• Plant cells contain?chloroplasts?which is the site of photosynthesis
• Chloroplasts are filled with a fluid known as the?stroma
• The?system of membranes?found in the stroma of the chloroplast consists of a series of flattened fluid-filled sacs known as?thylakoids
• In places, these thylakoids stack up to form structures known as?grana?(singular – granum)
• The?light-dependent stage?of photosynthesis occurs in the?thylakoid membranes?and the?thylakoid spaces?(the spaces inside the thylakoids)
• The thylakoid membranes contain the?pigments,?enzymes?and?electron carriers?required for the light-dependent reactions
• The membranes of the grana create a?large surface area?to?increase the number of light-dependent reactions?that can occur
• This membrane system provides a large number of pigment molecules in an arrangement that ensures?as much light as necessary is absorbed
• The pigment molecules are arranged in light-harvesting clusters known as?photosystems
• In a photosystem, the different pigment molecules are arranged in?funnel-like structures?the thylakoid membrane (each pigment molecule passes energy down to the next pigment molecule in the cluster until it reaches the primary pigment reaction centre)

An example of a photosystem in a chloroplast thylakoid membrane: a light-harvesting cluster of photosynthetic pigments involved in the light-dependent stage of photosynthesis

• The?stroma?is the fluid that fills the chloroplasts and surrounds thylakoids
• CO2, sugars, enzymes and other molecules are dissolved in the stroma
• The stroma is the site of the?light-independent stage?of photosynthesis