prokaryotic and eukaryotic...
TRANSCRIPT
Prokaryotic and Eukaryotic Cells
Structure and Function
In general microbes or microorganisms may be either
prokaryotic (bacteria) or eukaryotic (protists, fungi,
and some animals).
However, there are some microbial organisms that
appear to be intermediates between prokaryotes and
eukaryotes (they possess a nucleus but do not have
mitochondria or chloroplasts, an example is Giardia
intestinalis.
Prokaryotes differ from eukaryotes in several ways
including but not limited to:
Characteristics Prokaryotic Eukaryotic
Types bacteria (monerans) protists, fungi, plants, and animals
Organization unicellular usually multicellular (exception some
protists)
Cell size small (0.1-10um) larger (10-100um)
Membrane-bound organelles absent present
Reproduction asexual asexual and sexual
DNA circular linear
Proteins assoc. with DNA Basic Histone
Plasma membrane No sterols Sterols
Ribosomes 70S 80S
Cytoskeleton Absent present
PROKARYOTIC
CELLS
Key Functions of Cells
A boundary that keeps the cellular contents separate from the external environment but allows for the transfer of some substances into and out of the cell.
Replication of DNA
Synthesis of cellular components
The ability to obtain energy through metabolic processes
Appendages are basically involved in
movement or adhesion
Flagella (singular flagellum) are cellular appendages that consist of three parts:
• a filament that rotates for movement
• a hook where the filament attaches
• a basal body that anchors the hook to the cell
• the arrangement of the hook/basal body articulation allows the hook with its filament to rotate 360o
Arrangements of Flagella
polar - flagella are attached at one or both ends of the cell
monotrichous - a single flagellum at one end
lophotrichous - multiple flagella arising from one or both ends
amphitrichous – a single flagellum arises from each end
peritrichous - flagella are randomly dispersed over the cell surface
Axial filaments
are modified flagella that
occur in spirochetes
Non-locomotor appendages
Pili are longer and sparser
than fimbriae.
fimbriae are involved in
adhesion and pili (found
only in Gram - bacteria)
are involved in
conjugation ( a “mating”
process).
Cell envelopes differ between taxa
but they basically consist of three
layers:
The capsule or slime layer (outermost layer) differs greatly in thickness, organization and chemical composition depending on the bacterial species. T
Beneath the outer layer lies the cell wall.
The cell membrane is a thin flexible sheet that surrounds the contents of the bacterial cell. Its functions include: transport, energy extraction, nutrient processing, and synthesis
The Gram Stain
An important tool in the identification of bacteria is the Gram stain. Some bacteria are Gram + while others are Gram - (some however, do not show a Gram reaction). Gram + bacteria stain purple (the color of the primary dye) and Gram - bacteria stain pink (the color of the counterstain or second dye). The Gram stain is a differential staining technique because different species of bacteria stain differently. The difference is a result of the composition of the cell wall.
The protoplasm or cytoplasm
is the dense gelatinous
solution within the cell
membrane that is the
primary site for the cell’s
biochemical and synthetic
processes. The following
are found within the
protoplasm of the
prokaryotic cell:
chromatin body or the
bacterial chromosome
nucleoid or nuclear region
of the cell that is
associated with the
chromatin body
plasmids are tiny circular
extrachromosomal strands
of DNA
ribosomes are small
structures consisting of
RNA and proteins that are
involved in protein
synthesis
inclusions or granules are
areas where nutrients are
concentrated
Endospores are dormant
structures produced by
some species of Bacillus
and Clostridium.
Shapes and arrangements of bacteria
There are six common shapes of bacteria: coccus, bacillus, coccobacillus, vibrio, spirochete, and spirullum and there are several arrangements of these cells: single, chains (strepto-), clusters (staphylo-), pairs (diplo-) etc.
Eukaryotic Cell
Cell Membrane Cell membrane
Structure
Components
Arrangement
Functions include
Barrier
Transport (know diffusion, osmosis, facilitated diffusion and active transport)
Recognition (e.g., self vs. non-self)
Reception (for protein hormones)
Adhesion
Nucleus
Structure and Function
– membrane similar to cell
membrane (similar
function)
– Nucleolus (formation of
ribosomes)
– Chromosomes (gene
expression)
– Nucleoplasm (matrix)
Ribosomes
• Structure
– rRNA
– Proteins
• Function
– Site of protein formation
(translation)
• Found in both
prokaryotes and
eukaryotes (different
structurally)
Endoplasmic Reticulum
• Structure membranous system of tunnels and sacs
– Rough – with ribosomes on surface
– Smooth- no ribosomes on surface
• Function
– Rough – protein synthesis
– Smooth- lipid synthesis
Golgi Apparatus
• Structure also
membranous, kind of
like a stack of pancakes
• Function processing of
lipids and proteins
Lysosomes
• Structure membrane
bound sac containing
hydrolytic enzymes
• Function digestion
Mitochondria
• Structure – cigar-
shaped, double
membrane-bound
organelle
• Function – Energy
transfer by ATP
synthesis
Chloroplast
• Structure
– Also cigar or spindle
shaped, double
membrane-bound, green
• Function
– Site of photosynthesis
OTHER STUCTURES
• Cell walls, not in animal cells
• Vacoules
• Cytoskeleton
• Cytoplasm