BIO 1510: Chapter 9, 10, and 11 Notes
BIO 1510: Chapter 9, 10, and 11 Notes Bio 1510
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Date Created: 03/21/16
Chapter 10: How Cells Divide Introduction o Asexual reproduction reproduction without sex Mitosis is a type of asexual reproduction during which a parent cells divides once to produce 2 genetically identical daughter cells or offspring Somatic cells are all cells in our body (except egg and sperm) that are produced by mitosis “soma” means body Ex. Skin, blood, pancreatic, etc. Allows us to replace damaged or worn out body cells Egg and sperm are called gametes (also known as germ cells) produced by meiosis DNA o Consists of 2 strands of deoxynucleotides o Components of chromosome Chromosome is a structure made of a material called chromatin Chromatin is made up of DNA and proteins o A normal somatic cell in a human body has 46 chromosomes Structure of a Chromosome o Paternal chromosome 10 is from dad o Maternal chromosome 10 is from mom o They are homologous chromosomes They are from the same lengths and they have the same genes and loci which are position of genes on chromosomes, but not necessarily the same version or alleles of genes o Centromere are constricted regions of the chromosomes that link sister chromatids together before they separate May be found in the middle or closer to the top o Kinetochore is a protein complex to which microtubules that separate chromosomes bind o Telomeres are found at the ends of chromosomes They are repetitive noncoding regions of the DNA that don’t encode any proteins, but they protect chromosomes from degradation by nucleases and infusion with other chromosomes Each chromosome has 2 telomeres As our cells divide our chromosomes become shorter and cause cells to die and shorten Cancer cells have the ability to rebuild their telomeres The Human Karyotype o Picture of all chromosomes in a single cell o All somatic cells have chromosomes that will eventually look like this image o Chromosomes that are tightly packed we can differentiate them from each other o However if chromosomes are decondensed or loosely packed it is difficult to differentiate them Need to make the cell start dividing o A somatic cell in humans have 46 chromosomes or 23 pairs (23 chromosomes from dad and 23 chromosomes from mom) o Chromosomes 142 or chromosome pairs of 122 are called autosomes or non sex chromosomes Don’t determine the gender of the organism The 23 pair of chromosome is called sex chromosomes Sex chromosomes differ from male and female Female XX Male XY X and Y are nonhomologous chromosomes We have 25,000 genes 2,000 are on the x chromosomes 78 genes are on the y chromosome o Karyotype analysis helps determine these things: It allows us to determine the number of chromosomes whether the individual has normal or abnormal (Down Syndrome) Determines the gender of the organism Allows us to see the length and size of the chromosomes Heterochromatin vs. Euchromatin o DNA can be loosely or tightly packed o DNA is part of chromosome o In dividing cells, all chromatin is tightly packed, while only some of it is tightly packed in nondividing cells o Heterochromatin is a tightly packed chromatin whose DNA is tightly packed Tightly packed DNA cannot be expressed and used to make proteins Found at the centromeres and telomeres of chromosomes in both dividing and nondividing cells Euchromatin is loosely packed chromatin whose DNA is loosely packed and it is expressed and used to make proteins (nondividing cells ONLY) When Your Cells Are Not Dividing o Histones are DNA packaging proteins; they include H1, H2A, H2B, H3, and H4 H2A, H2B, H3, and H4 core histones Histone core consists of 8 core histones 2 of each o Nucleosome = complex of 9 core histones and DNA wrapped around them; it is the basic unit of DNA packaging o H1 linker histone that pulls nucleosomes together Cell cycle o Mature nerve and skeletal muscle cells do NOT divide o G1 = Gap 1 The cell grows but does not divide o G2 phase is a pause in G1 phase where mature nerve and skeletal muscle cells stay permanently, while liver cells stay for 6 months only o S phase = synthesizes Cell duplicates its DNA and chromosomes; also centrosome duplication begins Centrosome = microtubuleorganizing center a region where microtubules grow out from, forming mitotic spindle (guides the separation of chromosomes during cell division) o Each centrosome has 2 centrioles (in animals) o G2 = Gap 2 Cell continues to get bigger; centrosome duplication ends; gets ready to divide o Interphase = preparation of cell for division; longest phase in the cell cycle o M phase = mitotic phase Includes mitosis and cytokinesis Mitosis is when nucleus divides o Divided into 5 stages: prophase, prometaphase, metaphase, anaphase, and telophase Cytokinesis is when cytoplasm divides Duplicating the DNA in S phase o Cohesion is a protein that holds sister chromatids together o 2 