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 eukaryotesPlants: Multi-cellular photo-

synthetic eukaryotesAnimals: 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

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 

Unicellular vs. Multicellular organisms

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, FungusOf 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 cells- mycoplasma; 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 bacteria2. Reproduction by division into two like bacteria3. Own DNA that encodes some of their components in

the same manner4. Divide each time the organelle divides5. Use their organelle’s inner structure and ribosome to

transcribe and translate6. Have similar ribosome and rRNA as in bacteriaBoth organelles have distinct genetic system

separate from the nuclear genome of the cells

                                  

Plant Cell Animal Cell

Functional Features of Cells1. Acquire and Utilize Energy (photosynthesis or its

product e.g glucose)2. Utilize energy for maintenance (metabolism) &

reproduction3. Reproduce:Binary Fission, Conjugation, Mitosis

meiosis4. Respond to Stimuli (Positively/Negatively:

Receptor ?)5. Able to move (locomotion), transport, adhere to

form multicellular units, influence neighbors6. Self-regulating

Viruses and prions: living or non-living?

• 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- microscopy-Light, 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