Classification and Structure of Prokaryotic Cells

Question 1

Nucleoid region

Answer 1

Where the genetic material of prokaryotes is located: organized into a single circular molecule of DNA concentrated in this area of the cell

Question 2

Prokaryotic Domains

Answer 2

Archaea and Bacteria

Question 3

Archaea

Answer 3

Single-celled organisms that are visually similar to bacteria, but contain genes and several metabolic pathways that are more similar to eukaryotes than to bacteria.

Question 4

What is a notable trait of Archaea

Answer 4

Their ability to use alternative sources of energy: some are photosynthetic, and many are chemosynthetic and can generate energy from inorganic compounds

Question 5

Similarities between Archaea and eukaryotes

Answer 5

They start translation with methionine, contain similar RNA polymerases, and associate their DNA with histones.

Question 6

Similarities between Archaea and prokaryotes

Answer 6

Contain a single circular chromosome, divide by binary fission or budding, and share a similar overall structure to bacteria.

Question 7

Characteristics of bacteria

Answer 7

All bacteria contain a cell membrane and cytoplasm, and some have flagella or fimbriae (similar to cilia).

Question 8

Mutualistic symbiotes

Answer 8

The relationship between the human body and some bacteria, where both humans and bacteria benefit from the relationship.

Question 9

Cocci

Answer 9

Spherical bacteria, includes common pathogens such as streptococcus pyogenes

Question 10

Bacilli

Answer 10

Rod-shaped bacteria, like Escherichia coli

Question 11

Spirilli

Answer 11

Spiral-shaped bacteria, include such species as Treponema pallidum, which cause syphilis

Question 12

Obligate aerobes

Answer 12

Bacteria that require oxygen for metabolism

Question 13

Anaerobes

Answer 13

Bacteria that use fermentation, or some other form of cellular metabolism that does not require oxygen; there are different types.

Question 14

Obligate anaerobes

Answer 14

Anaerobes that cannot survive in an oxygen-containing environment: the presence of oxygen leads to the production of reactive oxygen-containing radicals in these species, which leads to cell death

Question 15

Facultative anaerobes

Answer 15

Bacteria that can toggle between metabolic processes, using oxygen for aerobic metabolism if it is present, and switching to anaerobic metabolism if it is not

Question 16

Aerotolerant anaerobes

Answer 16

Unable to use oxygen for metabolism, but are not harmed by its presence in the environment

Question 17

Physical characteristics of prokaryotic cells

Answer 17

They lack a nucleus and membrane-bound organelles, have a cell wall and cell membrane, and have flagella

Question 18

Envelope

Answer 18

Consists of the cell wall and cell membrane together in a prokaryotic cell: cell membrane is composed of phospholipids, similar to eukaryote

Question 19

What are the two main types of cell walls in bacteria

Answer 19

Gram positive and gram negative

Question 20

How is the type of cell wall determined

Answer 20

The Gram staining process: a crystal violet stain, followed by a safranin counterstain. If the enveloped absorbs the crystal violet stain, it will appear deep purple –> said is said to gram-positive.
If the envelope absorbs the safranin counterstain instead, then the cell will appear pink-red and is called gram-negative

Question 21

Physical properties of gram-positive cell walls

Answer 21

Consist of a thick layer of peptidoglycan, a polymeric substance made from amino acids and sugars –> structural and barrier functions, and may also aid a bacterial pathogen by providing protection from a host organism’s immune system.
Cell wall also contains lipoteichoic acid –> function not clear, but it may be activated by exposure to these chemicals

Question 22

Physical properties of gram-negative cell walls

Answer 22

Very thin and also contain peptidoglycan, but in much smaller amounts than gram-positive cells. Peptidoglycan cell walls of these bacteria are adjacent to the cell membrane, and are separated from the membrane by the periplasmic space.
Cell walls also have outer membranes containing phospholipids and lipopolysaccharides –> latter is what triggers and immune response in human beings.

Question 23

Chemotaxis

Answer 23

The ability of a cell to detect chemical stimuli and move forward or away from them

Question 24

Components of a flagella

Answer 24

A filament, basal body, and a hook

Question 25

Filament

Answer 25

A hollow, helical structure composed of flagellin

Question 26

Basal body

Answer 26

A complex structure that anchors the flagellum to the cytoplasmic membrane and is also the motor of the flagellum

Question 27

Hook

Answer 27

connects the filament and the basal body so that, as the basal body rotates, it exerts torque on the filament, which thereby spins and propels the bacterium forward.

Question 28

Plasmids

Answer 28

DNA acquired from external sources may be carried on these smaller circular structures. Plasmids carry DNA not necessary for the prokaryote’s survival but that may confer an advantage such as antibiotic resistance

Question 29

Different organelles between prokaryotes and eukaryotes

Answer 29

Prokaryotes lack mitochondria: instead, the cell membrane is used for the electron transport chain and generation of ATP.
A simpler cytoskeleton
Different ribosome size: prokaryotic ribosomes contain 30S and 50S subunits, whereas eukaryotic ribosomes contain 40S and 60S ribosomes