Lecture 3 - Prokaryotic Cell Flashcards
all living things are made up of what?
cells
what are cells?
the smallest unit of life
what is the cell theory?
That all living things are made up of cells which are the smallest unit of life. All cells arise from pre-existing cells, which is called biogenesis which was coined by Louis Pasteur.
do all cells arise from pre-existing cells? what is the term that describes this?
yes; biogenesis
who is the scientist that came up with biogenesis?
Louis Pasteur
T/F: every cell has a plasma membrane
TRUE
what are the similarities between prokaryotes and eukaryotes?
They both have plasma membranes, ribosomes (which synthesize proteins), cytosol, and DNA (but the way the DNA is present is different)
all cells arose from what?
all cells arose from a common prokaryotic ancestor 3.5-4 billion years ago
what is the difference between the dates of origin between prokaryotic vs. eukaryotic cells?
-Prokaryotic cells: first evolved about 3.5 billion years ago
-Eukaryotic cells: first evolved about 2.1 billion years ago
what is the difference between the domains where they are found between prokaryotic vs. eukaryotic cells?
-Prokaryotic cells: Found in Bacteria and Archaea domain
-Eukaryotic cells: Found in protists, plants, fungi, and animals
what is the difference between the complexity between prokaryotic vs. eukaryotic cells?
-Prokaryotic cells: simple, small
-Eukaryotic cells: large, complex
what is the difference of the structures between prokaryotic vs. eukaryotic cells? do they have cell walls? what else do they have?
-Prokaryotic cells: most have cell walls. Some have capsules, fimbriae, and/or flagella.
-Eukaryotic cells: Plant cells have cell walls; animal cells are surrounded by an extracellular matrix.
do prokaryotic vs. eukaryotic cells have a plasma membrane?
-Prokaryotic cells: Yes
-Eukaryotic cells: Yes
what is the difference of the internal organelles between prokaryotic vs. eukaryotic cells?
-Prokaryotic cells: No membrane-bound organelles
-Eukaryotic cells: Membrane-bound organelles (nucleus, ER, etc.)
what is the difference between the DNA of prokaryotic vs. eukaryotic cells?
-Prokaryotic cells: DNA is free in a nucleoid location (with a single circular chromosome)
-Eukaryotic cells: DNA is within the nucleus (and with one or more linear chromosomes).
do prokaryotic vs. eukaryotic cells have ribosomes?
-Prokaryotic cells: Yes
-Eukaryotic cells: Yes
define morphology
the shape and arrangement of a cell
what is the coccus shape of the cell?
spherical
what are examples of coccus cells?
-Diplococci: in pair (Neisseria gonorrhoeae)
-Streptococci: in chain (Streptococcus pyogenes; strep throat)
-Staphylococci: in grape-like clusters (Staphylococcus aureus; HAIs like sepsis, pneumonia, etc.)
what is the rod shape of the cell? another name for it?
Bacillus - short and rod like
what are examples of rod (bacillus) cells?
-Coccobacillus: short rod
-Bacillus anthracis, E. coli, Clostridium tetani
what are vibrio shaped cells?
short curved rod
what is an example of vibrio cells?
Vibrio cholerae: cholera
what is spirillum shaped cells?
rigid long curved rod (more spirally)
what are examples of spirillum cells?
-Helicobacter pylori: stomach ulcers
-Campylobacter jejuni: diarrhea
what is the spirochete cells?
flexible long curved rod (longer but also spirally)
what are examples of spirochete shaped cells?
-Treponema pallidum: syphilis
-Borrelia burgdorferi: Lyme disease
what is the average size of a prokaryotic cell?
0.3-2 um (micrometer)
Name a vibrio-shaped bacterium and a disease it causes.
Vibrio cholerae causes cholera.
Name a spirochete-shaped bacterium and a disease it causes.
Treponema pallidum causes syphilis.
what are the components of a prokaryotic cell?
