Transcript Function
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 (waterloving) and two non-polar fatty-acid “tails” that are hydrophobic (water-fearing); arranged in a bilayer 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