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 textbook Endeavour College of Natural Health endeavour.edu.au 2

3 BIOH111 Cell Module o Session 1 (Lectures 1 and 2): Cell organisation and function of specific organelles o Session 2 (Lectures 3 and 4): Plasma membrane organisation and function and Cell communication o Session 3 (Lectures 5 and 6): Cell communication and Cell division Endeavour College of Natural Health endeavour.edu.au 3

4 BIOH111 Session 3: Lectures 5 and 6 Cell communication and Cell division Bioscience Department endeavour.edu.au

5 Objectives Lecture 5: Cell communication Describe different types of cell communications with its environment and within itself (intracellular trafficking and cell signaling) Lecture 6: Cell division Define differences between 2 types of cell division and relate these processes to their steps and function Endeavour College of Natural Health endeavour.edu.au 5

6 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 6

7 Types of communication Trafficking o Physical movement of proteins and lipids within the cell Signalling 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 7

8 You have already encountered trafficking linked to the plasma membrane, but Proteins and lipids are transported around the cell using vesicles. These can originate at any point within the cell and can deliver their cargo to any part of the cell. E.g. vesicles originating in Golgi can be delivered to plasma membrane or lysosome; vesicles originating at plasma membrane can be delivered to Golgi or back to plasma membrane.. Endeavour College of Natural Health endeavour.edu.au 8

9 Signalling is linked to trafficking: specific molecules secreted from the cells act as signalling molecules Neurotransmitters secreted from neuron act on the downstream target muscle cell or another neuron Signalling molecules secreted from a signalling cell act locally on the target cell This is local signalling that ensures functioning of cells in very close proximity (e.g. within a tissue) Hormones secreted from endocrine cell act on the downstream target in a long-range manner where hormone is delivered to the target cell through circulation Endeavour College of Natural Health endeavour.edu.au 9

10 Neurotransmitters, signalling molecules and hormones act on their target cells using plasma membrane receptors Signalling molecule can be: hormone or neuro transmitter or any other protein secreted by a cell Target cell and receptor will depend on the signalling molecule. E.g. acetylcholine will be secreted by motor neurons and target cell (muscle) will contain acetylcholine receptor. This confers specificity of response only target cells with the right receptor will respond to the signalling molecule. Endeavour College of Natural Health endeavour.edu.au 10

11 Once signalling molecule interacts with its receptor it starts cell signalling cascades Cell signalling is a process of converting extracellular signal (signalling molecule) into intracellular response (gene transcription) via transduction cascade initiated by signal+receptor engagement. Endeavour College of Natural Health endeavour.edu.au 11

12 Transduction cascades are sequentially mediated Transaction cascade is initiated by signal/receptor engagement and leads to amplification of this signal. This is done by firstly activating secondary messenger systems, then activation of protein phosphorylation cascade which activates specific target proteins. Therefore, 1 signal+receptor engagement can lead to activation of multiple genes. Endeavour College of Natural Health endeavour.edu.au 12

13 Transduction cascades are sequentially mediated Transaction cascade is initiated by signal/receptor engagement and leads to amplification of this signal. This is done by firstly activating secondary messenger systems, then activation of protein phosphorylation cascade which activates specific target proteins. Therefore, 1 signal+receptor engagement can lead to activation of multiple genes and/or responses. Endeavour College of Natural Health endeavour.edu.au 13

14 Secondary messenger systems: a) G-protein b) camp c) cgmp d) PLC Ca 2+ activation Protein phosphorylation cascades: a) AKT b) MAPK activation Overall response Target proteins: a) Transcription factors b) Enzymes c) Cytoskeletal proteins activation Cellular response: a) Gene alternation b) Metabolism alternation c) Cell motility and shape alteration Endeavour College of Natural Health endeavour.edu.au 14

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16 Take home messages: 1. Trafficking of proteins and lipids responds to signalling event and signalling is initiated and propagated by trafficking. 2. Cells have evolved these complicated intracellular events in order to be able to communicate with each other and therefore exist in a multicellular environment. Endeavour College of Natural Health endeavour.edu.au 16

17 Lecture 5: Cell communication Objectives Describe different types of cell communications with its environment and within itself (intracellular trafficking and cell signaling) Lecture 6: Cell division Define differences between 2 types of cell division and realte these processes to their steps and function Endeavour College of Natural Health endeavour.edu.au 17

18 CELL DIVISION Definition: Cell division is the process by which cells reproduce themselves. It consists of nuclear division (mitosis and meiosis) and cytoplasmic division (cytokinesis). o Cell division that results in an increase in body cells is called somatic cell division and involves a nuclear division called mitosis, plus cytokinesis. o Cell division that results in the production of sperm and eggs is called reproductive cell division and consists of a nuclear division called meiosis, plus cytokinesis. Endeavour College of Natural Health endeavour.edu.au 18

19 COMPARISON OF MITOSIS AND MEIOSIS From your knowledge of chromosomes (lecture 1): what number is n? Endeavour College of Natural Health endeavour.edu.au 19