-Plasma membrane
-Cell wall (+/- meaning some have it but some don’t)
-Capsule (+/-)
-Flagella (+/-)
-Pili (+/-)
-Cytoplasm with cytosol, cytoskeleton, and internal structures including nucleoid
Plasma Membrane:
what are the structures of the plasma membrane? is it always present in the prokaryotic cell?
-phospholipid bilayer
-proteins
Yes, it is always present.
Plasma Membrane:
what are the functions of the plasma membrane?
-Protects and forms a border
-Semipermeable membrane
-Senses the environment using proteins
-Transports using proteins
-Energy production
Plasma Membrane:
which function is the most important of the plasma membrane?
Energy Production is the most important function! It creates energy in the plasma membrane. Prokaryotes don’t have mitochondria, which is the structure that makes energy.
So energy is produced here in the plasma membrane.
Plasma Membrane:
what are two ways of transport within the plasma membrane?
Passive and Active
Plasma Membrane:
what is passive transport?
When no energy is required and molecules go from high to low concentration - which is down the concentration gradient.
Plasma Membrane:
what are subtypes of passive transport?
-Simple diffusion: O2, CO2
-Facilitated diffusion: glucose (using the help of a protein)
Plasma Membrane:
what is osmosis? what type of transport is it?
Osmosis is the movement of water across a selectively permeable membrane.
It goes from less solute to more solute.
It is part of passive transport
Plasma Membrane:
what is isotonic solution?
When the solute in the cell = the solute outside of the cell.
There is no net water movement.
Plasma Membrane:
what is hypotonic solution? is there net water movement? what is the result?
It is when the solute concentration in the cell is greater and more than the solute concentration outside of the cell. There is net water movement toward the inside of the cell.
The result is lysis. The cell bursts.
Plasma Membrane:
what is hypertonic solution? Is there net water movement?
what is the end result?
It is when the solute concentration outside of the cell is greater than inside the cell.
There is net water movement toward the outside of the cell.
The result is plasmolysis and the cell shrinks.
Plasma Membrane:
what is active transport?
it is the opposite of passive transport. it transports molecules against the concentration gradient from low to high concentration.
It requires energy.
Give one similarity and one difference between simple and facilitated diffusion.
Simple and facilitated diffusion are both types of passive transport. However, simple diffusion doesn’t use the help of proteins, whereas facilitated diffusion does require proteins.
which of the following is NOT a function of the prokaryotic plasma membrane?
1. Protein production
2. Energy production
3. Osmosis
4. Protection
- Protein production; because ribosomes make protein and they are not located in the plasma membrane.
Cell wall:
where is the cell wall located?
is it always present in the prokaryotic cell?
Around the plasma membrane, surrounding it.
No, it isn’t always present.
Cell wall:
The cell wall has Peptidoglycan (PG) in bacteria. What is it?
The cell wall is made up of PG and has proteins and carbohydrates.
Cell wall:
In the PG, what are the proteins and carbohydrates?
Proteins: Peptide bridges
Carbohydrates: Sugar (glycan) chains
Cell wall:
what are the functions of the cell wall?
-Has a rigid border that provides protection
-Prevents cell lysis
-Gives shape
Cell wall:
Some cells are Gram positive or Gram negative. What is this from?
This is because of the cells located within the cell wall here.
what are examples of gram-positive cells?
Bacillus, Staphylococcus, Streptococcus
Cell wall:
what are gram-positive cells consisted of?
-Many PG layers (up to 30)
-Teichoic acids (help to stabilize and anchor the PG laters to the plasma membrane)
-has no outer membrane
Cell wall:
what do the teichoic acids consist of?
-Wall teichoic acids
-Lipoteichoic acids
Cell wall:
what are examples of gram-negative cells?
E. coli, Pseudomonas, Salmonella
Cell wall:
what are gram-negative cells consisted of?
-One to a few PG laters (thinner)
-Outer membrane
Cell wall:
In gram-negative cells, what do the outer membrane consist of?
