BIOH111. o Cell Biology Module o Tissue Module o Integumentary system o Skeletal system o Muscle system o Nervous system o Endocrine system

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1 BIOH111 o Cell Biology Module o Tissue Module o Integumentary system o Skeletal system o Muscle system o Nervous system o Endocrine system Endeavour College of Natural Health endeavour.edu.au 1

2 Textbook and required/recommended readings o Principles of anatomy and physiology. Tortora et al; 14 th edition: Chapter 3 Endeavour College of Natural Health endeavour.edu.au 2

3 BIOH111 Cell Module o Session 1 (Lectures 1): Homeostasis and Cell organisation and function of specific organelles o Session 2 (Lectures 2 and 3): Central Dogma and plasma membrane organisation and function o Session 3 (Lectures 4): Cell communication (vesicular transport) and extracellular matrix o Session 4 (Lectures 5 and 6): Cell communication (signalling) and Cell division Endeavour College of Natural Health endeavour.edu.au 3

4 BIOH111 Session 3: Lecture 4 Cell communication (vesicular transport) and extracellular matrix Department of Bioscience endeavour.edu.au

5 Preparation for this session o Complete any missing concepts and linking words from Session 3 o Bring the model of plasma membrane to Session 3 o Revise the plasma membrane structure and function for easier understanding of vesicular transport Endeavour College of Natural Health endeavour.edu.au 5

6 Lecture 4: Objectives Cell communication (vesicular transport) Define different types of vesicular transport endocytosis, exocytosis and transcytosis Describe different types of endocytosis Understand the differences between 3 different types of endocytosis: receptor-mediated, phagocytosis and macropinocytosis Describe different types of exocytosis Understand the differences between 2 different types of exocytosis: constitutive and regulated Extracellular matrix as a result of constitutive exocytosis Define elements and structure of extracellular matrix Define functions of different elements of extracellular matrix Exocytosis of neurotransmitters and glucose transporter as a result of regulated exocytosis Describe the process of exocytosis of neurotransmitters Describe the process of exocytosis of glucose transporter Endeavour College of Natural Health endeavour.edu.au 6

7 An interesting conundrum: If inside of an animal cell looks more like this, how is the cell able to talk to other cells and how do proteins know what to do inside the cell??? Marsh at al, 2001 Endeavour College of Natural Health endeavour.edu.au 7

8 Types of communication Transport/trafficking (vesicular) o Physical movement of proteins and lipids within the cell Signalling (next session) o Transport of a specific signal received from outside to elicit a cellular response The two communication types work together and are NOT separate from each other! Trafficking will influence signalling and signalling will influence trafficking! Endeavour College of Natural Health endeavour.edu.au 8

9 VESICULAR TRANSPORT Endocytosis o Internalisation of molecules into the cell Exocytosis o Secretion of molecules out of the cell Endeavour College of Natural Health endeavour.edu.au 9

10 ENDOCYTOSIS o In endocytosis, materials move into a cell in a vesicle formed from the plasma membrane. Types of endocytosis: 1. Receptor-mediated 2. Phagocytosis 3. Macropinocytosis 4. Autophagy (specialised type of endocytosis) 5. Caveolae Endeavour College of Natural Health endeavour.edu.au 10

11 RECEPTOR-MEDIATED ENDOCYTOSIS LDL particle full of phospholipids and cholesterol When this process fails accumulation of LDL outside the cells: Endeavour College of Natural Health endeavour.edu.au 11

12 PHAGOCYTOSIS Bacterium Pseudopods A. Entrapment by pseudopods B. Engulfment: pseudopods fuse to internalize prey in phagosome C. Digestion: phagosome fuses with lysosome Vesicles w lysosomal enzymes Phagosome Some bacteria have evolved to evade digestion in lysosomes, and live as intracellular parasites or pathogens Myxobacteria tuberculosis (tuberculosis) Listeria monocytogenes (listeria) Yersinia pestis (plague) Lysosome Performed by specialized cells e.g. macrophages Endeavour College of Natural Health endeavour.edu.au 12

