate the relationship
between the processes of photosynthesis
and cellular respiration.
 SPI 3210.3.3 - Compare and contrast
photosynthesis and cellular respiration in
terms of energy transformation.
Objectives
 Summarize
the reactants and
products of photosynthesis.
 Describe the reactants and
products of the light reactions.
 Describe the reactants and
products of the Calvin Cycle (dark
reactions).
 Summarize how the light reactions
and Calvin cycle work together to
create a continuous cycle of
photosynthesis.
Think – Pair - Share
Q: Where does the energy come from
in each stage of the food chain?
Autotrophs
Make
their own food
Heterotrophs
Cannot
food
make their own
WHAT is the energy?
 Much
of the energy used by living
organisms is in the form of ATP
Chemical Energy and
ATP
The
principal chemical
compound that cells use to
store and release energy is
called ATP (adenosine
triphosphate)
Storing Energy
ATP
stores energy in the
bond between the second
and third phosphate group
ATP is like a fully charged
battery
Energy
Think – Pair - Share
Releasing Energy
Q: How is the energy in ATP released?
A: Break bond between the second and 3rd
phosphates
2
ADP
ATP vs. ADP
ATP – has all 3 phosphate groups



Fully charged battery
Brief energy storage
Can remove a phosphate group to release
energy and form ADP
ADP – has only 2 phosphate groups


Partially charged battery
Can add a phosphate group to make ATP
ATP Availability
 Most
cells only have enough ATP for a few
seconds of activity
 Why?



Not good at storing energy over the long
term
Glucose stores 90 times the chemical
energy of ATP
Cells generate ATP from ADP as needed by
using the energy in foods (like glucose)
6-1:
Photosynthesis
Photosynthesis
The
process in which plants
use the energy of sunlight
to convert water and
carbon dioxide into high
energy carbohydrates –
sugars and starches – and
oxygen as a waste product
Photosynthesis
6CO2 + 6H2O
(Carbon Dioxide)
(Water)
LIGHT
C6H12O6 + 6O2
(Sun)
(Glucose)
(Oxygen)
Photosynthesis
The Visible Light Spectrum
Pigments
 Absorb
different wavelengths of light
(colors)
 Reflect (transmit) what they do not
absorb
 We see what is reflected back.
Chlorophyll
The
plant’s principal
pigment
absorbs light energy
 blue-violet
 red
Absorption of Light by
Chlorophyll a and Chlorophyll b
Absorption of Light by
Chlorophyll a and Chlorophyll b
Chlorophyll b
Chlorophyll a
V
B
G
YO
R
Think – Pair - Share
Q: Why are leaves green?
A: because chlorophyll
absorbs the blue-violet and
red light and reflects the
green back.
Because light is a form of energy…
 Anything
that absorbs light also absorbs
the energy from that light
 When chlorophyll absorbs light, much of
the energy is transferred to electrons in
the chlorophyll molecule, raising the
energy level of these electrons
 These high-energy electrons make
photosynthesis work
Photosynthesis Basics
Where
does photosynthesis
take place? In organelles called chloroplasts.
Thylakoids
Sac-like
photosynthetic
membranes arranged in
stacks
Grana
Stacks
of thylakoids
Granum
– singular
Grana - plural
Stroma
The
region outside the
thylakoid
The watery region in a
chloroplast
Similar
to the cytoplasm in
the cell
Photosynthesis occurs in two parts:
1.
2.
Light – dependent reactions
(takes place in the thylakoid
membranes)
Light – independent/Calvin
Cycle reactions (takes place
in stroma)
ANALYZE THE PICTURE
 List
1.
2.
 List
the reactants and products for
The light dependent reactions
The Calvin Cycle (light independent)
reactions
the location where each reaction
occurs
Pg. 123
Light Dependent Reactions


“photo” part of photosynthesis
Reactants:


H2O, energy from light (photons)
NADP+, ADP+ and phosphate
group
Products:

Oxygen gas, ATP, NADPH
Think – Pair – Share
Q: Where did the Oxygen,
produced by the light
dependent reactions
come from?
A: H2O
What you need to know:
Where
do the light reactions
occur?
In the thylakoids.
What
is needed (reactants)?
•Light (photons)
•water
What
is created (products)
•ATP & NADPH - go on to Calvin cycle
•Oxygen - that is released
Carrier Molecule
Compound
that can accept
a high energy electron and
transfer it along with most of its
energy to another molecule
Ex.)
NADP+ + H  NADPH
The Calvin Cycle
The
“synthesis” part of
photosynthesis
These reactions don’t require
light, therefore these
reactions are called Light –
Independent or Dark reactions
The Calvin Cycle
 Reactants:
ATP and NADPH (from light –
dependent reactions) and CO2
 Products:
high energy sugars (C6H12O6)
and NADP+ and ADP+ (which will go
back to light dependent reaction for
reuse)
Carbon Fixation
The
incorporation of CO2 into
organic compounds
The
Carbon in CO2 is “fixed” into
the usable energy form of sugar
6
CO2 molecules will go into
the cycle to produce each
organic molecule of 6-Carbon
sugar. (C6H12O6 )
Factors Affecting
Photosynthesis
Not
enough water
Temperature
Light intensity
CO2 levels
Objectives (Did we…)
 Summarize
the overall reactants
and products of photosynthesis.
 Describe the reactants and
products of the light reactions.
 Describe the reactants and
products of the Calvin Cycle (dark
reactions).
 Summarize how the light reactions
and Calvin cycle work together to
create a continuous cycle of
photosynthesis.