Membrane function
Membranes are boundaries that define the cell and various components of the cell like the vacuole or chloroplast.
Examples of membranes are the plasma membrane that surrounds the cytoplasm and the tonoplast that surrounds the vacuole.
Membranes function to:
1. Provide a matrix for certain enzymes to function; like in the chloroplast thylakoids where photosynthetic enzymes function.
Chloroplast
Membranes function to:
2. Regulate the movement of molecules inside and outside the cell or organelle.
Electron micrograph of a parenchyma cell.
Membranes are fluid structures.
They are made of a lipid bilayer composed mainly of phospholipids.
Phospholipids in the membrane have a hydrophylic head and a hydrophobic tail.
Water on the inside and outside of the membrane make the phospholipids line up head to tail to form a semipermeable membrane.
Transport of solutes across the membrane can be by passive diffusion or active transport.
