Part I: The Sun and Light

Plants make their own food using the process called photosynthesis. This process uses the raw materials, light (light is actually energy, electromagnetic energy to be exact), water and carbon dioxide to make glucose and oxygen. When the light energy from the sun gets to a green plant, all sorts of reactions can take place to store energy in the form of sugar molecules.

Not all the energy from the sun is absorbed by the plant but when light gets to a plant, the plant doesn't use all of it. It actually uses only certain colors to make photosynthesis happen. Plants mostly absorb red and blue wavelengths. When you see a color, it is actually a color that the object does NOT absorb. In the case of green plants, they do not absorb light from the green range.

Part II: The Chloroplast

Photosynthesis happens in the chloroplast. Within this cell organelle is the chlorophyll that captures the light from the Sun. The organelles are only found in plant cells and some protists such as algae. Animal cells do not have chloroplasts. Chloroplasts work to convert light energy of the Sun into sugars that can be used by cells.

Special Structures

STRUCTURE	FUNCTION	CHLOROPLAST
Double Membrane Inner and Outer Membrane	This separates the contents of the chloroplast from the rest of the cell so there is no interference from the cytoplasm. The outer and the inner membrane of the chloroplast enclose a semi-gel-like fluid known as the stroma
Chloroplasts contain approximately 3000 lamellae cluster	This increases the surface area available for the attachment of extra pigments molecules.
The shape of the lamellae is disc like	Maximum surface area for the attachment of enzymes involved in light dependent reactions.
The stroma surrounding the thylakoids is partitioned off.	This is so different, chemical reaction can take place without intereference
Small space inside the thylakoids	To enable a concentration gradient of protons H+
Thylakoid	The chloropyll molecule is on the surface of each thylakoid where it captures light energy from the sun.
Stroma	This is where carbon is fixed and sugar is synthesized.

Making Food

The main purpose of the chloroplast is to make food for the plant. When the energy from the sun is absorbed in the chloroplast and the chlorophyll molecules, the light energy is converted into the chemical energy and stored as ATP (Adenosine Triphosphate) and NADPH.

These compounds are then moved into the stroma where enzymes fix the carbon atoms from carbon dioxide (CO2 ), the molecular reactions continues until eventually create sugar and oxygen (O 2 ). The sugar (glucose) is used by both plants and animals for food and energy also the by product oxygen (O2) which is released is the same oxygen we inhale daily.

Part III: The Molecules

The chloroplast contains a green pigment called "Chlorophyll" that is used to trap the energy from the sunlight which is necessary for the initiation of the photosynthesis process. There are actully six (6) types of chlrophyll: a, b, c, d, f and bacteriochlorophyll. Chlorophyll can also be found in many microorganisms and even some prokaryotic cells. The chlorophyll a and b are those which can be found in green plants and algae.

Carbon dioxide and water combine with light to create oxygen and glucose.

Part IV: Light and Dark Reactions

The photosynthesis process can take place in both light and darkness hence the process is divided into two main parts: Light dependent reaction and light independent reaction. The light dependent reaction is when light energy from the sun is captured and converted to the chemical ATP. The light independent reaction takes place without the presences of sunlight, the ATP is used to make glucose by means of the Calvin Cycle.

Photosynthesis quiz