Prokaryote Cell Structure Flashcards
What five items constitute basic prokaryotic cell structure?
- Cytoplasmic membrane
- Cell wall
- Capsule or slime layer
- Filamentous protein appendages
- Internal structures
Capsules and slime layers are types of . . . .
Glycocalyx
What are two examples of filamentous protein appendages?
- Flagella
2. Pili
Name five prokaryotic internal structures.
- Chromosomes
- Ribosomes
- Plasmids
- Storage granules
- Endospores
What are the 2 main functions of prokaryotic membrane proteins?
- Receptors
2. Transport gates
What are the 3 roles of the cytoplasmic membrane?
- Define cell boundary
- Semi-permeable barrier
- Site of energy production (e- transport chain)
Which 3 types of molecules pass through the cytoplasmic membrane via simple diffusion?
- Water
- Some gasses
- Small hydrophobic (non polar) molecules
What is osmosis?
The ability of water to flow freely across the cytoplasmic membrane.
What cases water to flow into or out of a cell?
Water flows into areas of higher solute concentrations in an attempt to equalize them.
What tonicity do prokaryotes usually grow in, and what is the result?
Prokaryotes usually live in hypotonic locations. Water flowing into the cell exerts hydrostatic pressure, but the cell wall keeps the cell from bursting.
What will result from a damaged bacterial cell wall?
The cell will lyse.
What is facilitated diffusion?
Impermeable compound movement across a membrane by EXPlOITING a concentration gradient.
How can facilitated diffusion alter a concentration gradient?
It can lower or eliminate a gradient, but not create one.
How much energy is required for Glycerol to enter an E. coli bacterium? What type of transport is it?
No energy is expended for facilitated diffusion of Glycerol across an E. coli membrane.
What is active transport?
Impermeable compound movement across a cell membrane, AGAINST a concentration gradient.
What are the three primary mechanisms of active transport in prokaryotes?
- Proton motive force
- ATP binding cassette system
- Group translocation
How does proton motive force work?
- Transporters allow protons (H+) to enter
2. Protons either bring in or expel other substances
The permease that transports lactose into bacteria is an example of which kind of active transport?
Proton motive force
Efflux pumps in antibiotic- resistant bacteria use what kind of active transport?
Proton motive force
What is the ATP Binding Cassette System (ABC transport)?
Bacteria sometimes uses binding proteins to scavenge and deliver molecules to transport complex.
Maltose transport is an example of what type of active transport?
ATP Binding Cassette System
What is group translocation?
An active transport mechanism that chemically alters a molecule during passage. [Uptake of molecule does not alter concentration gradient.]
The phosphotransferase system is an example of which type of active transport?
Group Translocation
Describe how glucose enters a cell, driven by insulin?
Glucose utilizes group translocation. The sugar molecule is phosphorylated during transport. The molecular alteration means that the concentration gradient does not change.
Where is the site of energy production?
The cytoplasmic membrane.
How is energy produced on the cytoplasmic membrane?
The electron transport chain involves a series of embedded proteins. The proteins are used to form a proton motive force. The energy produced is used to drive transport mechanisms or to create ATP.
What is the rigid structure surrounding the cell membrane called?
The cell wall
What are two functions of the cell wall?
- Determines shape of cell
2. Prevents cell from lysing
Which chemical lends itself to the rigidity of the cell wall?
Peptidoglycan (PTG)
Describe the basic prokaryotic cell wall structure.
Alternating series of NAG and NAM, joined to form Glycan Chains. Glycan chains are held together by a string of 4-amino acids called a Tetrapeptide Chain.
Describe the two main components of a G+ cell wall.
- Relatively thick layer of PTG (<30 layers)
2. Teichoic Acid (gives cell a negative charge)
Give a description and location of PTG in a G- cell.
PTG is in a thin layer, sandwiched between an outer membrane and the cytoplasmic membrane.
What is a Gram- outer membrane composed of?
