Micrbio Midterm 6-10

What is the primary function of a bacterial cell wall?

To protect the cell from harsh external conditions.

What are the main components of peptidoglycan in bacterial cell walls?

Alternating (NAG) N-acetyl glucosamine and (NAM) N-acetylmuramic acid connected by peptide bridges.

How do Gram-positive and Gram-negative bacteria differ in terms of cell wall structure?

Gram-positive bacteria have cross-linked peptidoglycan by tetra peptide chains, while Gram-negative bacteria have tetrapeptide chains additionally linked by pentaglycine cross-bridges.

What is a unique characteristic of peptidoglycan?

It is unique to bacteria and can be targeted by antibiotics, exposing them to osmotic pressure.

What role does teichoic acid play in Gram-positive bacteria?

Teichoic acid carbohydrate chains extend through the peptidoglycan layers, increasing stability.

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

LPS acts as an endotoxin responsible for fever, hemorrhaging, and septic shock.

Describe the structure of Gram-negative bacterial cell walls.

Gram-negative bacteria have an inner membrane, a thin peptidoglycan layer, and an outer membrane containing lipopolysaccharides.

What is the periplasmic space?

A gel-like matrix between the plasma membrane and the peptidoglycan layer responsible for sensing environmental signals and transport of some molecules.

What are S-layer and glycocalyx in prokaryotic bacteria?

S-layer is a structural layer of glycoproteins serving as the cell wall. Glycocalyx is a sugar coat that can be an organized capsule or a less organized slime layer.

What are fimbriae and pili?

short bristle-like proteins important for adhering to surfaces, and other are longer projections involved in the transfer of genetic material.

How does binary fission occur in prokaryotic cells?

The cell grows, replicates its genome, and divides into two daughter cells with complete copies of the parental genome.

What is the role of FtsZ in bacterial cell division?

defines the cell division plane and forms the Z-ring at the center of the cell during cytokinesis.

How do Min and NOC systems regulate cell division in bacteria?

The Min system localizes FtsZ to the center of the cell, while the NOC system prevents FtsZ polymerization on chromosomes, allowing division to occur at the center.

What is generation time in bacterial growth?

Generation time is the time between the same points in the life cycle of two successive generations.

What is the significance of the formula Nn=N0 2n?

This formula calculates the number of cells at any generation based on the initial number of cells and the number of generations.

What is generation/doubling time?

The time it takes for the population to double through one round of binary fission.

What is culture density?

The number of cells per unit volume.

What is the stringent response?

Response during starvation when amino acids run low.

What is exponential growth?

Cells doubling at a constant rate with each generation.

What is batch culture?

Microorganisms grown in closed culture.

What is the growth divisome?

A protein complex in bacteria that is responsible for cell division.

How do growth rate and generation time differ?

Growth rate is the increase in the number of cells, while generation time is the time required to form two separate cells.

What formula relates growth rate and generation time?

Growth rate (k) = 1/generation time and Generation time (g) = hrs/ # of generations.

What are some methods used to determine viable cell counts?

Direct counting, viable counting (CFU method), spectrophotometry (OD600), and flow cytometry.

What limits bacterial growth?

Type of species or strain, type of nutrients, and unfit temperature.

Describe the lag phase in bacterial growth.

Cells are gearing up for the next phase of growth.

What happens during the log phase of bacterial growth?

Cells are actively dividing by binary fission and their number increases exponentially.

What characterizes the stationary phase of bacterial growth?

The total number of live cells reaches a plateau.

What occurs during the death phase of bacterial growth?

The number of dying cells exceeds the number of dividing cells, leading to an exponential decrease in the number of cells.

How does stringent response affect cell physiology?

Triggers changes such as decreased cell size, increased cell wall crosslinking, and increased motility.

What is metabolism?

All of the chemical reactions inside a cell, including anabolism and catabolism.

What is catabolism?

Exergonic pathways that break down complex molecules into simpler ones, releasing energy.

What is anabolism?

Endergonic metabolic pathways involved in biosynthesis, converting simple molecules into complex ones and requiring energy.

What are autotrophs?

Organisms that convert inorganic carbon dioxide (CO2) into organic carbon compounds.

What are heterotrophs?

Organisms that rely on complex organic carbon compounds as nutrients.

How do enzymes facilitate metabolism?

Enzymes act as biological catalysts that lower the activation energy of chemical reactions.

Why are oxidation-reduction reactions important in metabolism?

They allow the cell to transfer and use energy incrementally, avoiding destructive bursting.

What is the Proton Motive Force (PMF)?

Energy stored as an artificial gradient strengthened by the electrical attraction of positive and negative charges.

What role does NADH play in energy storage?

Stores high-energy electrons as reducing equivalents, essential for both catabolism and anabolism.

Why is ATP important in cellular metabolism?

It serves as a universal energy currency, providing energy for various cellular processes.

What is the function of NAD+, NADH, FAD, and FADH2 in cells?

They are used in energy extraction from sugars and play roles in anabolic reactions.

What is the structure and function of enzymes?

Enzymes serve as catalysts that lower activation energy and bind to substrates, changing shape for optimal fit.

Describe competitive enzyme inhibitors.

Molecules that resemble the substrate and compete for binding to the active site, blocking substrate access.

What are non-competitive enzyme inhibitors?

They bind to an allosteric site, causing a conformational change that reduces the enzyme's affinity for the substrate.

Why is Proton Motive Force, NADH, and ATP important in cells?

They are three ways cells store energy.