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Glucose Production
Noadswood Science, 2012
Tuesday, May 23, 2017
Glucose Production
• To understand how plants store and use the glucose produced
during photosynthesis
Equations
The word equation for photosynthesis is
carbon dioxide + water  glucose + oxygen
The symbol equation for photosynthesis is
6CO2 + 6H2O  C6H12O6 + 6O2
Glucose & Starch
• During photosynthesis glucose is produced (a simple sugar)
• However, plants cannot store glucose, so they convert it into
starch (many small glucose molecules are joined together)
• Starch is insoluble, meaning it can be stored easily (when you
wash some rice you can see the starch wash off)
Glucose
• Glucose can be used to make long chains of starch…
Glucose
molecules
Starch
molecule
• This glucose is then used by the plant as a store of energy and
some of it may be used for respiration
• The energy released from respiration can be used to make amino
acids or to build up fats and oils as a food store in seeds
Proteins
• Glucose is combined with nitrate ions (NO3-) (absorbed from the
soil) to make amino acids which are then made into proteins…
Starch Test
• How can we test for starch?
• How can we relate the presence of starch to the amount of
photosynthesis taking place?
• Iodine tests for starch – it turns blue/black in the presence of
starch
• If a plant photosynthesis a lot, then there should be more starch
present (as more glucose would have been made and converted
into starch)
Experiment
• Your task is to look at two
different types of leaf –one
normal leaf, and one which
has been kept in the dark
• You need to find out how
much starch is present in each
leaf…
• Follow the leaf starch
experiment worksheet
Starch Experiment
Boiling & Ethanol
• Why do we need to boil the leaf first, and then add it to the
ethanol?
• Boiling the plant damages the cell wall, and the ethanol extracts
the chlorophyll from the leaf allowing us to test if any starch is
present
Explanation
• Explain your results for the leaf in the light and the leaf in the
dark
• The leaf in the light has a good store of starch (photosynthesis
has taken place, converting the glucose produced to starch)
• The leaf in the dark cannot
photosynthesize, but has been
respiring (using up the starch
supply)
Storage
• Why store the glucose as starch?
• Remember, the starch is insoluble, so the plant can store it
conveniently without it getting dissolved within the cell which is
much more convenient than the soluble glucose
Minerals
• How do plants absorb the minerals they need?
• Roots are adapted to absorb the minerals needed to remain
healthy (although some plants have adapted some special ways
to get more minerals, e.g. a Venus fly trap)
• Venus fly traps often live in
areas where minerals are
scarce – to compensate they
can trap and digest insects,
getting valuable minerals
from them
Minerals
• There are 3 essential minerals: • Nitrates – needed for protein manufacture
• Phosphates – needed for respiration and photosynthesis
• Potassium – needed for enzymes involved in respiration and
photosynthesis
• Iron and magnesium are also needed in trace amounts for
chlorophyll production
Photosynthesis
Photosynthesis