Test 1 - Part II - Structure of the Bacterial Cell: Periplasm, Peptidoglycan, Gram Positive Cell Wall, and Gram Negative Cell Walls

Gram Negative Cell Walls 1) Composition? 2) Where is the peptidoglycan located in gram negative cells?

1) Composed of an outer membrane (made of lipopolysaccharide (LPS), phospholipid, and protein), and an underlying thin layer of peptidoglycan 2) There is a space between the outer and inner membrane where peptidoglycan lies in the periplasm

Lipopolysaccharide (LPS) 1) Recognized by the body as an...? 2) Is LPS permeable or not? 3) What things are it involved in? 4) Three regions? 5) Present only in...?

1) Endotoxin 2) It is permeable but only to low molecular weight hydrophilic molecules 3) Involved in adherence, or resistance to phagocytosis, or antigenic shifts 4) 1. Lipid A 2. Core (or R polysaccharide) 3. Repeating oligosaccharide (O-antigen or somatic antigen) 5) Gram negative cell walls

Location of the Periplasm 1) Where is the periplasm located in Gram Negative Bacteria? 2) Where is the periplasm located in Gram Positive Bacteria?

1) It is a compartment between the cell membrane and the outer membrane of gram negative bacteria 2) In gram positives, it is a very thin space between the cell membrane and the peptidoglycan layer.

Peptidoglycan of Archaea 1) What is the peptidoglycan of archaea like? 2) Describe the structure of the pseudopeptidoglycan in Archaea? 3) They are not all alike, they vary from...? 4) Archaeal cells walls never contain what three things?

1) Its a pseudopeptidoglycan 2) Consists of N-acetylglucosamine (NAT) and N-Acetyltalosaminuronic acid; has sugars linked by a B-1,3 glycosidic linkage 3) bacterial cell walls 4) peptidoglycan, polysaccharide, or protein

Two examples of using enzymes to destabilize the cell wall and how they work?

1) Lysozyme - enzyme that destroys peptidoglycan by hydrolyzing the glycosidic linkages (destroys the B-1,4 linkages) 2) Using antibiotics like penicillin, vancomycin, and bacitracin - they interfere with the synthesis of peptidoglycan and prevent cells from restraining turgor pressures.

6 periplasmic components?

1) Oligosaccharides 2) Solute Binding Proteins 3) Cytochrome C 4) Hydrolytic Enzymes 5) Detoxifying Agents 6) TonB proteins

Periplasmic Components: TonB Protein 1) For E. coli, how are they situated? 2) Why are TonB proteins required for the cell?

1) Originates in plasma membrane and extends to outer membrane in E. coli 2) required for uptake of certain solutes, including iron siderophores and vitamin B12 against a huge concentration gradient.

Periplasmic Components: Oligosaccharides 1) Involved in...?

1) Osmotic regulation

What four things do Peptidoglycan provide for the cell?

1) Strength and rigidity 2) Confers shape to the cell 3) Provides protection from mechanical damage 4) Protection from lysis in hypotonic solutions

Lipoteichoic Acids 1) Present only in...? 2) What is their structure? 3) Why are they amphipathic? 4) How are part of the cell wall? 5) What happens to them and what do they do?

1) The cell wall of gram positive cells 2) linear polymer of phosphodiester-linked glycerol phosphate covalently bound to lipid 3) b/c of (-) backbone of glycerol phosphate and hydrophobic lipid (establish a negative charge in periplasm at outer face of the membrane) 4) They are NOT covalently bound to the peptidoglycan. They are attached but their function is not completely understood. 5) They are secreted; they function as an adhesive to become part of the glycocalyx along the M protein

Teichuronic Acids 1) Present only in...? 2) What is their structure?

1) The cell wall of gram positive cells 2) polyanionic acidic polysaccharides containing uronic acid

Teichoic Acids 1) Present only in...? 2) What is their structure? 3) How are they attached to the cell wall?

1) The cell wall of gram positive cells. 2) polyanionic polymers of ribitol phosphate or glycerol phosphate joined by anionic phosphodiester bonds 3) Attached to peptidoglycan via covalent bonds between the phosphate of glycerol phosphate to N-acetylmuramic acid (NAM)

Periplasmic Components: Hydrolytic Enzymes 1) What is the purpose of hydrolytic enzymes?

1) They degrade nutrients to smaller molecules that can be transported across the cell membrane by transporters

Periplasmic Components: Cytochrome C 1) What is the purpose of Cytochrome C?

1) They oxidize carbon compounds or inorganic compounds and deliver the e- to the electron transport chain in the cell membrane

Composition of Gram Positive Cell Walls 1) How large are they? 2) Consists mostly of...? 3) Also consists of several polymers (in addition to peptidoglycan). What are three of them?

1) Thick structure (15-30nm wide) 2) peptidoglycan 3) Teichoic Acids, Teichuronic, and Lipoteichoic

Periplasmic Components: Solute Binding Proteins 1) What do they do? 2) What makes them important?

