MB 351 - Lectures 9, 10, 11 Flashcards
Atypical Cell Walls: -waxy lipid bound to peptidoglycan -what is this waxy lipid? and what kind of bacteria have this?
-Acid fast cell wall type -waxy lipid is mycolic acid -prevents the uptake of most dyes -mycobacterium and nocardia
Most bacteria are either….think type of cell wall
gram negative or gram positive
Atypical Cell Walls: -Lack cell walls
Mycoplasmas and Archaea
Mycoplasmas
-lack cell walls -sterols in plasma membrane (lipids that protect from lysis)
Archaea
-Wall-less or -Walls of pseudomurein (lack NAM and D-amino acids)
Why do microorganisms move, and what is the movement called?
Tactic (taxis) response behavior -looking for nutrients (C&N) -avoiding predators -catching prey
Stimuli that microbes move in response to: three of them
aerotaxis - move towards oxygen concentration phototaxis - photon intensity chemotaxis - chemicals that attract or repel microbes
Peritrichous
flagella all over cell
monotrichous and polar
single flagella
lophotrichous and polar
a tuft of flagella coming from one pole
amphitrichous and polar
flagella on both poles of the cell
Various patterns of motility: RUNS
a run or swim is when a bacterium moves in one direction for a length of time. Runes are interrupted by tumbles. Then a run resumes. Tumbles are caused by reversal of the flagellar rotation
Some bacteria with polar flagella will have reversible motors that allow them to move forward when it turns ______ and backwards when it goes ______.
CCW, CW -some are incapable of this, and may only travel in one direction (only CW flagella = unidirectional). They must stop, reorient in order to change directions
Flagella (gram -) three basic parts
-filament made of flagellin proteins -wider hook -basal body, which anchors the flagellum to the cell wall and plasma membrane
The basal body contains a small central rod inserted into a series of rings. What are these rings and where are they located?
-L ring is embedded in the OM and LPS -P ring is in the peptidoglycan -MS and C rings are embedded in the cytoplasmic membrane
Which proteins function as the flagellar motor?
Mot proteins (bound to MS and C ring)
Fli proteins function as?
function as the motor switch
A __________ model has been proposed to explain rotation of flagellum.
proton turbine. Protons flowing thru the Mot proteins may exert forces on charges present on the C and MS rings, thereby spinning the rotor and the attached filament. 20,000 rpm
-occur at the poles or can be evenly distributed over surface of cell -hairlike appendages that are shorter, straighter, and thinner than flagella -tend to adhere to each other and to surfaces, as a result, they are involved in forming _______
Fimbriae - also help bacteria to adhere to epithelial surfaces in the body biofilms
Pili
-usually longer than fimbriae and number fewer only 1-2 per cell -Pili are involved in DNA transfer – connect two cells for the exchange of genetic material -also aid in the attachment to host cells during infection
Pili involved in this kind of motility ________ and _________
-Twitching motility a special “type IV” pilus extends by the addition of subunits of pilin, makes contact with a surface and then retracts as the pilin subunits are disassembled. -called GRAPPLING HOOK MODEL (short, jerky, intermittent movements) -GLIDING motility - a smooth gliding movement of myxobacteria. Provides a means for microbes to travel in environments with low water content, such as biofilms and soil.
Prokaryotic cells lack: Also, cytoskeleton proteins are _______ to eukaryotes.
nucleus, no carbohydrates and usually lack sterols in their plasma membrane -Sterols are essential in all eukaryotic cell membranes. They modulate membrane fluidity and permeability. Sterols and carbs serve as receptors present in eukaryotes. SIMILAR
Plasma membrane contains
phospholipid bilayer with lipid-soluble proteins
Due to lack of ________ in the plasma membrane of prokaryotes, they are less rigid than eukaryotic membranes.
sterols
Phospholipid molecules contain:
polar head made of phosphate and glycerol that is hydrophilic (soluble in water), and nonpolar tails composed of fatty acids that are hydrophobic (insoluble in water)
Fluid mosaic model
phospholipids and proteins (reception and transport proteins) are not static, but move quite freely
Functions of the plasma membrane: three things
selective permeability, protein anchor, energy generating/conservation
Selective permeability
Most important function of the cell membrane is to serve as a selective barrier through which materials enter and exit the cell. Only certain molecules and ions can pass through the membrane. This function allows the cell to concentrate certain metabolites and excrete waste materials.
Protein anchor
Plasma membrane serves as the protein anchor, some proteins anchor together different layers of the cell envelope providing structure support. (Carrier proteins). Anchors for enzymes (ATP production, transport proteins).
Energy conservation
microbial energy generating processes involve the generation of a PROTON MOTIVE FORCE (PMF) where protons are selectively moved across the membrane.
Membrane Permeability Chart
Enzymes made within the cell, then released outside of the cell to begin the process of extracellular digestion. Used since large macromolecules cannot normally pass through the cell. These _______ can be classified on the basis of what kinds of molecules they hydrolyze:
Exoenzymes
hydrolyze: carbohydrates, lipids, proteins, nucleic acids
ex. amylase hydrolyzes starch into mono- and dissacharide subunits. Iodine binds to starch, but not to its breakdown products (clear streak)
