Lecture 2: Prokaryotic cells

Vocabulary flashcards covering key prokaryotic cell concepts from Lecture 2.

Prokaryote

A microorganism whose cells lack a membrane-bound nucleus; DNA is located in a region called the nucleoid.

Nucleoid

Region in a prokaryotic cell where the chromosome is concentrated; not bounded by a membrane.

Plasmid

Small, circular extrachromosomal DNA that can carry accessory genes; may be present in 1 to hundreds of copies per cell.

Cytoplasm

The gel-like interior of the cell containing water and dissolved substances; site of metabolism.

Plasma membrane

Inner membrane surrounding the cytoplasm; phospholipid bilayer with selective permeability (fluid mosaic).

Cell envelope

All external layers outside the plasma membrane, including the cell wall, capsule, and slime layer.

Capsule

Tightly organized glycocalyx layer firmly attached to the cell wall; contributes to pathogenicity and protection.

Slime layer

Loosely organized glycocalyx loosely attached to the cell wall; provides protection and assists adhesion.

Glycocalyx

External to the cell wall; polysaccharide/protein layer that includes capsule and slime layer.

Flagellum

Long, whip-like structure used for bacterial movement; can be single or multiple.

Fimbriae

Short, hair-like structures that mediate attachment; common in many Gram-negative bacteria and contribute to pathogenicity.

Pili

Longer than fimbriae; usually 1–2 per cell; involved in movement and DNA transfer (sex pilus).

Peptidoglycan

Rigid polymer of sugars and amino acids forming the bacterial cell wall; provides structural strength.

Gram-positive cell wall

Thick peptidoglycan layer with teichoic acids; no outer membrane.

Gram-negative cell wall

Thin peptidoglycan layer between inner and outer membranes with LPS in the outer membrane; periplasmic space.

Teichoic acid

Polymers in the Gram-positive cell wall that provide rigidity and negative charge.

Lipoteichoic acid

Teichoic acids anchored in the plasma membrane.

Lipopolysaccharide (LPS)

Endotoxin-containing molecule in the outer membrane of Gram-negative bacteria; contributes to pathogenicity.

Outer membrane

The outer lipid bilayer of Gram-negative bacteria containing LPS and porins.

Periplasmic space

Space between inner and outer membranes in Gram-negative bacteria; contains enzymes and transport systems.

Porin

Protein channels in the outer membrane that allow diffusion of small molecules.

Coccus

Spherical-shaped bacterial cell.

Bacillus (bacilli)

Rod-shaped bacterial cell.

Vibrio

Curved rod-shaped bacterium.

Coccobacillus

Short rod-shaped bacterium.

Spirillum

Rigid spiral-shaped bacterium.

Spirochete

Long, flexible helical spiral bacterium.

Diplococcus

Pair of cocci.

Streptococcus

Chain of cocci.

Staphylococcus

Cluster of cocci.

Endospore

Dormant, highly resistant structure that protects the genome under harsh conditions.

Sporulation

Process of endospore formation in response to stress.

Germination

Return of a spore to vegetative growth when conditions improve.

Ribosome (70S)

Bacterial ribosome composed of 30S and 50S subunits; responsible for protein synthesis; 70S total.

Ribosome (80S)

Eukaryotic cytoplasmic ribosome, composed of 60S and 40S subunits.

Nucleoid-associated proteins (NAPs)

Proteins that organize and compact the bacterial chromosome within the nucleoid.

Inclusions

Storage granules for excess nutrients; may be membrane-bound or protein-associated.

Membrane transport: Passive diffusion

Movement of small or nonpolar molecules down their concentration gradient without energy.

Membrane transport: Facilitated diffusion

Diffusion down a gradient via transporter proteins; no energy required.

Membrane transport: Active transport

Movement against a gradient; requires transporter proteins and energy (ATP).

Fluid mosaic model

Model of the plasma membrane as a phospholipid bilayer with embedded proteins that move laterally.

Phospholipid bilayer

Two layers of phospholipids forming the core structure of the plasma membrane; hydrophilic heads and hydrophobic tails.

Gram stain

Differential staining technique classifying bacteria into Gram-positive or Gram-negative based on cell wall; Gram-positive have thick peptidoglycan with teichoic acids; Gram-negative have thin peptidoglycan and an outer membrane containing LPS.

Germ theory

Idea that microorganisms are responsible for many diseases; supported by Pasteur and Koch.

Koch's postulates

Four criteria to establish a causal link between a microbe and a disease.