chromosomes, 4 chromatids, 4 DNA molecules o During replication, number of chromosomes doesn’t change, but the appearance of chromosomes change; each chromosome consists of 2 sister chromatids Liver cell has 46 chromosomes in the beginning of S phase, 46 DNA molecules at the end of 2 phase it will have 46 chromosomes, 92 chromatids, and 92 DNA molecules o Homologous chromosomes are nonidentical nonsister chromatids After the DNA is Duplicated o Centrioles are made up of microtubules o Cell has 2 centrosomes Each centrosome contains 2 centrioles o Each chromosome consists of 2 identical sister chromatids that are held together by cohesin o Nuclear envelope is intact Packaging DNA for Cell Division o Nucleosome = DNA + 8 core histones o Solenoid = H1 nucleosomes together o Chromatin loop = solenists coil around each other with the help of scaffold proteins o Rossetts condense into tightly packed chromosomes as seen in mitosis Prophase: The First Phase of Mitosis o Mitotic spindle begins to form o Chromosomes are tightly condensed due to condensing o Nuclear envelope is still present o 2 centrosomes; 4 centrioles Prometaphase o The cell still has 2 centrosomes o Nuclear envelope breaks apart o Kinetochore microtubules are attached to each sister chromatid of the chromosomes via kinetochore o 4 centrioles o Cohesins and condensins are still present Metaphase o The cell still has 2 centrosomes o Mitotic spindle brings all chromosomes to the middle of the cell o Chromosomes are aligned on metaphase plate o All kinetochore microtubules are about the same length o 4 centrioles o The metaphase chromosome 2 identical sister chromatids are held together by cohesion Each sister chromatid has a kinetochore microtubules Still has cohesin and condensing o The mitotic spindle at metaphase Consist of kinetochore microtubule, aster microtubules, and polar microtubule Kinetochore microtubule binds to the kinetochore of the chromosome Aster microtubule are short microtubules that radiate from the centrosome Polar microtubule from one pole of the cell interacts with polar microtubule from another pole of the cell with the help of motor proteins Anaphase o The cell still has 2 centrosomes and 4 centrioles o Cohesin proteins are destroyed o Sister chromatids move to opposite poles of the cell Now called daughter chromosomes o Kinetochore microtubules decrease in length, while polar microtubules become longer o Condensin proteins are still present Telophase o The cell still has 2 centrosomes and 4 centrioles o Mitotic spindle disassembles o Condensin proteins are destroyed Making chromosomes decondensed o Nuclear envelope reforms around each set of chromosomes Cytokinesis in Animal cells o Cytoplasm divides o It begins before telophase ends o Cleavage furrow – indentation in the cell surface It forms outside o Contracting ring the ring of actin filaments (microfilaments) It forms inside o At the end, 2 daughter cells are produced, which are genetically identical to each other and to the parent cell; each of them has the same number of chromosomes as the parent cell used to have o Only animal cells can make cleavage furrow and contracting ring Cytokinesis in Plant Cells o Contained cell wall combining with phragmoplast (complex of microtubules and actin filaments) to form a cell plate = a new cell wall that forms in the middle of the dividing plant cell Checkpoints During the Cell Cycle o Control mechanisms that ensure that fidelity of cell division o G1/S checkpoint Start or restriction point Cell ensures that DNA is not damaged Primary point for external signal influence o G2/M checkpoint Cell assesses success of DNA replication and centrosome duplication Makes a commitment to mitosis o Spindle Checkpoint Cell ensures that all chromosomes are aligned on metaphase plate and attached to mitotic spindle Cyclins/CyclinDependent Kinases: Controlling the Checkpoints o Are needed for the cell to progress through the cell cycle o Cyclindependent kinase = enzyme that phosphorylates proteins o Cyclin = protein that helps activate Cdk o Levels of Cdks don’t change but their activities do o Cyclin our cells make and destroy them o Activating phosphate activates Cdk o Inactive Cdk has cyclin and 2 different phosphates: activators and inhibitors attached to it o Active Cdk has cyclin and only activating phosphate attached to it Different Cyclins/Cdks at Each Checkpoint o G2/M Checkpoint (Cdk1/Cyclin B) Replication completed DNA integrity MPF = Mphase promoting factor which is needed for the cell to enter mitosis o Spindle Checkpoint (APC) APC = anaphase promoting complex protein complex that triggers the destructions of cohesins Sister chromatids come apart Chromosomes attached at the metaphase plate Other Proteins that Control the Cell Cycle o Protooncogenes code for protooncogene proteins that stimulate cell division (Ras protein and Src kinase) “proto” before “onco” = cancer They become oncogenes when