Photosynthesis
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Photosynthesis
•  Creates food (carbohydrates) for plants.
•  Photo= light
Synthesis= put together
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•  Goal of photosynthesis
is creating glucose
•  Glucose is
a monosaccharide
•  One Molecule of Glucose Stores 90 Times More
Chemical Energy Than One Molecule of ATP
•  Remember, C6H12O6 is not usable energy. It
must be broken down during cellular respiration
to be turned into ATP!
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Location of Photosynthesis
Structure
of the Chloroplast
•  Outer membrane- smooth
•  Inner membrane—stacks of connected sacs
called thylakoids
•  One thylakoid stack is called the granum
(grana-plural)
•  Gel-like material around grana called
stroma
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Pigments
•  The thylakoid
membrane contains
pigments (molecules
that absorb light).
•  Chlorophyll is the
primary lightabsorbing pigment.
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Why do plants appear green? Pigments only
absorb certain wavelengths of light and reflect
what they cannot absorb. We see the wavelength
that is reflected.
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Electromagnetic Spectrum
•  Visible Light Contains A Mixture Of
Wavelengths
•  Different Wavelengths Are Seen As
Different Colors
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2 STEPS OF
PHOTOSYNTHESIS
1)  LIGHT DEPENDENT REACTIONS
2)  LIGHT INDEPENDENT REACTIONS
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It Begins with Sunlight!
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Step 1: Light Dependent
Reactions
•  Occurs in the thylakoid membranes
•  Reactants: light energy and water
•  Products: oxygen, ATP, & NADPH
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LIGHT-DEPENDENT REACTIONS
Light Dependent Reaction
Summary
Where:
•  Thylakoid membrane
Reactants: (what
•  H2O
•  Light Energy
Products:
•  ATP
•  NADPH
•  Oxygen
goes in)
(what comes out)
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Light Dependent Reaction
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Step 2: Light Independent
Reactions
•  Light Independent reactions
(AKA Calvin Cycle) occur in
the stroma
•  GOAL: make carbohydrates
(sugars) like glucose (stored
energy) and cellulose
(strengthen the plant)
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Light Independent Reactions
Light Independent Summary
Location: stroma
Reactants:
CO2, ATP and NADPH
Products:
glucose, ADP and NADP+
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Photosynthesis Overview
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Photosynthesis in a Nutshell:
•  Light Dependent Reaction
– H2O and light go in
– ATP and NADPH come out and go
to the Light Independent
Reactions
– Oxygen comes out as waste
•  Light Independent Reaction
– CO2 goes in
– ATP and NADPH go in for energy
– Glucose (C6H12O6) comes out
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Factors that Affect Photosynthesis
LIGHT INTENSITY
____________________
More light increases rate of photosynthesis
up to a certain level until plant reaches its
maximum rate of photosynthesis
Factors that Affect Photosynthesis
AMOUNT
OF WATER
____________________
Water is one of the raw materials needed, so
slow or stop
A shortage of water can ________________
photosynthesis
Desert plants and conifers
that live in dry conditions
have a waxy coating on
their leaves to prevent
water loss.
Factors that Affect Photosynthesis
TEMPERATURE
Photosynthetic enzymes function
best between 0° C - 35° C
At temperatures above or below
this range, photosynthesis will
slow or stop
Conifers in winter may carry out
photosynthesis only occasionally
Remember:
Enzymes work BEST at a certain
temperature
pH and __________.
___
Conditions that are TOO ACIDIC
or TOO HOT cause proteins
DENATURE
to unwind or _________
Denaturing changes the shape of the
enzyme making it not work
HOMEOSTASIS (keeping pH and temperature
constant) is important for maintaining enzyme
function.
THE BIG PICTURE
PHOTOSYNTHESIS provides
the _____________
we breathe
OXYGEN
and the __________
sugars
heterotrophs (like us)
consume to survive
Carbon
WATER
dioxide + ____________
_____________
Sugars
Oxygen
_______________ + ____________
Concept Map
Section 8-3
Photosynthesis
includes
use
to produce
takes place in
take place in
of
uses
to produce
Concept Map
Section 8-3
Photosynthesis
includes
Lightdependent
reactions
Calvin cycle
use
take place in
Energy from
sunlight
Thylakoid
membranes
to produce
ATP
NADPH
O2
takes place in
Stroma
uses
ATP
NADPH
of
to produce
Chloroplasts
High-energy
sugars