Photosynthesis Flashcards
Photosynthesis converts
light energy to the chemical
energy of food
The light reactions convert
solar energy to the chemical
energy of A T P and N A D P H
The Calvin cycle uses the
the chemical energy of A T P and
N A D P H to reduce CO2
to sugar
photosynthesis nourishes
almost the entire living world
autotrophs
sustain themselves without eating anything from other organisms
autotrophs are
producers
producers
produce organic molecules from CO2 and other inorganic molecules
most plants are
photoautotrophs
photoautotrophs
use the energy from sunlight to make organic molecules
what organisms can do photosynthesis
plants
algae
protists
prokaryotes
heterotrophs
consumers
consumers
obtain organic molecules from other organisms
heterotrophs consume _____ directly and _____ indirectly
plants and animals
most heterotrophs depend on
photoautotrophs for food and O2
how are fossil fuels formed
organisms that died hundreds of millions of years ago
fossil fuels represent what
stores of solar energy from the past
chloroplasts are similar to the
photosynthetic bacteria that they evolved from
photosynthetic enzymes and other molecules are arranged
together in thylakoid membranes
why is having all photosynthetic enzymes and molecules together good
more efficient chemical reactions of photosynthesis can happen
where are the major locations of photosynthesis
leaves
where else can photosynthesis happen
anywhere that is green
chloroplasts are found in what type of cells in the leaves
mesophyll
how many chloroplasts in a mesophyll cell
30 to 40 each
what enters through the stomata
CO2
what leaves through the stomata
O2
what two gases can diffuse across membranes in and out of chloroplasts
CO2 and O2
chloroplasts are surrounded by
two envelope membranes
what do the two membranes enclose in chloroplasts
a dense interior fluid called the stroma
interior thylakoid membranes form
interconnected sacs
where is the pigment chlorophyll found
in thylakoid membranes
what makes the leaves green in plants
chlorophyll
what are the stacks of thylakoids called
grana
Chemical equation of photosynthesis
6CO2 + 12H2O → C6H12O6 + 6O2 + 6H2O
Net consumption of water photosynthesis equation
6CO2 + 6H2O → C6H12O6 + 6O2
the simplest possible form of the photosynthesis reaction
CO2 + H2O → [CH2O] + O2
what do the brackets mean in [CH2O]
not an actual sugar but represents the general formula for a carbohydrate
Need 6 repetitions of simplest equation to
produce a glucose molecule
The actual product of photosynthesis is a
three-carbon sugar that can be used to MAKE glucose
One of first clues to the mechanism of photosynthesis
discovery that O2 is given off by plants is derived from H2O and NOT from CO2
Chloroplast splits water into
hydrogen and oxygen
Photosynthesis in sulphur bacteria
Used hydrogen sulphide rather than water for photosynthesis
CO2 + 2H2S = [CH2O] + H2O + 2S
Oxygen-18 isotope
O2 from plants was labelled ONLY with this isotope if water was the source of the tracer
If this isotope was introduced to the plant in the form of CO2
it was not in the release of O2
electrons released by splitting water
incorporated into sugar
oxygen is released as a
by-product
what does CO2 give rise to in the equation
Carbon and oxygen in glucose
oxygen in water
what does water give rise to in the equation
hydrogen in glucose
hydrogen in water
oxygen
what is reversed in photosynthesis compared to respiration
electron flow
what is oxidized in photosynthesis
H2O
what is reduced in photosynthesis
CO2
photosynthesis is an ______ process
endergonic
two stages in photosynthesis
- light reaction
- Calvin reaction
where does light reaction happen
thylakoids
what four things does the light reaction do
- split water
- releases oxygen
- reduces NADP+ to NADPH
- generates ATP from ADP by photophosphorylation
Calvin cycle does what to carbon
fixes carbon and incorporates CO2 into organic molecules
what is used to drive the Calvin cycle
energy from ATP and NADPH in light reaction
chloroplast thylakoids transform
light energy into chemical energy of ATP and NADPH
light is a form of
electromagnetic energy or radiation
light travels in
waves
wavelength
the distance between crests of waves
wavelength determines
the type of electromagnetic energy
electromagnetic spectrum
the entire range of electromagnetic energy or radiation
visible light
wavelengths that produce colours we can see
light also behaves as discrete particles
photons
shorter wavelengths
higher energy
wavelength with most energy
gamma rays and purple light
longer wavelengths
lower energy
wavelength with lowest energy
radio waves and red light
pigments
molecules that absorb visible light
different pigments
absorb different wavelengths
wavelengths that are not absorbed
are transmitted
why do leaves appear green
chlorophyll is reflected and transmits green light
is green light used IN photosynthesis
no, its reflected
absorption spectrum
plots a pigment’s light absorption versus its wavelength
absorption spectrum of chlorophyll a
violet-blue and red wavelengths are best for photosynthesis
action spectrum
profiles the effect of different wavelengths on a process
Englemann experiment
the growth of algae in red and purple light was higher in gree light
chlorophyll a
main photosynthetic pigment
accessory pigments
chlorophyll b
carotenoids
chlorophyll b
broadens spectrum used for photosynthesis
carotenoids
absorb excess light that can damage chlorophyll and the cell
CH3 is in
chlorophyll a
CHO is in
chlorophyll b
what happens when a pigment absorbs light
it becomes excited but VERY unstable
what has higher energy ground or excited state
excited state
how can energy be released in the form of protons of light or heat
excited electrons have high energy and fall back to the ground state with lower energy
a solution of isolated chlorophyll will do what when illuminated
will fluoresce and give off red light and heat