It is a lipid bilayer (made of lipopolysaccharide), called LPS.
What is the region between the outer membrane and cytoplasmic membrane called?
The periplasm
Where are the binding proteins of ABC transport system located in G- bacteria?
The periplasm
Where are most secreted proteins contained in G- bacteria, unless transported across outer membrane?
The periplasm
What differences in G+ and G- cell walls account for differences in staining characteristics?
- Gram-positive bacterium retain crystal violet-iodine complex of Gram stain
- Gram-negative bacterium lose crystal violet-iodine complex
Which antimicrobials interfere with the synthesis of PTG?
- Penicillin
2. Lysozymes
How does Penicillin fight bacteria?
Binds proteins involved in cell wall synthesis and prevents cross-linking of glycan chains by tetrapeptides
Is Penicillin more effective against G+ or G- bacteria? Why?
More effective against Gram+ bacteria, because it can’t cross outer membrane.
[Penicillin derivatives produced to protect against G-.]
Where are Lysozymes produced?
In many body fluids including tears and saliva
How do Lysozymes fight bacteria?
They break bonds linking NAG and NAM
Which bacterium naturally lacks a cell wall? How is its membrane strengthened?
Mycoplasma contain sterols in membrane
What does Mycoplasma bacterium cause?
Mild pneumonia
What do Archea contain instead of peptidoglycan?
Pseudopeptidoglycan
What are the 2 Layers External to the Cell Wall?
Capsule and Slime layer
What is a capsule?
A distinct gelatinous layer surrounding a bacterium
What is a slime layer?
An irregular diffuse layer
What are the 2 general functions of slime layers and capsules?
- Protection from host defenses
2. Enables bacteria to adhere to specific surfaces
What are most slime layers and capsules made of?
Polysaccharide, referred to as glycocalyx
Glyco = sugar calyx = shell
Xanthomonas campestris produces a slime layer used to make what?
Xanthan gum, used as a gelling and stabilizing agent in salad dressings, ice creams, toothpastes, etc.
What are 2 types of Filamentous Protein Appendages?
Flagella and Pili
What are flagella?
Long protein structure, responsible for motility (propeller like movements to push bacteria, Chemotaxis)
How can flagellar location aid in identification of a bacterium?
E. coli have flagella over entire surface (peritrichous) while others have a polar flagellum (monotrichous)
How do pili compare to flagella?
They are considerably shorter and thinner than flagella.
What are the 3 functions of pili?
- Attachment - these pili called fimbriae
- Movement – twitching motility
- Conjugation - Mechanism of DNA transfer (ex F-pilus)
What are the two prokaryotic Genetic Internal Structures?
- Chromosome
2. Plasmid
What are 4 characteristics of prokaryotic chromosomes?
- Resides in cytoplasm, in nucleoid space
- Typically single chromosome
- Circular double-stranded molecule
- Contains all genetic information
What are 3 features of Plasmids?
- Circular DNA molecule (0.1% to 10% size of chromosome)
- Extrachromosomal (Independently replicating)
- Encode characteristic that potentially enhances survival (ex Antimicrobial resistance)
What is the ribosome’s function?
Protein synthesis
What do ribosomal subunits consist of?
riboprotein and ribosomal RNA
What size are Prokaryotic ribosomal subunits?
Large = 50S Small = 30S Total = 70S
How do prokaryotic ribosomes differ from eukaryotic ones, and what is the significance?
Prokaryotic ribosomes are smaller, and that difference is often used as target for antimicrobials
What are endospores?
Dormant cell types, produced through sporulation
~ Theoretically remain dormant for 100 years
When does endospore germination occur?
After exposure to heat or chemicals
How are Vegetative cells produced from endospores?
Through germination (not a source of reproduction)
What was Robert Koch was able to establish?
endospore role in disease transmission (Bacillus anthracis)
What did Tyndall attribute contamination issues in Pasteur’s experiments to?
Heat resistant life form, called endospore
