Chapter 4: Functional Anatomy of Prokaryotic and Eukaryotic Cells

Vocabulary-style flashcards covering key terms and concepts from Chapter 4 notes on prokaryotic and eukaryotic cell structure.

Prokaryote

• A cell lacking a nucleus

• one circular chromosome not enclosed by a membrane

• no histones or organelles

• typically with peptidoglycan cell walls (bacteria) or pseudomurein (archaea)

• reproduces by binary fission.

Eukaryote

• A cell with a nucleus and membrane-bound

• Eukaryotic cells have membrane-bound organelles and store their paired chromosomes inside a nucleus surrounded by a nuclear envelope.

• Histones

• When eukaryotic cells have cell walls, those walls are made of polysaccharides (big sugar molecules).

• Divides by mitosis.

Monomorphic (single shape)

• Describing a bacterial species that maintains a single shape throughout its life cycle, rather than exhibiting a variety of forms.

• Most bacteria are like this

Pleomorphic (many shapes)

• Referring to bacteria that can have multiple shapes or forms during their life cycle. Unlike monomorphic species, pleomorphic bacteria can change their shape in response to environmental conditions.

• A few bacteria are like this

Peptidoglycan

A rigid polymer of sugar chains (NAG–NAM) cross-linked by polypeptides that forms the bacterial cell wall.

N-acetylglucosamine (NAG)

• A type of sugar molecule that is one of the main building blocks of peptidoglycan, the material that makes up bacterial cell walls.

• Sugar in the peptidoglycan backbone.

N-acetylmuramic acid (NAM)

• N-acetylmuramic acid (NAM) is a sugar molecule that pairs with N-acetylglucosamine (NAG) to form the repeating units of peptidoglycan in bacterial cell walls.

Teichoic acid

• Anionic polymers in Gram-positive cell walls contributing to negative charge and wall maintenance; often covalently linked to peptidoglycan.

• Special molecules found in the cell walls of Gram-positive bacteria that help give the wall strength, help bacteria stick to surfaces, and can play a role in infection.

Lipoteichoic acid

Teichoic acids that span to the cytoplasmic membrane, anchoring the cell wall to the membrane.

Outer membrane

The outer lipid bilayer of Gram-negative bacteria containing LPS and porins; provides protective barrier.

Periplasmic space

The region between inner and outer membranes in Gram-negative bacteria containing enzymes and peptidoglycan.

Porin

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

Lipopolysaccharide (LPS)

Gram-negative outer membrane component consisting of O antigen, core polysaccharide, and Lipid A (endotoxin).

O polysaccharide

Variable polysaccharide portion of LPS that determines serotype.

Lipid A

LPS lipid portion that acts as an endotoxin.

Gram stain mechanism

Crystal violet–iodine forms in the cell; Gram-positive retain it due to thick peptidoglycan; Gram-negative decolorize with alcohol and take counterstain.

Gram-positive cell wall

Thick peptidoglycan layer with teichoic and lipoteichoic acids; no outer membrane.

Gram-negative cell wall

Thin peptidoglycan; outer membrane; periplasmic space; inner membrane.

Acid-fast cell wall

Waxy mycolic acid bound to peptidoglycan; resists decolorization; Mycobacterium and Nocardia; stained with carbolfuchsin.

Mycoplasmas

Bacteria lacking a cell wall; membranes contain sterols for strength.

Pseudomurein

Archaeal cell wall component; similar to peptidoglycan but different in chemistry; resistant to lysozyme.

Archaea cell wall

Archaea may have pseudomurein or be wall-less; distinct from bacterial cell walls.

Endospores

Dormant, highly resistant resting cells formed by Bacillus and Clostridium; withstand desiccation, heat, chemicals, and radiation.

Sporulation

Process of endospore formation inside a vegetative cell.

Endospore germination

Return of an endospore to a metabolically active vegetative cell.

Nucleoid

Region containing the bacterial chromosome; circular DNA not enclosed by a membrane.

Plasmid

Small extrachromosomal DNA elements carrying nonessential genes; replicate independently; not present in all bacteria.

50S subunit

Is the large subunit of the prokaryotic ribosome (70S ribosome). It works together with the small 30S subunit to make proteins by translating mRNA.

30S subunit

It is the small subunit of the prokaryotic 70S ribosome. Its main job is to read the mRNA and make sure the correct tRNA anticodon pairs with each codon during protein synthesis.

