INTRO TO CELL BIOLOGY
Discovery of cells
1. mid-1600s pioneering scientists used handmade microscopes
2. Robert Hooke discovery of cells
examination of a piece of cork show a porous structure = cells
empty cell walls of dead plant tissue
3. Anton van Leeuwenhoek examine pond water & described microscopic "animalcules"
first describe various forms of bacteria
4. 1838, Matthias Schleiden, a German lawyer turned botanist conclude plants were made of cells & plant embryo arose from a single cell
5. 1839, Theodor Schwann, German zoologist conclude cells of plants & animals are similar structures
propose 2 tenets of cell theory:
- all org are composed of one or more cells
- cell is structural unit of life
6. 1855, Rudolf Virchow, German pathologist propose third tenet:
- cells can arise only by division from a pre-existing cell
7. 1951, George Gey conduct first culture of human cells
cells were from a malignant tumor "HeLa cells" donor Henrietta Lacks
cells grown in vitro (in culture, outside body) are an essential tool for biomed scientists
Basic properties of cells
1. highly complexed & organized
2. possess genetic program & the means to use it
3. capable of reproducing more
4. acquire & utilize energy
5. perform a variety of chemical reactions
6. engage in numerous mechanical act
7. able to respond to stimuli
8. capable of self regulation
2 different classes of cells
1. Prokaryotes - bacteria
pro = b4, karyon = nucleus
genetic material in nucleoid
only have a single circular chromosomes with naked DNA
devoid of internal membranous structures
non-sexual org
some undergo conjugation - pass DNA btwn cells
posses flagellum
Types:
1. Archaea/Archaebacteria
extremophiles: live in extreme inhospitable environments
methanogens: convert CO2 & H2 into CH4 gas
halophiles: high salt environments Dead sea/Great Salt Lake
acidophiles
thermophiles: high temp
2. all classified in domain Bacteria/Eubacteria
includes smallest living cells = mycoplasma lacking cell wall
2. Eukaryotes - protists, fungi, plants, animals
evolve from prokaryotes, evidence: identical genetic language, common set of metabolic pathways, common structural features
eu = true
posses nucleus membrane = nuclear envelope
contain more DNA & chromosomes contain linear molecule of DNA with associated proteins
contain many membranous fx structures
mitochondria, ER, Golgi complex, vesicles, tubules & filaments
intracytoplasmic communication is important
divide by mitosis & meiosis - segregation & duplication of chromosomes
- daughter cells receive equivalent array of genetic material
posses variety of locomotor mechanisms
sperm cells posses flagella but more complex& generate movement differently
Both possess ribosomes (non-membranous particles) & cell wall with different chemical composition
Protists
most complex eukaryotes
unicell
all machinery required for complex act is complete in a single cell: sensing environment, trap food, expel excess fluid, evade predators
complex unicell represent 1 evolutionary pathway
different activities conducted by different types of specialized cells
multicell + specialized eukaryotes
slime mold amoeba, unspecialized cell can aggregate & form a multicell
cells differentiate & become specialized
when fertilized egg of a vertebrate progresses thro its course of embryonic development there hundreds of possible pathways of differentiation
differentiation depends on signals received from surrounding
stem cells, undifferentiated can be manipulated for cell replacement
cells of multicell composed similar organelles
a fat cell generates heat from chemical energy stored in fat = numerous mitochondria
a plasma cell produces Ab = more ER for protein synthesis, less mitochondria
Model org
1. Saccharomyces cerevisiae - budding yeast
2. Arabidopsis thaliana - mustard plant
3. Caenorhabditis elegans - nematode
4. Drosophila melanogaster - fruit fly
5. Mus musculus - mouse - major importance for culture specialized cells
Cell & cell components
1. cell & organelle size in um/nm
2. why cells are small?
cell can only produce limited no of mRNA
greater cytoplasmic volume, longer time to synthesize mssg
if cell grow beyond a certain size, surface not sufficient for absorb substances to support metabolic activities
larger cell, greater distance from surface to interior, longer time to diffuse in & out substances (metabolically active cell)
Viruses
1. end of 19 century, presence of bacteria infect plants and animals
2. studies of tobacco mosaic ds & foot-and-mouth ds (FMD) suggested another type of infectious agents
3. Characteristics:
smaller than bacteria
obligatory intracellular parasites
virion = a simple macromolecular package/infectious virus particle outside the cell
contains small amount of genetic material surrounded by capsid = a protein capsule
many viruses have capsids organized into a polyhedron
Adenovirus is icosahedral (20 sides)
many viruses have an outer envelope covering capsid
bacteriophages = bacterial viruses (most complex viruses)
most viruses have a narrow host range
not an organism and not alive
4. Replication mechanisms (enter a cell & incorporate its genetic material into the cell):
Redirection of host cell machinery to assemble new virions & disruption of normal synthetic activities followed by cell lysis & release of virions
Insertion of DNA into host DNA (provirus), cells are not lysed but new virions bud off, in cases of oncogenic viruses the cells divide uncontrollably
C1 ESSENTIAL CELL BIOLOGY
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