Prokaryotic Cell Structures - Chapter 2 Flashcards
What are the components of every prokaryotic cell?
DNA, membranes, ribosomes, and cytoplasm
What are the components of the cell true in?
Bacteria, archaea, fungi, algae, protozoa, and helminths
What are the components of the cell not true in?
Viruses as they can lack a plasma membrane, ribosomes, or DNA
What is the component of the cell that viruses have?
Cytoplasm as they will take some of the host cell’s cytoplasm
What is not in prokaryotes that are in eukaryotes?
Membrane-bound organelles such as the nucleus
Why are viruses not considered cells?
They can’t independently translate proteins, they exclusively rely on a host cell
What does a nucleoid contain?
Chromosomes and nuclear-associated proteins
What can you look for to find the nucleoid?
DNA
What are chromosomes usually in prokaryotes?
Haploid and circular
Haploid
One copy of the chromosome
What are chromosomes usually in eukaryotes?
Diploid and linear
How many chromosomes are in humans
23 unique chromosomes or 24 unique chromosomes in males (1 X, 1Y)
What is the nucleoid NOT?
It is not a nucleus or membrane-bound
What can plasmid also be referred to as?
Bonus DNA
What is the plasmid?
Circular double-stranded DNA
What is the size comparison between chromosomes and plasmid?
They are much smaller than bacterial chromosomes
Where is the plasmid located?
Throughout the cytoplasm
How many plasmids can you have?
1-100s, you can have multiple unique plasmids and multiple of the same plasmids
What do plasmids encode for?
Antibiotic resistance genes and virulence factors
Virulence factors
Different things that help bacteria infect us better
Is plasmid a part of the chromosome?
No
What does the ribosome do?
Protein synthesis
What is the ribosome made up of?
Proteins and RNA
What are the parts of a ribosome?
The large and small subunit
What is the size of the small subunit in prokaryotes?
30S
What is the size of the large subunit in prokaryotes?
50S
What is the total size of the ribosome in prokaryotes?
70S
What is the size of the small subunit in eukaryotes?
40S
What is the size of the large subunit in eukaryotes?
60S
What is the total size of the ribosome in eukaryotes?
80S
What is used to sequence in prokaryotes?
16S rRNA
What is used to sequence in eukaryotes?
18S rRNA
What does S stand for in the unit of the subunit?
Svenbergs
What do both prokaryotic and eukaryotic ribosomes have in common?
They both use mRNA to make proteins and are composed of proteins and RNA
What is the difference between prokaryotic and eukaryotic ribosomes?
-The size of the subunits (Prokaryotic - 30S, 50S, 70S Eukaryotic - 40S, 60S, 80S)
-What’s used for sequencing (Prokaryotic - 16S, Eukaryotic - 18S)
-The position (Prokaryotic - free-floating, Eukaryotic - free-floating or attached to the ER membrane)
Are inclusions in all bacteria?
No, they are not
Inclusions
Storage of nutrients, etc., similar to vesicles as we move things around in them, protein coat (shell) instead of lipid
Why do we have inclusions?
There are no membrane-bound organelles
What are the types of inclusions?
Lipid droplets, volutin, sulfur inclusions, gas bubbles, and magnetosomes
Lipid Droplets
Lipid storage
Volutin
Storage of inorganic phosphates, inclusion
Why do we want phosphates?
To make ATP for respiration
Sulfur Inclusions
Storage of sulfur, electron acceptor if there is no oxygen
What are sulfur inclusions used for?
Metabolism
Gas Bubbles
Inclusion that controls buoyancy
What are gas bubbles equivalent to?
Swim bladder
What are gas bubbles found in?
Aquatic bacteria as it helps them move
Magnetosomes
Bacteria that are magnetic, aid in movement as they can move towards or away from a pole
What do magnetosomes contain?
Magnetic metals such as iron oxide or iron sulfide
Are endospores in every bacteria?
No, they are not
Where are endospores found?
Inside the bacteria
Endospore Function
Protect bacteria in a dormant state from dying
What genera produce endospores?
Bacillus and Clostridia
How do endospores form?
The bacteria are lysed open, the bacteria technically die in this process
Sporulation
Process of becoming dormant/making endospores
Germination
Process of becoming active, happens in nutrient-rich and moist environments
When does sporulation occur?
When the bacteria are in a nutrient-poor or dry environment
Sporulation Steps
DNA replication, membranes form around the DNA, forespore forms additional membranes, protective cortex forms around the spore, protein coat forms around the cortex, spore is released
Cortex
The first protein coat
What does the protein coat around the cortex do?
It locks in moisture so that osmosis doesn’t occur
What is a characteristic of the plasma membrane?
Semi-permeable
Plasma Membrane Composition
Composed of lipids and proteins
Plasma Membrane Function
It controls transport into and out of the cell
What are the kinds of membrane transport?
Diffusion, facilitated diffusion, active transport, and endocytosis
Glycoproteins
Have sticky carbohydrates to interact with different surfaces
Endocytosis
Only in eukaryotes, invaginates things into the membrane
What does endocytosis need to occur?
A vesicle, a membrane-bound organelle, which bacteria lack
Sterols
Cholesterol or ergosterol
What are sterols unique to?
Eukaryotes
What is cholesterol found in?
Humans
What is ergosterol found in?
Fungi
Diffusion
Used in bacteria, high to low concentrations
Simple Diffusion
Move from areas of high to low concentrations without any help
Facilitated Diffusion
Move from areas of high to low concentrations, normally large molecules are transported this way as they can’t pass through the membrane and need the help of a protein channel
Active Transport
Move from areas of low to high concentrations, requires energy as it’s moving against the gradient
Cell Wall Function
Creates a rigid structure that protects the cell from harsh environments
What does the cell wall contain in bacteria?
