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Lecture 1

Biology 2290F/G Lecture 1: Introduction to Cell Biology

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Western University
Biology 2290F/G
Ray Zabulionis

Lecture 1: Introduction to Cell Biology Why study cells? - Part of the core in Biology - Fundamental unit of life - Many unanswered questions - Storehouse for thousands of genes - Determine what is “normal” so we can fix the “abnormal” - Lead to Nobel Prize What is a Cell? Ultimate goal: to understand how macromolecular systems and organelles work and cooperate to enable cells to function autonomously and in tissues Cell Culture - Cell culture is the technique used to grow cells/tissues outside the organism under strictly controlled conditions - Cells are isolated from any tissue by breaking down the cell-cell and cell-matrix interactions (use mechanical fragmentation, trypsin, EDTA) - Cells are supplied with proper nutrients (amino acids, minerals, vitamins, salts, glucose etc.), serum (insulin, growth factors) and grown usually at 37 degrees in a CO 2ncubator - Cells can grow as adherent cell cultures or suspension cell cultures - Cell culture: taking cells out of our bodies, try to get it growing in another environment - We then need to break all the cells apart from their glue-like proteins using mechanical fragmentation, trypsin (enzyme), EDTA - EDTA binds calcium, magnesium, which are important in helping stick proteins together o Taking away the calcium causes the proteins to unfold, which will allow the cells to be separated - Need to add a serum (taken from fetal bovine) which stimulates cells to divide and replicate o Also contains insulin, which stimulates glucose transport from outside of cell to inside - CO i2 used to help with pH control - Adherent cell cultures: adhere to a flat surface (e.g. fibroblast, epithelial cells) o Grown in petri dish or flash - Suspension cell cultures: grow in suspension (e.g. white/red blood cells) o Grown in spinner flasks, rolling bottles Cell culture continued - Primary cell culture refers to cells taken directly from an organism o These cells usually divide a limited number of times (~50 generations, Hayflick limit) o Also undergo contact inhibition if cell density is high - Cell line refers to cells which are transformed and are able to grow indefinitely o Also known as immortal cells o Less likely to exhibit contact inhibition - The first human cell line called HeLa was established in 195 by George Gey from cervical carcinoma biopsy of Henrietta Lacks - 2 types of cell cultures - Primary cell culture: plate cells on a dish, where they adhere o Start to spread out and divide, until the cells are all tightly packed against each other - callconfluent monolayer , which causes contact inhibition o Cells will divide until they start touching up against each other - Can add trypsin to the petri dish, which will cleave all the sticky proteins, causing the cells to detach - We can dilute the cells and move them to a different petri dish - called passaging of cells o This is limited by the Hayflick limit o By culturing cells repeatedly, they will eventually stop dividing (Hayflick limit) - about 50 passages for this to happen - So we can do cell cultures for a month of two, but then division will no longer occur - Cell line: cells are transformed (altered genetically, which overrides the cell cycle apparatus), so are able to grow indefinitely o Passage can occur as many times as preferred without stopping - known as "immortal cells" Morphology of normal vs. transformed fibroblasts - Normal cells are flattened, elongated, aligned, parallel o When they get closer in density, they stop dividing - contact inhibition - Transformed cells grow fast, in a disorganized manner o They also lose contact inhibition, making it a cancerous cell because it can't stop dividing Symmetric and Asymmetric Cell Division - Symmetric/asymmetric cell division occurs during development and in adult cells - Where do cells come from? - Sperm and gamete form a zygote, which divide over and over again - Symmetric cell division seen in simple eukaryotes o Mother cells divide into 2 daughter cells that are both very similar to their mom o Cells from symmetric cell division produce cells that have completely different functions from their mother cells o Asymmetric cell divisi
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