Bacterial Cell Structure and Function: Peptidoglycan, Membranes, and Motility

What is the peptidoglycan layer?

A layer found outside the cell membrane of bacterial cells that gives shape and prevents bursting from liquid influx.

What are the components of the peptidoglycan layer?

It is composed of N-acetylglucosamine, N-acetylmuramic acid, and a tetrapeptide linked by peptide bonds.

What distinguishes gram positive from gram negative organisms?

Gram positive organisms have a thick peptidoglycan layer, while gram negative organisms have a thinner layer and an additional outer membrane.

What is found in the outer membrane of gram negative bacteria?

Lipopolysaccharide (LPS), which forms the outermost layer of the cell wall.

What is an endotoxin and its role during an infection?

The Lipid A portion of LPS acts as an endotoxin that can cause blood vessels to dilate, leading to a dangerous drop in blood pressure if the concentration of Lipid A reaches a high level

How does active cell metabolism act within the peptidoglycan layer?

Active cell metabolism takes place between the peptidoglycan layer and cell membrane of bacteria which is called periplasm.

What is the periplasmic space?

The gap between the peptidoglycan layer and the cell membrane in gram negative organisms.

What component surrounds the peptidoglycan layer in Mycobacterium?

A hydrophobic waxy lipid called mycolic acid held by arabinoglactan.

Do Mycoplasma bacteria have cell walls?

No, they have a flexible wall with sterols instead.

What does the bacterial plasma membrane do?

The bacterial cell (plasma) membrane regulates movement of material into and out of a cell. It also is the location for the electron transport chain carrier compounds and ATP synthase.

What happens to a bacterial cell in a hypertonic solution?

solute concentration is higher outside the cell, water moves inside, leading to plasmolysis and inhibition of growth, cell wall shrinks

What happens to a bacterial cell in a hypotonic solution?

solute concentration is lower outside the cell, water moves in (due to osmosis), causing the cell to become turgid if a cell wall is present, or to burst if it is not.

What is simple diffusion?

The net movement of molecules from an area of high concentration to low concentration until evenly distributed.

What is facilitated diffusion?

Transport of solutes across the membrane via transporter proteins, moving from high to low concentration.

What is osmosis?

The movement of water across a selectively permeable membrane from high water concentration to low water concentration.

What is active transport?

The movement of substances against their concentration gradient, requiring ATP and transport proteins.

Why does the cell need to use ATP to move material across the cell membrane during active transport?

To move against concentration

How does the flagellum generate movement?

The basal body rotates like a motor, and the rotating filaments push the surrounding liquid, propelling the bacterium, & all depends on the bacteria's generation of energy

How do spirochetes move?

They rotate like a corkscrew using axial filaments (endoflagella) located inside the cell.

What are fimbriae?

Short, numerous pili that allow bacteria to adhere to surfaces and each other, aiding in colonization and infection.

What are pili?

Only 1-2 per cell, Motility and DNA transfer, Twitching motility: grappling hook, Gliding motility: for low water like where myxobacterium are, & Conjugation (sex): DNA from F+ cell connects w receptors on other bacteria cell = baby

What is the function of bacterial capsules?

They protect bacteria from phagocytosis, desiccation, immune recognition, and antimicrobial agents.

What is one function of a slime layer in bacteria?

To form biofilms and adhere to surfaces.

What is a key difference between eukaryotic and prokaryotic DNA?

Eukaryotic DNA is linear and located in a nucleus, while prokaryotic DNA is circular and located in a nucleoid.

What is a similarity between eukaryotic and bacterial ribosomes?

Both types of cells have ribosomes for protein synthesis.

E: 80s

P: 70s

Difference of plasma membrane compared to those structures in a bacterial cell

Eukaryotic: polysaccharide walls, sterols and carbohydrates serve as receptors, endocytosis

Prokaryotic: peptidoglycan walls or in archaea it is pseudomurein, carbohydrate and lack steroids, group translocation

Difference of flagella compared to those structures in a bacterial cell

Eukaryotic: Made up of microtubules

Prokaryotic: Made up of flagellin (protein building blocks)

Name one similarity between the 4 cellular components in point 16 when comparing the eukaryotic cell versus the bacterial cell.

DNA: Contain genetic information

Ribosomes: Both have them & protein synthesis

Plasma membrane: Both have one that regulates what comes in and out

Flagella: Both used for utility

What advantage does an endospore provide to a bacterial cell that can produce one?

Malachite green dye can be used to stain endospores, When resting the endospore cells' nutrients are depleted, & when released, they can survive extreme conditions

What advantage does an endospore provide to bacteria?

Endospores allow bacteria to survive extreme conditions and remain dormant until conditions improve.

Describe the core of an endospore.

It contains DNA, ribosomes, and dipicolinic acid (DPA), and is very dehydrated.

Name two genera of bacteria that can produce endospores and cause human disease.

Bacillus and Clostridium.