Autotroph
Heterotroph
(Producers)
(Consumers)
Make their own food
• Photosynthesis
• Chemosynthesis
- Plants
- Some bacteria & protists
Energy obtained by eating
Photosynthesis
6H20 +
6CO2

C6H12O6 + 6O2
How can plants do it?
• Plants contain the green
pigment chlorophyll, which
takes in sunlight and captures
it’s energy, in the chloroplasts.
– There are two main types of
chlorophyll, “chlorophyll a”
and “chlorophyll b”
• When chlorophyll absorbs light,
energy is transferred to
electrons in the chlorophyll
molecule, raising their energy
level.
• These high-energy electrons
make photosynthesis work.
Interpreting Diagrams
• Which wavelengths/
color(s) are absorbed
best?
• Which wavelengths/
color(s) are reflected?
• What is the relationship
between reflection of
light and the perception
of color?
Not all plants have green leaves…
They still have
chlorophyll!!
It is just hidden by
other pigments.
Why do leaves change colors?
• Chlorophyll breaks down in cold weather as the
strength of the sun’s rays weakens.
• The other colors, that were always there, show through.
How do we know?
Chromatography
• Method of separating
pigments
• The solvent moves past
the spot that was applied
• The pigments will differ
in solubility and in the
strength of their
adsorption to the
adsorbent
• Some will be carried
farther up the plate than
others.
Location of Photosynthesis
The Chloroplast
Process Overview
Two steps:
1. Light Dependent (Light Reactions)
-> thylakoid
2. Light Independent (Calvin Cycle)
-> stroma
A closer look…….
Light
H2O
CO2
NADP+
ADP + P
Lightdependent
reactions
O2
Calvin
cycle
Sugars
Light-Dependent Reactions
1. Light is absorbed by
chlorophyll in clusters
called photosystems
2. A flow of e- starts
3. This provides energy to
make ATP & NADPH
4. Water is split to replace eand allow the flow to
continue & O2 is released
5. ATP & NADPH go to the
stroma to fuel the Calvin
Cycle
NADPH
• When water is split to replace e- in PS-II, H+ are left over
• As free e- reach PS-I, two are picked up by NADP+,
resulting in NADP• This negative charge attracts H+ ions resulting in NADPH
NADP+ + 2e-  NADPNADP- + H+  NADPH
• NADPH carries electrons (energy source) as well as
hydrogen (to build sugars) to the stroma for the Calvin
Cycle.
Chemiosmosis
• Mechanism that generates ATP
• Uses potential energy of an H+
concentration gradient
• H+ flow across the thylakoid
membrane into the stroma
through an enzyme membrane
protein called ATP synthase
• This drives the (photo)
phosphorylation of ATP
Self-Assessment – L.D. Reactions
1. Where in the chloroplast do the light dependent
reactions take place?
2. What happens when a molecule of chlorophyll
absorbs light?
3. How is water used during the light dependent
reactions? (2 uses) What is the bi-product of using
water?
4. What two things does NADPH supply for the Calvin
Cycle?
5. What is chemiosmosis? What enzyme is involved in
this process? What supplies the energy for this
process?
Calvin Cycle
1. CO2 enters the stroma
2. It combines with a
5-C sugar RuBP using the
enzyme Rubisco to form a
3-C acid (carbon fixation)
3. Using energy from ATP &
NADPH high energy sugars
(G3P) are made for the
plant
4. ADP & NADP+ go back to
the thylakoid to be
“recharged”
In order for the “cycle” to continue, RuBP
must be regenerated. 3 “turns” of the
Calvin Cycle are needed to generate one
G3P molecule. In other words, 3 CO2
molecules are used to make 1 G3P and
remake RuBP.
Self-Assessment – Calvin Cycle
• What is “waiting” in the stroma to combine with CO2?
What enzyme catalyzes this combination?
• What is the direct result of this combination?
• What is the general name to describe this conversion
of inorganic CO2 into a molecule plants can use for
biosynthesis?
• Why is the Calvin Cycle called a “cycle”? How many
“turns” are needed to provide the plants with a
molecule of sugar?
Process Recap
The two sets of photosynthetic reactions work
together.
