Overview & Purpose
of Photosynthesis
Plants use sunlight to produce sugar = the plants food.
Plant converts 6 molecules of H2O, 6 molecules of CO = 1 molecule of sugar and 6 molecules of O2.
Manufacture food for the plant.
Equation of Photosynthesis
6CO2 + 6H2O + Energy ® C6H12O6 + 6O2
Structure of Mitochondria
Notes for Thea
Photosynthesis converts light energy into the chemical energy of sugars and
other organic compounds. This process consists of a series of chemical
reactions that require carbon dioxide (CO2) and water (H2O) and store
chemical energy in the form of sugar. Light energy from light drives the
reactions. Oxygen (O2) is a byproduct of photosynthesis and is released
into the atmosphere. The following equation summarizes photosynthesis:
6 CO2 + 6 H2O → 6(CH2O) + 6 O2Sugar. Photosynthesis transfers
electrons from water to energy-poor CO2 molecules, forming energy-rich
sugar molecules. This electron transfer is an example of an oxidationreduction process: the water is oxidized (loses electrons) and the CO2 is
reduced (gains electrons). Photosynthesis uses light energy to drive the
electrons from water to their more energetic states in the sugar products,
thus converting solar energy into chemical energy.
six molecules of water plus
six molecules of carbon
dioxide produce one
molecule of sugar plus six
molecules of oxygen
The cytoplasm of nearly all eukaryotic
cells contain mitochondria, although
there is at least one exception, the
protist Chaos (Pelomyxa) carolinensis.
They are especially abundant in cells and
parts of cells that are associated with
active processes. For example, in
flagellated protozoa or in mammalian
sperm, mitochondria are concentrated
around the base of the flagellum or
flagella. In cardiac muscle, mitochondria
surround the contractile elements.
Hummingbird flight muscle is one of the
richest sources of mitochondria known.
Thus, from their distribution alone one
would suspect that they are involved in
energy production. Multicellular
organisms probably could not exist
without mitochondria. The inability to
remove electrons from the system and
the buildup of metabolic end products
restrict the utility of anaerobic
metabolism. Through oxidative
phosphoryation mitochondria make
efficient use of nutrient molecules. They
are the reason that we need oxygen at
all.

The chloroplast is the organelle where photosynthesis occurs in photosynthetic
eukaryotes. The organelle is surrounded by a double membrane. Inside the inner
membrane is a complex mix of enzymes and water. This is called stroma and is
important as the site of the dark reactions, more properly called the Calvin cycle.

Embedded in the stroma is a complex network of stacked sacs. Each stack is called a
granum and each of the flattened sacs which make up the granum is called a thylakoid.
Each thylakoid has a series of photosystems and associated proteins. The
photosystems contain chlorophyll and other pigments and all these associated
structures in the thylakoid membrane are the site for the light reactions in which light
energy is converted to chemical energy needed for the Calvin cycle in the dark
reaction.

As the light reactions proceed, the inside of the thlyakoid develops a high
concentration of hydrogen ions, and this is important for the production of ATP by the
chloroplast.

By the way, chloroplasts and related organelles, called plastids are believed to have
arisen as free living bacteria that became symbiotic with the ancestors of
photosynthetic eukaryotes.