-Has a bilayer with porins that act as another permeability barrier
-Liposaccharides (LPS) from the outer part of the bilayer. It has O and core polysaccharides. Lipid A is an endotoxin
Gram-Postive vs Gram-Negative
+ : Thick PG layers
- : Thin PG layers
+ : Techoic acids
- : No techoic acids
+ : No bilayer
- : Bilayer
+ : No LPS
- : LPS
+ : no outer membrane
- : outer membrane w/ a bilayer consisted of LPS
Cell wall:
What is mycoplasma?
It is a type of bacteria that doesn’t have a cell wall
Cell wall:
What doe the mycoplasma cause?
Walking pneumonia
Cell wall:
what is archaea? does it have a cell wall?
It may lack cell walls. If it does have a cell wall, it is an unusual cell wall and not typical.
Cell wall:
what are examples of archaea unusual cell walls?
Pseudopeptidoglycan, Protein S-layers
what makes a good antibiotic?
-A good antibiotic should specifically kill the pathogen but NOT the host
what is an example of an antibiotic and what it attacks?
Penicillin; and it targets PG (peptidoglycan)
what does penicillin prevent?
it prevents the cross-linking of PG chains in growing and dividing cells
why is penicillin mainly only effective against Gram-positive cells?
It is mainly only effective against Gram-positive. This is because the outer membrane containing lipopolysaccharides of the Gram-negative bacteria cell wall acts as a permeability barrier that prevents the entry of the penicillin. (Porins are proteins in outer membrane)
can penicillin treat walking pneumonia?
No, walking pneumonia is caused by mycoplasma which doesn’t have a cell wall and therefore no PG. Penicillin attacks the PG. So it is not effective against mycoplasma.
where is “natural penicillin” found? what does it do?
Lysozyme is the body’s “natural penicillin” and it is found in tears, mucus, and saliva. It breaks down glycan chains
Antibiotics kill PG in the cell wall. do humans have a cell wall or PG?
no, neither
Explain if penicillin will be
effective against the following bacteria.
1. Bacillus subtilis
2. Escherichia coli
3. Mycoplasma
a. Bacillus subtilis: Penicillin would be effective against Bacillus subtils since it is a Gram-positive bacteria. Penicillin is able to attack and prevent the cross-linking of the exposed PG chains since it doesn’t have the outer membrane to block the entry.
b. Escherichia coli: Penicillin would not be effective against Escherichia coli because E. coli is a Gram-negative bacterium. This is because the outer membrane containing lipopolysaccharides of the Gram-negative bacteria cell wall acts as a permeeability abrrier that prevents the entry of the penicillin. (Porins are proteins in outer membrane)
c. Mycoplasma: Penicillin would not be effective against mycoplasma since it doesn’t have a cell wall, so the antibiotic wouldn’t be able to kill the PG, therefore not killing the pathogen.
Why do Gram-positive bacteria retain, and Gram-negative bacteria lose the primary
stain-crystal violet after the decolorization step in the Gram staining procedure?
Gram-positive bacteria don’t have outer membrane in their cell wall, and have a very thick cell wall that retains the crystal violet stain and it cannot leak out of the cell wall. On the other hand, Gram-negative bacteria have an outer membrane made of lipids that gets dissolved with the alcohol and the thin PG layer cannot retain the crytsal violet and it leaks out.
Capsule:
what is the structure of the capsule? is it always present in the prokaryotic cell?
-It has a gel-like external coat
-It is usually a polysaccharide (“sugar coat”; usually made of sugar)
-It is called the slime later if diffused
No, it isn’t always present.
Capsule:
what is the function of the capsule?
-Attachment
-Resists phagocytosis
-Protects from dehydration
which of the following represents a function of the bacterial capsule?
1. Prevention of osmotic lysis
2. Attachment to surfaces
3. Semipermeable membrane
4. Rigid border
- Attachment to surfaces
(explanation)
1. cell wall
3. plasma membrane
4. cell wall
Flagella:
What are the three parts of the structure of the flagella?
-Basal body: anchored in the plasma membrane
-Hook: curved
-Filaments: made of the flagellin protein
Flagella:
what are the functions? is it always present in the prokaryotic cell?
