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Lecture 1 - Intro to Cell Biology

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Biochemistry 2280A
Sashko Damjanovski

LECTURE 1: INTRODUCTION TO CELL BIOLOGY What is Cell Biology? • Cell biology is an academic discipline that studies cells, the basic structural, functional and biological unit of all known organisms • Cell biologists look at all aspects of the cell: o Cell structure o Cell organelles and membrane trafficking o Cell cycle, division and death o Cell movement o Cell signaling o Cell communication Why Study Cells? • • Part of the core in biology • Storehouse for thousands of • Lead to Nobel Prize • Fundamental unit of life genes • Determine what is “normal” • Many unanswered questions so we can fix the “abnormal” 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 How do we Study Cells? • Hypothesis-driven experiments • First, you’ll need the tools and methods to isolate and maintain cells in vitro (outside the cell, in an artificial system), to know how to view cells and what to look for, how to separate cell organelles and finally, how to identify and study how proteins drive a cell biological process • Once you have the tools, we can start to ask, and more importantly begin to answer biological questions pertaining to our approximately 75 trillion cells Cell Culture • Cell culture is the technique used to grow cells or 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) • Cell-cell separation can be done mechanically or with an enzyme called trypsin o The enzyme trypsin can be used in an enzymatic method to break protein-protein interactions found on the outer layer of cells that hold cells together – “chews apart” proteins found outside cells that help cells stick together o EDTA(divalent cation chelator that depletes the medium of free Ca ) can also be added o Metal chelating agents act like a big sponge that sucks up metals – metals function as cofactors for certain proteins to make them more stable • Cells are supplied with proper nutrients (amino acids, minerals, vitamins, salts, glucose, etc.), serum (insulin, growth factors) and grown usually at 37 C in 2 CO incubator (in an attempt to mimic conditions found in the body in the incubator) • Cells are supplied with a media which is a synthetic mixture that provides basic building blocks for cells and also helps maintain cellular processes • They are also supplied with a serum, which are blood-derived products that contains insulin (helps cells respond to take up glucose) and growth factors (helps cells stay alive through survival cues and helps cells replicate/divide/proliferate) • Carbon dioxide is profused into the incubator – when cells are cultured, they are exposed to atmospheric oxygen which is much higher than what they are used to o Carbon dioxide is increased in the incubator to mimic gas concentrations found in the body • Cells can grow as adherent cell cultures or suspension cell cultures o Adherent cell cultures – grow as a monolayer attached to the bottom of cell culture dish o Suspension cell cultures – free floating in the culture medium • Primary cell culture refers to cells taken directly from an organism. These cells usually divide a limited number of times (~50 generations, Hayflick limit). Also undergo contact inhibition if cell density is high. o Contact inhibition – natural process of arresting cell growth when two or more cells come into contact • Cell line refers to cells, which are transformed and are able to grow indefinitely. Also known as immortal cells. Less likely to exhibit contact inhibition o These cells are transformed, which means that they do not have normal regulatory processes and check points to stop cells from growing, thus they grow indefinitely o Cell lines are frequently derived from a tumour • The first human cell line called HeLa was established in 1952 by George Gey (Johns Hopkins University, Baltimore) from cervical carcinoma biopsy of Henrietta Lacks o HeLa cells had all the hallmark features of immortal cells and were instrumental in designing vaccines o Could grow indefinitely o Researchers could use these cells to grow quickly in labs without much effort/work Birth, Lineage and Death of Cells • All cells derive from stem cells • Stem cells can divide symmetrically, giving rise to two stems cells, and these divide to produce two stem cells each, and so on, producing more “carbon copies” of themselves • The fate of one of these “daughter cells” can vary, however, and this is known as asymmetric cell division o They can be committed, as stem cells, to making more copies of themselves; stem cells have a much higher ability to self-renew and maintain themselves (self-renewal)  Self-renewal leads to a cell lineage o They can differentiate and give rise to make differentiated cells with a defined function that contributes to tissue homeostasis or maintenance (differentiation)  Change of morphological, biological and physiological processes, and takes on a new function a) The two daughter cells resulting from symmetric division are essentially identical to
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