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Photosynthesis
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Photosynthesis
requirements: light, chlorophyll, raw materials, enzymes, chlorophyll-traps the light of the sun
raw materials: CO2, H2O (from the roots)
end product: glucose (C6H12O6)
equation:
light
6C02 + 12H2O
C6H1206 + 602 + 6H2O
enzymes
+
chlorophyll
LIGHT -provides energy for photosynthesis. Light is made of waves and also packets of energy called
photons. Visible light can be separated into a spectrum. This is what occurs when light passes through a
prism. The color of an object is the color of light reflected by the object.
CHLOROPHYLL-this substance is a pigment. Pigments absorb light. Chlorophyll absorbs energy from all
but the green portion of the light spectrum. When a photon strikes a chlorophyll molecule, the photon's
energy is transferred to an electron of the chlorophyll molecule. The electron is in an "excited" state, but it
cannot stay there for long. As the electron returns to its original energy level, it releases the absorbed energy
which is then used in chemical reactions.
CHLOROPLAST-consists of flattened membranous sacs (thylakoids) arranged in stacks called grana
Photosynthesis begins in the thylakoid internal membrane. The fluid filled gaps which surround the grana are
called stroma. All enzymes necessary for the process of photosynthesis are in the thylakoid membrane and
stroma.
PHOTOSYNTHESIS-this is a 2 step process. The first phase is called the light-dependent or light reaction,
and it requires light. The second phase is call the light-independent or dark reaction. It can proceed in the
dark but requires the products from the light reaction.
A. Light reaction-this occurs in a series of steps, some of which happen simultaneously.
1.
2.
Sun
Photons
3.
e-
ADP
ATP
Hydrogen
acceptor
e
4.
Energy
gradient
-
e-
2H+
5.
1
H2O
/2 O2
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The chlorophyll molecules in the grana absorb photons of light.
The energy from the photons boosts electrons (e-) from the
chlorophyll molecules to a higher energy level.
The energized electrons move from one molecule to another in a
series of reactions called an electron transport chain (ETC). Each
time a transfer is made, some energy is released.
The energy released from the electrons as they move down the
ETC is used to create a hydrogen ion (proton) gradient. This
gradient along with chemiosmosis is used to form ATP molecules
by uniting ADP molecules and phosphates. The electrons and
hydrogen ions ultimately end up on NADP+ to form NADPH.
The electrons lost from the chlorophyll molecule are replaced by
electrons from a water molecule. This process splits the water
molecule into hydrogen ions, electrons, and oxygen gas.
B. Dark reactions-CALVIN CYCLE
The dark phase requires several enzymes and forms several by-products. This phase takes
place in the stroma of the
1.Carbon Fixation: Carbon dioxide from the atmosphere
chloroplasts.
combines with RuBP (ribulose-1,5-bisphosphate) in a series
6CO2
12 PGA
12 ATP
6RuBP
12 ADP
6 ADP
6 ATP
10 G3P
2 G3P
1 Glucose
of reactions to form a substance called PGA (3phosphoglycerate), a molecule containing three carbon
atoms. Rubisco (ribulose bisphosphate carboxylase
/oxygenase) is the enzyme that catalyzes this reaction.
2. Reduction: PGA reacts with hydrogen from the light
reactions to form G3P (glyceraldehyde 3-phosphate). These
reactions use ATP as the energy source and NADPH as the
hydrogen donor.
3. Regeneration of RuBP: Most of the G3P formed during the
dark reactions is used to make more RuBP. This RuBP then
unites with more carbon dioxide, beginning another cycle of
dark reactions.
4. Some of the G3P is combined to form glucose. Two threecarbon molecules of G3P are required to form one molecule
of glucose (C6H12O6)
PLANT CELL-Plant and animal cells share many characteristics. Both are multicellular and
eukaryotic. They both contain many of the same cell organelles. However, there are some
differences. Plant cells contain 3 structures not found in animal cells; cell walls, large central
vacuoles, and plastids are characteristics of plant cells. Centrioles are found in some but not all
types of plant cells. Plant cells have no lysosomes.
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PLANT STRUCTURES
The basic plant structures are the root, stem, and leaf. Roots anchor the plant in the soil.
They also absorb H2O and minerals the plant needs to carry out photosynthesis. Stems support the
plants and softer tissues such as leaves and flowers. Stems also contain vascular tissues that
transport water, minerals, and food between the roots and leaves. The vascular tissue is composed
of xylem which transports water, and the phloem which transports food. Leaves produce food in
the process of photosynthesis. The broad part of the leaf contains most of the plant's photosynthetic
cells. Leaves also exchange gasses and water vapor with the atmosphere.
FLOWER
Plants can reproduce either asexually, sexually, or sometimes both. The organ involved in sexual
reproduction is the flower. Some flowers produce only male gametes, some only female gametes
and some produce both.
Stigma
Petal
Stamen
Anther
Filamen
t
Style
Pistil
Ovary
Ovule
Sepal
Receptacle
The following chart shows the function of various flowers parts
Female Structures
Stigma
Style
Ovule
Function
Produces sticky substance to which pollen grains attach
The pollen grains pass through here on the way to the ovule
Located at the swollen base of the pistil. There is where the egg cells are
produced.
Male Structures
Filament
Anther
Function
This the thin, stemlike portion
Pollen is produced here. This contain the male gametes
If the egg cells are fertilized, they developed into seed. The ovule develops into the fruit, when
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pollination occurs; the pollen is transferred to the stigma.
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