Cell Biology Lecture No. 1: Introduction to
Wednesday January 9 , 2013h
• Cell culturing is the in vitro technique used to grow cells or tissues outside the
organism under strictly controlled conditions.
• Cells are first isolated from any tissue by breaking down the cell-cell and cell-matrix
• This can be done in 3 ways:
o Mechanical fragmentation (cutting up the cells)
o Trypsin (a protease enzyme that helps chew apart membrane proteins and
make cells less cohesive)
o EDTA (a divalent cation chelator that depletes the medium of free Ca as
calcium is integral in binding to membrane proteins that make cells more
• Once dissociated, cells need to be maintained at favourable conditions in a specialized
CO 2ncubator that mimics optimal heat and gas conditions (CO and O2needed2 as well
as sufficient nutrients help keep cells alive.
• Cells are supplied with proper nutrients (amino acids, minerals, vitamins, salts, glucose,
etc.) and serum, a blood product devoid (boş, yoksun) of cells which contains insulin to
help take up sugar and growth (mitogenic) factors that help cells to divide.
• The liquid tissue culture media contains a dye known as phenol red, which is
specifically added to indicate the culture’s pH. • Acidic cultures arise when too many cells are present, consuming much resources,
resulting in a production of lactic acid that turns the media yellow. Under alkaline
conditions, the media turns purple.
• Cells can be grown in 2 ways:
o Adherent (yapiskan) cell cultures (require a surface, such as tissue culture
plastic or microcarrier)
o Suspension cell cultures (without being attached to a surface or cultured in
spinner flasks which cause mechanical agitation).
• Usually adherent cell cultures have been coated with something (either an attractive
electric charge or extracellular matrix proteins) which aid cells in adhering (yapismak) to
the plastic surface. Roller bottles can also allow for a suspension cell culture to grow by
Two Major Cell Cultures:
• A primary cell culture refers to cells taken directly from an organism (normal animal
tissues or whole embryos).
• As primary cell cultures grow, they move increasingly towards a confluent model
(tightly-packed population of cells), which initiates contact inhibition (a stop in the
growth of cells).
• When this occurs, the passaging of cells can be performed to enzymatically disrupt cell
adhesiveness and reallocate a portion of the culture to a low-density environment.
• These cells usually divide a limited number of times (about 50 generations) until they
reach what is called the Hayflick limit (when cells undergo senescence (to grow old)).
• In addition to senescence, cells also undergo contact inhibition (where cell-to-cell
contact can stimulate cell cycle arrest, causing cells to stop dividing) if cell density is
high. Senescent cells are related to ageing.
• A cell line refers to cells which are transformed and are able to grow indefinitely. Also
known as immortal cells, these transformed cells, which have lost feedback
mechanisms that regulate growth, are less likely to exhibit contact inhibition.
• The first human cell line called HeLa was established from the cervical carcinoma biopsy
of Henrietta Lacks. This line grew and doubled very quickly.
Morphology of Normal vs. Transformed Fibroblasts: • Normal cells such as fibroblasts (type of cells that synthesizes the extracellular matrix
and collagen) can be transformed by artificially introducing a gene that disrupts normal
• These once normal, elongated, aligned fibroblast cells are now transformed into a cell
line where fibroblasts rounded, hair-like and grow on top of one another.
Birth, Lineage & Death of Cells:
• The origin of all bodily cells can be traced back to stem cells (whether embryonic or
adult). When a stem cell divides it gives rise to two genetically identical cells.
• Each cell can undergo one of two possible fates:
o Asymmetric division (gives rise two types of differentiated cells with a finite
o Self-renewal (gives rise to more undefined, identical stem cells with potentially
• Symmetric division refers to a cell’s maturation that allows it to gain a function that
contributes to the overall function of a tissue.
• *Stem cells contribute no real function (except making differentiated