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Cells and Their
Housekeeping
Functions – Prokaryotes
and Eukaryotes
Shu-Ping Lin, Ph.D.
Institute of Biomedical Engineering
E-mail: [email protected]
Website: http://web.nchu.edu.tw/pweb/users/splin/
Size of Organisms
Basic unit of life in all organisms  Cells
 Too small to be seen with naked eyes
1 m = 100 cm = 1,000mm = 1,000,000 µ m = 1,000,000,000nm
1mm = 1,000 µ m = 1,000,000 nm
1 µ m = 1,000nm
Diagrams: http://www.cellsalive.com/howbig.htm
Cells
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Living things may be unicellular (30 million species on earth, most bacteria)
or multicellular (visible life forms, animals and plants).
In multicellular organisms: housekeeping functions common to all cells +
additional and specific functions for each type of “differentiated” cells 
Except housekeeping functions, retinal cells are able to perform chemical
process converting light into a signal that can be integrated by nervous
system. Other examples of “differentiated” cells: mechanical properties of
muscle, bone, and skin cells; ability of glands to secrete specific molecules;
oxygen-carrying capability of red blood cells  300 distinct cells in human
body have identical genomes but differ from each other in gene expression
In order to survive, several processes must be carried out by all cells
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Acquisition and assimilation of nutrients
Elimination of waste
Synthesis of new cellular material, movement, and replication
Cell structure is diverse but all cells share common characteristics:
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Entire genetic information of parent organism is stored in DNA and passed on to daughter
cells during dell division.
Cell membrane or cell wall separates interior from surrounding environment and maintain
distinct chemical identity, Ex: membrane is permeable to CO2, O2, and provides controlled
access to sugars, amino acids, and ions.
Two Categories of Cells
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Prokaryotes – Unicellular organisms that account for much of living
biomass on Earth, no nucleus - has a single compartment, 2 domains
– bacteria and archaea
Eukaryotes – Have nucleus - cells are compartmentalized, DNA is
stored in a nucleus, 1 domains – eukaryota, consists of organisms
with nuclei
Classification of life forms into 3 distinct domains: based on
assumption that all cells (organisms) descended from a “common
ancestor cell”, i.e. similarity (evolution) of an rRNA molecule found
in all organisms (Rather than cell structure or structure and content
of the genome of an organism)
Prokaryote
Eukaryote
Prokaryotic & Eukaryotic Cell, Mariana Ruiz
Prokaryotic Cells
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Nucleoid region (not enclosed within a separate nuclear envelope):
Hereditary information is stored in large circular DNA molecule that is
compacted in an area of cytoplasm.
Have mobility in aqueous environments because of the action of flagellum,
threadlike protrusion attached to cell membrane  Undulate like a whip or
rotate like a propeller
Average diameter: 2 um  Cell volume probably represents the lower limit
accommodating complex machinery of life and restricts cell size and
biological characteristics of organisms
Prokaryotic Mariana Ruiz
Prokaryotic Division
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Binary Fission
Reproduction in prokaryotes are
asexual because of seldom fusion with
another individual and mixing
genomes (sexual reproduction)
DNA is replicated and one copy
allocated to each daughter cell. 
Daughter cells are essentially clones
and nearly always bear exact genetic
characteristics of parent cell.
Genetic variations do occur in
prokaryotes
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Recombination: cells conjugate and
exchange genetic material
Mutation: due to exposure to radiation
or chemicals
Binary Fission, JW Schmidt
Prokaryotes – Plasma
Membrane as a Barrier
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Maintain sufficient surface area/volume ratio 
Universal need to emit waste, import nutrients,
as well as physical characteristics of diffusion
Primary function of plasma membrane →
Regulate movement of molecules entering or
leaving cell.
Movement of molecules across plasma
membrane requires energy.
Movement of molecules is passive if no energy
sources of the cell are expended  PASSIVE
TRANSPORT
Simple Diffusion: when molecules move from
a higher to a lower concentration
Physical constraints limit size of bacteria by
utilizing simple diffusion as an adequate
means for distributing nutrients throughout
the cell and within cells.
Diffusion Animation: biologycorner.com
Eukaryotes
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Cells with nuclei, ranging from
unicellular yeast to plants and
animals (billions of cells)
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Humans have about 100 trillion or
1014 cells; a typical cell size is 10 um
and a typical cell mass is 1 ng.
