Chapter 3 Bacterial Cell Structure, Membranes, and Cell Division: Key Concepts

What type of bacteria is Bdellovibrio bacteriovorus?

A Gram-negative bacterial cell.

What are the two main types of cells based on the presence of a nucleus?

Prokaryotes (Bacteria and Archaea) lack a nucleus, while Eukaryotic cells have a nucleus.

What is a key feature of bacterial cell membranes?

They have a phospholipid bilayer.

What distinguishes Archaea from Bacteria in terms of cell membrane composition?

Archaea have unique membrane lipids with ether links, making them more stable in extreme environments.

What are the fundamental traits shared by most bacteria?

1. Thick, complex outer envelope; 2. Compact genome; 3. Tightly coordinated cell functions.

What is the function of the bacterial cell envelope?

It protects the cell from environmental stress and mediates exchange with the environment.

What is the approximate percentage of water in a bacterial cell?

70%.

What are the main macromolecules found in bacterial cells?

Nucleic acids and proteins.

What is the role of peptidoglycan in bacterial cells?

It provides structural support to the cell wall.

What is the difference between Gram-positive and Gram-negative bacteria?

Gram-positive bacteria have a thick cell wall, while Gram-negative bacteria have a thin cell wall and an outer membrane.

What is the periplasm in Gram-negative bacteria?

A water-filled space containing nutrient-binding proteins and secretion machines.

What is the function of the bacterial cell membrane?

It serves as a selectively permeable barrier that separates internal cellular components from the external environment.

What are phospholipids composed of?

Glycerol with ester links to two fatty acids and a phosphoryl head group.

What is the significance of cardiolipin in bacterial membranes?

It localizes to the cell poles and increases under stress conditions.

How do saturated and unsaturated fatty acids affect membrane fluidity?

Saturated fatty acids decrease fluidity, while unsaturated fatty acids increase fluidity.

What are hopanoids and their role in bacterial membranes?

Hopanoids are planar molecules that reinforce bacterial membranes.

What is the impact of temperature on bacterial membrane lipid synthesis?

Bacteria can adjust the synthesis of unsaturated phospholipids in response to cold and heat.

What is the function of membrane proteins in bacterial cells?

They provide structural support, detect environmental signals, and secrete virulence factors.

What is the role of the enzyme enoyl reductase in bacteria?

It synthesizes fatty acids and is a target for antibacterial agents like triclosan.

What is the structure of the nucleoid in bacterial cells?

It contains chromosomal DNA wrapped around binding proteins.

What are specialized structures found in bacterial cells?

Vesicles, nanotubes, pili, and flagella.

What is chemotaxis in bacteria?

The movement of bacteria in response to chemical stimuli.

What is the function of pili in bacterial cells?

Pili are used for attachment and can play a role in conjugation.

What is the role of ribosomes in bacterial cells?

Ribosomes are responsible for protein synthesis.

How do bacteria maximize production from limited resources?

By having a compact genome with relatively little noncoding DNA.

What is the primary function of membrane proteins in ion transport?

They manage ion transport that generates gradients and stores energy.

What type of molecules can easily permeate the cell membrane?

Small uncharged molecules such as CO2, O2, and H2O.

What is passive transport?

The movement of molecules from an area of high concentration to an area of lower concentration, using the concentration gradient.

What is active transport?

The movement of molecules from an area of low concentration to an area of higher concentration, which requires energy.

What is the structure that confers shape and rigidity to bacterial cells?

The cell wall.

What is peptidoglycan?

A polymer consisting of repeating disaccharides (NAG and NAM) that forms the cell wall of bacteria.

How do Gram-positive and Gram-negative bacteria differ in their cell envelope structure?

Gram-positive bacteria have a thick cell wall with multiple layers of peptidoglycan, while Gram-negative bacteria have a thin cell wall and an outer membrane.

What role do teichoic acids play in Gram-positive bacteria?

They reinforce the peptidoglycan layers and help retain the Gram stain.

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

It is porous to ions and small organic molecules but prevents the passage of proteins and macromolecules.

What is lipopolysaccharide (LPS) and its significance in Gram-negative bacteria?

A component of the outer membrane that can act as an endotoxin, causing immune responses when released.

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

They act as transporters for nutrients like sugars and peptides.

What is the capsule in bacterial cells?

A slippery layer of loosely bound polysaccharide and glycoprotein that protects pathogens from phagocytosis.

What is the role of the S-layer in bacteria?

It is an additional protective layer commonly found in free-living Gram-positive and Gram-negative bacteria.

What is the function of the cell envelope in prokaryotes?

It protects the cell membrane and includes structural supporting layers like the cell wall and outer membrane.

What is the significance of the mycoplasmas in relation to cell envelopes?

Mycoplasmas have a cell membrane with no outer layers, unlike other bacteria.

How does the structure of peptidoglycan contribute to its function?

Its interlinked structure provides rigidity and shape, allowing the cell to withstand turgor pressure.

What happens when antibiotics like penicillin target peptidoglycan?

Penicillin inhibits the transpeptidase enzyme that cross-links peptides in peptidoglycan, weakening the cell wall.

What is the function of the capsule in Staphylococcus aureus?

It protects the bacteria from being engulfed by white blood cells.

What is the role of the glycosyl layer in Gram-positive bacteria?

It can provide an additional protective layer, though not always present.

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

It consists of an inward-facing leaflet with phospholipids and lipoproteins, and an outward-facing leaflet with lipopolysaccharides.

What are the two major groups of bacterial cell envelopes?

Gram-positive and Gram-negative.

