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Cell biology
Introductory tutorial
What is a cell?
• The cell is the structural and functional
elementary unit of life, characterized by:
– Self-replication and transmission of hereditary
traits to daughter cells
– Self-regulation and adaptive ability for survival
– Being the result of a long evolutionary process
• http://www.nature.com/scitable/topic/cell-biology13906536
What is cell biology?
• The study of cell structure and functions
• A cell contains all the information needed for its
survival in its genetic material (DNA)
The main types of cells
- Based on the location and form of genetic
material within the cell, there are 2 major
categories of cells:
- Prokaryotes – bacteria and archaea
- Eukaryotes – cells found in most living
organisms, from plants, protozoa to
mammalians
- Different by general cell morphology, genetic
machinery, organelle diversity, and functions
The life of an eukaryotic cell
• A cell takes birth from another cell, by cell division
• Time spent between two cell divisions is called
interphase
• During its adult life, a cell will develop its organelles
to perform specific functions (to become
specialized)
Stem cells
• Some cells remain in undifferentiated state in
the adult organisms – stem cells
• Characteristics of stem cells:
– Undifferentiated
– Multipotent
– Self-renewed
Differentiated cells
• The specialization (differentiation) process of
a cell into adult form is largely influenced by
other cells through signaling cues
• Physiologically, a cell dies through a
programmed process (usually apoptosis)
The eukaryotic cell
The eukaryotic cell
• Organelle – an intracellular element,
characterized by a complex, specific
molecular organization, inducing a distinct
morphology and proper function(s).
• Organelle classification:
– Membrane bounded ( nucleus, endoplasmic
reticulum, Golgi apparatus, lysosome,
peroxisome, mitochondrion)
– Without membrane (ribosome, cytoskeleton,
proteasome, apoptosome)
How large is a cell?
(Cell dimensions)
• The average size of a cell is 20-30 μm
• The largest cell is the oocyte – 200 μm
• Red blood cells have 7-8μm
The human eye can see things as small as 0.1mm
(can you transform that in μm?)
Eukaryotic cell types
• Cell biology provides knowledge about a
MODEL (“all doing” cell), but living organisms
are formed by different types of cells
(differentiated cells)
• The human body contains over 200 types of
cells
Cell study
• The first tool used to study cells was the
bright field light microscope (LM)
• Details about cell organization came from
electron microscopy (EM)
• Deciphering mechanisms of cell functions
came from LM, EM, biochemistry, biophysics
etc.
Differentiated cells
The sum of events by which a cell acquires a
specific form and function is called
differentiation
Each differentiated cell type means changes
in morphology that help perform specific
functions (become specialized)
Transport of oxygen
Mucus clearence
Fighting bacterial infection
How can cells be studied?
• First microscopy was used, but in order to
keep cells morphologically intact and well
preserved, they need special treatment, so
they would no longer be living entities
fossil-collection.com
Even preserved…
Paraffin
embedded
cartilage under
a light
microscope
http://biology.clc.uc.edu/Fankhauser/Labs/Cell_Biology/Cells_Lab/cartilage_chicken_100x_PA021963c.JPG
More details are made visible by staining
Cells unstained
Cells stained
apbrwww5.apsu.edu
Even more details are obtained
through electron microscopy
Nucleus
How else can cells be studied?
• Microscopy offers morphologic details of a cell/
cell type
• We are also interested in obtaining information
about biochemical composition and/or functions
of a cell/cell type
How can cells be studied at
molecular level? (I)
• We can break them apart and separate the
contents
Osmotic shock
N.B. these approaches allow us to correlate with
organelle/cell functions
How can cells be studied at
molecular level? (II)
• We can solubilize cells/organelles to isolate
and/or purify biochemical components :
proteins, fat (lipids), sugars (oligo-, mono
saccharides)
• Specialization of a cell can be highlighted not
only by morphologic characteristics, but also
by identification of specific proteins / lipids
How can cells be studied at
molecular level? (III)
• We can also study living cells, using cell
cultures – cells are kept in a Petri
dish/culture flask in an incubator
How can living cells can be studied?
Conclusions
• The cell is the elementary structural and
functional unit of life
• An eukaryotic cell is surrounded by a
membrane and contains a nucleus and
cytoplasm with organelles
• We can study cells – living or dead (fixed) –
through microscopy and biochemical
methods