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Cell Types: Procaryotic and Eucaryotic Cells and Their Morphological Differences, Study notes of Microbiology

An overview of the two main types of cells, procaryotic and eucaryotic, based on their morphology and organization. It covers the similarities and differences in biochemical activities and genetics, cell morphology and organization, and cell division processes. Procaryotic cells, represented by bacteria, lack internal membranous organelles, have smaller ribosomes, and undergo binary fission for cell division. Eucaryotic cells, which make up the majority of cellular life forms, contain membranous organelles, have a true nucleus, and undergo mitosis for cell division.

Typology: Study notes

Pre 2010

Uploaded on 08/18/2009

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bio2230_cell_types 1/21/04
BIOL 2230 REEDER
CELL TYPES BASED ON MORPHOLOGY AND ORGANIZATION
I. Cellular Life
A. Biochemical and Genetic Activities
l. Tremendous similarities in the biochemical activities and genetics of all cellular life forms
a. DNA as the chief heritable genetic material
b. Similar mechanisms of fermentation and aerobic respiration utilized for the formation
and storage of energy as well as photosynthetic processes
c. Almost identical methods of protein synthesis, nucleic acid synthesis, and polysaccharide
synthesis
2. Important morphological variations exist resulting in two structural types of cells composing
the majority of life (viruses as the exception): procaryotic and eucaryotic
B. Cell Morphology and Organization
l. Procaryotic
a. Represented by members of the Kingdoms Eubacteria and Archaebacteria
b. Considered to be the most primitive cellular life forms as well as the oldest (fossilized
cyanobacterium dated 3.8 to 3.5 billion years old).
l) Absence of internal lipid membranous organelles in the cell's cytoplasm such as the
nucleus, mitochondria, chloroplasts, lysosomes, endoplasmic reticulum, etc.
a) Possess ribosomes that are smaller than eucaryotic ribosomes: 70s in prokaryotes,
80s in eukaryotes.
2) Cytoplasmic streaming absent for internal transport due to a lack of microtubules;
simple diffusion related with the cell's small size is sufficient for intercellular
transport
3) Most prokaryotes possess a cell wall external to the cytoplasmic membrane
containing peptidoglycan (polymer of amino acids and sugars), which is not found in
eucaryotic cell walls; some Gram neg. types lack a wall completely (Mycoplasma)
4) Endocytosis can only occur on soluble material, therefore, no phagocytosis; external
digestion with a secretion of enzymes.
5) Lacks a true nucleus: the genetic material is not separated from the cytoplasm by a
distinct two-layered nuclear membrane; instead, the DNA is in the cytoplasm.
a) Also, the DNA is not organized into multiple distinct chromosomes, but exists as
a circular, single, continuous thread attached to the cytoplasmic membrane at a
certain number of sites (nucleoid); haploid
b) The chromosome also lacks the histone proteins in its DNA chromosome
structure
c) Small circular pieces of extrachromosomal DNA, called plasmids, are also found
in the cytoplasm that confer certain auxiliary metabolic capabilities
6) A procaryotic gene is transcribed directly into messenger RNA; requires no
enzymatic removal of "nonsense" intervening sequences (introns) followed by
splicing together to make functional RNA as normally occurs in eucaryotes.
7) Typically of very small size: a cell's size affects its growth rate because of the
relationship between a cell's surface area & volume of its contents
a) Surface-to-volume ratio for a typical bacterium is 20 times greater than that for a
typical human cell: procaryotic cells meet their nutritional needs easily & grow
rapidly
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bio2230_cell_types 1/21/

BIOL 2230 REEDER

CELL TYPES BASED ON MORPHOLOGY AND ORGANIZATION

I. Cellular Life A. Biochemical and Genetic Activities l. Tremendous similarities in the biochemical activities and genetics of all cellular life forms a. DNA as the chief heritable genetic material b. Similar mechanisms of fermentation and aerobic respiration utilized for the formation and storage of energy as well as photosynthetic processes c. Almost identical methods of protein synthesis, nucleic acid synthesis, and polysaccharide synthesis

