3.D- Cell Communication

Transcription

1 3.D- Cell Communication Big Idea 3: Living systems store, retrieve, transmit and respond to information essential to life processes. EU 3.A: Heritable information provides for continuity of life. EU 3.B: Expression of genetic information involves cellular and molecular mechanisms. EU 3.C: The processing of genetic information is imperfect and is a source of genetic variation. EU 3.D: Cells communicate by generating, transmitting and receiving chemical signals. EU 3.E: Transmission of information results in changes within and between biological systems. A. Communication involves transduction of stimulatory or inhibitory signals from other cells, organisms or the environment. [See also 1.B.1] B. Correct and appropriate signal transduction processes are generally under strong selective pressure. C. In single-celled organisms, signal transduction pathways influence how the cell responds to its environment. 1. Use of chemical messengers by microbes to communicate with other nearby cells and to regulate specific pathways in response to population density (quorum sensing) 1

2 2. Use of pheromones to trigger reproduction and developmental pathways 3. Response to external signals by bacteria that influences cell movement D. In multicellular organisms, signal transduction pathways coordinate the activities within individual cells that support the function of the organism as a whole. 1. Epinephrine stimulation of glycogen breakdown in mammals 2. Temperature determination of sex in some vertebrate organisms 3. DNA repair mechanisms 2

3 EK 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. A. Cells communicate by cell-to-cell contact. 1. Immune cells interact by cell-cell contact, antigen-presenting cells (APCs), helper T-cells and killer T-cells. [See also 2.D.4] 2. Plasmodesmata between plant cells allow material to be transported from cell to cell. EK 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. B. Cells communicate over short distances by using local regulators that target cells in the vicinity of the emitting cell. 1. Neurotransmitters 2. Plant immune response 3. Quorum sensing in bacteria 4. Morphogens in embryonic development EK 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. C. Signals released by one cell type can travel long distances to target cells of another cell type. 1. Endocrine signals are produced by endocrine cells that release signaling molecules, which are specific and can travel long distances through the blood to reach all parts of the body. a) Insulin b) Human growth hormone c) Thyroid hormones d) Testosterone e) Estrogen A. Signaling begins with the recognition of a chemical messenger (a ligand) by a receptor protein. 1. Different receptors recognize different chemical messengers, which can be peptides, small chemicals or proteins, in a specific one-to-one relationship. 2. A receptor protein recognizes signal molecules, causing the receptor protein s shape to change, which initiates transduction of the signal. a) G-protein linked receptors b) Ligand-gated ion channels c) Receptor tyrosine kinases 3

4 B. Signal transduction is the process by which a signal is converted to a cellular response. 1. Signaling cascades relay signals from receptors to cell targets, often amplifying the incoming signals, with the result of appropriate responses by the cell. 2. Second messengers are often essential to the function of the cascade. a) Ligand-gated ion channels b) Second messengers, such as cyclic GMP, cyclic AMP, calcium ions (Ca2+), and inositol triphosphate (IP3) 3. Many signal transduction pathways include: a) Protein modifications 1) methylation changes the signaling process 2) Methylated histones can act epigenetically b) Phosphorylation cascades in which a series of protein kinases add a phosphate group to the next protein in the cascade sequence EK 3.D.4: Changes in signal transduction pathways can alter cellular response. A. Conditions where signal transduction is blocked or defective can be deleterious, preventative or prophylactic. 1. Diabetes, heart disease, neurological disease, autoimmune disease, cancer, cholera 2. Effects of neurotoxins, poisons, pesticides 3. Drugs (Hypertensives, Anesthetics, Antihistamines and Birth Control Drugs) END Neurotransmitters A. At least 50 kinds of neurotransmitters B. Neurotransmitters that increase membrane permeability to sodium ions are excitatory. C. Neurotransmitters that decrease membrane permeability to sodium ions are inhibitory. Back Plant Immune Response A. Innate (non-specific), immediate B. A pathogen attack produces a phytohormonal blend from plant C. This signal signature results in the activation of a specific set of defense-related genes D. Hormone signaling pathways are important regulatory mechanisms by which the plant may be able to tailor its immune response to the type of invader encountered. 4

5 Quorum Sensing A. Increase population in specific area. B. Creates biofilms A. Signal tissue development B. Diffusion creates gradients that affect development. Morphogens Insulin A. Secreted by Pancreas in response to elevated glucose levels B. Signals uptake of glucose by cells Human Growth Hormone A. From Anterior Pituitary B. Stimulates cell growth Thyroid Hormones A. Increases metabolism and heat production (calorigenic effect) in most cells B. Required for normal development (regulate Ca + levels) C. Ca + ions regulate response D. Secrete calcitonin Testosterone A. Secreted by testes, ovaries, and adrenal glands B. Binds to AR (androgen receptors) C. Acts as a selective transcription factor D. Response depends on target tissue 5

6 Estrogen A. Major sex steroid hormone produced by ovaries in women. B. Also produced in a lesser amount in men. C. Receptors include the brain, bones, and blood vessels D. Estrogen targets appear at 3 different cellular levels. A. Membrane targets. (estrogen receptors (ER) and ion channels) B. Cytosolic targets (signal pathways for gene expression or protein activation) C. Nuclear targets (direct modulation of gene expression ). Diabetes A. Type 1- Defect in insulin production B. Type 2- Defect in glucose transport signal Neurotoxins A. Block Calcium channels B. Prevent release of neurotransmitters A. Beta-blockers compete with catecholamines (NO, E) for adrenergic receptors. B. Block the adrenergic binding sites on the myocardial tissue C. Inhibiting or alleviating muscle contraction, high blood pressure, and increased cardiac output. Hypertensives 6