Topic 3.8 and 8.2 Explain Type Outcomes
Explain the light-dependent reactions.
non cyclic photophospohorylation in photosystems
photon of light absorbed by photosystem II and transferred to other
pigment molecules until it reaches chlorophyll a in the reaction center
water split to release hydrogen ions and oxygen
process called photolysis
electron transport chain transfers the electrons and energy is used
to drive chemiosmosis
electrons are re-energized in photosystem I and is passed down
second ETC and NADP+ is reduced to produce NADPH and ATP
Explain photophosphorylation in terms of chemiosmosis.
phospholyration: production of ATP using the energy of sunlight
process made as a result of chemiosmosis
chemiosmosis: movement of ions across a selectively permeable
membrane down a concentration gradient
Process:
light is absorbed by chlorophyll molecules
electrons in molecules raised to higher state
electrons travel through photosystem II, a chain of e- carriers and
photsystem I
as electrons travel through chain, energy is released
energy used to pump hydrogen across thylakoid membrane and to
inner space of within thylakoid
a concentration gradient of hydrogen forms within space
hydrogen move across thylakoid membrane, down concentration
gradient through ATP synthase
ATP synthase uses energy released tp synthesize ATP from ADP and
inorganic phosphate
Topic 3.8 and 8.2 Explain Type Outcomes
Explain the light-independent reactions.
- The reaction occurs within the stroma or cytosol-like region of
chloroplast
-ATP&NADPH provide the energy and reducing power
-RuBP binds to CO2 molecule in the process of carbon fixation in
Calvin Cycle/ it is catalyzed by an enzyme called RuBP carboxylase
-Unstable 6-carbon compound breaks down to two three carbon
compounds (glycerate-3-phosphate)
-Glycerate-3-phosphate act with ATP and NADPH to form triose
phosphate (reduction reaction)
-TP becomes sugar phosphate or continuein the cycle to produce
more RuBP
-Cycle uses ATP to regain RuBP from TP
Explain the relationship between the structure of the chloroplast and
its function.
A chloroplast is located in plant cells only, and is referred to as a
photosynthetic machine
Chloroplast contains an extensive membrane surface area of the
thylakoids has small space with the thylakoids, stroma region similar
to the cytosol of the cell, double membrane on the outside.
Extensive membrane surface area allows greater absorption of the
light by photosystems.
Lumen in thylakoids allows faster accumulation of protons to create
a concentration gradient.
stroma region allows for the enzymes necessary for Calvin cycle
double outer membrane isolates the working parts and enzyme of
the chloroplast from surrounding cytosol.
relationship of structure to function is a universal theme.
structure allows light dependent and light independent to proceed
efficiently
Topic 3.8 and 8.2 Explain Type Outcomes
Explain the relationship between the action spectrum and the
absorption spectrum of photosynthetic pigments in green plants.
absorption spectrum is the percentage of the wavelengths of visible
light that are absorbed by two common forms of chlorophyll;
action spectrum is percentage use of wavelengths of light in
photosynthesis;
Action and absorption spectra
are closely correlated;
the wavelength of light
absorbed partially determines
the rate of photosynthesis/
more light absorbed at a
wavelength the more
photosynthesis;
pigments absorb light energy
used in photosynthesis;
blue and red light show the
greatest absorption and they
also represent the peaks in the
rate of photosynthesis/ green light absorption corresponds to the
lower rate of photosynthesis
Explain the concept of limiting factors in photosynthesis, with
reference to light intensity, temperature and concentration of CO 2.
limit between factors that limit and factors that effect
recognize only one factor is limiting, same as in chemistry (the
lowest: peanut butter sandwich example)
Light intensity is most effective in the 500-2000 foot-candle range
after 2000 foot-candles, light intensity stops increasing the rate of
photosynthesis
optimal CO2 saturation range is
between 500-1000 ppm range
also levels off
optimum temperature is 25oC
follows
this shape.