Credit to STEPHEN ESPOSITO 2011 BSC2010 Stroupe UNIT 4 LECTURE 20 Big picture cell growth and development details cell cycle DNA replication protein synthesis biology is hierarchical molecules matter I development development A cytoplasmic determinants contents in the cytoplasm of the egg that plays a role in B cell differentiation cells specialize as they grow C morphogenesis process of cells taking their specialized shape II early embryonic development in sea urchin A fertilization egg and sperm coming together 1 Acrosomal reaction to turn 2 haploid cells into one diploid cell Sperm head releases enzyme that degrades the eggs jelly layer and vitelline coat This allows the acrosomal process to present its proteins to the eggs receptors they interact through 4 protein protein interactions acrosome the vesicle that holds the enzymes FAST BLOCK FOR POLYSPERMY 2 To avoid polyspermy the fast block happens in sea urchins Once the plasma membranes fuse Na from the sperm cause the egg to depolarize and no more sperm can bind 3 Cortical reaction triggered by the fusion of cortical granules with the plasma membrane Enzymes are secreted that change the vitelline layer into a hard fertilization Credit to STEPHEN ESPOSITO 2011 BSC2010 Stroupe envelope The remaining receptors are cleaved by prokases protein enzymes that break polypeptide bonds This process is Ca 2 dependent 4 Activation of the egg The rate of respiration and protein synthesis increase Ca 2 is alone sufficient to trigger this rxn 5 In mammals SLOW BLOCK a sperm travels through a layer of follicle cells nutrient source to get to the zona pellicuda extracellular matrix of the egg Travels through the zona pellicuda to reach the receptors This binding of sperm to receptor triggers the cortical reaction This in turn triggers the SLOW BLOCK to polyspermy by changes to the zona pellicuda b the nuclear envelope dissolves and the haploid nuclei combines to make the diploid cell They line up to divide but don t make a nuclear envelope until they divide B Cleavage 1 after fertilization rapid cell division occurs a S phase DNA is synthesized b M phase mitosis where the cells split c Little no Gap Phase G1 G2 d Little protein synthesis e New cells not growing just more of them called blastomeres f Blastula ring of cells around central blastocoel center hollow part g early head tail anterior posterior top bottom dorsal central form decisions are made by the placement of the yolk stored nutrients yolk Credit to STEPHEN ESPOSITO 2011 BSC2010 Stroupe side with yolk vegetal pole side without yolk animal pole all determined by the first 2 divisions that dictate how the cytoplasm divides where the maternal proteins and RNA s go determines how the cells develop h Cleavage continues until the ratio of NUCLEUS CYTOPLASM is sufficiently large small cells are supported by the division of maternal material Cell division slows tissues are ultimately formed by cells taking special positions These are III Morphogenesis A Gastrulation large cellular movements 2 gastrula embryo at the point of gastrulation 3 hollow blastula collapses to give layers of cells in mammals called germ layers 4 embryo germ layers in mammals a ectoderm outer b endoderm inner c mesoderm line tubes and glands 5 cell motility motor proteins changes the cells shape while it grows cell adhesion adhesion molecules on the cells surface Credit to STEPHEN ESPOSITO 2011 BSC2010 Stroupe 6 in mammals blastocyte is a hollow sphere of 100 cells The inner cell mass sits at one end of those cells embryo a tropoblast outer epithelium of the blastocyte Initiates implantation by secreting enzymes that BREAK DOWN endometrium lining of the uterus So blastocyte can then invade and hook into the circulatory system b after implantation gastrulation begins Mesoderm and endoderm form Cells pull inward to make the three layers Placenta embryo hooks into the uterus is made from the tropoblast some mesodermal cells and endometrial tissue B ORGANOGENESIS 1 Three germ layers develop into organs 2 Localized changes in cell shape occur to form the differentiated tissues 3 Dorsal mesoderm Notochord once the cells are segregated local signals dictate that nearby cells will join them to become the neural plate IV MORPHOGENESIS MECHANISMS A Changes in cell shape position and adhesion 1 cytoskeletal proteins drive changes a microtubules cylindrical protein assemblies help to form wedge like shapes that facilitate invaginations that drive changes like the neural tube formation Credit to STEPHEN ESPOSITO 2011 BSC2010 Stroupe b actin and activators helps the cell to crawl depolymerizes and repolymerizes at different ends 0 0 0 00000 0 0 0 0 0 picture in notes 2 cell adhesion molecules CAM glycoproteins on cell surface bind transmembrane proteins on nearby cells to facilitate communication B Apoptosis programmed cell death V Development fate of a cell depends on the cells history A embryonic cells start to differentiate early in cleavage 1 because of uneven distribution of cytoplasm in the egg a mRNA s small mRNA s b proteins cytoskeletal proteins transcription factors enzymes B Once a cell is specialized cell cell interactions influence the fate of surrounding cells that maintain specialization Credit to STEPHEN ESPOSITO 2011 BSC2010 Stroupe LECTURE 21 Cells grow and divide That s life I CELL DIVISION RESULTS IN TWO DAUGHTER CELLS A Genetic information is stored in the DNA sequence of the genome DNA is packaged as a chromosome 1 Human somatic cells each have 46 chromosomes 23 from each parent 2 Gametes have 23 chromosomes 3 Chromosomes are made from chromatin DNA and histone proteins B Distribution of chromosomes during cell division 1 DNA Chromosomes One linear DNA molecule is in each chromosome 2 DNA replicates then recondenses Then identical chromatids pair with their sister chromatid a sister chromatids attached to eachother by COHESIN protein b centromere place where sister chromatids are most closely attached c arms are where the chromatids aren t attached 3 MITOSIS the division of the nucleus 4 CYTOKINESIS cytoplasm splits and nuclei go to daughter cells II CELL CYCLE what happens during the life of a cell A Interphase G1 first gap S DNA synthesis replication G2 second gap Credit to STEPHEN ESPOSITO 2011 BSC2010 Stroupe Mitotic Phase prophase prometaphase metaphase anaphase telophase cytokinesis REMEMBER BY MITOTIC PHASE P Prometa MAT cyto III MITOTIC SPINDLE the part of the cell that physically pulls apart the
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