Download Plant Processes: Photosynthesis

Photosynthesis
Plant Processes: 1
Introduction
• Within a plant, many physiological processes are
constantly occurring, to allow for the plant’s
growth and survival.
Plant Processes
• Plant processes that occur within a plant include:
1.
2.
3.
4.
Photosynthesis
Respiration
Transpiration
Translocation
Photosynthesis
• The term photosynthesis derives from the
words, photo, which means light, and
synthesis, which means putting together.
• Photosynthesis is the process by which
green plants, algae, and certain classes of
bacteria, capture solar energy and use it to
make simple sugar molecules.
Photosynthesis Cont’d
• Chemical reactions within the leaves produce
sugar molecules.
• Water molecules move these sugar molecules
to all the cells throughout the plant.
• Organelles within the cells convert the sugar
molecules into energy for cell division and
expansion.
Photosynthesis Cont’d
• These simple sugars are then used as an
energy source for growth and development.
• Photosynthesis is the single most important
plant biological process because it provides
food and oxygen needed for human survival.
Photosynthesis Cont’d
• The process of photosynthesis occurs within
the chloroplasts of plant cells.
• These cell organelles contain numerous
chlorophyll pigments, which absorb mostly
blue and red wavelengths of sunlight.
Photosynthesis Cont’d
• Most photosynthesis occurs in the plant
leaves because the cells within these plant
organs have the highest concentration of
chloroplasts.
Photosynthesis Cont’d
• In the presence of light energy, six carbon
dioxide molecules combine with six water
molecules.
• This reaction produces one simple sugar
molecule, along with six molecules of
oxygen.
Photosynthesis Formula
• The chemical reaction formula for
photosynthesis is:
• 6CO2 + 6H2O = C6H12O6 + 6O2
Oxygen in Photosynthesis
• A plant uses the oxygen molecules produced
during photosynthesis for other chemical
processes occurring at the same time as
photosynthesis.
• Excess oxygen molecules pass through the open
stomata of the plant leaves and escape into the
air.
Water in Photosynthesis
• Water within the plant transports the sugar
molecules from the leaves to other parts of
the plant, where they are converted into
molecules of carbohydrates, lipids, proteins,
cellulose, and lignin.
Photosynthesis Facts
• A plant uses about 25% of the sugar
manufactured during photosynthesis for
energy.
• The remainder of the manufactured food
reserve is stored throughout the plant.
Reactions in Photosynthesis
• Two types of reactions are involved in the process of
photosynthesis:
• Light reaction
• Dark reaction.
Light Reactions
• Light reactions occur within the thylakoids
and change light energy into chemical
energy.
Dark Reactions
• Dark reactions result in carbon fixation (the production
of sugar molecules); they also produce amino acids and
lipids for cellular functions.
• Dark reactions occur mostly during the day, but light is
not required for these reactions to occur.
• Dark reactions of photosynthesis provide the raw
materials to produce almost everything a plant needs!