🦠Chapter 3: Structure of Microbes

True or False: Compounds unique to bacteria or certain other microbial groups can be detected by 'alarm systems' in the body.

True

What can the prokaryotic cell envelope consist of?

Cell wall, Cytoplasmic membrane, Capsule, Nucleoid, Cytoplasm, Extracellular matrix

What is the inner thick substance of a cell filled with nutrients, ribosomes, and enzymes?

Cytoplasm

In prokaryotes, where is the cell's chromosome found?

Nucleoid

True or False: Although bacteria and archaea have the same general structure, they are not closely related genetically.

True

Are bacterial components unique to bacteria potential targets for antibacterial medications?

True

What separates the interior of a prokaryotic cell from its outside environment?

Cytoplasmic membrane

What are the surface layers of a prokaryotic cell collectively referred to as?

Cell envelope

In a cytoplasmic membrane, the lipid tails are ___ and face towards the inside of the cell.

Hydrophobic

In a cytoplasmic membrane, the phosphate heads are ___ and face towards the environment.

Hydrophilic

What is the part of the cell that is enclosed by the cell envelope called?

Cytosol or cytoplasm

What is the main difference between the nucleoid and the nucleus?

The nucleoid is not membrane bound.

Which cell envelope component has a fluid structure?

Cytoplasmic membrane

Why do descriptions of cell structure often lump bacteria and archaea together?

They share the same general structure.

What are the functions of the proteins embedded in the cytoplasmic membrane?

Allowing the cell to monitor and adjust to its surroundings, Allowing nutrients to enter and waste products to exit

Which two macromolecules are the major components of cytoplasmic membrane?

Proteins and Lipids

Identify two differences between cytoplasmic membranes of bacteria and archaea.

The archaeal membrane contains isoprenoid tails while bacterial membranes contain fatty acid tails.

What does the fluid mosaic model reflect?

How proteins in a cytoplasmic membrane drift within the phospholipid bilayer.

If the proteins were removed from a bacterial cytoplasmic membrane, which of the following would NOT result?

The membrane would become rigid.

What indicates that bacteria live in a hypotonic medium?

The antibiotic penicillin prevents cell wall formation, causing the cells to burst.

How are archaeal cytoplasmic membranes compared to those of bacteria?

Structurally similar to, but chemically distinct from.

Which structure provides strength and rigidity to a cell?

Cell wall

Identify all the molecules that can move freely through the phospholipid bilayer.

Water, Oxygen, Carbon dioxide, Small hydrophobic compounds

The structure of peptidoglycan can best be compared to what?

Multilayered fence

In which bacteria are interbridges found linking tetrapeptide chains?

Gram-positive only

How does the cell wall of Gram-positive bacteria compare to Gram-negative bacteria?

Thicker

If a bacterial cell is placed in a hypertonic medium, where will water flow?

Out of the cell

Which of the following is a component of Gram-negative cells but not Gram-positive?

Outer membrane

What can differences in cell wall structure be used to identify?

Gram-positive and gram-negative

What does the outer membrane of a Gram-negative cell contain?

Lipopolysaccharide

Identify three components of peptidoglycan.

N-acetylmuramic acid, N-acetylglucosamine, Tetrapeptide

What is the substance referred to as endotoxin?

Lipopolysaccharide

Which amino acid is unique to the cell walls of Gram-negative bacteria?

Diaminopimelic acid

What are the specialized channel-forming proteins in the outer membrane of Gram-negative cells called?

Porins

True or False: Periplasm is only found in Gram-negative bacteria.

False

What is diamino pimelic acid?

A compound only found in Gram-negative bacteria.

What are porins?

Specialized channels that span the outer membrane of Gram-negative bacteria.

How does the peptidoglycan layer of Gram-negative bacteria compare to that of Gram-positive bacteria?

It is considerably thinner.

What is the effect of penicillin on peptidoglycan?

It prevents the cross-linkage of adjacent glycan chains.

Which bacterium is more sensitive to penicillin: Escherichia coli or Streptococcus pyogenes?

Streptococcus pyogenes.

What happens with low amounts of LPS?

It causes drops in blood pressure.

What happens with high amounts of LPS?

It may cause life-threatening shock.

Why are Gram-negative bacteria more resistant to lysozyme?

They have an outer membrane as part of their cell wall.

What is periplasm?

A gel-like substance between the cell wall and cell membrane.

What is a biofilm?

A polymer-encased community of microorganisms.

What is the term for the flagellar arrangement where flagella are distributed around the surface of a cell?

Peritrichous.

What is chemotaxis?

Movement of a cell toward or away from a certain chemical in the environment.

What is a bacterial plasmid?

A small, circular piece of DNA.

