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2014 SOME SUMMARY INFORMATION ON ORGANELLES Plasma (cell membrane) Structure Fluid-mosaic bilayer of phospholipids, proteins, cholesterol, glycolipids Functions Semipermeable – regulates solute traffic into/out of cell Proteins – form channels, act as transporters, form receptors, act as enzymes, form cell-cell recognition sites Cytosol/cytoplasm Structure Water, solutes, suspended particles, inclusions Plasmasol – more liquid phase Plasmagel – more gel-like phase Functions Site of many chemical (metabolic) reactions Cell shape, cell movement Nucleus (“brain of cell”) Structure Double membrane (nuclear envelope) with nuclear pores Contains DNA, RNA and proteins Functions Segregates genetic material (DNA) from rest of cell DNA: Genes = hereditary factors = instructions for making proteins Uncoiled DNA = chromatin Coiled DNA forms chromosomes for cell division (mitosis, meiosis) Nucleolus Structure Found within nucleus No separate membrane Contains DNA, RNA and proteins Functions Ribosome subunits produced here Ribosome Structure rRNA + proteins Two subunits make up a functional ribosome Produced in nucleolus Assembled in cytoplasm Function Site of protein synthesis (translation) 2014 Ribosomes may be: a. “Free ribosomes” – float free in cytoplasm Produce proteins for use within cell cytoplasm (e.g. enzymes of glycolysis) b. Attached to Rough Endoplasmic Reticulum Produce proteins for Export from cell Inclusion in cell membranes Inclusion in lysosomes Endoplasmic Reticulum (ER) Structure Membrane system runs throughout cell Continuous with nuclear envelope Functions a. Rough ER (RER) Has attached ribosomes (see above) New proteins move to Smooth ER, Golgi for modification b. Smooth ER (SER) New proteins enclosed in transport vesicles move to Golgi Produces lipids (e.g. steroids) Detoxifies poisons (e.g. alcohol) Storage area (e.g. stores calcium ions, especially in skeletal muscle cells) Golgi apparatus (body) Structure Stacked hollow membranous discs (cisternae) Functions Acts like the Post Office: Sorts, packages, modifies proteins for delivery to their sites of action Releases secretory vesicles Vesicles Endocytosis = entrance of substances into cell (e.g. phagocytosis, pinocytosis) Exocytosis = release of substances from cell (e.g. neurotransmitters) Lysosomes Structure Membrane-bound sacs containing digestive (hydrolytic) enzymes Functions a. In conjunction with phagocytosis: Destroys engulfed particles (e.g. bacteria) b. Autophagy (“self eating”) Breaks down worn out cell components for recycling 2014 Mitochondrion (plural = mitochondria) “The powerhouse of the cell” Produces lots of ATP when oxygen is available (Lots more on these later in the term) Cytoskeleton Structure Various types of proteins Overall functions Promote cell shape, structural organization, movement Microtubules Structure Tubulin (a protein) e.g. in cilia, flagella, centrioles Function Physical support, maintain shape of cell Movement of organelles, mucus or entire cell Kinesins and dyneins are motor proteins involved with microtubule movements Microfilaments (or Actin filaments) Structure Actin (a protein) Function Move pseudopods during phagocytosis With myosin, involved in muscle contraction Mechanical support for microvilli Intermediate filaments Structure Composed of several different proteins Thicker than microfilaments, thinner than microtubules Function Anchor organelles Resist mechanical stresses on cells