2 Prokaryotic and Eukaryotic Cells Structure and Function Flashcards
(73 cards)
– No Nucleus and No Organelles
– Cell Wall of peptidoglycan
– Binary Fission
– 1 circular chromosome
-Do not have membrane surrounding their DNA
-Lack various internal structures bound with phospholipid membranes
-Are small, ~1.0 µm in diameter
-Have a simple structure
-Composed of bacteria and archaea
prokaryotes
– has Nucleus and Organelles
– If cell wall, Cellulose or chitin
– Mitosis
– Linear chromosomes
- Have membrane surrounding their DNA
-Have internal membrane-bound organelles
-Are larger, 10-100 µm in diameter
-Have more complex structure
-Composed of algae, protozoa, fungi, animals and plants
eukaryotes
a coating or layer of molecules external to the cell wall. it serves protective, adhesive and receptor functions
– Gelatinous, sticky substance surrounding the outside of the cell
– Composed of polysaccharides, polypeptides, or both
*In Eukaryotic Cells
– Never as organized as prokaryotic capsules
– Help anchor animal cells to each other
– Strengthen cell surface
– Provide protection against dehydration
– Function in cell-to-cell recognition and communication
Glycocalyx or Glycocalyces
the site where the large DNA molecule is condensed into a packet. DNA is the code that directs all genetics and heredity of the cell
-is an irregularly shaped region that contains the cell’s chromosome and numerous proteins
* Bacterial cells contain ONE chromosome
* Circular in structure
* Just DNA, no associated proteins
* Bacterial chromosomes are longer than the length of the cell.
* Some cells contain PLASMIDS
Bacterial chromosome or Nucleoid
-an elongate, hollow appendage used in transfers of DNA to other cells and in cell adhesion
– Tubules composed of pilin
– Also known as conjugation pili
– Longer than fimbriae but shorter than flagella
– Bacteria typically only have one or two per cell
– Mediate the transfer of DNA from one cell to another
Pilus or Pili
an extension of the cell membrane that folds into the cytoplasm and increases surface area
- invagination of the plasma membrane that increases the surfaces area of the plasma membrane during binary fission
-also serves as a site for the attachment and distribution of genetic material during binary fission.
-considered analogous to the cristae in mitochondria of eukaryotic cells, enhancing the surface area for metabolic activities
Mesosomes
specialized appendage attached to the cell by a basal body that holds a long rotating filament. the movement pushes the cell forward and provides motility
– Are responsible for movement
– Have long structures that extend beyond cell surface
– Are not present on all prokaryotes
- Rotation propels bacterium through environment
- Rotation reversible, can be clockwise or counterclockwise
- Bacteria move in response to stimuli (taxis)
– Runs
– Tumbles
*In Eukaryotic Cells
-Do not rotate, but undulate rhythmically. move like a
whip
Flagellum or Flagella
-fine, hair like bristles from the cell surface that help in adhesion to other cells and surfaces
Hollow tubes that protrude from some bacteria
Compose of protein – fimbrin
- Sticky, bristlelike projections
- Used by bacteria to adhere to one another, to hosts, and to substances in environment
- Shorter than flagella
- May be hundreds per cell
- Serve an important function in biofilms
- Virulence factor
Fimbriae
stored nutrients such as fat, phosphate, or glycogen deposited in dense crystals or particles that can be tapped into when needed
inclusion or granule
a semirigid casing that provides structural support and shape for the cell
cell wall
a thin sheet of lipid and protein that surrounds the cytoplasm and controls the flow of materials into and out of the cell pool
cell membrane
-tiny particles composed of protein and RNA that are the sites of protein synthesis
-are the site of protein synthesis, and large numbers of them are found in nearly all cells.
Ribosomes
External covering outside the cytoplasm
The Cell Envelope
The Cell Envelope is Composed of two basic layers that Maintains cell integrity:
cell wall
cell membrane
- Two generally different groups of bacteria
demonstrated by Gram stain:
Gram-positive bacteria
Gram-negative bacteria
- macromolecule composed of a repeating framework of long glycan chains cross-linked by short peptide fragments
- provides strong, flexible support to keep bacteria from bursting or collapsing because of
changes in osmotic pressure
peptidoglycan (cell wall) aka murein
- The backbone of the
peptidoglycan layer is
made of alternating sugar
molecules:
N-acetylglucosamine (NAG/ GlcNAc) and N-acetylmu ramic acid (NAM/ MurNAc).
the sugars of peptidoglycan are linked together
through;
β-(1,4)-glycosidic bonds
4 Groups Based on Cell Wall
Composition
- Gram positive cells
- Gram negative cells
- Bacteria without cell walls
- Bacteria with chemically unique cell walls
FOUR DIVISIONS OF BACTERIA
Division Gracilicutes – gram negative
Division Firmicutes - gram positive
Division Tenericutes - without cell wall
Division Mendosicutes - lack peptidoglycan in their cell wall and are similar to Archaea/archaebacteria
- Consists of
– a thick, homogenous sheath of peptidoglycan 20-80 nm thick
– tightly bound acidic polysaccharides - including teichoic acid and lipoteichoic acid
– cell membrane - Retain crystal violet and stain purple
Gram Positive Cell Wall
- Consists of
– an outer membrane containing lipopolysaccharide (LPS)
– thin shell of peptidoglycan
– periplasmic space
– inner membrane - Lose crystal violet and stain red from safranin counterstain
- Protective structure while providing some flexibility and sensitivity to lysis
Gram Negative Cell Wall
– endotoxin that may become toxic when released during infections
– may function as receptors and blocking immune response
– contains porin proteins in upper layer
* Regulates molecules entering and leaving cell
lipopolysaccharide (LPS)
– Referred to as phospholipid bilayer; composed of lipids and associated proteins
– Approximately half composed of proteins that act as recognition proteins, enzymes, receptors, carriers, or channels
* Integral proteins
* Peripheral proteins
* Glycoproteins
– Fluid mosaic model describes current understanding of membrane structure
Prokaryotic Cell Membrane