mutated Oncogenes can cause cancer (uncontrolled growth of cells) Src kinase “sarc” = sarcoma Cancer that affects bones, muscles, and other connective tissues o Tumorsuppressor genes encode tumorsuppressor proteins that inhibit cell division (p53 protein and Rb protein) Rb protein retinoblastoma cancer that affects the retina of the eye Chapter 11: Sexual Reproduction and Meiosis Introduction o Sexual reproduction involves the exchange of genetic material (DNA) between 2 organisms of opposite sex o Gametes are required and they are called germ cells (egg and sperm) o Meiosis vs. Mitosis During mitosis the parent cell divides once and produces 2 genetically identical daughter cells which are genetically identical to the parent cell Daughter cells that are made after mitosis are called somatic cells The number of chromosomes stay the same between the parent and each daughter cell During meiosis the parent cell goes through 2 rounds of cell division to produce 4 daughter cells and are genetically different from each other and genetically different to the parent cell Daughter cells that are made after meiosis are called germ cells The number of chromosomes is reduced in half with each daughter cell having ½ of the chromosomes of the parent cell Somatic vs. Germ Cells o Body cells (somatic cells) are produced via mitosis and are diploid (2n) Has 2 sets of chromosomes In humans 2n = 46 chromosomes 1 set comes from mom and the other from dad N=23 chromosomes o Germ cells or gametes include egg and sperm, which are produced via meiosis Gametes are haploid (n), having one set of chromosomes In humans sperm has 23 chromosomes and egg has 23 chromosomes Sexual reproduction o Fertilization (syngamy) is the fusion of sperm and egg to form a diploid zygote (2n) o Diploid = somatic cells o Haploid = germ cells o Germ LINE cells are DIPLOID o Zygote is also called a fertilized egg It is diploid because it has 2 sets of chromosomes o Embryo is diploid (46 chromosomes) o Baby fetus is diploid (46 chromosomes) Meiosis: Producing Gametes through 2 Rounds of Division o At the end of meiosis 1, 2 daughter cells are genetically different from each other and from the parent cell is haploid o Before Meiosis 2 interphase does not have chromosome replication 4 daughter cells that are genetically different from each other at the end of meiosis 2 o Starts with parent cell or germline cell and in humans it has 46 chromosomes (46 DNA molecules) o Then it goes through interphase it has 46 chromosomes, 92 chromatids, and 92 DNA molecules o The cell then goes through meiosis 1 and at the end of meiosis 1, two daughter cells are produced (each of them haploid 23 chromosomes, 46 chromatids, and 46 DNA molecules) o Following interphase, each daughter cell has 23 chromosomes, 46 chromatids, and 46 DNA molecules they then go through meiosis 2 o At the end of meiosis 2, four daughter cells are produced each daughter cell is haploid having 23 chromosomes and 23 DNA molecules Can either be sperm or egg cells o Another name for meiosis is reduction division because of the number of chromosomes is reduced in half o Both meiosis 1 and meiosis 2 includes 4 stages: prophase, metaphase, anaphase, and telophase Duplicating the DNA in S phase o Chromosomes duplicate and are now considered sister chromatids they are also homologous chromatids o S phase is part of interphase Prophase I: Meiosis Begins o Mitotic spindle begins to form and nuclear envelope breaks apart o Chromosomes are tightly condensed due to condensins o Homologous chromosomes pair up and form tetrads Each tetrad consists of 4 chromatids or 2 chromosomes Synapsis is when homologous chromosomes pair up which form tetrads o Crossing over occurs o Synapsis and formation of tetrads are unique to prophase I What is a Tetrad? o 2 sister chromatids are held together by cohesin o Homologous chromatids are not identical They are held together by synaptonemal complex Synaptonemal complex layer of proteins that holds 2 homologous chromosomes together Crossing Over o Involves the exchange of DNA between nonidentical (but homologous) chromatids of homologous chromosomes o Chiasma is a site of crossing over (pl. chiasmata) o Physical break and share regions with one another o Not identical because they might have different alleles o It occurs ONLY during prophase I of meiosis 1 o One of the main reasons why we don’t look identical to our parents o Synapsis, formation of tetrads, and crossing over are unique to prophase 1 Metaphase I o Tetrads are aligned on the metaphase plate o Microtubules from one pole are attached to the kinetochore of one chromosome of each tetrad o Microtubules from the other pole are attached to the kinetochore of the other chromosome Different Combinations of Tetrads During Metaphase I o Kinetochore microtubules are attached to the kinetochores of only outer chromatids while kinetochores of inner chromatids are not linked to them o Tetrad consists