What is the function of the capsule in virulent strains of Haemophilus influenzae?

It protects the bacteria from the host's immune system, contributing to its virulence.

What is the role of the capsule in biofilm formation?

It helps bacteria adhere to surfaces and form protective biofilms.

What is the significance of the negative charge of teichoic acids in Gram-positive bacteria?

It helps retain the Gram stain and contributes to the overall thickness of the cell wall.

What is the effect of LPS when released by a lysed cell?

It can overstimulate the host's immune system, potentially causing lethal endotoxic shock.

What protein polymerizes to form the Z-ring in bacteria?

FtsZ

What shape does FtsZ help maintain in bacterial cells?

Round shape

What is the role of MreB in bacterial cells?

Guides peptidoglycan elongation and helps create a rod shape.

What does CreS do in crescent-shaped bacteria?

Forms a polymer that bends the rod-shaped cells into a crescent shape.

What is the process of bacterial cell division called?

Bacterial fission

What is required for bacterial cell division?

Highly coordinated growth and formation of all cell parts.

What does septation refer to in bacterial cell division?

The formation of the septum that divides the envelope.

What complex manages the process of septation?

Divisome

What is the role of FtsN in bacterial cell division?

Helps regulate the timing of constriction of the septum.

What is the nucleoid in prokaryotic cells?

A region that contains the cell's DNA, not enclosed by a membrane.

How is DNA organized in the nucleoid?

Loops of DNA are supercoiled and bound to DNA-binding proteins.

What is the difference between leading and lagging strands during DNA replication?

Leading strand is synthesized continuously; lagging strand is synthesized in short segments.

What happens to the DNA ori site during replication?

The ori site moves apart as replication continues.

What are thylakoids?

Extensively folded intracellular membranes found in photosynthetic bacteria.

What is the function of carboxysomes?

Packed with the enzyme Rubisco for CO2 fixation.

What are gas vesicles in bacteria?

Hollow protein structures that collect gases to increase buoyancy.

What are pili/fimbriae used for in bacteria?

Attachment and motility, including genetic material transfer in conjugation.

What is the composition of a bacterial flagellum?

Composed of spiral filament of protein monomers called flagellin.

What is chemotaxis?

Movement of a bacterium in response to chemical gradients.

What causes the flagella to rotate in a CCW direction?

Attractants like sugars and amino acids.

What happens during a 'tumble' in bacterial movement?

The bacterium briefly stops and changes direction.

What is the role of the proton motive force in flagellar movement?

Drives the rotation of the flagellum.

What is the function of storage granules in bacteria?

Store energy sources like glycogen and other polymers.

What are sulfur granules composed of?

Elemental sulfur, which may help cells avoid predation.

What is the function of stalks in bacteria?

Attachment organelles that help form biofilms.

What is the significance of the divisome in bacterial cell division?

It coordinates the formation of the septum during cell division.

How does the ribosome function in bacterial cells during transcription?

Ribosomes bind to mRNA and begin translation even before transcription is complete.

What are the two main categories of cells based on the presence of a nucleus?

Prokaryotes (Bacteria and Archaea) lack a nucleus, while Eukaryotic cells have a nucleus.

What distinguishes Archaea from Bacteria?

Archaea have unique membranes that enable survival in extreme environments.

What is the primary function of the bacterial cell envelope?

To protect the cell from environmental stress and mediate exchange with the environment.

What is the composition of a Gram-positive bacterial cell wall?

It is thick and made of peptidoglycan.

What is the role of the periplasm in Gram-negative bacteria?

It is a water-filled space containing nutrient-binding proteins and secretion machines.

What are the main components of a bacterial cell?

Water, essential ions (i.e., potassium, magnesium, and chloride ions), small organic molecules (i.e., lipids and sugars), and macromolecules (i.e., nucleic acids and proteins.)

What percentage of a bacterial cell's total weight is water?

70%.

What is the function of lipopolysaccharides in Gram-negative bacteria?

They are part of the outer membrane and contribute to the structural integrity of the cell.

What is the role of the nucleoid in bacterial cells?

It contains chromosomal DNA wrapped around binding proteins.

What is the function of bacterial flagella?

They are involved in motility and chemotaxis.

What is the structure of a phospholipid?

A glycerol backbone with ester links to two fatty acids and a phosphoryl head group.

What is the significance of the ester linkage in phospholipids?

It connects the glycerol and fatty acids, forming the backbone of the phospholipid.

What is the approximate composition of proteins in a bacterial cell?

16% of the total weight.

How do membrane lipids vary in bacteria?

They differ in structure based on environmental conditions, such as temperature and habitat.

What is the function of ribosomes in bacterial cells?

They are involved in protein synthesis.

What is the main role of metabolites in bacterial cells?

They serve as biosynthetic precursors for various cellular processes.

What is the difference between Gram-positive and Gram-negative bacteria regarding their cell envelope?

Gram-positive bacteria have a thick peptidoglycan layer, while Gram-negative bacteria have a thin layer and an outer membrane.

What is the significance of the compact genome in bacteria?

It allows for efficient reproduction and maximizes resource use.

What type of environment do many Archaea thrive in?

Extreme environments, such as hot springs.

What is the function of the cytoplasm in bacterial cells?

It contains enzymes, mRNA, and ribosomes, and is involved in replication, transcription, and translation.

What is the approximate percentage of RNA in a bacterial cell?

6%.

What is the role of specialized structures like pili in bacteria?

They assist in attachment and genetic exchange.

What is the function of the cell membrane in bacteria?

It acts as a selectively permeable barrier separating internal cellular components from the external environment.