Peptidoglycan
What are the types of bacteria?
Gram-negative and gram-positive
What does the cell wall contain in plants?
Cellulose
Periplasmic Space/Periplasm
Space between the cell wall and the plasma membrane
Gram-Positive Bacteria
Thick cell wall -> more protective, but also more vulnerable to temperature changes, detergents, and soaps
What do gram-positive bacteria have?
Teichoic acid and lipoteichoic acid
Gram-Negative Bacteria
Thin cell wall and an outer membrane
Outer Membrane
A bonus membrane that is more permeable to different types of molecules compared to the plasma membrane, contains special glycolipids
What do gram-negative bacteria have?
LPS which is the lipid part embedded in the outer leaflet of the outer membrane
Mycoplasma sp
Lack a cell wall so to determine the category it has to go through 16S sequencing
Peptidoglycan Types
N-acetylglucosamine (NAG), N-acetylmuramic acid (NAM), and tetrapeptide
What peptide is only in gram-positive bacteria?
Pentapeptide
Tetrapeptide
Link peptides
Pentapeptides
Help stack top to bottom to get a thicker peptidoglycan, gram-positive
How do gram-negative bacteria connect their peptides?
Through horizontal connections to get a thinner peptidoglycan
Lipopolysaccharide (LPS)
Structural component of the outer membrane, a toxin that over-activates the immune response, gram-negative bacteria
What part of LPS is toxic?
The lipid portion
Are the majority of the gut bacteria gram-positive or gram-negative?
Gram-negative
When does LPS have a toxic effect?
It is embedded in the membrane so it has to come out of the membrane to have a toxic effect
What removes LPS from the membrane?
Enzymes such as antibiotics, disruption by soaps, or cell division
What projects off the surface of the cell?
Carbohydrates are on the outer membrane, O antigen, and core
Where are lipids embedded?
Lipids are embedded in the outer leaflet of the outer membrane closer to the fatty acid side
Gram Stain Process
Crystal violet, iodine, alcohol, and safranin
Crystal Violet Stain
Primary stain added to the specimen smear
What effect does crystal violet stain have on cells?
It stains both gram-positive and gram-negative cells purple or blue
Iodine Stain
Mordant makes dye less soluble so it adheres to cell walls, helps dye stick better
What effect does iodine have on cells?
Cells remain purple or blue
Alcohol Stain
Decolorizer/destainer washes away stains from gram-negative cell walls
What effect does alcohol have on cells?
Gram-positive cells remain purple or blue. Gram-negative cells are colorless.
Safranin Stain
Counterstain/secondary stain which allows dye to adhere to gram-negative cells
What effect does safranin have on cells?
Gram-positive cells remain purple or blue. Gram-negative cells appear pink or red.
Are acid-fast bacteria gram-negative or gram-positive?
Gram-positive as it has a plasma membrane and layer of peptidoglycan
What happens when acid-fast bacteria stain?
It won’t stain gram-positive as it has an extra layer called mycolic acid
Mycolic Acid
Waxy substance which prevents gram stain dyes to penetrate
Acid Fast Stain
Dyes mycolic acid red as it’s specific to mycobacterium s.p.
Mycobacterium s.p.
Bacteria causing TB and leprosy
Glycocalyces
Capsule or slime layer
What do glycocalyces help in?
Help bacteria stick to surfaces and aid in biofilm formation
Biofilm
Communities of bacteria living together
What is the s-layer commonly found in?
Archaea
S-Layer
Substitute cell wall
Fimbriae
Short bristle-like protein projections off the cell, coat the bacteria
Fimbriae Function
Help bacteria adhere to surfaces
Pili
Medium-length protein projections, less numerous
Pili Function
Help bacteria adhere to surfaces and aid in DNA transfer -> specifically plasmid DNA (conjugation)
Flagellum
Longest protein projections
Flagellum Function
Aid in movement
What are flagellum made of?
The protein flagellin which are eukaryotic flagella made of actin and microtubules
Types of Flagella
Monotrichous, amphitrichous, lophotrichous, peritrichous
Monotrichous
One flagella
Amphitrichous
One flagella at each end, two together
Lophotrichous
Several flagella at the same end
Peritrichous
Lots of flagella are found everywhere
What do gram-positive bacteria have to pass through?
Peptidoglycan and the inner membrane
What do gram-negative bacteria have to pass through?
2 membranes with peptidoglycan in the middle
What are flagella and cilia made up of?
Actin and tubulin
What do flagella and cilia form?
Bundles that project out of the cell
What are cilia similar to?
Fimbriae
Where are cilia not found?
Not found in prokaryotes
How do bacteria move?
Tumbling or running of flagella (like a motor to propel them forward)
Tumbling of Bacteria
Clockwise rotation of flagella, causes flagella to splay which will slow down, turn it, or stop it
Running of Bacteria
Counter-clockwise rotation of flagella, flagella bundle together, bacteria move forward
What do bacteria follow when moving?
Nutrients or other signals
Chemotaxis
Moving toward or away from a chemical
Bacteria Shapes
Coccus, bacillus, vibrio, coccobacillus, spirillum, and spirochete
Coccus Shape
Round
Bacillus Shape
Rod-shaped
Vibrio Shape
Curved rods
Coccobacillus Shape
Short rod, ovalish shape
Spirillum Shape
Wave-shape
Spirochete Shape
Coil
Diplococcus
Pair of 2 cocci
Tetrad
Grouping of 4 cells arranged in a square
Streptococcus
Chain of cocci
Staphylococcus
Cluster of cocci
Streptobacillus
Chain of rods