of 2 homologous chromosomes (one maternal and one paternal) o Random orientation of tetrads on the metaphase plate is responsible for independent assortment of chromosomes Crossing over and independent assortment of chromosomes lead to genetic variation which is why we don’t look similar to our parents o Independent assortment of chromosomes ONLY occur in metaphase 1 o A human cell has 23 different tetrads; therefore, there are several million ways that the maternal and parental chromosomes align Anaphase I o Pairs of homologous chromosomes separate because synaptonemal complex is destroyed Synaptonemal complex is destroyed allowing homologous chromosomes to come apart and cohesins are still present still consists of nonidentical sister chromatids o Each chromosome consists of 2 nonidentical sister chromatids held together by cohesin They are nonidentical because of crossing over that occurred in prophase I o Kinetochore microtubules become shorter, while polar microtubules become longer o In contrast to anaphase in mitosis cohesins come apart Meiosis I vs. Mitosis o Meiosis I Metaphase I Chiasmata hold homologues together Kinetochores of sister chromatids fuse and function as one Microtubules can attach to only one side of each centromere o Mitosis Metaphase Homologous do not pair; kinetochores of sister chromatids remain separate; microtubules attach to both kinetochores on opposite sides of the centromere o Meiosis I Anaphase I Microtubules pull the homologous chromosomes apart, but sister chromatids are held together o Mitosis Anaphase Microtubules pull sister chromatids apart Telophase I and Cytokinesis o Mitotic spindle disassembles o Nuclear envelope reforms around each set of chromosomes o Chromosomes uncoil because condensins become destroyed o Each chromosome consists of sister chromatids o Contractile ring pinches the cell in half o Only centrosomes become duplicated for Interphase (Meiosis 2) Prophase II o Begins after interphase (without chromosome replication) o Nuclear envelope breaks apart and mitotic spindle forms o Each chromosomes consists of 2 nonidentical sister chromatids Metaphase II o Brings chromosomes to the middle of the cell o Kinetochore microtubules are attached to kinetochores of all chromatids o Nonidentical sister chromatids Anaphase II: Sister Chromatids Say Goodbye o Cohesins are destroyed allowing sister chromatids to come apart and are called daughter chromosomes o Condensins are still present o Kinetochore microtubules become shorter o Polar microtubules become longer Telophase II and Cytokinesis: Daughter Cells Produced, but they are Not Twins… o Nuclear envelope reforms around 4 sets of daughter chromosomes o Chromosomes decondense o Cytokinesis follows o Mitotic spindle disassembles o Four haploid daughter cells are produced Each daughter cells is genetically distinct from the others and from the parent cell Variety Produced By Independent Assortment (and Think What Crossing Over can Do…) o The number of potential gametes can be predicted using 2 , where n is the haploid number of chromosomes o This formula only takes into consideration with crossing over o 4 reasons why we don’t look identical to our parents Crossing over Independent assortment Mutations Permanent changes in the DNA Random fertilization of gametes Chapter 9: Cell Communication Cell “Talk” o Another name for a signaling molecule is a ligand Ligand can be a protein, peptide, amino acid, steroid hormone, fatty acid derivative, or dissolved gas o Signaling cell sends the signal while the target cell receives the signal The target has receptors which receives the signal Without receptors the target cell can’t receive the receptor o Membrane or cell surface receptor is found in the plasma membrane Hydrophilic ligand can’t move through hydrophobic lipid bilayer Can be a protein, peptide, or polar amino acid o Intracellular receptor is found in the cell Use hydrophobic ligand can pass through plasma membrane Use simple diffusion to move across the plasma membrane and bind to the receptors inside the cell Can be steroid hormone, fatty acid derivative, or dissolved gas How Do Cells Know What’s Going on Around Them? o Signal transduction pathway converts the information in the signal into a cellular response Different Types of Signaling o Direct contact (contactdependent) When molecule on the plasma membrane of one cell contacts the receptor molecule on an adjacent cell Signaling molecule is membrane bound and is inserted in the membrane Both molecules are membranebound signal Gap junctions are also known as communicating junctions and form between plasma membranes of animal cells They involve the formation of gap or channels That gap is made up of proteins called connexins Important in early development Can be iron, amino acid, or sugar ligand o Paracrine signaling “para” means near The signaling cell is called secretory cell Ligands released in the extracellular fluid