Animal Cell Structure and Function

smooth ER

ER network of membranous channels; no attached ribosomes; processes lipids, fats, and steroids that are then packaged and dispersed by the Golgi apparatus

rough ER

ER with attached ribosomes; instrumental in protein synthesis and packaging and transport of materials within the cell

endoplasmic reticulum

a large organization of folded membranes responsible for the delivery of lipids and proteins to certain areas within the cytoplasm

nuclear membrane

boundary between the nucleus and the cytoplasm; double membrane that allows certain molecules to pass through the nuclear pores

mitochondria

centers of cellular respiration; more numerous in cells that require more energy (muscle/liver); self-replicating and contain own DNA, RNA, and ribosomes; double membrane - inside = cristae where cellular respiration takes place

endocytic vesicle

during endocytosis, the pinched off piece of membrane engulfing a large particle that can move within the cytoplasm or stay packaged inside the cell

Golgi apparatus

instrumental in storing, packaging, and shipping of proteins via the ER to the part of the cell where they will be used or to the cell membrane to be excreted

lysosomes

membrane-bound organelles containing digestive enzymes that break down unused material, damaged organelles, or materials absorbed by the cell for use

nucleus

organelle surrounded by two lipid bilayer membranes; contains chromosomes, nuclear pores, nucleoplasm, and a nucleolus

secretory vesicles

packets of material packaged by ER or Golgi apparatus that fuse with the cell membrane and allow the materials to escape through exocytosis

cell membrane

plasma membrane; phospholipid bilayer with embedded globular proteins; elastic; controls movement in and out of cell with selective permeability

nuclear pores

points at which the double nuclear membrane fuses together forming a passageway between the inside of the nucleus and the cytoplasm outside the nucleus; allow the cell to selectively move molecules in and out of the nucleus

microvilli

projections extending from the cell membrane to increase the surface area of the membrane; can be used for absorption and contain enzymes involved in digesting certain types of nutrients

cytoskeleton

provides structural support to the animal cell; microtubules (framework for cytoplasm and at base of cilia or flagella), microfilaments (double stranded chains of proteins for structure stability), centrioles (microtubules in a pinwheel shape/make microtubules/active in mitosis and meiosis)

attached ribosomes

ribosomes attached to the endoplasmic reticulum; destined for use within the membrane-bound organelles

free ribosomes

ribosomes that float unattached within the cytoplasm and are used within the cytoplasm, not within the membrane-bound organelles

nucleolus

rounded area within the nucleus of the cell where ribosomal RNA (rRNA) is synthesized and then incorporated into ribosomes after exiting the nucleus; there may be several within a nucleus

ribosomes

site of protein synthesis within cells; composed of certain protein molecules and RNA

endosymbiont hypothesis

the concept that mitochondria are an evolved form of a primitive bacteria (prokaryote) that lived in a symbiotic relationship with eukaryotic cells more than 2 billion years ago; explains why mitochondria have own DNA/RNA/ribosomes and are such an integral part of eukaryotic cells