70S ribosome

Is the type of ribosome found in prokaryotes (bacteria and archaea). It is made up of a small 30S subunit (decoding mRNA) and a large 50S subunit (making peptide bonds) that work together to build proteins.

Inclusion bodies

Cytoplasmic granules storing nutrients or elements (e.g., phosphate, glycogen, lipids, sulfur, carboxysomes, gas vacuoles, magnetosomes).

Metachromatic granules (volutin)

Phosphate reserves stored in inclusion bodies.

Carboxysomes

Protein-encased microcompartments containing RuBisCO for carbon fixation in photosynthetic bacteria.

Gas vacuoles

Protein-bound cylinders that provide buoyancy control in aquatic bacteria.

Magnetosomes

Iron oxide inclusions used for magnetotaxis.

Flagella

• Long

• Filamentous appendages that propel bacteria made of flagellin (for locomotion)

• Consists of filament, hook, and basal body

• When bacteria have flagella, the protein in those flagella acts as a marker (H antigen) that the immune system can detect—they carry H antigens.

• Are made of protein flagella

Axial filaments (a.k.a Endoflagella)

• Located beneath the outer membrane in spirochetes

  • E.g., Treponema pallidum (syphilis)

  • Borrelia burgdorferi (lyme disease)

• Rotation produces corkscrew motility.

• Anchored at one end of the cell.

Archaella

Archaea flagella-like structures made of archaellins; rotate to move.

Fimbriae

• Hair-like attachments for surface attachment

• Common on many Gram-negative bacteria and some Gram-positives.

Pili

• Present in both gram-positive and gram-negative bacteria.

• Can be used for attaching to a surface during infection.

• Hair-like appendages used for attachment and DNA transfer (conjugation pili).

Glycocalyx

External to the cell wall; gelatinous layer of polysaccharide/polypeptide; two types: capsule (organized) and slime layer (unorganized).

Capsule

Neatly organized, firmly attached glycocalyx; enhances virulence by preventing phagocytosis and aiding biofilm formation.

Coccus

Spherical bacterium.

Spirillum

Rigid spiral-shaped bacterium.

Spirochete

Flexible, lengthwise spiral-shaped bacterium with axial filaments.

Diplococci

Pairs of cocci.

Vibrio

Comma- or curved-rod-shaped bacterium.

Streptococci

Chains of cocci.

Staphylococci

Clusters of cocci.

Diplobacilli

Bacilli that occur in pairs.

Streptobacilli

Bacilli that form chains.

Tetrads

Cocci that occur in groups of four.

Sarcinae

Cocci that occur in cube-like arrangements of eight.

Bacillus

• A genus of rod-shaped bacteria that can be found in various environments and includes both free-living and pathogenic species.

• Shape: bacillus, rod-shaped

Glycocalyx

• A gelatinous and viscous, carbohydrate-rich layer surrounding the cell wall of some bacteria, providing protection and aiding in adhesion.

• Two types of glycocalyx: Capsule (neatly organized and firmly attached) and slime layer (unorganized and loose)

Purpose of Glycocalyx

• Contributes to bacterial virulence

  • Prevents phagocytosis

  • Capsule helps bacteria to form biofilms (helps cells to attach to surfaces and each other)

  • Some but not all, bacteria have capsules.

Parts of the Flagella

• Filament: Outermost region

• Hook: Attaches to the filament

• Basal body: Consists of rod and pairs of rings—this anchors flagellum to the cell wall and membrane.

Serovars

Serovars are different groups (strains) of the same species of bacteria that are identified by differences in their surface antigens (like O antigens or H antigens).

E.g., Escherichia coli O157:H7

Archaella

• A type of flagellum found in Archaea, resembling bacterial flagella but using a different mechanism for movement. Made of glycoprotein archaellins

• Anchored to the cell

• Rotate like flagella

The Cell Wall

• Prevents osmotic lysis and protects the cell membrane

• Made of peptidoglycan (in bacteria)

• Contributes to pathogenicity (the ability to cause disease)

Protoplast

A plant or bacterial cell that has had its ENTIRE cell wall removed, consisting of the plasma membrane and its contents.

It is found in Gram-positive bacteria

Spheroplast

A bacterial cell that has had PART of its cell wall removed but still retains some of its structure and plasma membrane.

It is found in Gram-negative bacteria

L form

A bacterial variant that can grow without a cell wall, often resulting from antibiotic treatment or environmental stress. L forms can revert to normal bacterial forms under certain conditions.

