Ch. 22.2 Structure of Prokaryotes
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119 Terms
What are the four structures found in all cells?
Plasma membrane, cytoplasm, DNA, and ribosomes.
What does the plasma membrane do?
Acts as a barrier and separates the cell from its environment.
What is cytoplasm?
The complex fluid/solution containing organic molecules and salts inside the cell.
What is the function of DNA?
It is the cell’s informational archive, containing genetic informational archive, containing genetic information.
What do ribosomes do?
Protein synthesis.
Do both prokaryotic and eukaryotic cells have ribosomes?
Yes. All cells have ribosomes.
Do both prokaryotes and eukaryotes have DNA?
Yes. All cells have DNA.
MEMBRANE =
BARRIER
CYTOPLASM =
INSIDE FLUID
DNA =
INFORMATION
RIBOSOME =
PROTEINS
What is a prokaryote?
A cell/ organism that lacks a nucleus and membrane-bond organelles.W
Are prokaryotes usually unicellular?
Yes.
Do prokaryotes have a nucleus?
No.
Do prokaryotes have a membrane-bound organelles?
No.
Where is the major difference between prokaryotes and eukaryotes?
Prokaryotes lack a nucleus and membrane-bound organelles; eukaryotes have them.
What are cocci?
Spherical/round prokaryotic cells.
What are bacilli?
Red-shaped prokaryotic cells.
What are spirilli?
Spiral-shaped prokaryotic cells.
How can prokaryotes be classified based on appearance?
By their cell shape, including cocci, bacilli, and spirilli.
cocci =
circles
Bacilli =
bars
Spirilli =
spirals
What is a nucleoid?
The region of a prokaryotic cell where its chromosome is located.I
Is the nucleic surrounded by a membrane?
No.
What shape is the main prokaryotic chromosome usually?
Circular.
What type of DNA is the prokaryotic chromosome?
Usually double-stranded DNA.
How many main chromosomes do prokaryotes usually have?
Usually one.
What are plasmids?
Small pieces of extra-chromosomal DNA.
Where can plasmids be found?
In many bacteria and archaea.
Are plasmids part of the main chromosome?
No. They are extra-chromosomal DNA.
Where is the prokaryotic cell wall located?
Usually outside the plasma membrane.
What does the cell wall do?
Provides protection and helps determine the cell’s shape.
Do most prokaryotes have a cell wall?
Yes. Most have one outside the plasma membrane.
Is the cell wall the same as the plasma membrane?
No. The plasma membrane surrounds the cytoplasm; the cell wall is an additional protective layer outside it.
What is a capsule?
A protective layer found outside the cell wall in some bacteria.
What does the capsule help bacteria do?
Attach to surfaces.
How can a capsule protect against immune cells?
It can protect bacteria from phagocytic cells.
How can capsules affect pathogens?
They can make pathogens more resistant to immune responses.
CAPSULE =
ATTACH + PROTECT
What are flagella used for?
Locomotion/movement.
What is the singular form of flagella?
Flagellum.
What is pili used for?
Attachment to surfaces, including other cells.
What is the singular form of pili?
PilUS (pilus)
Are flagella found in every prokaryote?
No.
Are pili found in every prokaryote?
No.
What’s the easiest distinction between flagella and pili?
Flagella = movement; pili = attachment
FLAGELLA =
MOVE
PILI =
ATTACH
What are the three domains of life?
Bacteria, Archaea, and Eukarya
Which two domains contain prokaryotes?
Bacteria and Archaea.
Which domain contains eukaryotes?
Eukarya
Are bacteria and archaea the same?
No. They are different enough to be placed in separate domains.
What domain do humans belong to?
Eukarya
What is the evolutionary relationship between Archaea and Eukarya described here?
An ancestor of modern Archaea is believed to have given rise to Eukarya.
What is the prokaryotic plasma membrane made of?
A lipid bilayer.
How thick is the prokaryotic plasma membrane?
About 6-8 nanometers.
What does the plasma membrane surround?
The entire cell.
What does the plasma membrane separate?
The inside of the cell from the outside environment.
What does selectively permeable mean?
The membrane allows some substances to pass while restricting others.
Why is selectively permeability important?
The membrane allows some substances to pass while restricting others.
What does the membrane keep inside the cell?
Important molecules such as ions, proteins, and other molecules.
What is the general structure of a cell membrane?
A phospholipid bilayer consisting of two layers of lipid molecules.
Why is osmotic pressure high inside prokaryotic cells?
Their cytoplasm contains a high concentration of dissolved solutes.
What could happen if water enters a prokaryotic cell uncontrollably?
The cell could swell and burst.
What is osmotic lysis?
Bursting of a cell due to increasing volume from water entering the cell.
What prevents osmotic lysis in most prokaryotes?
The cell wall.
Where is the cell wall located?
Outside the plasma membrane.
What are the two major functions of the cell wall?
Protects the cell and gives it shape/ rigidity.
Is the cell wall chemically identical in all prokaryotes?
No its differs between Bacteria and Archaea and among bacterial species.
What is peptidoglycan?
A major structural component of bacterial cell walls.
What is peptidoglycan made of?
Polysaccharide chains cross-linked by peptides.
What is unusual about the amino acids in bacterial peptidoglycan?
It contains both L- and D- amino acids.
Name two D-amino acids found in peptidoglycan.
D-glutamic acid and D-alanine
Why is peptidoglycan important medically?
Many antibiotics target bacterial cell-wall development.
Do human cell walls contain peptidoglycan?
No. Peptidoglycan is characteristic of bacterial cell walls.
What are the two major groups of bacteria based Gram staining?
Gram-positive and Gram-negative
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What is the characteristic of Gram-positive bacteria?
A thick peptidoglycan cell wall and generally no outer membrane.
How much of the Gram-positive cell wall can be peptidoglycan?
Up to about 90%
What are teichoic acids?
Acidic substances found in Gram-positive cell walls.
What are lipoteichoic acids?
Teichoic acids linked to lipids that help anchor the cell wall to the plasma membrane.
What is characteristic of Gram-negative bacteria?
A think peptidoglycan layer plus an outer membrane.
How much of the Gram-negative bacteria?
A think peptidoglycan layer plus an outer membrane.
What is characteristic of Gram-negative bacteria?
A think peptidoglycan layer plus an outer membrane.
How much of the Gram-negative cell wall is peptidoglycan?
HAbout 10% if the total cell-wall structure described here.
What does the Gram-negative outer membrane contain?
Lipopolysaccharides (LPS) and lipoproteins
What are porins?
Proteins in the Gram-negative outer membrane that allow substances to pass through.
What is the periplasmic space?
The space between the inner plasma membrane and outer membrane of Gram-negative bacteria.
Which group has the thicker peptidoglycan layer?
Gram positive.
Which group has an outer membrane?
Gram-negative.
Which group has LPS?
Gram-negative.
Which group has teichoic acids?
Gram-positive.
How do prokaryotes reproduce?
Asexually, usually through binary fission.
What is binary fission?
A process where one prokaryotic cell replicates its DNA and divides into two cells.
Do prokaryotes undergo mitosis?
No.
What happens to the chromosomes during binary fission?
The chromosome is replicated, and the two copies separate as the cell grows.
What happens after DNA replication?
The cell grows and pinches inward at its equator.
What are the resulting cells called?
Daughter cells/clones that are generally genetically very similar.
Does binary fission itself create genetic recombination?
No.
Why can prokaryotes still develop genetic diversity?
Through mutation and DNA exchange mechanisms such as transformation, transduction, conjunction.