• The light-dependent reactions trap sunlight
energy in chemical form (ATP and NADPH).
• The light-independent reactions use that
chemical energy to produce stable, highenergy sugars.
Global Impact of Photosynthesis
•Carbon cycle
•Greenhouse effect
•Greenhouses gases in
atm. prevent some heat
from the sun from
escaping
•CO2, methane, H2O vapor
are the main GH gases
•Global warming
•Excessive levels of GH
gases result in more heat
being trapped
•This is not the same
thing as ozone depletion
Food & Energy
Food serves as a source of raw materials, or
building blocks, for the cells in the body and also
as a source of energy.
Animal Cells
Animal
Mitochondrion
Plant
Plant Cells
Chemical Energy & Food
• Cells don't “burn” glucose. Instead, they
gradually release the energy from glucose and
other food compounds.
• Cellular (aerboic)respiration is the process that
releases energy by breaking down glucose and
other food molecules in the presence of oxygen.
• This process occurs in the mitochondria.
Structure of the Mitochondria
Cellular Respiration
Oxygen + Glucose  Carbon Dioxide + Water + ATP
(6O2 + C6H12O6 
6CO2 +
6H2O + ATP)
• Cellular respiration is an aerobic process because it
requires oxygen (aerobic respiration)
• There are three steps in cellular respiration
– Glycolysis
– Krebs Cycle (a.k.a. “Citric Acid Cycle”)
– Electron Transport Chain (ETC)
• In the absence of oxygen, glycolysis is followed by
fermentation. This is called anaerobic respiration.
Overview of Cellular Respiration
Mitochondrion
Cytoplasm
Glycolysis
• Occurs in the cytoplasm
• One molecule of glucose (6-C) is split, producing
two molecules of pyruvic acid (3-C)
• The cell uses two molecules of ATP to start the
process and when glycolysis is complete 4 gross
or 2 net ATP and 2 NADH are produced.
2 ATP
2 ADP
4 ADP
4 ATP
Fermentation
1. Alcoholic Fermentation:
-
Performed by yeasts and a few other microorganisms
pyruvic acid + NADH → alcohol + CO2 + NAD+
2. Lactic Acid Fermentation:
-
in cells, such as muscle cells, the pyruvic acid from
glycolysis is converted to lactic acid
- pyruvic acid + NADH → lactic acid + NAD+
**Fermentation regenerates NAD+ so that
glycolysis can continue
Kreb’s Cycle & E.T.C.
• In the presence of oxygen, pyruvic acid enters the
Kreb cycle where it is further broken down,
releasing carbon dioxide.
• ATP is generated in a series of complex reactions
that involves high energy electrons moving through
the electron transport chain.
• Oxygen serves as the final electron acceptor,
allowing energy to be released to cells
Kreb’s Cycle
• Entering the mitochondria, the
pyruvic acids from glycolysis
are converted to 2-C acetyl
CoA molecules by losing a
molecule of CO2
• The acetyl CoA molecules enter
the Krebs cycle in the matrix
and join a 4-C acceptor
molecule to form citric acid.
• This molecule is then broken
down in a series of reactions
releasing CO2 and producing
the energy molecules ATP,
NADH and FADH2
E.T.C.
• Electron carriers NADH and FADH2 drop off electrons and
release H+ ions along the inner cristae membrane.
• The energy from the electron flow pumps (against gradient)
the H+ ions across the cristae into the inter-membrane space.
• The ions that diffuse back across the cristae through ATP
synthase providing energy to bind ADP + P to make ATP.
Energy Totals
• Glycolysis produces just 2 net ATP molecules per
molecule of glucose.
• Krebs Cycle & the ETC produce up to 36 additional
ATP. Two (per glucose) from Krebs & up to 34 from
the ETC.
• The complete breakdown of glucose through cellular
respiration, including glycolysis, results in the
production of 38 molecules of ATP (net).
Photosynthesis v. Cellular Respiration
• Photosynthesis:
• Respiration:
• Photosynthesis removes carbon dioxide from the atmosphere
and cellular respiration puts it back.
• Photosynthesis releases oxygen into the atmosphere and
cellular respiration uses that oxygen to release energy from
food