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

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

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

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

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

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

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

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

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

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