C1.3 Photosynthesis Flashcards
C1.3.1—Transformation of light energy to chemical energy when carbon compounds are produced in
photosynthesis
This energy transformation supplies most of the chemical energy needed for life processes in ecosystems
C1.3.2—Conversion of carbon dioxide to glucose in photosynthesis using hydrogen obtained by splitting
water
Students should be able to write a simple word equation for photosynthesis, with glucose as the product
C1.3.3—Oxygen as a by-product of photosynthesis in plants, algae and cyanobacteria
Students should know the simple word equation for photosynthesis. They should know that the oxygen
produced by photosynthesis comes from the splitting of water.
C1.3.4—Separation and identification of photosynthetic pigments by chromatography
Application of skills: Students should be able to calculate Rf
values from the results of chromatographic
separation of photosynthetic pigments and identify them by colour and by values. Thin-layer
chromatography or paper chromatography can be used
C1.3.5—Absorption of specific wavelengths of light by photosynthetic pigments
Include excitation of electrons within a pigment molecule, transformation of light energy to chemical
energy and the reason that only some wavelengths are absorbed. Students should be familiar with
absorption spectra. Include both wavelengths and colours of light in the horizontal axis of absorption
spectra.
C1.3.6—Similarities and differences of absorption and action spectra
Application of skills:
Students should be able to determine rates of photosynthesis from data for oxygen
production and carbon dioxide consumption for varying wavelengths. They should also be able to plot
this data to make an action spectrum.
C1.3.7—Techniques for varying concentrations of carbon dioxide, light intensity or temperature
experimentally to investigate the effects of limiting factors on the rate of photosynthesis
Application of skills: Students should be able to suggest hypotheses for the effects of these limiting
factors and to test these through experimentation.
NOS: Hypotheses are provisional explanations that require repeated testing. During scientific research,
hypotheses can either be based on theories and then tested in an experiment or be based on evidence
from an experiment already carried out. Students can decide in this case whether to suggest hypotheses
for the effects of limiting factors on photosynthesis before or after performing their experiments. Students should be able to identify the dependent and independent variable in an experiment.
C1.3.8—Carbon dioxide enrichment experiments as a means of predicting future rates of photosynthesis
and plant growth
Include enclosed greenhouse experiments and free-air carbon dioxide enrichment experiments (FACE).
NOS: Finding methods for careful control of variables is part of experimental design. This may be easier in
the laboratory but some experiments can only be done in the field. Field experiments include those
performed in natural ecosystems. Students should be able to identify a controlled variable in an
experiment.
C1.3.9—Photosystems as arrays of pigment molecules that can generate and emit excited electrons
Students should know that photosystems are always located in membranes and that they occur in
cyanobacteria and in the chloroplasts of photosynthetic eukaryotes. Photosystems should be described as
molecular arrays of chlorophyll and accessory pigments with a special chlorophyll as the reaction centre
from which an excited electron is emitted.
C1.3.10—Advantages of the structured array of different types of pigment molecules in a photosystem
Students should appreciate that a single molecule of chlorophyll or any other pigment would not be able
to perform any part of photosynthesis.
C1.3.11—Generation of oxygen by the photolysis of water in photosystem II
Emphasize that the protons and electrons generated by photolysis are used in photosynthesis but oxygen
is a waste product. The advent of oxygen generation by photolysis had immense consequences for living
organisms and geological processes on Earth.
C1.3.12—ATP production by chemiosmosis in thylakoids
Include the proton gradient, ATP synthase, and proton pumping by the chain of electron carriers. Students
should know that electrons are sourced, either from photosystem I in cyclic photophosphorylation or from
photosystem II in non-cyclic photophosphorylation, and then used in ATP production.
C1.3.13—Reduction of NADP by photosystem I
Students should appreciate that NADP is reduced by accepting two electrons that have come from
photosystem I. It also accepts a hydrogen ion that has come from the stroma. The paired terms “NADP and
reduced NADP” or “NADP+
and NADPH” should be paired consistently
C1.3.14—Thylakoids as systems for performing the light-dependent reactions of photosynthesis
Students should appreciate where photolysis of water, synthesis of ATP by chemiosmosis and reduction of
NADP occur in a thylakoid.
C1.3.15—Carbon fixation by Rubisco
Students should know the names of the substrates RuBP and CO2
and the product glycerate 3-phosphate.
.
They should also know that Rubisco is the most abundant enzyme on Earth and that high concentrations
of it are needed in the stroma of chloroplasts because it works relatively slowly and is not effective in low
carbon dioxide concentrations
