Biology Cellular Organelles Organelles = Cell Parts Cell membrane: Structure: phospholipid bilayer cholesterol floating proteins (channel proteins, receptor proteins) Function: controls what enters and exits the cell. Cellular Organelles (cont) Endoplasmic reticulum (ER): Structure: series of tubes Function: transport of molecules within the cell. Smooth ER Rough ER: imbedded with ribosomes. Cellular Organelles (cont) Ribosomes: Structure: pieces of protein & RNA. Function: put amino acids together in the correct order to make proteins. Some are embedded in ER; others are free-floating in the cell. (Although they are often drawn greatly simplified, ribosomes are, in reality, very complex structures. ) (picture: DNA, James Watson, 2003) Cellular Organelles (cont) Golgi apparatus: Structure: stacks of membranes Function: modifies & packages (puts a membrane around) proteins as they leave the ER. Cellular Organelles (cont) Mitochondria: Structure: highly folded tiny structures of enzymes and other proteins. Function: break down lipids & carbohydrates to release energy from them. (powerhouses of the cell). Cellular Organelles (cont) Lysosomes: Structure: bags of digestive enzymes Function: break down worn-out cell parts inside the cell. Cellular Organelles (cont) Cilia & Flagella Structure: identical: thin, whiplike structures Flagella look like tails Function: movement Cellular Organelles (cont) Microfilaments & microtubules: Structure: tiny, thin protein tubes. Function: serve as the structure that holds up a cell (cellular skeleton). Cellular Organelles (cont) Nucleus: Structure: round structure. Function: site of DNA storage within a cell.