Photosynthesis

Chloroplasts are membranous structures that house the thylakoids, which are tiny pancake-shaped objects that form stacks, called grana.  The chloroplast can be thought of as a factory.  The factory provides shelter for the workers inside and the various objects being assembled just as the chloroplast provides shelter for the thylakoids producing glucose.  

 

Similar to mitochrondria, chloroplasts have a double membrane.  The double membrane functions similarly to a person wearing two coats.  The first coat allows some of the cold air to enter, and the second coat allows much less cold air through.  The same theory is applied to the double membrane. There is a space between them called the intermembrane space.  The outer membrane is permeable to small, organic molecules.  This is vital because CO2 and water must be able to get into the chloroplast for photosynthesis to occur.  The inner membrane is less permeable, but water and carbon dioxide are allowed passage into the stroma, the fluid inside the chloroplast that surrounds the grana.

 

The stroma holds all of the enzymes required to synthesize glucose once the light-dependent reactions have occurred and the light independent reactions are under way.  In addition, the stroma holds copies of the chloroplast genome so that it can repair itself and maintain conditions shoudl something happent to the chloroplast.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The most important structure within the chloroplast is the thylakoid.  The thylakoid is the structure in which photosynthesis actually takes place.  There are three areas related to the thylakoid that are important in photosynthesis.  The first is the thylakoid lumen, the inside of the thylakoid.  The light dependent reactions occur within this space.  The second area is the thylakoid membrane, which holds the electron transport chain that will carry electrons that eventually reduce NADP.  The last important area is the stroma, in which the light independent reactions occur.  These reactions require ATP and NADPH, which are already outside the thylakoid becaues they were synthezied on the thylakoid membrane.  The thylakoid can be thought of as a person working within the factory that assembles a product from different parts and sends them to the next stage of the process, which is the light independent reactions.