20 HOW DO WE GET A 2n CELL (starting cell for both division types)? o Cell division is initiated by duplication of its genetic material o This is done in interphase of cell division which consists of 3 phases: G1, S and G2 phase. Endeavour College of Natural Health endeavour.edu.au 20

21 INTERPHASE STAGE o G1 phase cell metabolic increase o S phase DNA replication and chromosome condensing o G2 phase conclusion of metabolic increase o End result double of everything in the cell why? DNA replication details: session 17 BIOB111 Endeavour College of Natural Health endeavour.edu.au 21

22 Entry point into mitotic (nuclear) division followed by cytokinesis (cytoplasmic) division Endeavour College of Natural Health endeavour.edu.au 22

23 MITOTIC PHASE Definition: Mitosis is the movement of two sets of chromosomes - one set into each of two separate nuclei. Mitosis stages: o Prophase o Metaphase o Anaphase o Telophase Endeavour College of Natural Health endeavour.edu.au 23

24 S phase: DNA replication details: session 17 BIOB111 PROPHASE Early prophase: Chromosome condensation: Lecture 1 BIOH111 Early prophase: Chromatin condenses and shortens into visible chromosomes Pair of identical chromatids held together by a centromere Late prophase: Nucleolus & nuclear envelope disappear Each Centrosome starts to move towards opposite ends of cell via mitotic spindle Endeavour College of Natural Health endeavour.edu.au 24

25 METAPHASE The centromeres line up at the exact center of the mitotic spindle, a region called the metaphase plate Endeavour College of Natural Health endeavour.edu.au 25

26 ANAPHASE Anaphase is characterized by the splitting and separation of centromeres (early) and the movement of the two sister, V-shaped chromatids of each pair toward opposite poles of the cell (late) Endeavour College of Natural Health endeavour.edu.au 26

27 Telophase begins as soon as chromatid movement stops then: TELOPHASE - the identical sets of chromosomes at opposite poles of the cell uncoil and revert to their threadlike chromatin form - microtubules disappear or change form and mitotic spindle breaks up - new nuclear envelope forms and new nucleoli appear Endeavour College of Natural Health endeavour.edu.au 27

28 CYTOPLASMIC DIVISION: Definition: Cytokinesis is the division of a parent cell s cytoplasm and organelles. The process begins in late anaphase or early telophase with the formation of a cleavage furrow. When cytokinesis is complete, interphase begins, but only if needed why? CYTOKINESIS Endeavour College of Natural Health endeavour.edu.au 28

29 CONTROL OF CELL DESTINY The four possible destinies of a cell are: 1. Survival without further division 2. Division 3. Differentiation (progenitor cell (e.g. common myeloid progenitor cell) differentiates into a terminal cellular phenotype (e.g. RBC or mast cell)) 4. Death (apoptosis and necrosis) Can you: 1. Think of a cellular process that would be able to control the cell s destiny? 2. Name situations where each of these cellular destinies are important for maintaining health? Endeavour College of Natural Health endeavour.edu.au 29

30 REPRODUCTIVE CELL DIVISION o Meiosis results in the production of haploid cells that contain only 23 chromosomes. o During meiosis, a single round of DNA replication is followed by 2 successive cycles of cell divisions: meiosis I and meiosis II. o In meiosis I homologous chromosomes are segregated and meiosis II is similar to mitosis o So, process of meiosis starts with a cell that has just finished interphase. How many chromosomes does this cell have? Endeavour College of Natural Health endeavour.edu.au 30

31 MEIOSIS I Meiosis I consists of four phases: prophase I, metaphase I, anaphase I, and telophase I Segregation of homologous chromosomes is achieved in prophase I by: 1. Formation of tetrads (process called synapsis) 2. Crossing over (process called homologous recombination) Endeavour College of Natural Health endeavour.edu.au 31

32 PROPHASE I TETRAD FORMATION Definition: Synapsis is a process where homologous chromosomes are associated with each other via a proteinbased complex to form a tetrad (2 chromosomes; 4 chromatids) Endeavour College of Natural Health endeavour.edu.au 32

33 PROPHASE I CROSSING OVER Definition: Homologous recombination is a process where chromosomes are cleaved and the fragments rejoined to give new combinations. Can you give a reason why this is good in meiosis and really bad in mitosis? OF CHROMOSOMES Endeavour College of Natural Health endeavour.edu.au 33

34 MEIOSIS I Endeavour College of Natural Health endeavour.edu.au 34

35 MEIOSIS II o Meiosis II consists of prophase II, metaphase II, anaphase II, and telophase II o These phases are similar to those in mitosis, but result in four haploid cells. Endeavour College of Natural Health endeavour.edu.au 35

36 List the differences between the meiosis and mitosis and outline why these differences exist, speculate how they are controlled and why are they important.. Endeavour College of Natural Health endeavour.edu.au 36

37 COMPARISON OF MITOSIS AND MEIOSIS Endeavour College of Natural Health endeavour.edu.au 37

38 Examples when things go wrong o Cell aging o Cancer o Down syndrome Endeavour College of Natural Health endeavour.edu.au 38

39 Review videos o Meiosis o Mitosis Endeavour College of Natural Health endeavour.edu.au 39

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