STRUCTURE OF A BACTERIAL CELL

Question 1

Cell wall

Answer 1

Gives bacteria shape and protection from breaking (lyse) up in a dilute solution

Rigid barrier that keeps the cell contents from bursting out

Rigidity is due to peptidoglycan layer found only in bacteria.

Certain antibiotics including Penicillin prevent the synthesis of peptidoglycan. The enzyme lysozyme also targets peptidoglycan.

Certain bacteria (Mycoplasma) lack cell wall and are made up of polysaccharide.

Question 2

Flagella

Answer 2

• Extremely thin, long, hair-like appendages attached to some bacterial cells
• Cannot be visualized directly with the light microscope, but only after staining with special flagella stains
• Composed of protein subunits called flagellinoz

Question 3

Types of glycocalyx

Answer 3

– Capsule: glycocalyx is well organized, rigid, firmly attached to the cell wall, and not easily washed off

– Slime layer: glycocalyx is unorganized, lacks rigidity, is loosely attached to the cell wall, and easily washed off.

Question 4

Functions of the glycocalyx

Answer 4

• Protective covering against attack by phagocytes and viruses, desiccation, and toxic materials;
• Reservoir of stored food;
  • In disease causing bacteria it increases the infectivity of the bacterial cell by aiding bacterial attachment to host cells and resisting phagocytosis;
  • Can trap nutrients and water and thus aid in the concentration and uptake of essential elements;
  • Site for waste material.

Question 5

Nucleoid

Answer 5

Gel-like area containing DNA, the genetic material
• Also known as Chromosome
It is a single, double stranded DNA molecule that contains all the genetic information required by a cell.
the bacterial chromosome is not enclosed inside of a membrane-bound nucleus but instead resides inside the bacterial cytoplasm

Question 6

Plasmids

Answer 6

Circular, super coiled, double-stranded DNA molecules.
May carry a few or many genes.
A single cell may carry many plasmids.
Not required by the cell for growth
However, they encode characteristics that may be needed to overcome some environmental conditions; production of enzymes that destroy certain antibiotics
Can be easily gained or lost by a bacterium
Can be transferred between bacteria as a form of horizontal gene transfer

Question 7

Gas Vacuoles (Vesicles)

Answer 7

• Small, rigid compartments enclosed in a protein covering
• Allow for buoyancy of the cell.
Gases (not water) flow freely into the vesicles, thereby decreasing its density.
Allow bacteria cells to float or sink to its ideal position, e.g. in search of light.
Some microbes store soluble nutrients such as nitrate in vacuoles.

Question 8

Ribosomes

Answer 8

the most numerous intracellular structure in most bacteria
• All prokaryotes have 70S (S=Svedberg units) ribosomes while eukaryotes contain larger 80S ribosomes in their cytosol.
• Ribosomes are intimately involved in protein synthesis. They facilitate the joining of amino acids.

Question 9

Endospores

Answer 9

• unique dormant cells produced by a process called sporulation within cells of certain bacterial species, primarily Bacillus and Clostridium
May remain dormant for years and are resistant to heat, desiccation, toxic chemicals or ultraviolet radiation.
Germinate into the vegetative cell (the actively multiplying form) when conducive environmental conditions return.
Spore may be spherical or oval
It differs from reproductive spores in that only one spore is formed per cell resulting in no net gain in cell number upon endospore germination.
The location of an endospore within a cell is species- specific and can be used to determine the identity of a bacterium.

Question 10

Cytoplasmic (Plasma) Membrane

Answer 10

Semi-permeable

surrounds the cell

acts as a barrier between the external environment and the interior of the cell.

Location of many metabolic processes, such as respiration and photosynthesis

Detection of environmental signals for chemotaxis