UNIT 5: Photosynthesis and
Respiration
BIG IDEA: Energy is produced and
released by making and breaking
chemical bonds
Think About It:
• With your partner, come up
with a list of activities that you
do that requires energy
• What gives us energy?
Energy
• Directly or indirectly , all energy in living
things comes from the sun
Obtaining Energy
• Autotrophs
• Organisms that are capable of
making food (energy) from
simple inorganic substances
• EX: green plants, algae
Two Types of Autotrophs
• 1. Photoautotrophs: use carbon
dioxide and light energy to
drive reactions needed to make
food
Next type…
• 2. Chemoautotrophs: utilize
inorganic chemicals for the
energy to drive food making
reactions
Obtaining Energy
• Heterotrophs
• Organisms that cannot make their
own food (energy) and must
depend on other plants or animals
as food source (energy)
• Examples: Humans, dogs, cats
Photosynthesis
• Process of capturing energy of
sunlight and transforming it
into chemical energy
• CO2 + H2O----glucose + O2
Photosynthesis
• Two stages
– Light reactions- light energy is
converted into chemical energy of
two intermediate molecules
– Calvin cycle-Organic molecules are
formed from CO2
Photosynthesis
• Sunlight, sometimes called white
light, is a form of energy that
travels in waves
• Wavelength: the distance between
the crest of one wave and the crest
of the next wave
Visible Light Spectrum
•
•
•
•
•
•
Depends on wavelength
Blue: 380 (nm)
Green: 500 (nm)
Yellow 560 (nm)
Light red: 600 (nm)
Darker red: 750 (nm)
Photosynthesis
• Pigments: absorb light
• EX: a red object absorbs all the visible
colors of the spectrum except red
which is reflected and gives the object
the red color
Types of Photosynthetic Pigments
a. Chlorophylls: absorb red and blue
light, appear green
b. Carotenes: absorb blue, appear
orange
c. Xanthophylls: appear yellow, may not
be used to absorb light
The color of an egg yolk
is from the xanthophyll
carotenoids lutein and
zeaxanthin
• The color of an egg yolk is from the
xanthophyll carotenoids lutein and
zeaxanthin
CHLOROPLAST
• Site of Photosynthesis
PARTS OF THE CHLOROPLAST
Inner and outer membrane
Thylakoids
Grana
Stroma
Parts of the Chloroplast
• Thylakoid- Membrane of the
thylakoid contains
photosynthetic pigments;
flattened sacs
• Site of the light reactions
Parts of the Chloroplast
• Grana- Stacks of thylakoids
• Stroma-Region b/t grana
– Site of the light independent
reactions
Photosynthesis Reactions
• Light Dependent Reactions-energy from
light makes the reaction happen
• Light Independent Reactions- Doesn’t need
the energy from light to make the reaction
happen but they do need products of the
light reaction to proceed.
Steps in Light Dependent
Light Dependent Reactions- In the
Chloroplast
•
Pigments in the photosynthetic
membranes absorb light (pigments are
located in Photosystem I & II
•
When the light hits the chlorophyll in
Photosystem II the electrons become
excited and jump up.
•
The electrons are captured by the
electron transport chain.
•
We need to replace the electrons that are
lost so we steal some from water . This
breaks the water molecule apart forming
H+ and O
•
As we transport electrons
down the chain we use
their energy to produce
ATP
•
The electrons now go to
Photosystem I and it loses
electrons to NADP+ to
make it NADPH.
The final products of the light
reaction
•
At the end of the light reaction we have
made
1. NADPH
2. ATP
3. O2
Reactants used during the light
reaction
• Water
• Also used sunlight
Light independent reaction
( Calvin Cycle)
• A. Use CO2 , ATP, NADPH
• B. Uses products from light reaction (Light
is not necessary for this reaction)
• C. Location stroma
Steps in Light Independent
Reaction:
• 6 CO2 reacts with the sugar, ribulose phophate
(RuBP)sugar called phosphoglycerate (PGA)
• PGA12 phosphoglyceraldehyde (PGAL)
• NADPH and ATP from light reaction provide
energy for this step
Steps in Light Independent Reaction
(con’t)
• PGAL does 2 things:
a. Makes more RuBP to continue cycle
(requires 10 PGAL to do this)
b. Form 1 glucose (requires 2 PGAL)
Concept Map
Section 8-3
Photosynthesis
includes
Lightdependent
reactions
use
Energy from
sunlight
Calvin cycle
Thylakoid
membranes
to produce
ATP
NADPH
takes place in
take place in
Stroma
of
O2
Chloroplasts
uses
ATP
NADPH
to produce
High-energy
sugars
Figure 8-7 Photosynthesis: An Overview
Section 8-3
Light
CO2
Chloroplast
Chloroplast
NADP+
ADP + P
LightDependent
Reactions
Calvin
Cycle
ATP
NADPH
O2
Sugars
Factors Affecting Photosynthesis
•
a.
b.
c.
d.
Four main types:
Light intensity
Temperature
Water
Mineral availability
Cellular Respiration
• Release of the
energy stored in
food
• Occurs in the
inside of the cells
of both autotrophs
and heterotrophs
Adenosine Triphosphate (ATP)
• Energy released during cellular
respiration is stored as ATP
• Consists of
adenine, ribose
and three
phosphates
How is energy stored in ATP?
• Energy is stored in the bonds. Once a
bond breaks (causing ATP to lose a
phosphate group), there is a release of
energy.
Release of Energy
Adenosine diphosphate or (ADP)
• Two phosphate groups, adenine,
and ribose
• Where would the energy be in ADP
Two Types of Cellular
Respiration
Aerobic Respiration:
• Occurs in presence of oxygen
• Occurs in the mitochondria
• Produces about 36 ATP
Second Type of Cellular
Respiration
Anaerobic Respiration:
• Occurs without oxygen
• Occurs in the cytoplasm
• Produces 2 ATP
Which type of cellular respiration is
more efficient?
• Aerobic because it produces
more ATP (more energy)
Two types of Anaerobic
Respiration:
• 1. Alcoholic Fermentation: yeast
produces alcohol
• 2. Lactic Acid Fermentation: muscles
produces lactic acid when they don’t
have enough oxygen
What is the equation for cellular
respiration?
GLUCOSE+ 6O26 CO2 + 6 H2O + Energy (36
ATP)
What is the relationship between
photosynthesis and cellular
respiration?
• Opposite reactions
• Let’s write the two reactions to see