Gram-Negative Cell Walls

• Have a thin peptidoglycan layer surrounded by an outer membrane containing lipopolysaccharides.

• This structure contributes to their overall resistance to certain antibiotics and environmental factors.

• Have lipopolysaccharide (LPS) - made of O polysaccharide

Gram-Positive Cell Walls

• Composed of a thick peptidoglycan layer without an outer membrane

• They remain purple/violet in Gram staining

• They are usually easier to kill with antibiotics that attack peptidoglycan.

Bacterial Cell Walls

Structures that provide shape and protect bacteria from environmental stress, composed mainly of peptidoglycan in various configurations, differing between Gram-positive and Gram-negative bacteria.

Mycobacterium

A genus of bacteria characterized by a thick cell wall made of mycolic acid, making them more resistant to antibiotics and staining methods. They are typically associated with diseases like tuberculosis.

Norcadia

A genus of bacteria known for its filamentous structure and ability to survive in harsh environments. They can cause infections in humans, particularly in immunocompromised individuals.

Mycolic acid

A long-chain fatty acid found in the cell walls of certain bacteria, particularly those in the genus Mycobacterium, contributing to their impermeability and resistance to chemical damage.

Archaea

Single-celled microorganisms that are similar to bacteria but genetically and biochemically different. They often live in extreme environments (like hot springs, salty lakes, or deep oceans), but some also live in normal conditions.

Simple diffusion (passive process)

• A passive transport process where molecules move from an area of higher concentration to an area of lower concentration across a membrane without the need for energy.

• Continue until molecules reach equilibrium

Facilitated diffusion (passive process)

• A passive transport process in which molecules move across a cell membrane via special transport proteins, allowing substances that cannot directly cross the lipid bilayer to enter or exit the cell.

• Transports ions and larger molecules across a membrane with the concentration gradient

Osmosis (passive process)

The movement of water molecules through a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration.

Osmotic pressure (passive process)

The pressure needed to stop the movement of water across the membrane

Isotonic solution (passive process)

• Solute concentrations equal inside and outside of the cell.

• Water is at equilibrium.

Hypotonic solution (passive process)

• Solute concentration is lower outside than inside the cell

• Water moves into the cell.

• Water moves into the cell, leading to swelling or lysis.

Hypertonic solution (passive process)

• Solute concentration is higher outside of cell than inside.

• Water moves out of the cell, causing the cell to shrink.

Active transport (active transport)

• The process of moving molecules across a cell membrane against their concentration gradient.

• Requiring energy, usually in the form of ATP.

Group translocation (active process)

A process in which a molecule is chemically modified during its transport across a membrane, allowing it to be actively moved into the cell.

Plasma membrane

• The dynamic lipid bilayer that surrounds the cell, controlling the passage of substances in and out of the cell.

• It is present in living cells.

Ways the plasma membrane can be damaged

1. Alcohols (like in hand sanitizers)

2. Quaternary Ammonium Compounds (quats, in detergents)

3. Polymyxin Antibiotics

4. Causes leakage of cell contents & death of cells.

Passive processes

Substances move from high concentration to low concentration; no energy expended.

Active processes

Substances move from low concentration to high concentration; energy (ATP) expended.

Cytoplasm

The gel-like substance within the plasma membrane of a cell, containing water, salts, and organic molecules. It serves as the medium for biochemical reactions and houses cell organelles.

Cytoskeleton

A network of protein filaments and tubules that provides structural support, maintains cell shape, and facilitates movement within the cell.

Bacterial chromosome

• The circular DNA molecule found in prokaryotic cells that contains the genetic information necessary for the cell's functions and replication.

• All bacteria have chromosomes.

Plasmids

• Extrachromosomal genetic elements carry non-crucial genes (e.g., antibiotic resistance, production of toxins).

• Not present in all bacteria

• Can replicate autonomously

Ribosomes

• SItes of protein synthesis

  • No ribosome, no protein synthesis.

• Made of protein and ribosomal RNA

• The bacterial ribosome is 70S.

  • Have two subunits

  • 50S + 30S subunits

Endospores

• Resting cells, produced when

  • Nutrients are depleted.

  • CHange in temperature

• Resistance to desiccation, heat, chemicals, and radiation

• Produced by species of Bacillus and Clostridium

Sporulation

When bacteria form a tough spore to survive harsh conditions.

Germination

When a spore becomes an active bacterial cell again.