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Do all organisms require sunlight to
carry out life processes? If not,
what do all organisms require?
No! All organisms require energy!
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Can animals that eat only other
animals and no plants still use carbs
for energy?
You bet!
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What molecule is the source of
energy for chemical reactions in
cells?
ATP
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What is a biochemical pathway?
Series of linked reactions;
products of one are used as
reactants in the next
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Is ATP a stable molecule?
NO… phosphate groups are all
negatively charged and repel one
another
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What type of pigment is the major
light-absorbing pigment in plants?
chlorophyll
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Differentiate autotrophs and
hetertrophs. Give an example of
each.
Autotrophs – use sun/inorganic compounds to
produce organic compounds; plants
Heterotrophs – consume organic compounds;
animals, fungi
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Why is chlorophyll green?
It reflects green light
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Why is the sun considered the
ultimate energy source for life on
Earth?
Almost all organisms depend on it
directly or indirectly for energy.
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What is the role of chlorophyll?
To absorb light
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Describe the structure of a
chloroplast.
It’s surrounded by two membranes; has a system of
membranes inside called thylakoids; stacks of
thylakoids = grana; fluid around grana = stroma
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What can happen when light strikes
an object?
It can be reflected, transmitted, or
absorbed.
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Do plant pigments absorb all
wavelengths of light?
No… only some wavelengths are
absorbed.
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What is a photosystem?
A cluster of 100s of pigment
molecules and proteins
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Where are photosystems located?
They’re embedded in the
thylakoid membrane.
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What happens to light when it hits
plant pigments?
It’s either absorbed or reflected.
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Why is NADP+ important in
photosynthesis?
It’s needed to make NADPH for the Calvin
cycle. It can provide protons and electrons
for reactions in the form of H.
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Plant cells use light to make what
energy storage molecules?
ATP and NADPH
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What happens to electrons of
chlorophyll a molecules when they
are raised to a higher energy level?
They go to the P.E.A.
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What happens to chlorophyll a
molecules when they absorb light
energy?
They lose electrons.
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What is the source of the oxygen
produced in photosynthesis?
Photolysis (water splitting)
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What is chemiosmosis responsible
for?
Providing energy for
phosphorylation
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What is the phosphorylation
reaction that occurs?
ADP + PO4- → ATP
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What three things does the proton
gradient in the light reaction depend
upon?
1.
Photolysis
2.
H+ being pumped into the thylakoid
3.
Structure of chloroplasts (thylakoid membrane is semi-permeable)
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What product from the light reaction
provides the energy for the Calvin
cycle? What product shuttles p+
and e-?
ATP; NADPH
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What happens to the electrons at
the thylakoid membrane in terms of
energy?
Lose energy (return to original
state) as they move along ETC
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Where do the replacement electrons
come from for PS I?
PS II
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Where do the replacement electrons
come from for PS II?
Photolysis (splitting of water)
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Trace the pathway of electrons from
PS II.
PS II → PEA → ETC → PS I
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Trace the pathway of electrons from
PS I.
PS I → PEA → ETC → stroma →
combine with NADP+ and H+ to
form NADPH
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Where do the light reactions occur?
In the thylakoids
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What are our names for the three
phases of the Calvin cycle?
Carbon fixation, carbon
reshuffling, and regeneration
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What is removed from ATP to
release energy?
a PO4- group
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How many total ATP molecules are
needed in the Calvin cycle if 3 CO2
molecules are used?
9 (6 needed in reshuffling phase and
3 needed in the regeneration phase)
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Where does the energy that drives
the Calvin cycle come from?
Light reactions: ATP and
NADPH - which provides e-
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What molecules does the Calvin
cycle require? Does the cycle
require light?
Requires: ATP for energy , NADPH for protons and
electrons, and CO2 for a carbon source
It doe not require light!
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Where does the Calvin cycle occur?
In the stroma
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What’s another name for PGAL?
G3P
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If 3 CO2 molecules enter the Calvin cycle, how
many PGALs are made? How many PGALs
remain in the cycle and are converted back into
RuBP?
6 are made; 5 remain
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What products can be produced
from the PGAL that leaves the
Calvin cycle?
Glucose; but also lipids and
amino acids to build proteins
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Why is NADPH needed in the
Calvin cycle? In which phase is it
used?
To make PGAL; used in carbon
reshuffling
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During the Calvin cycle, what are
the carbon-containing molecules
produced from?
CO2 from the air, H from NADPH
and RuBP
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How many carbon atoms does
PGAL have? How many PGALs
then are needed to make 1
glucose?
PGAL has 3 carbons therefore 2
are needed to make a 6 carbon
glucose
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Only 1 PGAL leaves the Calvin
cycle. What happens to the others?
What molecule results?
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Remain in the cycle for
regeneration phase; resulting
molecule is RuBP
How does the amount of water used
by C4 and CAM plants compare to
the amount used by C3 plants?
They use less water than C3
plants.
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When do CAM plants have their
stomata open? How does this
compare to C3 and C4 plants?
CAM stomata are open at night
while C3 and C4 stomata open
during the day.
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Does the light reaction depend upon
light? Does the Calvin cycle?
Yes! No!
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What is the final overall product that
plants make in photosynthesis?
Glucose (from PGAL)
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Do plants need light to carry out the
reactions that generate ATP and
NADPH?
Yes – these products are made in
the light reactions!
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What does the rate of
photosynthesis depend upon?
CO2 levels; temperature; light
intensity
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Define photosynthesis.
A biochemical pathway that
converts light energy into organic
compounds
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What is the chemical equation for
photosynthesis?
6CO2 + 6H2O + light → C6H12O6 + 6O2
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What can the carbon atoms in all
organic molecules be traced back
to?
CO2 from the atmosphere
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In which stage of photosynthesis are
carbohydrates produced?
Calvin cycle
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What major byproduct of
photosynthesis is released into the
atmosphere?
oxygen
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