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Pages 62-75 © 2015 Pearson Education, Inc. It is important to know the organelles within the cell and to understand the general functions of each ◦ Organelles > cell ◦ Organs > system ◦ Organ systems > human body © 2015 Pearson Education, Inc. Nucleus = control center; houses DNA Plasma Membrane = selective; boundary Ribosomes = site of protein synthesis Mitochondria = site of cellular respiration Endoplasmic Reticulum = transportation network ◦ Rough = finalizing protein synthesis - folding ◦ Smooth = fat metabolism and detoxing Golgi Bodies =protein packaging; become vesicles Vesicles = move products via endocytosis/exocytosis Lysosomes = garbage crew Peroxisomes = detoxification/neutralizers Cytoskeleton = structural organelle Centrioles =direct cell division via mitotic spindle Smooth endoplasmic reticulum Chromatin Nucleolus Nuclear envelope Nucleus Plasma membrane Lysosome Mitochondrion Rough endoplasmic reticulum Centrioles Ribosomes Golgi apparatus Peroxisome Secretion being released from cell by exocytosis Plasma Membrane Junctions ◦ Cells are bound together in three ways: 1. Glycoproteins act as an adhesive or cellular glue 2. Wavy contours of the membranes of adjacent cells fit together in a tongue-and-groove fashion 3. Special membrane junctions are formed, which vary structurally depending on their roles 1. 3 different junctions © 2015 Pearson Education, Inc. Extracellular fluid (watery environment) Glycoprotein Glycolipid Cholesterol Sugar group Polar heads of phospholipid molecules Bimolecular lipid layer containing proteins Nonpolar tails of phospholipid molecules Channel Proteins Filaments of cytoskeleton Cytoplasm (watery environment) Tight (impermeable) junction Microvilli Desmosome (anchoring junction) Plasma membranes of adjacent cells Connexon Gap Underlying Extracellular basement space between (communicating) junction membrane cells Tight junctions ◦ Impermeable junctions made up of the plasma membrane ◦ Bind cells together into leakproof sheets ◦ Prevent substances from passing through extracellular space between cells © 2015 Pearson Education, Inc. Desmosomes ◦ Anchoring junctions that prevent cells from being pulled as a result of mechanical stress ◦ Created by “buttonlike” thickenings of adjacent plasma membranes kind of like the rivets in the pockets of your jeansthey keep the material together © 2015 Pearson Education, Inc. Gap junctions ◦ allow direct diffusion of ions and small molecules between adjacent cells ◦ Hollow cylinders of proteins (connexons) function like tunnels to send messages Molecules can travel directly from one cell to the next through these channels © 2015 Pearson Education, Inc. Tight (impermeable) junction Microvilli Desmosome (anchoring junction) Plasma membranes of adjacent cells Connexon Gap Underlying Extracellular basement space between (communicating) junction membrane cells Active Transport of bulk materials Endocytosis: ◦ Plasma membrane engulfs product from extracellular space to bring into cell ◦ Becomes travelling vesicle inside cell Exocytosis: ◦ Vesicle from inside the cell fuses with plasma membrane to dump contents outside of cell Extracellular Plasma membrane fluid SNARE (t-SNARE) Secretory vesicle 1 The membranebound vesicle Vesicle migrates to the SNARE (v-SNARE) plasma membrane. Molecule to be secreted Cytoplasm Fusion pore formed Fused SNAREs 2 There, v-SNAREs bind with t-SNAREs, the vesicle and plasma membrane fuse, and a pore opens up. 3 Vesicle contents are released to the cell exterior. (a) The process of exocytosis (b) Electron micrograph of a secretory vesicle in exocytosis (190,000×) Extracellular fluid Cytosol Vesicle 1 Vesicle fusing with lysosome for digestion Plasma membrane Lysosome Release of contents to cytosol 2 Transport to plasma membrane and exocytosis of vesicle contents Detached vesicle Ingested substance Pit (a) 3 Membranes and receptors (if present) recycled to plasma membrane Cilia: whiplike extensions ◦ Propels substances along passageways Found in respiratory passageways, uterine tubes, kidneys, inner ear Flagella: longer whiplike extensions ◦ Propels the cell The sperm is the only flagellated cell in the human Microvilli: extensions of cell membrane ◦ Increases cell surface area (often for absorption) Found along entire small intestine; large numbers along the proximal convoluted tubule in the nephron Blood vessels serving the small intestine Muscle layers Villi Microvilli (brush border) Lumen Circular folds (plicae circulares) Absorptive cells Lacteal (a) Small intestine (c) Absorptive cells Villus Blood capillaries Lymphoid tissue Intestinal crypt Muscularis mucosae Venule Lymphatic vessel Submucosa (b) Villi Flagellum Nucleus Sperm (g) Cell of reproduction Cells can vary in structure and function Variations include: ◦ Modified shape ◦ More of a particular organelle ◦ Modified organelles Cells are classified based on their structure and function This is known as Histology ◦ the study of the structure of cells and their formation into tissues and organs An Histologist can identify abnormalities in tissues obtained from cultures/biopsies Epithelial ◦ Secrete and aborb Connective ◦ Hold structures together, store nutrients Muscular ◦ Movement Nervous ◦ communication EPITHELIAL Epithelial cells Nucleus Intermediate filaments MUSCULAR Skeletal muscle cell Contractile filaments Nuclei Smooth muscle cells CONNECTIVE Fibroblasts Rough ER and Golgi apparatus No organelles Nucleus Erythrocytes NERVOUS Processes Rough ER Nerve cell Nucleus