(PROCESS OF FOOD
PRODUCTION BY PLANTS)
WHAT IS PHOTOSYNTHESIS
The process that occurs in green plants, whereby solar energy is
converted into chemical energy and stored as organic molecules by
making use of carbon dioxide, sunlight, and water. Water and Oxygen
are formed as byproducts.
can be summarized in the following equation:
6 CO2 + 12 H2O + Light energy
C6H12O6 + 6 O2 + 6 H2O
WHY DO PLANTS PHOTOSYNTHESIZE
provide nutrients and oxygen for heterotrophs.
are dependent on autotrophs, because
they cannot produce there own food.
WHO OR WHAT CAN PHOTOSYNTHESIZE
Green plants, algae, Plants
cyanobacteria and green protists.
Green, protists ,Algae , Cyanobacteria
WHAT PART OF THE PLANT IS
RESPONSIBLE FOR PHOTOSYNTHESIS
occurs in the chloroplasts of plant cells.
chloroplasts are mainly concentrated in the mesophyll cells of leaves.
contain chlorophyll – green pigment that absorbs sunlight.
fill the space in the thylakoid membrane.
RAW MATERIALS OF PHOTOSYNTHESIS
The raw materials of photosynthesis
carbon dioxide and
HOW RAW MATERIALS REACH THE
Water is absorbed through the root hair into the
xylem of the roots, into the xylem of the
stem, through the xylem of the leaves into the
mesophyll cells and finally into the chloroplasts
Carbon dioxide diffuses from the atmosphere through the
stomata, into the intercellular airspaces in the leaves, and finally
into the chloroplasts of the mesophyll cells.
The chlorophyll and other pigments in the thylakoid membrane
absorb the solar energy to drive photosynthesis
PHOTOSYNTHESIS CONSIST OF 2
LIGHT REACTION PHASE (Dependent on light)
DARK PHASE/ CALVIN CYCLE
LIGHT REACTION PHASE
place in the thylakoids of the chloroplasts.
absorbs solar energy from the sun.
a chlorophyll pigment absorbs light (photon of energy), it excites the
electrons, which goes from ground state to an excited state, which is unstable,
but can be used as potential energy.
unused excited e- fall back to the ground state, photons and heat are
THE ELECTRONS ARE EXCITED IN THE
PHOTOSYSTEMS FOUNT IN THE THYLAKOID
THIS POTENTIAL ENERGY IS THEN USED FIRSTLY TO SPLIT
WATER – INTO HYDROGEN & OXYGEN.
2H2 + O2
OXYGEN IS RELEASED AS A BYPRODUCT – DIFFUSE
THROUGH STOMATA INTO ATMOSPHERE.
THE HYDROGEN REDUCES NADP+ TO NADPH
SOME ENERGY IS THEN USED TO
PHOTOPHOSPHORYLATE ADP TO GENERATE ATP.
ADP + P
Carbon dioxide diffuses through the stomata of the leave and finally
into the stroma of the chloroplast.
The carbon dioxide is accepted by a 5C molecule called ribulose
biphosphate (RuBP) which then forms an unstable 6C compound.
6C compound dissociates into 2 x 3C compounds called
PGA is then reduced to phosphoglyceraldehyde (PGAL/ G3P) by
accepting a phosphate from ATP and a hydrogen electron from NADPH.
Thus changing ATP back to ADP and NADPH to NADP.
PGAL are now used for the following reactions:
Some PGAL are used to make RuBP again, so that the cycle can start over
Some PGAL are used to form hexose sugars like glucose and fructose.
Which combine to form disaccharides and polysaccharides.
* The carbohydrates can then be converted to other biological compounds
like proteins or fats by adding mineral salts like nitrates and phoshates
THE NATURE OF SUNLIGHT
is a form of energy = ELECTROMAGNETIC ENERGY/
electromagnetic energy travel in waves.
between crests of electromagnetic waves =
range from ≤ 1nm (gamma rays) –
≥ 1 km (radio waves)
entire range of radiation wavelengths =
THE MOST IMPORTANT PART FOR LIFE IS THE VISIBLE LIGHT
(380NM – 750NM)
WE CAN SEE THIS LIGHT AS VARIOUS COLOURS.
LIGHT CONSIST OF PARTICLES = PHOTONS
PHOTONS HAVE ENERGY- THE SHORTER THE WAVE
LENGTH THE GREATER THE ENERGY OF THE PHOTON.
THEREFORE VIOLET LIGHT HAS MORE ENERGY THAN RED
PHOTOSYNTHESIS ARE DRIVEN BY VISIBLE LIGHT OF THE
MAIN PIGMENTS USED DURING
a – Absorb violet, blue and red light. Reflects and transmits
green light (that is why plant leaves appear green)
b – Absorb violet, blue and red light. Reflects and transmits
green light (that is why plant leaves appear green).
– Play an accessory role in photosynthesis. They are shades
of yellow and orange and able to absorb light in the violet-blue-green
range. These pigments become noticeable in the fall when chlorophyll
HOW A PHOTOSYSTEM HARVESTS
thylakoid membrane of a chroloplast contains several
photosystem consist of a protein complex called a reactioncentre complex surrounded by several light harvesting
the diagram to understand the process of light
THE IMPORTANCE OF PHOTOSYNTHESIS: A
entering chloroplasts as sunlight gets stored as chemical energy
in organic compounds
made in the chloroplasts supplies chemical energy and carbon
skeletons to synthesize the organic molecules of cells.
store excess sugar as starch in structures such as
roots, tubers, seeds, and fruits
addition to food production, photosynthesis produces the O2 in our
by paprescott on Jan 29, 2012
by Rachel Hill, Sales Assistant at Affleck Sports on Jun 08, 2012