microbiology exam 1 CHAPTER 4

Cell membrane

flexible structure that surrounds and encloses the cell's contents

Cytoplasm

the cell’s contents, everything enclosed by the cell membrane

chromosome

separate, independent, gene carrying body

characteristics of prokaryotes

 No nucleus (their DNA is not enclosed in a membrane bound internal cellular structure)

One, circular chromosome of pure DNA

No membrane-enclosed organelles 

Cell walls are composed of the complex carbohydrate peptidoglycan 

Reproduces by binary fission

Small simple cells

Always unicellular 

characteristic of eukaryotes

DNA is found in the cell's nucleus 

Several linear chromosomes of DNA  and protein

Membrane-enclosed organelles

Cell walls, are chemically simple

Cell division by mitosis

Large, complex cells,

Unicellular or multicellular

Reproduce by sexual reproductions 

shapes of bacteria- Cocci:

( berries ) round or sphere shaped

shapes of bacteria bacilli :

(little staffs) straight, rod shaped cells

shapes of bacteria spiral

(vibrio- comma shaped, spirochetes- flexible S shaped, spirilla- rigid, corkscreww shape) : curved rods, never straight

arrangements of bacteria - diplo

a pair

arrangements of bacteria - strepto

a chain

arrangements of bacteria - tetrad

a group of four

arrangements of bacteria - sarcinae

a cube of eight

arrangements of bacteria- staphylo

a grapelike cluster

glycocalyx

many prokaryotes secrete on their surface of glycocalyx

“sugar coat” substances that surround cells

a viscous (sticky) gelatinous (jelly like) substance external to the cell wall

composed of polysaccharide

glycocalyx functions

protect pathogenic bacteria from phagocytosis by cells of the host

enables the cells to survive by attaching to various surfaces in their natural environment

can protect a cell against dehydration 

can be a source of nutrition

flagella :

a long filamentous appendage that propels the bacteria cell

Motility:

The ability of an organism to move by itself

fimbriae

an appendage on a bacterial cell used for attachment

number from few to hundred

ave a tendency to adhere to each other and to surfaces (liquids,glass, rocks,epithelial surfaces)

Pili

An appendage on a bacterial cell used for conjugation

longer than fimbriae number only 1 or 2 per cell

the cell wall

a complex, semirigid structure that surrounds the underlying fragile plasma (cytoplasmic) membrane

almost all prokaryotes have cell walls

cell wall functions

prevents bacterial cells from rupturing by protecting the fragile cell membrane

responsible for shape of cell

point of anchorage for structures external to it

contributes to some bacteria G- to cause disease

site of action for some antibiotics

chemical composition and structure used to differentiate major types of bacterias G+ G-

peptidoglycan

consists of a repeating disaccharide attached by polypeptides to form a lattice that surrounds and protects the entire cell 

Gram-positive bacterial cell wall

many layer of peptidoglycan

thick rigid structure, teichoic acids

no outer membrane

resists decolorization retais crystal violet

appears purple in gram staining

susceptible to antibiotics,detergents, lysozyme

Gram-negative bacterial cell wall

one or few layers of peptidoglycan

no teichoic acid

outer lipid membrane

decolorizes and takes up counter stain safranin

appears pink, red in gram staining

more resistant to antibiotics,detergents, lysozyme

structures internal to the cell wall : plasma (cytoplasmic membrane)

thin structure lying inside the cell wall and enclosing the cytoplasm of the cell

functions of the cell membrane : selective permeability

the most important function of the plasma membrane, the ability of a cell membrane to allow certain substances to pass through it (enter or leave the cell), while preventing other substances from passing through it . 

simple diffusion

the movement of a substance from a high concentration to a low concentration

facilitated diffusion

the movement of glucose from a high concentration of glucose to a low concentration of glucose across a cell membrane with the help of a specific cell membrane carrier protein

Osmosis

the movement of WATER from a high concentration of WATER , to a low concentration of WATER , across selectively permeable cell membrane that only allows the solvent WATER across and not the solute

isotonic

an equal amount of water outside the cell as there is inside the cell , no net gain or loss of water , the cell remains unchanged

hypotonic

there is more water (less solute) outside the cell than inside, water enters the cell, cells with weak or damaged cell walls can burst (osmotic lysis)

Hypertonic

less water (solvent) outside the cell than inside, water leaves the cell

plasmolysis

the shrinkage of a cell's contents in a hypertonic solution, but not the entire cell because of its rigid, external cell wall.

Only occurs in cells with a cell wall and in a hypertonic solution

bacteriostatic

active processes

the cell does do work, does use cellular ATP energy

active transport

the movement of a substance from a low concentration to a high concentration (against the concentration gradient)

allows a cell to accumulate needed substances

group translocation

occurs exclusively in prokaryotes, the substance is chemically altered during transport across the membrane

nucleoid area

a single circular molecule of pure DNA, contains the cell's genetic information , which carries all the information required for the cell's structures and functions.

Plasmids

small circular double-stranded molecules of DNA, 

extrachromosomal genetic elements

Replicates independently of the main bacterial chromosome

Carry genes for antibiotic resistance, tolerance to toxic metal, production of toxins, synthesis of enzymes

Transfered from one bacteria to another

Ribosomes

All eukaryotic and prokaryotic cells contain this 

small granular structures ( composed of RNA and protein ) that are the sites of protein synthesis ( translation )

inclusions

Chemical reserve deposits (nutrients) that cells accumulate when they are plentiful and then use when they are deficient in the environment. 

examples : metachromatic granules ( inorganic phosphate ) , polysaccharide granules ( glycogen or starch ) , lipids , sulfur granules

endospores

when essential nutrients are depleted , certain Gram - positive bacteria ( Clostridium , Bacillus ) form specialized " resting cells called (...),  

highly resistant resting structures that some bacteria form response to harsh environmental conditions

vegetative cells

a metabolically active cell obtaining nutrients,

endospores can remain dormant for thousands of years

sporulation (sporogenesis

the process of endospore formation

germination

occurs when an endospore returns to a metabolically active cell obtaining nutrients (vegetative cells)