Cell Structure and Microbiology (Chapters 3 & 4)

Flashcards covering cell theory, prokaryotic and eukaryotic structures, bacterial growth, and specialized microbiology categories of microorganisms as discussed in Chapters 3 and 4.

Cell

A term meaning 'small room' ($cella$ in Latin), coined by R. Hooke in 1655; it is the basic structural and functional unit of all living organisms.

Cell theory

A doctrine proposed by Schleiden and Schwann (1838) stating the cell is the smallest form of life, all life is composed of cells, and all cells come from preexisting cells.

Prokaryotic Cell Size

A range typically between $0.2 - 60\thinspace\text{μm}$.

Eukaryotic Cell Size

A range typically between $5 - 100\thinspace\text{μm}$.

Prokaryotic Ribosome

A protein synthesis site characterized as $70S$.

Eukaryotic Ribosome

A protein synthesis site characterized as $80S$.

Fluid-mosaic membrane structure

A model of the plasma membrane where components are not solid but free to move laterally and are constantly changing.

Integral proteins

Transmembrane proteins embedded in the phospholipid bilayer, such as channel proteins and receptors.

Peripheral proteins

Proteins located on the inside or outside of the membrane, sometimes partially embedded.

Glycocalyx

A 'sugar coat' or network of polysaccharides outside the plasma membrane used for communication, protection, and biofilm formation.

Peptidoglycan

A rigid hexose sugar polymer composed of N-acetylglucosamine ($NAG$) and N-acetylmuramic acid ($NAM$) that forms the bacterial cell wall.

Gram-positive Bacteria

Bacteria with a thick peptidoglycan layer ($20-80\thinspace\text{nm}$) that stains blue and contains teichoic acid.

Gram-negative Bacteria

Bacteria with a thin peptidoglycan layer ($5-10\thinspace\text{nm}$), a large periplasmic space, and an outer membrane containing lipopolysaccharides; stains pink or red.

Monotrichous

A flagellar arrangement consisting of a single polar structure at one end of the bacterium.

Lophotrichous

A flagellar arrangement consisting of flagella in tufts at one or both ends.

Amphitrichous

A flagellar arrangement consisting of a single polar structure at each end.

Peritrichous

A flagellar arrangement where flagella are distributed over the general surface of the cell.

Sex pili

Longer, less numerous ($1-6$) surface appendages in prokaryotes used for genetic recombination.

Microvilli

Membrane extensions on eukaryotic cells, such as intestinal epithelial cells, used for absorption.

Biofilm

A collection of surface-associated microbes enclosed by an extracellular polysaccharide matrix, appearing on living tissues or medical devices.

Cytoskeleton

A dynamic network found in both cell types consisting of actin filaments (microfilaments), intermediate filaments, and microtubules.

Golgi apparatus

An organelle composed of flattened cisternae that modifies and packages proteins, lipids, and carbohydrates and produces lysosomes.

Mitochondria

The ATP-producing powerhouse of the cell that divides by binary fission and contains maternal $DNA$.

Endosymbiosis model

The theory explaining the origin of mitochondria as formerly independent prokaryotic organisms.

Transcription

The process where $RNA$ polymerase uses a $DNA$ template to form $mRNA$, occurring in the nucleus (eukaryotes) or cytoplasm (prokaryotes).

Codon

A base triplet of three nucleotides on $mRNA$; there are $64$ total, including the start codon $AUG$ (methionine).

Semiconservative replication

A process of $DNA$ synthesis where each resulting double strand consists of one new and one old template strand.

Binary Fission

A form of asexual reproduction in prokaryotes and yeast where a single cell separates into two identical daughter cells.

Mitosis

The phase of the eukaryotic cell cycle involved in the separation of chromosomes, consisting of prophase, metaphase, anaphase, and telophase.

Meiosis

A cell division process in gonads resulting in four gametes, increasing genetic diversity through crossing over and random assortment.

