Download Document

Ch. 7 Photosynthesis
Using Light to Make Food
7.1 -7.5
• What is
photosynthesis?
• Light energy (from
sun) is used to make
sugar & other food
from CO2 & H2O
• Can too much
sunlight harm a plant?
• Yes. It can overwhelm
the plant.
How it all happens
• Is there a chemical equation for photosynthesis?
• Yes. Carbon dioxide (CO2) is reduced to
glucose & water (H2O) is oxidized to oxygen gas
(O2)
• Where does the O2 come from?
• From water, H2O
• What is an
“autotroph?”
• It means a “selffeeder”
• Are all plants
autotrophs?
• Yes, they make their
own carbohydrates
from CO2 which is a
great fuel & don’t eat
other organisms to
live.
Examples of autotrophs
• Even thought they are
autotrophs, what do
plants require to
synthesize sugar?
• Light=energy, CO2 &
H2O to make sugar, this
is endergonic so it stores
the energy from light
(Ch.5)
• Oak tree, cactus, Kelp (a
large alga photosynthetic
protist), and
photosynthetic bacteria
Producers
• Why are plants considered
producers of the biosphere?
• They make the biosphere’s
organic food supply from raw
material (CO2)
• What is the biosphere?
• The portion of Earth that is
living, all life & where it lives
• Are plants the only producers?
• No, some bacteria, archaea
and protists also make food
from inorganic materials. All
organism that use light energy
to make food are
photosynthetic autotrophs.
Where it all happens
• Where does photosynthesis
take place?
• In eukaryotic organelles called
Chloroplasts (photosynthetic
bacteria have no organells)
• Why are plants green?
• Chlorophyll, a pigment in the
chloroplasts. It absorb all
colors but green,(which reflect
back at you) the light energy
and then chloroplasts convert
that into food.
Parts of a leaf
• Where are chloroplasts
concentrated?
• In the mesophyll cells,
green tissue on the
interior of leaf.
• How does gas enter &
exit plants? (CO2 & O2)
• Stomata (stoma,
singular), the tiny pores
on the leaf.
Parts of a Chloroplast
• Stroma, is a thick fluid, found
in the inner membrane. What
happens there?
• Stroma is the location of
the Calvin cycle (CO2 ->
sugar)
• Thylakoids are suspended in
the stroma. What do they do?
• Thylakoids are the Location of
light reaction. They are
stacked into grana and contain
the chlorophyll, that capture
light energy.
• Where does O2 gas
come from?
• It comes from water
(H2O) and not carbon
dioxide (CO2)
• What is the ratio of
water molecules
needed for each
molecule of O2 gas
• 2:1, 2 water (H2O)
molecules for every
molecule of O2,
• Why is photosynthesis called Redox?
• Leo goes ger - lose an electron oxidation / gain
an electron reduction
• Water is split apart yielding O2, oxidized, the loss
of electrons along with hydrogen ions (H+)
• Carbon dioxide is reduced to sugar, gaining
electrons along with hydrogen ions (H+)
• What is the opposite of photosynthesis?
• The energy releasing process of cellular
respiration.
Using energy in glucose by oxidizing sugar and
reducing O2 to H2O.
Photosynthesis occurs in two
stages linked by ATP & NADPH
•
•
•
•
•
What happens in the light
reaction?
Light energy is absorbed by
chlorophyll (in thylakoids) and
covert it into chemical energy
(ATP & NADPH) (O2 is waste
product)
What happens in the Calvin Cycle
and why has it been called the
dark reaction?
Occurs in stroma of chloroplast,
series of reactions that assemble
sugar using CO2 & energy from
light reaction.
Called the dark reaction because
it does not require light directly.
Does run during day cause of ATP
& NADPH from light cycle.