Bacterial Cell Wall Structure

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary function of the bacterial cell wall?

Generate energy for the cell

Act as a storage site for nutrients

Facilitate the movement of molecules

Provide structural support and protection (correct)

Which process expends ATP to transport molecules against their gradient?

Simple diffusion

Protein synthesis

Group translocation (correct)

Endocytosis

In the context of ion gradients, what serves to store energy for metabolism or drive transport of other molecules?

Proton pumps (correct)

ABC transporters

Ribosomes

Cell walls

Which bacterial taxonomic group is characterized by having a Gram-positive cell envelope?

Firmicutes Signup and view all the answers

What is the function of the murein lipoprotein in Gram-negative bacteria?

Links the cell wall to the outer membrane Signup and view all the answers

What is the main component of the bacterial cell wall that provides its structure?

Peptidoglycan Signup and view all the answers

How do membrane-permeant weak acids affect the internal pH of a cell?

Cause a drop in pH Signup and view all the answers

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

Inward- /outer-facing leaflets differ in lipid composition Signup and view all the answers

Which structure in Gram-negative bacteria acts as an endotoxin when the cell dies?

Lipopolysaccharide layer Signup and view all the answers

Where is the periplasm located in a bacterial cell?

Between the inner membrane & outer membrane Signup and view all the answers

Which bacteria have a cell wall comprised of pseudomurien?

Archaea Signup and view all the answers

What is the function of a bacterial capsule?

Forms a protective layer outside the cell envelope Signup and view all the answers

What is the main difference between capsules and slime layers in bacteria?

Capsules are more tightly associated with the cell than slime layers. Signup and view all the answers

What is the main characteristic of biofilms?

They are multi-cell populations surrounded by an exopolysaccharide matrix. Signup and view all the answers

What is the main component of peptidoglycan in bacterial cell walls?

Carbohydrates Signup and view all the answers

Which antibiotic specifically targets the synthesis of peptidoglycan in bacteria?

Penicillin Signup and view all the answers

Which type of bacteria has a more complex cell envelope, Gram-positive or Gram-negative?

Gram-negative Signup and view all the answers

What is the function of ion gradients and membrane-permeant weak acids/bases in prokaryotic cells?

Maintaining osmotic balance Signup and view all the answers

Which antibiotics have an effect on peptidoglycan synthesis in bacterial cells?

Penicillin and vancomycin Signup and view all the answers

How do Gram-negative bacterial envelopes differ from Gram-positive bacterial envelopes?

Gram-negative envelopes have an inner and outer membrane Signup and view all the answers

Which of the following is a key difference in cell envelope composition between Archaea and Mycoplasma?

Mycoplasma has no cell wall Signup and view all the answers

What are ABC transporters responsible for in prokaryotic cells?

Active transport of molecules against their concentration gradient Signup and view all the answers

Which external structures to the cell envelope play a role in adhesion to surfaces?

Flagella and pili Signup and view all the answers

What is the main component of a bacterial cell wall structure?

Peptidoglycan Signup and view all the answers

Which enzyme is targeted by penicillin to prevent cell wall synthesis?

Beta-lactamase Signup and view all the answers

What is the role of vancomycin in bacterial cell wall synthesis?

Prevents cross-bridging by binding to terminal alanine dipeptide Signup and view all the answers

What is the function of MreB in rod-shaped bacterial cells?

Directs the helical direction of peptidoglycan synthesis Signup and view all the answers

Which bacterial species have cell wall synthesis occurring only at the midpoint of fission?

Streptococcus and Staphylococcus Signup and view all the answers

What type of bacteria have thick cell walls with multiple peptidoglycan layers penetrated with teichoic acids?

Firmicutes Signup and view all the answers

Study Notes

Prokaryote Cell Structure and Function

Prokaryote cell composition: a cell envelope, protected by one or more structural support layers, including a cell wall, S-layer, outer membrane, and complex layers (e.g., mycobacterial species).

Cell Membrane Structure

Prokaryote cell membranes are composed of different lipid types, including bacterial and archaeal membrane lipids.
Transport processes: passive (osmosis) and active (requiring energy to move molecules against their gradient).
Ion gradients: store energy for metabolism or drive transport of other molecules.
Membrane-permeant weak acids/bases: small, neutral molecules that can diffuse into the cell and affect internal pH.

Active Transport

Requires energy to move molecules against their gradient.
Mechanisms: ABC transporters (e.g., amino acid, carbohydrate transport) and group translocation (modification of substrate during transport).

Cell Envelope

Refers to the chemical structure external to the inner membrane.
Composed of peptidoglycan (murein), a polymer of disaccharides cross-linked with peptide tetramers.

Peptidoglycan Synthesis

Involves many enzymes, including penicillin-binding proteins.
Penicillin targets the enzyme that cross-links peptides, while vancomycin binds to the terminal alanine dipeptide, preventing cross-bridging.
Bacterial resistance mechanisms: beta-lactamase (cleaves penicillin) and vancomycin resistance.

Cell Envelopes of Gram-positive and Gram-negative Bacteria

Gram-positive bacteria: thick cell wall, multiple peptidoglycan layers penetrated with teichoic acids.
Gram-negative bacteria: thin cell wall, 1-2 peptidoglycan layers, bridged to outer membrane via the murein lipoprotein.

Outer Membrane of Gram-negative Bacteria

Lipopolysaccharide (LPS) layer: an endotoxin released when the cell dies.
Outer membrane proteins: non-specific porins that transport sugars, peptides.
Lipid A: short chain fatty acids linked to glucosamine dimers.

Atypical Cell Walls

Mycoplasma: smallest bacteria, lack cell wall.
Archaea: cell wall is comprised of pseudomurien.
Mycobacteria: contain waxy lipids (mycolic acids) in addition to peptidoglycan.

Structures External to the Cell Envelope

Capsule: a polysaccharide layer that lies outside the cell envelope, can be protein in nature.
Slime layer: a looser assemblage of polysaccharides.
Biofilm: a multi-cell population surrounded by an exopolysaccharide matrix.

Comparison of Cell Envelopes

Gram-positive vs. Gram-negative bacteria: differences in cell wall composition and structure.
Archaea and Mycoplasma: unique cell envelope compositions.
Mycobacterial cell envelope: contains waxy lipids (mycolic acids) in addition to peptidoglycan.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Learn about the structure of a bacterial cell wall, including its composition, functions, and the enzymes involved in cell wall synthesis. Explore how antibiotics like penicillin and vancomycin target specific enzymes in the cell wall.