Bacterial Cell

Question 1

What are the main differences between bacterial and eukaryotic cells discussed in Lecture 2?

Answer 1

The differences include cell envelope structure, ribosomes, genetics (chromosome + plasmids), metabolism, protein secretion, and pathogenicity-related functions.

Example sentence: Bacterial cells have a cell wall made of peptidoglycan, while eukaryotic cells do not.

Question 2

What are the components of the bacterial inner (plasma) membrane?

Answer 2

The inner membrane consists of a phospholipid bilayer and membrane proteins.

Additional information: The membrane proteins include transporters, receptors, and enzymes.

Question 3

What are the main functions of the bacterial inner membrane?

Answer 3

Its functions include acting as a permeability barrier, transporting solutes, and housing enzyme systems for energy generation.

Additional information: The inner membrane is also involved in electron transport chain reactions.

Question 4

What is the periplasmic space, and what does it contain?

Answer 4

The periplasmic space is an aqueous compartment packed with proteins, including potentially harmful enzymes like RNAse and proteases, and transport proteins.

Example sentence: The periplasmic space is essential for maintaining cell integrity.

Question 5

What is peptidoglycan, and where is it found?

Answer 5

Peptidoglycan (PG) is a rigid exoskeleton in bacterial cell walls that prevents osmotic lysis and gives the cell its shape.

Example sentence: Penicillin targets the synthesis of peptidoglycan.

Question 6

What is the function of lipopolysaccharide (LPS) in Gram-negative bacteria?

Answer 6

LPS acts as an endotoxin, stimulates the immune system, and contributes to the outer membrane’s permeability and defense mechanisms.

Additional information: LPS is composed of lipid A, core polysaccharide, and O-antigen.

Question 7

How does the bacterial outer membrane protect against antibiotics?

Answer 7

The outer membrane contains porins, which allow selective permeability, limiting the entry of harmful substances, including antibiotics.

Example sentence: Porins regulate the passage of nutrients into the bacterial cell.

Question 8

What are porins, and what role do they play in bacterial outer membranes?

Answer 8

Porins are transmembrane proteins that form water-filled pores, allowing passive diffusion of small hydrophilic molecules across the outer membrane.

Additional information: Porins are essential for nutrient uptake in bacteria.

Question 9

How does penicillin target bacterial cells?

Answer 9

Penicillin targets peptidoglycan biosynthesis by inhibiting transpeptidase enzymes, leading to the weakening of the bacterial cell wall.

Example sentence: Penicillin is a beta-lactam antibiotic that disrupts cell wall synthesis.

Question 10

What are penicillin-binding proteins (PBPs)?

Answer 10

PBPs are enzymes involved in bacterial cell wall biosynthesis that catalyze transglycosylation and transpeptidation.

Additional information: PBPs are the targets of beta-lactam antibiotics like penicillin.

Question 11

What are techoic acids, and where are they found?

Answer 11

Techoic acids are polymers found in the cell walls of Gram-positive bacteria, contributing to cell wall rigidity.

Example sentence: Techoic acids play a role in bacterial adhesion to host cells.

Question 12

What is the role of bacterial capsules?

Answer 12

Capsules help bacteria evade the immune system by preventing macrophages from capturing them and aiding in adhesion.

Additional information: Capsules are often associated with bacterial virulence.

Question 13

How do bacterial ribosomes differ from eukaryotic ribosomes?

Answer 13

Bacterial ribosomes are 70S, composed of 50S and 30S subunits, while eukaryotic ribosomes are 80S, composed of 60S and 40S subunits.

Example sentence: Ribosomes are the cellular machinery responsible for protein synthesis.

Question 14

Why are bacterial ribosomes significant drug targets?

Answer 14

Antibiotics like tetracycline and erythromycin target bacterial ribosomes, inhibiting protein synthesis without affecting human ribosomes.

Example sentence: Erythromycin binds to the bacterial ribosome, preventing protein production.

Question 15

What are plasmids, and what role do they play in bacteria?

Answer 15

Plasmids are small, extrachromosomal DNA molecules that can carry genes for antibiotic resistance and pathogenicity, facilitating horizontal gene transfer.

Additional information: Plasmids are often used in genetic engineering.

Question 16

What is bacterial conjugation?

Answer 16

Bacterial conjugation is the process where one bacterium transfers plasmid DNA to another through a pilus, aiding in genetic exchange.

Example sentence: Bacterial conjugation can transfer antibiotic resistance genes.

Question 17

What are transposons, and how do they function?

Answer 17

Transposons are “jumping genes” that can move within the genome or between chromosomes and plasmids, often carrying antibiotic resistance genes.

Example sentence: Transposons can induce genetic variability in bacterial populations.

Question 18

How is MacConkey agar used in bacterial diagnostics?

Answer 18

It distinguishes bacteria based on their ability to ferment sugars like lactose, with lactose-fermenting bacteria turning the medium red due to acid production.

Additional information: MacConkey agar is selective for Gram-negative bacteria.

Question 19

What is the Sec translocation pathway in bacteria?

Answer 19

The Sec pathway transports newly synthesized proteins across the inner membrane of bacteria for secretion or cell surface incorporation.

Example sentence: The Sec pathway is crucial for protein export in bacteria.

Question 20

What is the role of signal peptides in bacterial protein secretion?

Answer 20

Signal peptides target specific proteins for export by interacting with the secretion machinery in bacteria.

Additional information: Signal peptides guide proteins to the Sec translocation pathway.