1. Plasma Membrane
Function – physical barrier for the cell; separates internal and external environments; selective permeability
Location – surrounding the cell, outer surface
Membrane lipids—phospholipids have a polar phosphate “head” which is hydrophilic (water-loving) and two non-polar fatty-acid “tails” that are hydrophobic (water-fearing); arranged in a bi-layer with the hydrophilic heads facing the inside and the outside of the cell
Fluid mosaic model – plasma membrane behaves more like a fluid than a solid; it is very dynamic; proteins move within the membrane

3. Nucleus
Function – control center of the cell; contains DNA; filled with a fluid called nucleoplasm
Nuclear envelope – double-layer membrane composed of phospholipids; keeps nuclear contents separate from the rest of the cell; nuclear pores allow for information to get into and out of the nucleus when necessary
Nucleolus – dense area within the nucleus; produces ribosomal RNA

5. Mitochondria
Function – site of cellular respiration; the transfer of energy from organic molecules to ATP (adenosine triphosphate); double-layered membrane; number of mitochondria varies depending on the energy needs of cells – ex: muscle cells have a lot, fat cells have few
Mitochondrial DNA – DNA that is separate from the DNA that is in the nucleus; mitochondria can only reproduce by the division of pre-existing mitochondria

7. Ribosomes Function – sites of protein synthesis
Location – in cytoplasm and on rough endoplasmic reticulum

8. Endoplasmic Reticulum
Function – series of membrane bound tubes and sacs that allow for the transport of substances throughout the cell
Rough ER – contains ribosomes; functions in protein synthesis
Smooth ER – doesn’t have ribosomes; functions in lipid synthesis

10. Golgi Apparatus
Function – packaging, modifying and shipping of cellular products

11. Vesicles
Lysosomes – membrane-bound sacs that contain digestive enzymes; break down/digest bacteria, old or damaged organelles
Peroxisomes – similar to lysosomes; produce hydrogen peroxide when they break down alcohol and engulf bacteria

13. Microtubules
Function – Hollow tubes made of protein, hold organelles in place, maintain cell shape
Location – Radiate outward from the center called centrosome near the nucleus

14. Cilia and Flagella Cilia Short and present in large numbers Flagella
Long extensions of the cell, usually one that helps with the cell moving
Function – Assist in movement
Location – Outside of the cell

15. Centrioles
Function – Two short cylinders of microtubules that organize cell division
Location – Near the nuclear envelope
*Occur only in animal cells