13 MACROPINOCYTOSIS ( bulk or fluid-phase endocytosis) non-selective! macro - large and pinocytosis - cell drinking Fluid-phase endocytosis can be followed in live cells with fluorescent dyes As many as ~2500 coated vesicles/min (~2-3% of surface area)! Contents are delivered to lysosome and digested Bacteria use this pathway to gain entry into the cells and replicate Endeavour College of Natural Health endeavour.edu.au 13

14 Two types: o Constitutive when the molecule secreted is needed in constant levels (e.g. albumin for extracellular matrix) EXOCYTOSIS o Regulated the protein is secreted in response to a stimulus therefore it is secreted only when needed Endeavour College of Natural Health endeavour.edu.au 14

15 CONSTITUTIVE EXOCYTOSIS Definition when the molecule secreted is needed in constant levels (e.g. albumin for extracellular matrix or collagen for collagen fibers) Endeavour College of Natural Health endeavour.edu.au 15

16 ELEMENTS OF EXTRACELLULAR MATRIX o Extracellular proteins can be used as anchor points for cells (e.g. multiadhesive protein in epithelial tissue) or as support for space between cells (e.g. collagen fibers in connective tissue) Endeavour College of Natural Health endeavour.edu.au 16

17 ELEMENTS OF EXTRACELLULAR MATRIX o Ground substance can be fluid, gelatinous and solid (calcified) depending on its composition and function; found in abundance in connective tissue, but also present outside any cell in any tissue - Structure: water and large organic molecules (combination of the complex adhesion proteins (fibronectin) and polysaccharides called glycosaminoglycans (GAG s) (these include: hyaluronic acid, chondroitin sulfate, dermatan sulfate, and keratin sulfate) - Function: support and interaction ground for connective tissue cells, stores water and provides medium for molecule diffusion from cells to bloodstream Endeavour College of Natural Health endeavour.edu.au 17

18 REGULATED EXOCYTOSIS Definition the protein is secreted in response to a stimulus therefore it is secreted only when needed Endeavour College of Natural Health endeavour.edu.au 18

19 Regulated secretion of neurotransmitters STIMULUS (action potential) v-snare t-snares t-snare complex Ca 2+ SNARE complex Endeavour College of Natural Health endeavour.edu.au 19

20 Regulated secretion of glucose transporter Glucose transporter is NOT needed until there is glucose in the blood. So, it is stored in the vesicles in the cell until a stimulus (insulin+insulin receptor) signals transporter is needed to take up glucose. Once it has done it s job the transporter is endocytosed back to the vesicles inside the cells STIMULUS (insulin interacting with its receptor) Endeavour College of Natural Health endeavour.edu.au 20

21 Intestinal lumen IgG in milk IgG receptor TRANSCYTOSIS Apical membrane Apical Endosome Basolateral Endosome Milk duct e.g. movement of maternal IgG across 2 epithelial layers IgG is secreted across the mammary epithelium into milk by transcytosis Receptor-mediated endocytosis from basolateral domain Secretion from apical membrane domain IgG is transcytosed into the neonate blood Endocytosis from apical domain and secretion to basolateral membrane Epithelial cell IgG receptor IgG in blood Neonate blood Basolateral membrane Maternal blood Polarized epithelial cells have distinct apical and basolateral endosome compartments Endeavour College of Natural Health endeavour.edu.au 21

22 Recap of vesicular transport Endeavour College of Natural Health endeavour.edu.au 22

23 Preparation for next session o Complete any missing concepts and linking words from Session 3 o Bring the model of plasma membrane to Session 4 o Watch the video animation of cell signalling (see Activity 1, Session 4) and review what is a receptor Endeavour College of Natural Health endeavour.edu.au 23

24 Review videos o Passive vs active transport o Revision video o Osmosis o Endocytosis and exocytosis o Exocytosis of neurotransmitters o Endeavour College of Natural Health endeavour.edu.au 24

25 Endeavour College of Natural Health endeavour.edu.au 25