Microbiology - Bacterial Cell Shapes, Structures, and Transport Mechanisms

Vocabulary flashcards covering bacterial morphology, membrane components, transport types, organelles, and cell wall structures from Chapter 1 and 2 lecture transcript.

Coccus

A sphere or ball-shaped bacterial cell (3D)

Bacillus

A rod-shaped bacterial cell.

Vibrio

A bent rod-shaped bacterial cell.

Spirillum

A rigid, corkscrew-shaped bacterial cell.

Spirochete

A flexible, typically longer spiral-shaped bacterial cell.

Diplo-

A prefix describing bacteria that exist in pairs of attached cells, such as diplococcus or diplobacillus

Tetrad

An arrangement of bacterial cells forming a square pattern of four cells.

-division in 2 perpendicular planes

Sarcina

An arrangement of bacterial cells forming a cube pattern of eight cells.

-division across 3 planes

Strepto-

A prefix describing bacterial cells that grow attached in a chain. ex: streptococcus, Streptobacillus

Staphylo-

A prefix describing bacterial cells that grow in large clusters.

Plasma membrane

The outer boundary structure of a cell composed of a phospholipid bilayer that regulates entry and exit.

Phospholipid bilayer

A two-layered membrane structure consisting of hydrophilic phosphate heads facing outward and hydrophobic fatty acid tails facing inward.

Hydrophilic

Polar molecules or regions that have electrical charges and interact readily with water. -phosphate heads

Hydrophobic

Nonpolar molecules or regions without electrical charges(evenly distributed) that do not mix with water. -fatty acid tails

Integral membrane protein

A protein embedded within the plasma membrane made of folded amino acid chains with both polar and nonpolar regions.

Channel

An integral membrane protein with a specific central opening that allows particular molecules or ions to pass through passively.

Brownian motion

The random vibration and collision of molecules in liquids and gases driven by thermal energy. Higher temps=faster vibration

Diffusion

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

Passive transport

Passive transport

The movement of substances across a cell membrane driven by diffusion without cell energy expenditure.

Transporter Proteins

An integral membrane protein that performs active transport by expending energy to move specific substances across the membrane.

Active transport

An energy-expending process that transports unmodified substances across a membrane regardless of concentration gradients. -Cells accumulate critical nutrients internally even when external concentrations are extremely low

Group translocation

A transport mechanism unique to bacteria in which an integral membrane protein chemically modifies a molecule as it crosses the membrane by harvesting energy from it.

Receptor

An integral membrane protein facing the cell exterior that binds specific chemical signal molecules to sense the environment.

Transducer

A protein attached to the intracellular side of a receptor that is released into the cell upon signal binding to initiate a response.

-When an external signal molecule binds to the receptor, it undergoes conformation (shape) change that releases the transducer into the cytoplasm

Cytoplasm

The thick, gooey interior liquid of a cell composed of about $80\%$ water and $20\%$ dissolved nutrients and molecules.

Nucleoid

The region in a prokaryotic cell containing the compacted, circular DNA molecule without a enclosing nuclear membrane.

Eukaryotic cell

A cell containing a true nucleus enclosed by a distinct membrane boundary + membrane bound organelles

Prokaryotic cell

A cell, such as a bacterium or archaeon, that lacks a true membrane-bound nucleus (contains nucleoid area)

Ribosomes

Structures composed of RNA and protein where protein synthesis occurs; bacterial cells contain $70\text{s}$ ribosomes in prokaryote cell

Cytoskeleton

A network of protein fibers located inside the plasma membrane that maintains cell shape and assists in cell division.

Inclusion bodies

Non-universal storage regions within the bacterial cytoplasm where excess nutrients such as proteins, carbohydrates, fats, or iron are stored. Must have nutrient surplus (not permanent)

Peptidoglycan

A strong structural cell wall component (unique to bacteria cell walls) composed of alternating chains of N-acetylglucosamine and N-acetylmuramic acid cross-linked by tetrapeptides on glycan backbone

Gram-positive cell

A bacterium whose cell wall consists solely of a multilayered thick layer of peptidoglycan outside the plasma membrane. No outer lipid layer

-Gram positive result on gram stain procedure

Gram-negative cell

A bacterium whose cell wall consists of a thin layer of peptidoglycan surrounded by an additional outer membrane (lipid bilayer)

Outer membrane

The outermost bilayer of a Gram-negative cell wall, contains phospholipids in the inner leaflet and lipopolysaccharide(LPS) in the outer leaflet.

Lipopolysaccharide (LPS)

Also known as endotoxin, a toxic molecule in the Gram-negative outer membrane made of lipid A, core oligosaccharide, and O antigen.

Lipid A

The hydrophobic lipid component of lipopolysaccharide that anchors into the Gram-negative outer membrane (fatty acid chains attached to glucosamine backbone(Toxic component))

O antigen (O specific polysaccharide)

The outer hydrophilic sugar chain varies among bacteria and is used for species identification. It extends from core oligosaccharides into the extracellular environment

Certain shape & arrangement terms double as formal genus names example

All bacteria in the genus Streptococcus exhibit the streptococcal arrangement & shape; not all bacteria with a streptococcal arrangement belong to the genus Streptococcus.

AKA cocci in chains but not all chains will be cocci(spheres)

Bacteria cells reproduce by binary fission, splitting into daughter cells across their

Short axis

Bacilli can form what arrangemnts?

Diplobacillus or streptobacillus arrangements, but they cannot form a tetrad or sarcina arrangement

What arrangements can a coccus cells form?

Coccus (spherical) cells can form all arrangements (singles, diplo(pairs), tetrads(square group of 4), sarcinae(cube pattern of 8), strepto(chains of cells), & staphylo(large clusters)

Peptide Cross-Links

Attach to N acetyl muramic acid (NAM) residues in the glycan chains

Tetrapeptides

Short chains of amino acids containing 4 amino acids. They extend from adjacent glycan chains & form covalent cross links w/ one another, making individual chains into a continuous high tensile sheet

Endotoxins (Lipid A) are responsible __

Severe inflammatory responses in humans

Core Oligosaccharide

Hydrophilic short chains of sugars covalently linked directly to Lipid A