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

Transcription

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 4: Lecture 5 and 6 Cell communication (signalling) and Cell division 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 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 5

6 Lecture 5: Cell communication (signaling) Objectives Describe involved in process of cell signaling Understand how signaling leads to the outcome of cell division 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 6

7 Types of communication Transport (vesicular) 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 Signalling is linked to transport: 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 8

9 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 9

10 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 10

11 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 11

12 Ligand (signal) engages receptor (on PM) activation of response inside the cell Secondary messenger systems: a) G-protein b) camp c) cgmp d) PLC Ca 2+ activation Protein phosphorylation cascades: a) AKT b) MAPK Overall response activation Target proteins: a) Transcription factors b) Enzymes c) Cytoskeletal proteins activation Cellular response: a) Gene expression regulation b) Metabolism alternation c) Cell motility and shape alteration Video showing process of signalling with gene expression as a cellular response Endeavour College of Natural Health endeavour.edu.au 12

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14 Take home messages: 1. Transport 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 14

15 Lecture 5: Cell communication (signaling) Objectives Describe involved in process of cell signaling Understand how signaling leads to the outcome of cell division 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 15

16 DNA CHROMOSOMES - revision Reproductive cells have 23 chromosomes. Why? How? Non-dividing cell DNA condensation (histones) Human somatic cells have 46 chromosomes arranged in 23 pairs. Dividing cell Endeavour College of Natural Health endeavour.edu.au 16

17 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 17

18 COMPARISON OF MITOSIS AND MEIOSIS From your knowledge of chromosomes (lecture 1): what number is n? Endeavour College of Natural Health endeavour.edu.au 18

19 HOW DO WE GET 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 19

20 INTERPHASE STAGE o G1 phase cell metabolic rate increases 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 20

21 Entry point into mitotic (nuclear) division followed by cytokinesis (cytoplasmic) division Endeavour College of Natural Health endeavour.edu.au 21

22 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 22

23 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 23

24 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 24

25 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 25

26 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 26

27 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 27

28 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 28

29 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 29

30 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 30

31 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 31

32 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 32

33 MEIOSIS I Endeavour College of Natural Health endeavour.edu.au 33

34 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 34

35 Ligand (signal) engages receptor (on PM) activation of response inside the cell Secondary messenger systems: a) G-protein b) camp c) cgmp d) PLC Ca 2+ activation Protein phosphorylation cascades: a) AKT b) MAPK Overall response activation Target proteins: a) Transcription factors b) Enzymes c) Cytoskeletal proteins activation Cellular response: a) Gene expression regulation b) Metabolism alternation c) Cell motility and shape alteration Endeavour College of Natural Health endeavour.edu.au 35

36 Cells die in 2 different ways o Necrosis: uncontrolled cell death that is usually caused by external factors (e.g. physical injury, ischemia or nutrient depravation) cells appear to explode in a manner that does not have any identifiable sequence defence mechanism of cells but can lead to local injury and/or inflammation o Apoptosis programmed cell death that is initiated by the extracellular signal and undergoes a series of intracellular enzymatic reactions that break down everything inside the cell including DNA cells show plasma membrane blebbing and sequential fragmentation of cytoplasm and plasma membrane normal process of cell replacement Endeavour College of Natural Health endeavour.edu.au 36

37 Recap of Session 4 Using Activity 1 in Tutorial describe process of cell signalling List the differences between the meiosis and mitosis and outline why these differences exist and why are they important.. Endeavour College of Natural Health endeavour.edu.au 37

38 Preparation for next session o Complete any missing concepts and linking words from Session 4 o Revise the following from Sessions 1, 2 and 3: different types of integral membrane proteins different types of cytoskeleton constitutive exocytosis Endeavour College of Natural Health endeavour.edu.au 39

39 Examples when things go wrong o Cell aging o Cancer o Down syndrome Endeavour College of Natural Health endeavour.edu.au 40

40 Review videos o Meiosis o Mitosis Endeavour College of Natural Health endeavour.edu.au 41