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Give a basic description of prokaryotic cells.
small and structurally simple
most are unicellular
most have a cell envelope
T?F: The cell envelope is always a single homogenous layer.
False. It can be a complex, multilayered structure.
How does the cell envelope prevent osmotic lysis.
It contains the pressure with a layer external to the cell membrane that resists expansion of the cell volume.
What terms are used to describe shapes of multicellular microbes?
mycelium (like a branched filament)
Describe the make-up of the gram-negative envelope.
periplasmic space containing little murein/peptidoglycan
Describe the make-up of the gram-positive envelope.
multiple layers of murein
Describe the make-up deinococcal envelope.
multiple layers of murein
Describe the make-up planctomyces envelope.
layer of protein
What term is used to describe prokaryotes without a defined cell envelope layer that have their membranes strengthened by glycolipids?
Mycoplasmas contain an extracellular layer called lipoarabinomannan. What is it and what is its function?
It is a wax that gives rigid structure to mycoplasmas.
Does mycoplasma stain Gram + or Gram -? Explain.
It doesn't stain at all because it lacks peptidoglycan altogether.
Some free living prokaryotes lack a cell envelope altogether. What to they tend to have to strengthen their membranes?
a large amount of glycolipids
Murein is a form of petidoglycan in which the individual glycan strands are cross-linked to each other by the _____.
What specific type of peptide linkage exists between the two sugars that make up murein?
beta 1-4 linkage
What do NAG and NAM stand for (spell their names)?
NAG - N-acetylglucosamine
NAM - N-acetylmuramic acid
NAM has an R group composed of amino acids. The length and sequence of every chain varies except for the last two amino acids. What are they?
NAM has an R group composed of amino acids. The amino acids that is third from the end of the chain always contains what?
free amino group
Covalent linkages form between side chains of adjacent murein strands. Specifically, where do these linkages form?
Between the D-Alanine of one side chain and the amino acid with a free amino group (third from the end) of another side chain
What is the name of the enzyme involved in making a peptide bond between different strands of murein?
How does archaeal pseudomurein differ from bacterial murein?
1. Contains N-acetyltalosaminuronic acid instead of NAM
2. Linkages are beta 1-3 instead of beta 1-4
3. All L amino acids in the side chain instead of D and L
Name and describe the two types of teichoic acids.
Lipoteicholic acids - linked to membrane phospholipids
Wall teichoic acids - covalently linked to murein
There are many enzymes secreted by bacteria or by fungi that attack some of the different types of murein in the Eubacteria Domain. Give an example.
lysozyme - cleaves beta 1-4 linkage between NAG and NAM
Why can Gram + bacteria tolerate loss of murein on the outer surface but Gram - can not?
Gram + have a thick layer of murein but Gram - have a very think layer that makes them vulnerable.
In a gram - bacteria, the outer leaf of the outer membrane consists of _____ and the inner leaf of the outer membrane consists of _____.
What does the Braun lipoprotein in the inner leaf of the outer membrane of gram - bacteria do?
connects the outer membrane to the murein
The outer membrane of gram - bacteria contains porin proteins that allow for what?
solute diffusion across the outer membrane
Describe the structure of the lipid A portion of a lipopolysaccharide.
Consists of a dimer of glucosamine phosphate to some or all of whose free hydroxyl and amino groups are attached fatty acids with saturated side chains. Some of the fatty acids have a beta-OH group, which allows the attachment of additional fatty acids. (6-8 fatty acids)
Describe the function of the lipid A portion of a lipopolysaccharide.
The phosphates present create large charge density that form many hydrogen bonds to water and to the other side chains preventing nonpolar compounds from permeating the membrane.
Also, the saturated side chains are able to pack together tightly preventing hydrophobic compounds from slipping between the lipid molecules.
Describe the structure of the R-core portion of a lipopolysaccharaide.
It contains various sugars and sugar derivatives. Constant in a species.
Describe the structure of the O-specific side chain portion of a lipopolysaccharide.
It contains a sequence of five to six sugars tat repeat many times to make along chain. It varies within a species.
Give the two reasons that the outer membrane of a gram - bacteria is impermeable to both hydrophobic and hydrophilic compounds.
1. The high density of charges at the outer surface of the membrane.
2. The hydrocarbon side chains or the lipid A are saturated.
What is the periplasm of a gram - bacteria?
The compartment between the cell membrane and the outer membrane.
What are functions of the dense solution of protein present in the periplasm?
What two main functions does the cell membrane have?
1. It separates the cytoplasm from the exterior environment.
2. Allows the cytoplasm to have a chemical composition different form the environment.
Some things in a cell are needed in a spacial manner and must be anchored in someway to limit their diffusion. Give an example.
FtsZ ring - starts cell division so it needs to be in the middle of the cell.
T/F: The prokaryotic cell membrane has fewer protein and fewer different proteins than most membranes.
False. It has more protein and more different proteins.
Most prokaryotes have membrane-embedded electron transport proteins to get energy from _____ or _____.
respiration or photophosphorylation
The prokayotic cell membrane is the site of synthesis of 4 types of proteins. Name them.
cell membrane proteins
outer membrane proteins
In prokaryotic cell membranes, _____ proteins allow the cell to determine certain aspects of the chemical or physical conditions of the environment.