Signaling cell releases shortlived ligands that affect nearby target cells Growth factors are short lived ligands (they are proteins that stimulate cell division and cell growth) Target cells must be nearby Involved in wound healing o Endocrine signaling Signaling cell releases longlived ligands (hormones) that travel through circulatory system to induce changes in several distant target cells Target cells are far away from the signaling cell Signaling cell is called endocrine cell Both animals and plants use this mechanism extensively KEY WORDS: endocrine cells, longlived ligands, circulatory system (blood), and distant target cells Ex. Beta cells of pancreas (gland) release insulin (hormone) and insulin becomes released into the blood and it becomes delivered to several distant target cells such as skeletal muscles, liver cells, and fat cells It tells these cells to convert glucose into glycogen Only cells that have insulin receptors can respond with insulin o Synaptic signaling Nerve cell releases shortlived ligands (neurotransmitters), into the gap (synapse), which forms between nerve and target cells Target cell can be another neuron, muscle, gland, or endothelial cell Endothelial cells line blood vessels such as capillaries, arteries, and veins KEY WORDS: neuron, neurotransmitter (chemical signals and majority of them are released by nerve cells of nervous system), and synapse o Autocrine signaling Cell sends signals to itself T cells of immune system o Detects harmful invaders o Produces ligands (growth factors) bind on the receptors on the actual T cell o T cell responds to its own signals which tells T cells to divide which increases the magnitude of the response o All of them begin with ligand binding to the receptor How Do Intracellular Receptors Function? o Use hydrophobic ligands (steroid hormones) o Found in the cell o Uses simple diffusion o Steroid receptor is a nuclear receptor Because it causes changes in the nucleus of the cell Specifically in gene expression And in eukaryotes transcription (DNA to RNA) is in the nucleus Turns gene transcription on or off Nitric Oxide Signaling o Guanylyl cyclase (NO receptor) intracellular receptor Binds to nitric oxide gas o Begins with nerve cell in the synaptic gap o Arteries and veins have smooth muscle on the outside that make them wider dilating or constricting them o Nitric oxide is a gas and diffuses out and enters several smooth muscle cells When smooth muscle relax, blood vessels dilate and this leads to an increase of blood flow Viagra o Used to treat erectile dysfunction in men o When men cannot get an erection erection occurs when smooth muscle cells of penal arteries relax allowing an increased blood flow into the penis Membrane (CellSurface) Receptors o Chemicallygated ion channels (ligandgated ion channels) o Enzymatic receptors o G proteincoupled receptors (GPCRs) ChemicalGated Ion Channels (LigandGated Ion Channels) o Open to let specific ions such as Na , K, Ca, or Cl to pass through the membrane in response to the binding of a ligand (neurotransmitter) ligand is a neurotransmitter that is a shortlived ligand o Acetylcholine receptor is chemically gated ion channel found in the plasma membrane of our skeletal muscle It acts as sodium ion channel which becomes open when neurotransmitter (acetylcholine) binds to it The rush of sodium ions into skeletal muscle cells causes them to contract Enzymatic (EnzymeLinked) Receptors o Have enzymatic activity Almost all are protein kinases, which phosphorylate themselves and/or other proteins o Act as enzymes or they interact with proteins which are enzymes o Enzymatically active if the ligand interacts with it Receptor Tyrosine Kinases (RTKs) o Influence cell cycle, cell migration, cell metabolism, and cell proliferation o Each RTK is an alpha helix that passes through the plasma membrane Are made up of many tyrosine amino acids o Dimerization means to come together which makes kinases active o Steps: When ligand binds to RTKs, 2 RTKs come together to form a dimer (dimerization) Dimerization activates kinases Kinases then phosphorylates tyrosines of its dimer partner by transferring phosphate groups from ATPs to tyrosines (autophosphorylation) Phosphorylated tyrosine kinases interact with other proteins or they phosphorylate other proteins relaying the initial signal to the cell’s interior Insulin Receptor o Belongs to RTKs o Is activated by insulin, which lowers blood glucose Lowers blood sugar levels by converting glucose into glycogen o Insulin receptors are enzyme coupled receptors o These receptors can be found in the skeletal muscles and liver cells which are RTKs Kinases vs. Phosphatases Big Players in Membrane Receptor Signaling o Phosphatases – enzymes that dephosphorylate phosphorylated proteins o Protein kinases phosphorylates proteins making them active or inactive o There are tyrosine kinases (it phosphorylates tyrosine amino acid ONLY) o Kinases