<P> A thylakoid is a membrane - bound compartment inside chloroplasts and cyanobacteria . They are the site of the light - dependent reactions of photosynthesis . Thylakoids consist of a thylakoid membrane surrounding a thylakoid lumen . Chloroplast thylakoids frequently form stacks of disks referred to as grana ( singular : granum ) . Grana are connected by intergranal or stroma thylakoids , which join granum stacks together as a single functional compartment . </P>
<P> A thylakoid is a membrane - bound compartment inside chloroplasts and cyanobacteria . They are the site of the light - dependent reactions of photosynthesis . Thylakoids consist of a thylakoid membrane surrounding a thylakoid lumen . Chloroplast thylakoids frequently form stacks of disks referred to as grana ( singular : granum ) . Grana are connected by intergranal or stroma thylakoids , which join granum stacks together as a single functional compartment . </P>
little stacks of disks that make up the thylakoid membrane system
little stacks of disks that make up the thylakoid membrane system
grana ( singular : granum )
grana ( singular : granum )