WHAT IS PHOTOSYNTHESIS?
- “Photosynthesis is a metabolic
pathway that converts carbon dioxide into organic compounds, especially
sugars, using the energy from sunlight.”
- Photosynthetic organisms are called photoautotrophs.
IMPORTANCE
OF PHOTOSYNTHESIS
- Crucially important for life on
Earth
- Maintaining the normal level of
oxygen in the atmosphere.
- Nearly all life either depends
on it directly as a source of energy.
- Indirectly as the ultimate
source of the energy in their food.
- The amount of energy trapped by
photosynthesis is immense, approximately 100 terawatts
which is about six times larger than the yearly power consumption of human
civilization.
- In all, photosynthetic
organisms convert around 100,000,000,000 tonnes of carbon into biomass
per year.
VISIBLE LIGHT
& PHOTOELECTRIC EFFECT
- Light behaves as if it were
composed of "units" or "packets" of energy that travel
in waves. These packets are photons.
- Light behaves both as a wave
and a particle.
- Wave properties of light
include the bending of the wave path
- The particle properties are
demonstrated by the photoelectric effect.
PHOTOSYNTHETIC
PIGMENTS
- “Pigments are molecules that
absorb light.”
- Chlorophyll a is the main photosynthetic
pigment in all organisms except bacteria.
- Accessory Pigments
“Other pigments called accessory
pigments absorb slightly different wavelengths of light.”
- Increases the range of colors that plants can use in
photosynthesis.
- Include chlorophyll b
and a group of pigments called carotenoids.
- They do not participate
directly in photosynthetic reactions but are able to pass their
energy to chlorophyll a.
- When a photon of light strikes
a photosynthetic pigment, an electron in an atom contained within the
molecule becomes excited. Energized Electrons move further
from the nucleus of the atom.
- The excited (energized) molecule can pass the energy to another molecule or release it in the form of light or heat.
STRUCTURE OF CHLOROPLAST
- Chloroplast structural components are; outer double membrance, thylakoide membrane and inner stroma fluid.