  1. Important morphological variations exist resulting in two structural types of cells composing the majority of life (viruses as the exception): procaryotic and eucaryotic B. Cell Morphology and Organization l. Procaryotic a. Represented by members of the Kingdoms Eubacteria and Archaebacteria b. Considered to be the most primitive cellular life forms as well as the oldest (fossilized cyanobacterium dated 3.8 to 3.5 billion years old). l) Absence of internal lipid membranous organelles in the cell's cytoplasm such as the nucleus, mitochondria, chloroplasts, lysosomes, endoplasmic reticulum, etc. a) Possess ribosomes that are smaller than eucaryotic ribosomes: 70s in prokaryotes, 80s in eukaryotes.
  1. Cytoplasmic streaming absent for internal transport due to a lack of microtubules; simple diffusion related with the cell's small size is sufficient for intercellular transport
  2. Most prokaryotes possess a cell wall external to the cytoplasmic membrane containing peptidoglycan (polymer of amino acids and sugars), which is not found in eucaryotic cell walls; some Gram neg. types lack a wall completely (Mycoplasma)
  3. Endocytosis can only occur on soluble material, therefore, no phagocytosis; external digestion with a secretion of enzymes.
  4. Lacks a true nucleus: the genetic material is not separated from the cytoplasm by a distinct two-layered nuclear membrane; instead, the DNA is in the cytoplasm. a) Also, the DNA is not organized into multiple distinct chromosomes, but exists as a circular, single, continuous thread attached to the cytoplasmic membrane at a certain number of sites (nucleoid); haploid b) The chromosome also lacks the histone proteins in its DNA chromosome structure c) Small circular pieces of extrachromosomal DNA, called plasmids, are also found in the cytoplasm that confer certain auxiliary metabolic capabilities
  5. A procaryotic gene is transcribed directly into messenger RNA; requires no enzymatic removal of "nonsense" intervening sequences (introns) followed by splicing together to make functional RNA as normally occurs in eucaryotes.
  6. Typically of very small size: a cell's size affects its growth rate because of the relationship between a cell's surface area & volume of its contents a) Surface-to-volume ratio for a typical bacterium is 20 times greater than that for a typical human cell: procaryotic cells meet their nutritional needs easily & grow rapidly

bio2230_cell_types 1/21/

  1. Simplified and rapid rate of cell division a) Chromosome separation is achieved by invagination by the cytoplasmic membrane between the sites of DNA attachment resulting in division into two identical daughter cells: binary fission (asexual); no mitosis. b) Fission can occur in as little as l5 minutes compared with an l8- to 24- hour time of division for eucaryotic cells c) Have several ways of gaining new genetic material (sexual-like resulting in recombination)
  2. Inability to synthesize cholesterol, as well as other sterols in their cell membrane unlike eukaryotes; exception: the wall-less Mycoplasma has sterols in its membranes.
  1. Eucaryotic a. Represented by the majority of cellular life forms: kingdoms Protista, Fungi, Plantae, and Animalia b. Considered the more complex cellular life form l) Contains many distinct membranous organelles within the cytoplasm that endow specific functions to the cell and provide for compartmentalization: mitochondria, chloroplast, lysosome, Golgi apparatus, smooth and rough endoplasmic reticulum, microtubules, etc. besides ribosomes as well 2) Possess a true, distinct nucleus composed of a two-layered membrane enclosing linear strands of DNA and histones organized into distinct chromosomes that are fixed in number per species; usually diploid. (human: 46, cat: 38, fruit fly: 8) a) Cell division involves an elaborate and complex mitotic process consisting of DNA replication, karyokinesis, and cytokinesis resulting in two identical daughter cells to that of the parent cell. b) More complex transcription process in protein synthesis involving enzymatic editing and splicing in the production of functional messenger RNA 3) Phagocytic capability as well as pinocytic ("cell drinking"): endocytosis 4) Sterols in the cell membrane