1. Photosynthesis Plants and Oxygen Plant Respiration Parts of Photosynthesis Light Reactions. Photosynthesis. - PowerPoint PPT Presentation
1. Photosynthesis Plants and OxygenPlant RespirationParts of
Photosynthesis is essential to all life on earth; both plants
and animals depend on it. It is the only biological process that
can capture energy that originates in outer space (sunlight) and
convert it into chemical compounds (carbohydrates) that every
organism uses to power its metabolism.2Photosynthesis
Photosynthesis uses carbon dioxide and water to assemble
carbohydrate molecules and release oxygen as a waste product into
the atmosphere.3The Plant Cell
NucleusCell WallCentral VacuoleChloroplastsLike all organisms,
plants have cells. But unlike animal cells, plant cells have more
components in them, such as the cell wall.
Major components in a plant cellsCell wall- gives the cell a
definite shapeCell membrane- controls the movement of substances in
and out of a cellCytoplasm- allows substances in the cell to move
aboutCentral vacuole- a large part in a plant cell to store food
the plant needsNucleus- controls activities in a cell and contains
genetic informationChloroplasts- contains chlorophyll which
photosynthesizes and makes food for the plantHowever, some parts of
the plant do not contain chloroplasts, such as the roots as no
sunlight reaches underground and no photosynthesis can take
place.4Plants and Oxygen ProductionCyanobacteria, like these in
Yellowstone National Park, were the worlds first Oxygen
This Oxygen Revolution transformed early earths atmosphere. It
was good for some (allowing for increased efficiency with O2
respiration) but bad for others (in the form of mass extinction of
5StromatolitesStromatolitesare special rock-like structures that
form in shallow water.
They are formed bycyanobacteria that use water, carbon dioxide,
and sunlight to create their food, and put out oxygenas a
by-product. The Earliest Evidence of Stromatolites: 3.5 BYA!
6This world map shows Earths distribution of photosynthesis as
seen via chlorophyllaconcentrations. On land, this is evident via
terrestrial plants, and in oceanic zones, via phytoplankton.
Percentage of Earth's Surface Area
Pretty Big! HUGE!
Average net primary production (g/m2/yr)Low Productivity! High
Productivity! Percentage of Earth's net primary productionWay
higher than the others!Oceans and Rainforest are vital to oxygen
production on Earth! What will happen if they arent
protected?Photosynthesis/RespirationPhotosynthesis:Plants use H2O
and carbon dioxide and produce starch and oxygen
H2O + CO2 = Starch/sugar + O2RespirationAnimals use starch/sugar
and oxygen, and produce H2O and carbon dioxide
Starch/sugar + O2 = H2O + CO2 1111Respiration and photosynthesis
are complementary processes
Photosynthesis is a multi-step process that requires sunlight,
carbon dioxide (low in energy) and water as substrates.
Photosynthesis releases oxygen and produces simple carbohydrate
molecules (which are high in energy) that can subsequently be
converted dozens of other sugar molecules.
These sugar molecules contain energy and the energized carbon
that all living things need to survive.1212Point out that equation
is balancedStomata on the underside of a leaf
1313a stoma (also stomate; plural stomata) is a tiny opening or
pore that is used for gas exchange.
Air containing carbon dioxide and oxygen enters the plant
through these openings where it is used in photosynthesis and
respiration. Waste oxygen produced by photosynthesis exits through
these same openings. Also, water vapor gets into the atmosphere
through these pores in a process called transpiration.
The pore is formed by a pair of specialized cells known as guard
cells which are responsible for regulating the size of the opening
and found mostly on the under-surface(epidermis) of a plant leaf.An
open (left) and closed (right) stoma of a spider plant
(Chlorophytum colosum) leaf. When guard cells are turgid, the stoma
is open (left).
Stomata on the underside of a leaf141415
1515Oxygen bubbles form on underwater plants. 16The
Most of the living world depends on chloroplasts for its
Two membranes on outsideComplex membrane structure on inside
Photosynthesis takes place in two sequential stagesIn
thelight-independent reactions, the chemical energy harvested
during the light-dependent reactions drive the assembly of sugar
molecules from carbon dioxide.In thelight-dependent reactions,
energy from sunlight is absorbed by chlorophyll and that energy is
converted into stored chemical energy. 1818
Absorbed and Reflected LightAbsorbed LightReflected
LightTransmitted LightPlants are green because chlorophyll reflects
green light.1919Light comes in spectrum plants dont use all light,
only certain wavelengths = we will see this in later labs
2020Plants use visiable light Diff plants use diff parts of
specThey have pigments to harness energy we will talk about that
Leaf > Cell with Chloroplasts > Chloroplasts Interior >
Pigment molecules around the light reaction chamber. 21
PhotosystemExcited electrons are the key to photosynthesis.
Grannum (stack of thylakoids)Within the membrane of each
thylakoid arecountless clusters of pigments. These pigments are
The pigments act as antenna, bouncing photons towards the
Primary Electron Receptor2222A photosystem consists of a
light-harvesting complex and a reaction center. The first
photosystem of photosynthesis is called photosystem 2.
Light harvesting complexReaction CenterPhotosystem 2 23
Pigments in the light-harvesting complex pass light energy (in
the form of photons) to two special chlorophyllamolecules in the
Chlorophyllamolecules Click once to animate this slide. 24
The light excites an electron from the chlorophyllapair, which
passes to the primary electron acceptor.Primary Electron
Acceptore-Photosystem 2 Click once to animate this slide. 25
The chlorophyll molecule must get a new electron from somewhere!
Its electron is replaced by the splitting of a watermolecule. When
a molecule of water is split energy (and oxygen) is
released.OHHOHHe-For every two water molecules that are split, one
molecule ofO2, the oxygen we breathe, is produced.Click once to
animate this slide. 26
Meanwhile, the excited electron that was raised to the primary
electron acceptor is transferred to a mobile carrierprotein, that
moves it along the electron transfer chain.
As it moves along the electron transfer chain it releases works
to produce ATP, the currency of energy, that a cell uses. However,
as it produces ATP becomes less and less
excited.e-ATPATPATPPhotosystem 2 Click once to animate this slide.
At the end of the Electron Transfer Chain, the electron is no
longer excited. It enter Photosystem 1 and is excited again by the
photons boosting it back into its high energy state.
e-Photosystem 1 Photosystem 2 Click once to animate this slide.
ATPATPATPThe re-excited electron is again transferred to a
mobile carrierprotein, that moves it along the electron transfer
chain, however this time it is combined with another electron, one
proton, and a molecule of NADP+to create a molecule
ofNADPH.e-NADP+e-HNADPHPhotosystem 1 Click once to animate this
slide. 29Active Transport: Proton pumpsThe ATP released during the
ETC transfer is used to drive proton pumps which sets up a
concentration gradient of high H+ inside the thylakoid (lumen) and
a low H+ outside the thylakoid (stroma)
HHInside of ThylakoidOutside of ThylakoidATPATPHHHHClick once to
animate this slide. 30
ATPase ActivityHInside of ThylakoidOutside of
ThylakoidADPProtons (H+) flow down concentration gradient through
ATPase, an enzyme that synthesizes ATP.PATPHHHHHHH
323233Light ReactionsLight boosts electrons in Photosystem II,
high energy electrons passed along chain of carriers Electrons
replaced by splitting waterPassage of electrons down chain releases
energy used to fuel proton pumps to generate ATPChain ends in
Photosystem I, electron energy boosted again, passed on to
NADPHATP, NADPH (fuel) produced by light reactions provide energy
to power Calvin Cycle (making sugar)3333