What is the size of a bacterial ribosome?

70S.

What is the function of fimbriae?

Attachment to a surface.

What is the composition of the cell wall in archaea?

Mostly pseudopeptidoglycan.

What is the function of pili in bacteria?

Attachment to surfaces and motility.

What is the longest component of the bacterial flagellum?

Filament.

What is lysozyme?

An antibacterial enzyme.

What is the role of the outer membrane in Gram-negative bacteria?

It protects against antibiotics like penicillin.

What is the difference between prokaryotic and eukaryotic ribosomes?

Prokaryotic ribosomes are 70S; eukaryotic ribosomes are 80S.

What are S-layers in archaea?

Sheets of flat protein or glycoprotein subunits.

What is the effect of removing the outer membrane from a Gram-negative bacterium?

It would be more susceptible to penicillin.

What is the term for a distinct gelatinous layer surrounding a cell?

Capsule.

What is the function of bacterial fimbriae?

Adhering to surfaces.

What is the arrangement of flagella called when there is a single flagellum at one end of a cell?

Polar flagellum or monotrichous arrangement.

What is the term for the movement of bacteria in response to oxygen gradients?

Aerotaxis.

What does the term 'haploid' mean in relation to bacteria?

Bacteria carry only one copy of their chromosome.

What is the role of the capsule in bacteria?

To protect against host immune responses.

What is the function of the cell wall in bacteria?

To provide structure and protection.

What is a slime layer?

A loose layer of polysaccharides surrounding some bacteria.

What is the role of the basal body in a flagellum?

Anchors the flagellum to the cell membrane.

What is the significance of the hook in a flagellum?

Connects the filament to the basal body.

What is the difference between a capsule and a slime layer?

Capsules are well-defined, while slime layers are more diffuse.

What is the primary component of the bacterial cell wall?

Peptidoglycan.

What is the role of teichoic acids in Gram-positive bacteria?

They help maintain cell wall structure.

What is the main function of the bacterial cell membrane?

Regulates the entry and exit of substances.

What is the role of flagella in bacteria?

To provide motility.

What is the function of the cytoplasmic membrane in bacteria?

It acts as a barrier and site for metabolic processes.

What does the bacterial chromosome look like?

It looks circular.

What internal structure helps control cell shape and is involved in cell division?

Cytoskeleton.

Which statement is NOT true of a plasmid?

It is typically required for normal cell function.

What is the purpose of storage granules produced by some bacteria?

To store nutrients.

What are ribosomes directly involved in?

The synthesis of proteins.

What are small, rigid, protein-bound compartments that provide buoyancy to some aquatic bacterial cells called?

Gas vesicles.

How is the bacterial ribosome best described?

30S + 50S = 70S.

What do bacterial microcompartments contain?

Enzymes required for certain reactions.

What type of chromosome does a typical bacterium possess?

A single, circular chromosome.

What are three advantages of endospore formation in bacteria?

Withstand dry conditions, resistance to disinfectants, and resistance to radiation and heat.

Which of the following is NOT considered a function of the bacterial cytoskeleton?

Aiding movement.

What triggers endospore formation in certain cells?

Nutrient limitation.

What are accumulations of high-molecular weight polymers synthesized from a nutrient that a cell has in relative excess called?

Storage granules.

What are the events in order during sporulation?

1. The cell stops growing and duplicates its DNA; 2. A septum forms, dividing the cell asymmetrically; 3. The larger compartment engulfs the smaller compartment; 4. The smaller compartment develops into a forespore; 5. The mother cell is degraded and the endospore is released.

Which factors contribute to the environmental resistance of bacterial endospores?

Polysaccharide capsule, spore coat, and lower water content.

What is the advantage of packaging enzymes into microcompartments?

The cell is protected from toxic metabolites.

What can induce endospore germination?

Moisture.

What is an endospore?

A dormant cell type.

How many vegetative cells does one endospore give rise to?

One.

What makes receptor-mediated endocytosis different from pinocytosis?

Receptor-mediated endocytosis has specific receptors that must bind for the substance to be engulfed.

What is the role of cytoplasmic membrane proteins in eukaryotic cells?

They function in facilitated diffusion and active transport of nutrients.

What is the sorting signal that directs a polypeptide to the endoplasmic reticulum?

The signal sequence.

How is the eukaryotic ribosome found outside the mitochondria best described?

40S + 60S = 80S.

What are the types of endocytosis?

Pinocytosis, receptor-mediated endocytosis, and phagocytosis.

What is the process by which cells take up liquids from the surrounding environment?

Pinocytosis.

What are the true statements regarding membrane channels?

They form pores in the cytoplasmic membranes and allow a cell to control what enters and moves across the membrane.