The prokaryotic cell membrane may invaginate into the cell to provide extra surface area. What is the benefit to having more surface area?
It allows more places for proteins to have interaction with the outside world.
Some prokaryotes have intracellular membrane bound organelles. Give an example.
ExPortal (GAS) and thylakoids in cyanobacteria
What type of lipids make up the bilayer or monolayer of archaeal cell membranes?
ether lipids; specifically glycero-lbiphytane-diethers (instead of glycerol-fatty acid diesters)
What did the ExPortal Paper discussed in lab contain?
Gold particles were placed on antibodies that allowed them to be seen under an electron microscope. They were congregated in a specific location on the edge of the cell showing a specific function.
What type of linkages and chains to the lipids of eukarya and bacteria have?
ester linkages and linear chains
In prokaryotic cells, the genetic material in a cell is a structure that lacks a nuclear envelope and a membrane. What is the structure called?
Does the size of the nucleoid change with the complexity of the cell?
Yes because more complexity means there are more genes
What is a plasmid and what distinguishes it from a chromosome?
A small circular DNA molecule that lacks genes essential for growth under all conditions and for core cellular functions
T/F: A microbe that lives in an area with a highly changing environment needs more genes to deal with different conditions.
T/F: Only a few bacteria have a single supercoiled chromosome (DNA Gyrase and Histone-like proteins)
False. Most bacteria have one.
How does a supercoiled chromosome form?
1. DNA gyrase take a loop of DNA
2. Makes a double stranded cut where the loop crosses over
3. Then passes the top part of the loop through the gap, and reseals the broken DNA. This introduces one new twist to the DNA.
T/F: The nucleoid is arranged with the origin of replication and the terminus at the same end.
False. The origin of replication and the terminus are at opposite ends.
The middle part of a prokaryotic chromosome is condensed into approximately ___ loops by special condensing proteins.
Why is coupling in protein synthesis so important?
It is the basis for attenuation. which is a mechanism of gene regulation.
Compaction of DNA into the nucleoid requires what to be done to the DNA by polyamines?
neutralization of DNA charges
_____ are small organic compounds with two, three, or four amino groups spaced approximately as far apart as the phosphates in DNA.
T/F: Because the amino groups are protonated at neutral pH, they can effectively neutralize the charges on the DNA and allow it to pack tightly.
What are two functions of an actin-like cytoskeleton?
maintains cell shape
moves material during division (no mitosis)
Rod-shaped and spiral bacteria have a helical band of filaments made of an actinlike protein called _____.
Structurally, how are MreB and actin similar?
nothing alike as chain of amino acid
How does FtsZ aid in cytokinesis of bacterial cells?
If forms a band of filaments around the middle of a prokaryotic cell and when chromosome segregation is completed, the ring contracts constricting the cell and initiating cytokinesis.
The cytoplasm of prokaryotes is a concentrated solution of proteins and small molecules. What organelle is densely packed into the cytoplasm?
Storage granules of reserve nutrients are present in cyctoplasm. Name two common ones.
glucose that forms glycogen
beta-hydroxybutyric acid forms polyhydroxubutyrate (PHB)
Describe how an acidocalcisome functions.
1. An ATP-driven calcium pump transports Ca2+ into the acidocalcisome.
2. Phosphate is transported into the acidocalcisome as pyrophosphate, then polymerized into poly-P.
3. A proton pump driven by pyrophosphate hydrolysis acidifies the acidocalcisome.
_____ _____ have highly hydrophobic interior surfaces and are composed of many individual gas vesicles.
Magnetosomes consist of a row of granules of a _____ mineral enclosed in a membranous invagination of the cell membrane.
Most bacteria with magnetosomes are microaerophiles, and they use the magnetosomes to fin the right concentration of _____.
What are the purposes of the Ca+2 and H+ in an acidocalcisome?
Ca - keeps charge balanced
H - keeps it from hardening from Ca by keeping low pH
Why do gas vauoles regulate the amount of gas in a cell?
to control the depth they are in the liquid environment
Give four main functions of a capsule.
1. avoid phagocytosis
3. pathogens use it to prevent immune system recognition
4. absorb moisture during times of dehydration
What is a biofilm?
an aggregation of cells held together in a common matrix of capsular material (often extracellular polysaccharides)
Why do pores and channels for throughout a biofilm?
So that bacteria in all parts of the biofilm can get adequate nutrients.
_____ are fine, hair-like appendages protruding from the cell surface made up of many molecules of globular protein.
Molecules at the tip of pili are termed _____, and they have specific binding sites that allow the pilus to attach to specific structures (like proteins or anchor to start growing).
Pilins are synthesized by ribosomes on the cell membrane and secreted into the periplasm. _____ _____ proteins escort the pilins across the periplasm and transfer them to the growing pilus.
What causes the basal body (or rotary motor) of flagella to spin in eukaryotes and prokaryotes?
eukaryotes - hydrolysis of ATP
prokaryotes - H+ gradient
What three things can the flagella do to control the movement of the cell?
3. Change direction - spin opposite direction = tumble
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