-Motility: it moves and rotates on its axis enabling the cell to swim
-“protein motor”: helps bacteria move
No, it isn’t always present.
Pili:
what is the structure? is it always present in the prokaryotic cell?
-It is thinner and shorter than flagella
-It is also anchored in the plasma membrane
No, it isn’t always present.
Pili:
what are the functions?
-Has attachments (fimbriae); few to many
-Conjugation: one or two; means of genetic exchange, not reproduction. It transfers DNA from one cell to another.
Cytoplasm:
what is the cytosol made of? is it always present in the prokaryotic cell?
Cytosol is 80% water and has solutes
-Yes, it is always present.
Cytoplasm:
what else does it consist of?
The cytoskeleton (proteins) and internal structures
what is the function of Siderophores?
Siderophores - function: to take/extract iron from the host and provide this essential metal nutrient (iron; Fe) to the microbes.
what is Klebsiella pneumoniae?
Klebsiella pneumoniae is part of the normal microbiota of our GI tract. It can cause healthcare-associated infections (HAIs), including pneumonia, bloodstream infections, wound or surgical site infections, and meningitis, in immunocompromised people. K. pneumoniae is spread through personal contact or via contaminated medical devices. Infections by drug-resistant strains like KPC-producing strains are very hard to treat and are becoming more prevalent.
internal structures:
what is a nucleoid? is it always present in the prokaryotic cell?
it is a general area where the DNA is located; it is not a compartment
-yes, it is always present.
internal structures:
within the nucleoid, what are the characteristics of the DNA?
-it is one circular single-stranded chromosome
-it is supercoiled
internal structures:
what are plasmids? is it always present in the prokaryotic cell?
they are extrachromosomal DNA within the cytoplasm
-No, it isn’t always present.
internal structures:
what is within the plasmids?
fewer nonessential genes (genes are small pieces of DNA w/ info for protein)
internal structures:
what are examples of plasmids?
The plasmid carries extra genes, for example antibiotic resistance, nutrient use, and/or toxin production.
internal structures:
how many plasmids can be present in a bacteria?
Bacteria:
-Can have none, one, or many plasmids.
-Can have multiple copies of the same plasmid.
-Can gain or lose different plasmids over time (if those genes are not needed anymore)
internal structures:
what do ribosomes do? is it always present in the prokaryotic cell?
they make proteins
-Yes, it is always present.
internal structures:
for prokaryotes, what is always the number of the ribosomes?
70s (30s + 50s subunits).
There is always a big subunit and a small subunit and when they are combined here they are 70s even though it doesn’t add up).
internal structures:
what does the 70s consist of?
-consists of proteins and rRNA (ribosomal RNA)
internal structures:
what are endospores? are they always present in the prokaryotic cell?
they are hibernation chambers (they are dormant and don’t need food or anything, they are basically just sleeping)
-NO, they aren’t always present. Only in Bacillus and Clostridium species
internal structures:
what are endospores made by?
Bacillus and Clostridium bacteria
internal structures:
why are endospores dormant?
to resist poor conditions
internal structures:
what conditions are endospores resistant to?
heat, drying, chemicals (like cleaning), radiation
are endospores always present?
NO only in Bacillus and Clostridium species
internal structures:
how long can endospores survive? are there contamination concerns?
for thousands of years, and there are contamination concerns
internal structures:
is the forming of endospore reproduction?
NO, forming endospores is not a form of reproduction.
internal structures:
how are endospores formed?
sporulation is formed into an endospore by:
1. Vegetative growth stops and DNA is duplicated.
2. A septum forms, dividing the cell asymmetrically.
3. The larger compartment engulfs the smaller compartment, which forms a forespore within a mother cell.
4. Pepidoglycan-containing material is laid down between the two membranes that now surround the forespore (the thick material around the smaller compartment formed).
5. The mother cell is degraded and the smaller compartment, now the endospore, is released.
which of the following are the functions of pili in the prokaryotic cell?
