Lipopolysaccharide LPS Overview

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Questions and Answers

What is the primary function of the Golgi apparatus in bacterial cells?

Protein glycosylation (correct)

Gene replication

Energy production

Cell wall synthesis

Which of the following components is characteristic of Gram-negative bacteria?

Outer membrane containing lipopolysaccharides (correct)

Teichoic acids in the cell wall

Thick peptidoglycan layer

Single membrane structure

What role do pili play in bacterial cells?

Movement through flagella

Attachment to surfaces and other cells (correct)

Nutrient absorption

Cellular respiration

Which statement is true regarding the bacterial cell wall structure?

It is composed mainly of peptidoglycan. Signup and view all the answers

How do bacterial cells move towards attractants?

Using flagella for run and tumble swimming Signup and view all the answers

What is a key characteristic of the lipopolysaccharide (LPS) found in Gram negative bacteria?

It consists of a very constant core polysaccharide. Signup and view all the answers

Which component is responsible for antigenic variation in Gram negative bacteria?

The O antigenic side chain of LPS. Signup and view all the answers

How do Gram positive bacteria differ from Gram negative bacteria in terms of their cell wall structure?

They possess a thick peptidoglycan layer with additional polymers. Signup and view all the answers

What role does the plasma membrane have in prokaryotic cells?

It acts as a selectively permeable barrier for nutrient transport. Signup and view all the answers

What can occur as a result of very small amounts of lipopolysaccharide (LPS) in the bloodstream?

Anaphylactic shock. Signup and view all the answers

Why do Gram positive bacteria not require porin proteins?

Solutes can diffuse through the thick peptidoglycan layer. Signup and view all the answers

Which statement about S. aureus is true regarding its cell wall?

Proteins attached to peptidoglycan contribute to antigenic variation. Signup and view all the answers

How does a mesosome function in a prokaryotic cell?

It possibly assists in cross-wall formation during cell division. Signup and view all the answers

What is the primary function of the endoplasmic reticulum in eukaryotic cells?

Protein synthesis and modification Signup and view all the answers

Which components are primarily involved in glycosylation of proteins?

Endoplasmic reticulum and Golgi complex Signup and view all the answers

What characterizes Gram-negative bacteria compared to Gram-positive bacteria?

Presence of an outer membrane with lipopolysaccharides Signup and view all the answers

What is the role of porin proteins in the Gram-negative cell wall?

Facilitating the transport of solutes through the outer membrane Signup and view all the answers

Which of the following best describes the structure of the Golgi complex?

A stack of flattened membrane-bound sacs (cisternae) Signup and view all the answers

What is a key function of lipoprotein in Gram-negative bacteria?

Connecting the peptidoglycan layer to the outer membrane Signup and view all the answers

What distinguishes the peptidoglycan layer in Gram-positive bacteria?

It is composed of extensive cross-linked networks of sugars and amino acids Signup and view all the answers

In which cellular component does the initial glycosylation of proteins occur?

Endoplasmic reticulum Signup and view all the answers

Study Notes

Lipopolysaccharide (LPS) in Gram-Negative Bacteria

Each LPS molecule contains five lipid chains.
Core polysaccharide is consistent within species and across genera.
O antigenic side chain exhibits high variability, contributing to antigenic variation.
Known as endotoxin; can be more toxic than other bacterial toxins.
Minimal LPS amounts in blood may cause lethal anaphylactic shock.

Gram-Positive Cell Wall Structure

Peptidoglycan layer is significantly thicker than that of Gram-negative counterparts.
Contains other polymers, such as Teichoic acid.
Lacks an outer membrane; solutes diffuse through the thick peptidoglycan.
Proteins covalently linked to peptidoglycan extend into the environment, aiding in immune evasion.
Common pathogenic example: Staphylococcus aureus.

Prokaryotic Structures and Functions

Plasma Membrane:
- Selectively permeable barrier and mechanical cell boundary.
- Facilitates nutrient and waste transport, and hosts metabolic processes (e.g., respiration, photosynthesis).
- Plays a role in detecting environmental cues for chemotaxis.
Mesosome:
- Potentially involved in cross-wall formation and chromosome distribution during cell division.

Protein Secretion in Eukaryotic Cells

Protein glycosylation initiates in the endoplasmic reticulum (ER) and continues in the Golgi complex.
Secretory proteins, such as IgG, undergo extensive processing before reaching the external environment.

Bacterial Cell Classification

Primary classification of bacteria via Gram stain identifies two groups: Gram-positive and Gram-negative.
Named after Christian Gram in 1884, correlating staining with cell envelope structure.

Gram-Negative Cell Wall Structure

Multilayered wall with thin peptidoglycan and an outer membrane featuring LPS.
Contains two membranes; outer membrane is rich in lipopolysaccharides.
Peptidoglycan, also known as murein, provides osmotic strength and structural integrity.
Lipoprotein links the peptidoglycan layer to the outer membrane.
Porins are abundant protein pores allowing nutrient passage through the outer membrane.
The space between inner and outer membranes is called the periplasmic space.

Bacterial Motility

Bacteria display a run and tumble mode of locomotion.
Flagella facilitate movement towards attractants while tumbling provides directional change.

Pili Structure and Function

Pili are hair-like structures on bacterial surfaces, with various types serving different functions.
E. coli has Type I pili for attachment to mammalian cells and larger F pili for mating processes.

Key Points to Remember

Understand the mechanisms of protein targeting and secretion pathways.
Familiarize with the chemical composition and differences in Gram-negative and Gram-positive cell walls.
Learn how bacterial locomotion occurs through the run and tumble method.

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Description

Explore the structure and function of lipopolysaccharides (LPS) found in Gram-negative bacteria. This quiz will cover the components of LPS including the lipid chains, core polysaccharide, and the variable O antigenic side chain that contributes to antigenic variation among species.