Study of Cell Biology
Swapan K. Ghosh, Ph.D
lsghosh@isugw.indstate.edu
812-237-2416 (O)
Office Hour: 9-6 PM
What is cell biology
• Reductionist’s approach: cut a living entity
down to the smallest possible unit that is
still alive and study that unit’s property
• Cells are that smallest unit of all living
organisms
• Further breaking leads to nonliving
elements
• Life originates with the formation of cells
Introduction to Cell Biology
•Historical perspective about the origin of life: Bada
JL, Lazcano A., Origin of life. Some like it hot, but not the first
biomolecules Science 2002 Jun 14;296(5575):1982-3.
•Living and nonliving; classification of living system;
Evolution.
•Unit of life-: The cell theory, Basic properties of cell;
prokaryotes and eukaryotes.
•Morphologic and structural features of cells; Relationship
of pro- and eukaryotes in evolutionary terms.
•Viruses-their origin, mode of propagation, prions.
what is the difference between living and
non-living matter?
All life contains products made of the element
carbon. Elemental composition includes: 60%
H, 25% O, 12% C, 5% N. some P, S, and traces
of Na, K, Ca, Fe, Cl, Mg, Mn etc. Do nonliving
substances grow? Of course, crystals grow, but
not in the same sense as living matter. Cells are
the units of living systems but their constituents
are all non-living.
First attempt to study biology is taxonomical
classification into kingdoms:
Monerans: bacterium or prokaryotes
(origin: 3.5 billion years ago).
Protistans: single-celled eukaryotes,
but larger than bacterium
Fungi: Multi-cellular eukaryotes
Plants: Multi-cellular photosynthetic eukaryotes
Animals: Multi-cellular eukaryotes.
Charles Darwin’s Theory of Natural Selection:
• Random variability in a population of individuals varying in
forms, function and behavior (DIVERSITY).
• Some forms are heritable traits (UNITY) helping to adapt and
survive, the basis of unity in diversity.
• Natural selection means survival of the fittest; best adapted
retaining TRAITS that permit survival and reproductive
success.
• Populations constantly evolve as some traits are acquired or
lost (MUTATION) in response environmental changes that
support propagation
Discovery of cells
• Robert Hooke in London about 400 years
ago (1665) invented microscope and
discovered cells in corks. He coined the
word cells (Latin for “little rooms”).
• Anton Von Leewenhook in Belgium refined
further and saw living cells in pond water
for the first time.
The Cell Theory of Schwann,
Schleiden and Virchow
1. All living organisms are composed
of cells (one or more).
2. The cells constitute the living unit
of all organisms.
3. All cells arise from pre-existing
cells (now we say, mitosis, meiosis).
Unity in Diversity
All cells :
share fundamental properties conserved through
evolution.
DNA is the genetic material (surrounded by
membranes in eukaryotes but not in prokaryotes)
Generate energy and utilize nonliving matters from
the environment
Proliferate, divide, and show motility
Unicellular vs. Multicellular organisms
Human body has over 200 different cells doing
specialized functions: epithelial cells, cells of the
connective tissues, blood, muscle, and nervous
system. All produced as a result of differentiation.
Plants have fewer cells: Ground tissue containing
Parenchyma, collenchyma and scherechumal cells,
dermal cells and Vascular cells.
Protozoans and monerans are unicellular
Fundamentally Different Cell
Classes
Prokaryotes (before nucleus): two types: Archeaons &
Eubacteria 3.5 billion years. Largest bacteria are cyano
bacteria and smallest is mycoplasma
Eukaryotes (true nucleus): From Eukaryotes (1.8 billion
years) to multicellularity. Ex: plants, animals, Fungus
Of course RBC in eukaryotic system does not have a
nucleus or organelles either.
Types of Prokayotic cells: Two
Domains
• A. Domain archea (oldest), ex: Methanogens,
Laophiles, Acidophiles and Thermophiles
• B. Domain Bacteria: Smallest known cellsmycoplasma; eubacteria (true bacteria) and
Cynobacteria (blue-green algae).
• Both are single-celled (1-2 m) with a single
chromosomecontaining DNA and polyamines.
They reproduce asexually by binary fission.
Types of Eukaryotes
• A. Unicellular Eukaryotes (larger than
prokarypotes (about 10X)
• B. Multicellular Eukaryotes
– Characteristics: differentiation into specialized cells
different from mother cells
– Numbers and arrangements of organelles in relation to
function
– Common features
• Distinct nucleus, organelles, motility, Division
Bacteria versus mitochondria and chloroplasts
1. Similar size as bacteria
2. Reproduction by division into two like bacteria
3. Own DNA that encodes some of their components in
the same manner
4. Divide each time the organelle divides
5. Use their organelle’s inner structure and ribosome to
transcribe and translate
6. Have similar ribosome and rRNA as in bacteria
Both organelles have distinct genetic system
separate from the nuclear genome of the cells
Plant Cell
Animal Cell
Functional Features of Cells
1. Acquire and Utilize Energy (photosynthesis or its
product e.g glucose)
2. Utilize energy for maintenance (metabolism) &
reproduction
3. Reproduce:Binary Fission, Conjugation, Mitosis
meiosis
4. Respond to Stimuli (Positively/Negatively:
Receptor ?)
5. Able to move (locomotion), transport, adhere to
form multicellular units, influence neighbors
6. Self-regulating
Viruses and prions: living or nonliving?
• Viruses are Nonliving pathogens that become live in hosts
(obligate parasite)
• A virion is a virus outside the host cell
• Genetic material in virus: DNA or RNA . Capsid proteins
surround genetic material.
• Infect either by lytic or integratic mechanisms
• Most likely, viruses evolved after the hosts as fragments of
host chromosomes
• Viroids are pathogens having only small naked RNA
• Prions are abnormal chaperone proteins that cause
neurological disorders.
Food for thought
• Cells are the living units of life, but not
their components - true or false?
• We can isolate and study the properties of
cellular components in vitro. They seem to
function as predicted from cells’ behavior.
Why are they not considered living?
Prokaryote or Eukaryote?
Prokaryote or Eukaryote?
Methodologies for study of cell
biology
• Morphology: tools &techniques- microscopyLight, Phase-contrast, fluorescence, video,
confocal, EM: transmission and scanning
• Biochemical: homogenization & centrifugation,
radioisotope tracer techniques, immunoassays,
enzyme assay, SDS-PAGE, Autoradiography etc
• Molecular: DNA, RNA, Plasmids, PCR