Need to Know

Amphipathic molecules

Molecules that have both hydrophilic (water-attracting) and hydrophobic (water-repelling) parts.

Hydrophilic head

The part of a phospholipid that is attracted to water.

Hydrophobic tail

The part of a phospholipid that repels water, composed of fatty acid chains.

Phospholipid bilayer

A double layer of phospholipids that forms the cell membrane, with hydrophilic heads facing outward and hydrophobic tails facing inward.

Peptidoglycan

A macromolecule that makes up the cell wall of bacteria, composed of sugars and amino acids.

Gram-positive bacteria

Bacteria that have a thick peptidoglycan layer in their cell wall and stain purple in Gram staining.

Gram-negative bacteria

Bacteria that have a thin peptidoglycan layer and an outer membrane, staining pink in Gram staining.

Teichoic acids

Polymers found in the cell wall of Gram-positive bacteria, linked to peptidoglycan.

Lipopolysaccharide (LPS)

A component of the outer membrane of Gram-negative bacteria, consisting of a lipid portion (Lipid A) and a carbohydrate portion.

Biofilm

A community of microorganisms living within a shared mass of secreted slime, often attached to a surface.

Fimbriae

Short, hair-like structures on bacteria used for attachment to surfaces.

Pili

Longer, hair-like structures that assist bacteria in adhering to surfaces and in the exchange of genetic material.

Flagella

Long, whip-like structures that provide motility to bacteria, allowing them to swim.

Conjugation

A method of genetic transfer between bacteria that involves direct contact, often via pili.

Transformation

The uptake of free DNA from the environment by a bacterial cell.

Transduction

The process of transferring bacterial DNA from one bacterium to another by a virus.

Chromosomal DNA

The main genetic material in bacteria, typically a single circular DNA molecule.

Plasmid

A small, circular piece of DNA in bacteria that is separate from the chromosomal DNA and can replicate independently.

Transposon (jumping gene)

A segment of DNA that can move from one location to another within a genome.

Exotoxins

Proteins secreted by bacteria that damage host cells and can inhibit their functions.

Endotoxins

Toxins associated with the outer membrane of Gram-negative bacteria, causing illness when the bacteria die.

Osmosis

The movement of water across a semi-permeable membrane from an area of lower solute concentration to an area of higher solute concentration.

Antibiotic resistance

The ability of bacteria to survive and multiply despite the presence of antibiotic drugs.

Virulence factor

A characteristic or component of a microorganism that enhances its ability to cause disease.

Cell wall

A rigid structure that surrounds the cell membrane of bacteria, providing shape and protection.

Mechanisms of Microbial Growth

The processes and conditions that influence microbial reproduction and population dynamics.

Exponential growth phase

The phase of microbial growth where the cells divide at a constant rate, leading to an increase in population size.

Stationary phase

The phase of microbial growth where the rate of cell division slows and balances with the rate of cell death due to limited resources.

Death phase

The phase of microbial growth where cells die at an exponential rate due to depleted resources.