Lag phase

The initial phase of the bacterial growth curve where cells are metabolically active and adjusting to the medium but not yet dividing.

Logarithmic/exponential growth phase

The phase where the bacterial growth rate increases and cells double through binary fission.

Stationary phase

The phase where growth slows as essential nutrients are depleted and metabolic byproducts accumulate.

Turbidity

A measure of cell mass using a spectrophotometer in optical density ($OD$) units based on the cloudiness of the sample.

Mesophiles

Microbes with optimal growth in moderate temperatures, generally between $25^{\text{°}}C$ and $40^{\text{°}}C$.

Thermophiles

Heat-loving organisms that grow best at temperatures of $45^{\text{°}}C$ or higher.

Psychrophiles

Cold-loving organisms that can grow at $0^{\text{°}}C$ or lower, with optimal growth around $15^{\text{°}}C$.

Obligate anaerobes

Organisms that grow only in the absence of oxygen and are inhibited or killed by its presence, such as $Clostridium\thinspace botulinum$.

Facultative anaerobes

Organisms that can grow in either the presence or absence of oxygen, such as $Escherichia\thinspace coli$.

Acidophiles

Microbes that grow best at a $pH$ below $5.5$, such as $Helicobacter\thinspace pylori$.

Coliform Bacteria

A group of Gram-negative, rod-shaped, facultative anaerobes that are nonsporulating, use lactose, and produce gas.

Mycoplasmas

The smallest free-living bacteria ($0.3 - 0.8\thinspace\text{μm}$) that lack a cell wall and are resistant to penicillin.

Methanogens

Archaea that produce methane as a metabolic byproduct and are killed by oxygen.

Taq DNA polymerase

An enzyme derived from extreme thermophiles that can function at $95^{\text{°}}C$, making it useful in $PCR$.

Cocci

Spherical-shaped bacteria that can occur singly, in pairs (diplococci), in chains (streptococci), or in clusters (staphylococci).

Bacilli

Rod-shaped bacteria that can be found as single cells or in chains.

Spirilla

Spiral-shaped bacteria that can be rigid (spirilla) or flexible (spirochetes).

Vibrios

Comma-shaped bacteria, a type of curved rod.

Actinobacteria

Gram-positive bacteria known for their filamentous structures and include important genera like Streptomyces, which produces antibiotics.

Firmicutes

A phylum of Gram-positive bacteria with thick cell walls, including genera like Staphylococcus and Bacillus.

Proteobacteria

A major phylum of Gram-negative bacteria, encompassing a wide variety of pathogens and non-pathogens, including Escherichia and Salmonella.

Cyanobacteria

Photosynthetic bacteria often referred to as blue-green algae; important in oxygen production and nitrogen fixation.

Chlamydiae

Obligate intracellular pathogens that can cause various diseases in humans and animals, such as Chlamydia trachomatis.

Spirichatae

A category of bacteria that includes generas such as Spirochaete that are characterized by their spiral shape.

Streptococcus pyogenes

Causes strep throat, scarlet fever, and skin infections such as impetigo.

Escherichia coli (E. coli)

Certain strains can cause food poisoning, urinary tract infections, and gastrointestinal infections.

Mycobacterium tuberculosis

Causes tuberculosis (TB), a serious respiratory disease.

Neisseria gonorrhoeae

Causes gonorrhea, a sexually transmitted infection.

Clostridium botulinum

Produces a toxin that causes botulism, a rare but serious illness affecting the nervous system.

Vibrio cholerae

Causes cholera, a severe diarrheal disease transmitted through contaminated water.

Helicobacter pylori

Associated with gastric ulcers and chronic gastritis.

Salmonella enterica

Causes salmonellosis, a type of food poisoning, often from contaminated food or water.

Chlamydia trachomatis

Causes chlamydia, a common sexually transmitted infection that can lead to reproductive health issues.

Bacillus anthracis

Causes anthrax, which can affect the skin, lungs, and gastrointestinal tract, depending on the route of exposure.