Large degree of
compartmentalization
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Nucleus: genome and replication
machinery
System of internal membranes:
protein synthesis is carried out here
Mitochondria: energy production
performed by membrane-bound
structures
Compartments in Eukaryotes
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Organelles: compartments in
eukaryotes  Has distinct
function and contains
collection of specific enzymes
catalyzing requisite chemical
reactions
Membrane-bound structures
are several hundred times that
of bacterial cell  Ratio of
cell surface area to cell
volume↓ Cell size↑in
comparison with prokaryotes
Acquire many more active
transport systems in plasma
membrane and within the cell
Image: Mariana Ruiz
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Plant
Cells
Chloroplasts: convert energy of light into chemical energy (Captures Sunlight
Energy & Makes ATP)  Nickname: Solar Panels
Cell wall: outside plasma membrane that restricts shape change and mobility
Vacuole: collecting and storing nutrient molecules and waste products 
Reservoir
Release oxygen during photosynthesis: increase oxygen content of the
atmosphere, enabling evolution of oxygen-breathing animal  Earliest form of
multicellular life
Image: Mariana Ruiz
Photomicrograph Plant Cell, biology.unm.edu/.../Summaries/Cell.html
Osmosis Plant Cell, Mariana Ruiz
Image: Ollin Wiki
Comparison of Structures
Between Animal and Plant Cells
Typical animal cell
Organelles •Nucleus
• Nucleolus (within
nucleus)
•Rough endoplasmic
reticulum (ER)
•Smooth ER
•Ribosomes
•Cytoskeleton
•Golgi apparatus
•Cytoplasm
•Mitochondria
•Vesicles
•Lysosomes
•Centrosome
• Centrioles
http://en.wikipedia.org/wiki/Cell_(biology)
Typical plant cell
•Nucleus
• Nucleolus (within
nucleus)
•Rough ER
•Smooth ER
•Ribosomes
•Cytoskeleton
•Golgi apparatus (dictiosomes)
•Cytoplasm
•Mitochondria
•Plastids (chloroplasts) and
its derivatives
•Vacuole(s)
•Cell wall
Two Basic Types of Cells
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Prokaryotes:
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Almost always single-celled (except for
prokaryote colonies).
Reproduce by binary fission (another copy by
cell division)
No cell nucleus or any other membranebound organelles. DNA travels openly around
the cell.
All bacteria are prokaryotes.
Eukaryotes:
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Most organisms that we can see, such as
trees, grass, worms, flies, mice, humans,
mushrooms and yeast are eukaryotes.
Can either be single-celled or multi-celled
Can reproduce in one of several ways (Ex.
meiosis, mitosis)
Have cell nucleus within containing its DNA.
Nucleus most evident distinction between
these cell types.
Images: Mariana Ruiz
Comparison of Features of
Prokaryotes and Eukaryotes
http://en.wikipedia.org/wiki/File:Celltypes.svg
Prokaryotes
Typical organisms bacteria, archaea
Cells are small so they can exchange
materials with their surroundings.
Eukaryotes
protists, fungi, plants, animals
~ 10–100 µm (sperm cells, apart from the tail,
Typical size
~ 1–10 µm
are smaller)
Type of nucleus nucleoid region; no real nucleus real nucleus with double membrane
linear molecules (chromosomes) with histone
DNA
circular (usually)
proteins
RNA-/proteinRNA-synthesis inside the nucleus
coupled in cytoplasm
synthesis
protein synthesis in cytoplasm
50S+30S  70S
60S+40S  80S
Ribosomes
Cytoplasmatic
highly structured by endomembranes and a
very few structures
structure
cytoskeleton
flagella and cilia containing microtubules;
Cell movement flagella made of flagellin
lamellipodia and filopodia containing actin
one to several thousand (though some lack
Mitochondria
none
mitochondria)
Chloroplasts
none
in algae and plants
single cells, colonies, higher multicellular
Organization
usually single cells
organisms with specialized cells
Cell division
Binary fission (simple division) Mitosis (fission or budding), Meiosis
http://en.wikipedia.org/wiki/Cell_(biology)