BACTERIAL CELL STRUCTURE MORPHOLOGY AND FUNCTIONS Flashcards
Prokaryotes differ from eukaryotes in ____ and _____
size and simplicity
reproduce by fission while some bacteria produce spores.
Archaea
consists of three RNA whereas bacteria consists of single RNA.
Archaea
can sustain in harsh environments which are extreme such as hot springs, oceans, gut of humans and Marshlands.
Archaea
are generally found in organic matter, soil, bodies of animals and plants, water, radioactive waste.
bacteria
is a nucleic acid present in all living cells that has structural similarities to DNA.
Ribonucleic acid
is the molecule that carries genetic information for the development and functioning of an organism.
Deoxyribonucleic acid
determined by plane of division – determined by separation or not
arrangement
cocci and rods most common – various others
shape
varies
size
Shape and Arrangement-1
- Cocci (s., coccus) – spheres
– diplococci (s., diplococcus) – pairs
– streptococci – chains
– staphylococci – grape-like clusters
– tetrads – 4 cocci in a square
– sarcinae – cubic configuration of 8 cocc
Shape and Arrangement-2
- bacilli (s., bacillus) – rods
– coccobacilli – very short rods - vibrios – resemble rods, comma shaped
- spirilla (s., spirillum) – rigid helices
- spirochetes – flexible helices
Shape and Arrangement-3
- mycelium – network of long, multinucleate filaments
- pleomorphic – organisms that are variable in shape
Bacterial structure is considered at three levels
- Cell envelope proper: Cell wall and cell membrane.
- Cellular element enclosed with in the cell envelope: Mesosomes, ribosomes, nuclear apparatus, polyamies and cytoplasmic granules.
- Cellular element external to the cell envelope: Flagellum, Pilus and Glycocalyx.
Bacterial Cell Organization Common Features:
♦ Internal Structure
♦ Surface Structure
♦ Appendages
consists of a tangle of double-stranded DNA, not surrounded by a membrane and localized in the cytoplasm.
Nucleoid
DNA is stabilized by small polyamines and Mg ions and associated with histone-like proteins
Nucleoid
Bacterial DNA is Haploid.
Nucleoid
are small, circular, non-chromosomal, double-strand DNA molecules that are capable of self-replication.
Plasmids
There are five main types of plasmids:
a. Fertility plasmid
b. Col Plasmid
c. Resistance plasmid
d. Virulence Plasmids
e. Degradative Plasmids
Also known as F plasmid. It contains a transferred gene that allows genes to be transferred from one cell to another through conjugation.
Fertility plasmid
contains genes that help the bacteria cell defend against the environment, factors such as poisons or antibiotics.
Resistance plasmid
contains genes that make bacteriocins (also known as colicins), which are protein that kills other bacteria.
Col Plasmid
When a _______ is inside a bacterium, it turns that bacterium into a pathogen, which is an agent of disease.
virulence plasmid
help the host bacterium to digest compounds that are not commonly found in nature, such as camphor, xylene, toluene, and salicylic acid.
Degradative Plasmids
are minute particles composed of ribosomal RNA (rRNA) and protein.
Ribosomes
contains a large number of solute low- and high-molecular weight substances, RNA and ribosomes.
cytoplasm
is also frequently used to store reserve substances (glycogen depots, polymerized metaphosphates, lipids).
cytoplasm
Also known as the plasma membrane.
cytoplasmic membrane
It is basically a double layer of phospholipids with numerous proteins integrated into its structure. The most important of these membrane proteins are permeases, enzymes for the biosynthesis of the cell wall, transfer proteins for secretion of extracellular proteins, sensor or signal proteins, and respiratory chain enzymes.
cytoplasmic membrane
The most Important Bacterial Cytoplasmic Membrane Proteins:
- Permeases
- Biosynthesis enzymes
- Secretion system proteins
- Sensor proteins (also known as signal proteins)
- Respiratory chain enzymes
Active transport of nutrients from outside to inside against a concentration gradient.
Permeases
Required for biosynthesis of the cell wall (e.g., its murein)
Biosynthesis enzymes
The secretion systems differing in structure and mode of action. Proteins are moved out of the cell with the help of these systems. The common feature of all systems is the formation of protein cylinders that traverse the cytoplasmic membrane and in Gram- negative bacteria, the outer cell wall membrane as well.
Secretion system proteins
Transmit information from the cell’s environment into its interior.
Sensor proteins (also known as signal proteins)
Occur in bacteria with aerobic metabolism.
Respiratory chain enzymes
refers to that portion of the cell envelope that is external to the cytoplasmic membrane and internal to the capsule or glycocalyx.
cell wall
is a complex polymer consisting of three parts: A backbone, composed of alternating N-acetylglucosamine and N-acetylmuramic acid connected by β1→4 linkages;
Peptidoglycan
This molecular complex is comprised of the lipid A, the core polysaccharide, and the O-specific polysaccharide chain.
Lipopolysaccharide (LPS)
is the space between the inner and outer membrane in Gram-negative bacteria.
periplasm
Is a network of polysaccharides that project from cellular surfaces of bacteria, found just outside the bacterial cell wall.
Glycocalyx
is a well-defined structure of polysaccharide surrounding a bacterial cell and is external to the cell wall.
1.Capsule
Refers to a loose network of polysaccharide fibrils that surrounds some bacterial cell walls.
2.Slime Layer
are thread-like appendages consist of a basal body, hook, and a long filament composed of a polymerized protein called FLAGELLIN. They are the organs of locomotion for the forms that possess them.
Flagella
Three types of arrangement are known:
- monotrichous (single polar flagellum).
- lophotrichous (multiple polar flagella).
- peritrichous (flagella distributed over the entire cell).
They are rigid surface appendages composed of structural protein subunits termed pilins. Minor proteins termed adhesins are located at the tips of pili and are responsible for the attachment properties.
Pili (Fimbriae)
Two classes can be distinguished:
Ordinary pili and sex pili
which play a role in the adherence of bacteria to host cells.
Ordinary pili
which are responsible for the attachment of donor and recipient cells in bacterial conjugation.
Sex pili
The spore is a resting cell, highly resistant to desiccation, heat, and chemical agents; when returned to favorable nutritional conditions and activated, the spore germinates to produce a single vegetative cell.
Endospores
is an aggregate of interactive bacteria attached to a solid surface or to each other and encased in an exopolysaccharide matrix.
biofilm
Appendages
Pili and flagella
Are surrounded by complex envelope layers that differ in composition among the major groups.
Prokaryotic cells
It is a double layer of phospholipids with numerous protein integrated in its structure
Cytoplasmic membrane
Active transport of nutrients from outside to inside againsts a concentration gradient.
Permeases
Internal structures
-nucleoid
-ribosomes
-storage granules
-endospore
Surface structure
- Capsule
- Cell wall
- Cell membrane
- Cytoplasm
- Plasma membrane