are very specific o Protein phosphatases that dephosphorylate phosphorylated proteins remove phosphate groups from phosphorylated proteins Like kinases are divided into 2 groups 2 tyrosine phosphatases Remove threonine and serine Can make proteins active or inactive by dephosphorylating proteins o Proteins that are activated by phosphorylation become inactive by dephosphorization (vice versa can work too) Kinase Cascades – Making a Signal “Bigger” o Series of protein kinases that phosphorylate each other in succession o Signal amplification to make a signal bigger MAP (mitogenactivated protein) kinases amplify the signal because a few signal molecules can elicit a large cell response The RasMAP Kinase Pathway o Ras – a protein that stimulates cell division Links RTKs to MAP kinase cascade A G protein that stimulates cellular division Active when G3P is attached to it and inactive when GDP is attached to it G – Protein Coupled Receptors (GPCRs) o The most common receptors in our plasma membrane o It consists of 67 alpha helices o It is coupled with G protein o G protein consists of 3 subunits such as alpha, beta, and gamma o It exists in 2 forms (active or inactive) G protein is active when its alpha helix subunit is bound to GTP and inactive when it is bound to GDP G protein activates an effector protein (usually an enzyme) o G protein coupled receptors start with ligand binding to receptor It can be a hormone or a neurotransmitter It allows it to bind to G protein o G protein can only bind to alpha subunit o When G protein is active beta gamma complex dissociates from GTP bound alpha subunit Each of them can affect a different effector protein Beta gamma complex can affect a different effector protein as well o GTP bound subunit hydrolyzes GTP to GDP and inorganic phosphate o GDP bound subunit reassociates with beta gamma complex making G protein inactive When Effector Protein, Adenylyl Cyclase is activated nd o Adenylyl cyclase produces cyclic AMP (cAMP) = 2 messenger Adenylyl cyclase is an enzyme It becomes active when GTP bound alpha subunit of G protein binds to it It catalyzes ATP to cAMP (adenosine monophosphate) Second messenger signaling molecule that forms inside the cell Ligand is an example of the first or primary messenger and it is a signaling molecule that forms outside of the cell o cAMP binds to and activates that enzyme protein kinase A (PKA) protein kinase A (PKA) phosphorylates particular proteins for different cellular responses PKA phosphorylates specific proteins cAMP Effects o Adrenaline G proteincoupled receptor G protein adenylyl cyclase cAMP PKA (1) response protein 1 increase in heart rate (2) response protein 2 breakdown of glycogen to glucose in skeletal muscles (3) response protein 3 breakdown of fats to fatty acids in fat cells o A single ligand (adrenaline) can lead to different effects in different cells because different response proteins are phosphorylated in different cells o Heart, skeletal muscles, and fat cells (adrenaline affects these) o Adrenaline is a hormone that is also called epinephrine It is produced by adrenal glands in response to stress It affects different proteins in different parts of the body o The earlier you target the signaling pathway the more side effects affect you will get, however, the further you target the signaling pathway the more specific the drug will be When Effector Protein, Phospholipase C is activated o Phospholipase C cleaves phosphatidylinositol – 4,5,biphosphate (PIP ) to2 inositol1,3,5triphosphate (IP3) and diacylglycerol (DAG) Both act as 2 messengers o IP t3 vels to the endoplasmic reticulum where it binds to the calcium ion channel (found in the membrane of SER) o IP opens calcium channel and releases calcium (2 messenger) 3 Channel then opens allowing calcium ions to go from the lumen to the cytoplasm Calcium ions are higher in the ER than outside (down their concentration gradient and use facilitated diffusion) Bind to calcium ion binding proteins can be calmodulin or PKC (protein kinase C) Phospholipase C Effects o Know acetylcholine is a neurotransmitter Affects pancreatic and smooth muscle cells differently Pancreatic amylase breaks down polysaccharides Causes smooth muscle to contract This happens due to the different response proteins since pancreas and smooth muscle cells have different response proteins Different Ligands…Same Effect o Different receptors can produce the same 2 messengers o Hormones glucagon and epinephrine can both stimulate liver cells to breakdown glycogen to glucose Both act by same signal transduction pathway Associated with endocrine signaling Increasing the concentration of glucose in our blood Liver cells have different receptors they have epinephrine specific g protein receptors and glucagon receptor and both increase glucose in our blood o Cross talk is when 2 or more signaling pathways cross each other
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