1) assist in solute transport by binding to solutes and delivering them to specific transporters in the cell membrane. 2) They are important for bringing in nutrients

Gram Negative Cell Wall: Murein Lipoprotein 1) What is their structure? 2) How is it situated? 3) What is its function?

1) lipid attached to amino-terminal end of protein 2) The lipid end extends into and binds hydrophobically with lipids in the outer membrane. The protein end is bound to peptidoglycan. 3) Since one end is bound hydrophobically to the outer membrane and one end is bound to peptidoglycan, it acts to anchor the outer membrane to peptidoglycan

Gram Negative Cell Walls: Porins and Other Proteins 1) What are porins and where are they located? 2) What do porins form and for what reason? 3) What three major porins does E. coli have? a) When are each type of porin present? 4) What size molecules can travel through porins? 5) E. coliI also has LamB. What is the point of LamB? a) Why is it named LamB?

1) major proteins in outer membrane 2) Form small hydrophilic channels through outer membrane to allow for diffusion of small solutes 3) OmpF, OmpC, and PhoE a) OmpF and OmpC are always present. PhoE is present only when phosphate is in limited supply 4) Porins only allow molecules <600kDa into cell 5) It forms channels for maltose and maltodextrins a) Its named LamB because it is the binding site for lambda bacteriophage to gain entry. Lambda bacteriophage targets E. coli. Lambda stands for lysogenic cycle meaning to sit dormant and integrate into the cell.

Gram Negative Cell Walls: LPS 1) What composes the Lipid A region? 2) What composes the Core Region and where is it located? a) What 2 unusual sugars are present? 3) What composes the O-antigen region and where is it located? a) What two things are special about this region?

1) membrane anchoring region of LPS; NAG dimer with 6-7 FAs (all saturated) 2) attached to 6 position of one of the NAGs and is a chain of sugars a) KDO and heptose 3) attached to the core; contains up to 40 repeats of 3-5 sugars a) Its the hydrophilic portion of LPS and its also the major antigenic determinant in gram negative cells.

What is the murein sacculus?

A sac of pure, isolated peptidoglycan that surrounds the cell membrane only in gram negative cells

What does the periplasm of gram positives contain?

Believed to contain proteins and salts

2 means to destabilize the cell wall?

Chemical means and enzymes

What does the periplasm of gram negative bacteria contain?

Contains protein, oligosaccharide, salts, and the peptidoglycan

Periplasmic Components: Detoxifying Agents

Detoxify stuff I guess

Differences between gram positive and gram negative peptidoglycan?

In Gram Negative Cells 1) Peptidoglycan can be isolated as a sac of pure peptidoglycan that surrounds the cell membrane; this sac is the murein sacculus. 2) The cross linking direct (between one tetrapeptide and another tetrapeptide both attached to NAM) In Gram Positive Cells 1) Peptidoglycan is covalently bonded to various polysaccharides and teichoic acids. 2) Cross-linking usually involves a peptide bridge

What's the difference between isotonic, hypotonic, and hypertonic solutions?

Isotonic solutions show no net water movement because the amount of solutes are equal inside and outside the cell. Hypotonic solutions have less solutes than inside the cell (this can cause lysis as water moves to the area with most solutes inside the cell). Hypertonic solutions have more solutes than inside the cell.

Describe the structure of peptidoglycan

It is composed of glycan chains crosslinked by peptides. Glycan consists of alternating residues of N-acetylmuramic acid (NAM) and N-acetylglucosamine (NAG) attached to each other by B-1,4 linkages. Attached to NAM (and only NAM) is a tetrapeptide that crosslinks the glycan chains via peptide bonds. Strength is provided by the covalent bonds throughout by the glycosidic and peptide linkages.

What is the peptidoglycan of archaea like?

Its a pseudopeptidoglycan

Peptidoglycan is also known as...?

Murein

What type of lipoprotein is present in the cell wall of gram negative cells?

Murein lipoprotein

In the structure of peptidoglycan, tetrapeptide is only attached to...?

N-acetylmuramic acid (NAM)

Which structure is bigger, NAG or NAM?

NAM

Of the three major porins that E. coli has, when are each present?

OmpF and OmpC are always present. PhoE is present only when phosphate is in limited supply

What on gram negative cell walls does the body recognize as an endotoxin?

Specifically the O-antigen region of lipopolysaccharide (LPS)

What region of LPS is responsible for toxicity (endotoxin)?

The O-antigen

What domain is hydrophilic in the three regions of LPS?

The O-antigen region is hydrophilic

O is for...?

The o portion of the o-antigen

What do siderophores do?

They competitively bind iron from the environment

Example of a chemical method of destabilizing the cell wall?

Using an ionic detergent such as sodium dodecyl sulfate

K is for...?

capsular

H is for...?

flagella

The presence of a peptide bridge (3,4 peptide linkage between one tetrapeptide and another) implies the cell is...?

gram positive

What type of solution carries the risk of lysis for a cell

hypotonic solutions

What kind of molecules is LPS permeable to?

low molecular weight hydrophilic molecules