1. Sporulation and germination
2. Storage of extrachromosomal DNA
3. Attachment and conjugation
4. Motility and protein production
- Attachment and conjugation.
Pili that are used for attachment are called fimbriae.
Pili that are used for conjugation/bacteria sex are called: sex pilus
(1- Endospores; 2- Plasmids; 4- Flagella).
Which of the following is NOT a characteristic of the prokaryotic plasma membrane?
1. It is selectively permeable.
2. It contains a phospholipid bilayer
3. It contains proteins
4. It contains cholesterol
5. It can transport substances actively or passively
- It contains cholesterol (the mycoplasma contains cholesterol)
Which of the following is true about the cell wall of Gram-positive bacteria?
1. It determines the shape of the cell
2. It prevents osmotic lysis of the cell
3. It contains many layers of peptidoglycan
4. It is targeted by lysozyme
5. All of the above are true
- All the above are true.
Endotoxin is:
1. Continuously secreted from a living cell
2. Associated with Gram-positive bacteria
3. Part of the Gram-negative cell wall
4. The cause of walking pneumoniae
5. Not a problem if released systemically
- Part of the Gram-negative cell wall.
The nucleoid of prokaryotes:
1. Is membrane-bound with pores for communication
2. Contains a nucleolus
3. Contains one single-stranded chromosome
4. Contains extrachromosomal plasmids
5. Is an area for supercoiled DNA
- Is an area for supercoiled DNA
Which of the following statements is true?
1. Endospores are the same as capsules
2. One vegetative cell reproduces to make many endospores
3. Endospores are sensitive to chemicals, drying, heat and radiation
4. One vegetative cell produces one endospore
5. Endospores are easily stained in a Gram stain
- One vegetative cell produces one endospore
In 1985, a 0.5 mm cell was discovered in surgeonfish. It was presumed to be a protozoan. In 1993, researchers determined that it was actually a Gram-positive bacterium. What do you think caused the initial identification of this organism as a protozoan? What evidence would change the classification to a Gram-positive bacterium?
This organism is very large and would be presumed to be eukaryotic based on size. However, since it was discovered to be a Gram-positive bacterium, it must have specific Gram-positive characteristics such as a cell wall with many layers of peptidoglycan and wall teichoic/lipoteichoic acids.
Do prokaryotic cells contain a nucleus?
No, they contain DNA in a nucleoid region
Bacterial cells stain differentially with the Gram staining procedure due to differences in the structure of their:
Cell wall
Which organism will be sensitive to an antibiotic that targets teichoic acids?
Gram-positive bacteria
Which structure do bacterial cells use for DNA transfer?
Pili
are plasmids present in the nucleoid region?
NO. they are just in the general region of the cytoplasm.
Give 3 differences between cell wall structures of Gram-positive and Gram-negative
bacteria.
- Gram-positive bacteria:
-Has many layers of peptidoglycan, causing a very thick cell wall.
-Has teichoic acids which help to anchor and stabilize the peptidoglycan layers to the plasma membrane.
-Has no outer membrane - Gram-negative bacteria:
-Has only a few peptidoglycan layers.
-Has an outer membrane with a bilayer consisting of lipopolysaccharides.
-Has no teichoic acids.
what are siderophores?
Siderophores are molecules secreted by bacteria to scavenge iron from the host.
Iron is an essential nutrient for the host as well as for most microbes. In the host, free iron levels are extremely low as the metal is largely bound to proteins like lactoferrin and transferrin. To obtain iron, some bacteria produce siderophores, which can steal iron from host proteins and deliver it to the bacterial cell.
what type of cell is Klebsiella pneumoniae?
a Gram-negative, non-motile, rod-shaped bacterium.
what are virulence factors?
There are three structures in the cell that help K. pneumoniae attach to our cells and hide from our immune system. We call such traits of a microbe that promote pathogenicity - virulence factors.
what are the 3 virulence factors of K. pneumoniae?
- Fimbriae
- Capsule
- Lipopolysaccharide (LPS)
- Siderophores
