Microbiology: Chapter 4 (Prokaryotic cells & Eukaryotic cells)

What characteristics do all living things share?

• Heredity

• Reproduction

• Growth

• Metabolism

• Responsiveness

• Transport

What is heredity?

The ability to pass genetic information from one generation to the next.

What is reproduction?

The ability to produce new organisms or cells.

What is metabolism?

The chemical processes used to obtain and use energy and materials.

What is responsiveness?

The ability to sense and respond to changes in the environment.

What is transport?

The movement of materials into, out of, and within a cell.

Do viruses share all characteristics of life?

No. Viruses are not cells and depend on host cells to reproduce.

Why are viruses generally not considered living?

They lack cellular structure, do not reproduce independently, and rely on host cells for reproduction.

What is a cell?

The basic structural and functional unit of life.

What are the two basic types of cells?

Prokaryotic and eukaryotic cells.

What are prokaryotic cells?

Cells that lack a membrane-bound nucleus and membrane-bound organelles.

What are eukaryotic cells?

Cells that contain a membrane-bound nucleus and membrane-bound organelles.

What are examples of prokaryotic cells?

Bacteria and Archaea.

What are examples of eukaryotic cells?

• Animal cells

• Plant cells

• Fungal cells

• Protist cells

How are prokaryotic and eukaryotic cells different?

Prokaryotes lack a membrane-bound nucleus and membrane-bound organelles, while eukaryotes have them.

What structures do all prokaryotic cells have?

• Cell membrane

• Cytoplasm

• Ribosomes

• One or more chromosomes

What structures are found in some prokaryotic cells?

• Cell wall

• Glycocalyx

• Flagella

• Pili

• Fimbriae

• S layer

• Endospores

• Inclusions

• Other specialized structures

What is the fluid mosaic model?

A model describing the cell membrane as a flexible lipid bilayer with proteins embedded throughout it.

What is the bacterial cell membrane made of?

A phospholipid bilayer containing proteins.

What are the functions of the bacterial cell membrane?

It regulates what enters and leaves the cell and provides a site for important cellular processes.

What are the major bacterial shapes?

• Cocci

• Bacilli

• Spirilla

• Spirochetes

What are cocci?

Spherical or round bacterial cells.

What are bacilli?

Rod-shaped bacterial cells.

What are spirilla?

Rigid spiral-shaped bacterial cells.

What are spirochetes?

Flexible, slender spiral-shaped bacterial cells.

What are coccobacilli?

Short, oval rods that appear intermediate between cocci and bacilli.

What are vibrios?

Curved or comma-shaped bacteria.

What are common bacterial arrangements?

• Pairs

• Chains

• Clusters

• Tetrads

• Cubical packets

What is a diplococcus arrangement?

Cocci arranged in pairs.

What is a streptococcus arrangement?

Cocci arranged in chains.

What is a staphylococcus arrangement?

Cocci arranged in irregular clusters.

What is a tetrad?

Four cocci arranged together.

What is a sarcina arrangement?

Cocci arranged in cubical packets.

What are bacterial flagella?

Surface structures that provide bacterial motility.

What are the three parts of a bacterial flagellum?

• Filament

• Hook

• Basal body

What is the function of the bacterial flagellar filament?

It is the long, helical portion that propels the cell.

What is the function of the flagellar hook?

It connects the filament to the basal body.

What is the function of the flagellar basal body?

It anchors the flagellum and allows it to rotate.

How do bacterial flagella move?

They rotate like tiny propellers.

What are the four flagellar arrangements?

• Monotrichous

• Lophotrichous

• Amphitrichous

• Peritrichous

What is monotrichous?

A single flagellum located at one pole of the cell.

What is lophotrichous?

A tuft of flagella located at one pole of the cell.

What is amphitrichous?

Flagella located at both poles of the cell.

What is peritrichous?

Flagella distributed over the entire surface of the cell.

How do prokaryotic and eukaryotic flagella differ?

Prokaryotic flagella rotate like propellers, while eukaryotic flagella move by whipping or undulating back and forth.

What are periplasmic flagella?

Internal flagella found in spirochetes that produce twisting and flexing movement.

How do spirochetes move?

Periplasmic flagella cause the cell to twist and flex as it moves.

What are fimbriae?

Short bacterial appendages primarily used for attachment.

What are pili?

Bacterial appendages involved in attachment, movement in some bacteria, and genetic exchange.

How do fimbriae and pili differ?

Fimbriae are primarily used for attachment, while specialized pili can transfer DNA or assist in movement.

What are the two major groups of prokaryotes?

Bacteria and Archaea.

Are Archaea more closely related to Bacteria or Eukarya?

Eukarya.

What characteristics distinguish Archaea from Bacteria?

Archaea lack peptidoglycan and have distinctive membrane and genetic characteristics.

What is a glycocalyx?

A carbohydrate-rich coating surrounding some bacterial cells.

What are the two types of glycocalyx?

Slime layer and capsule.

What is a slime layer?

A loosely attached glycocalyx that helps with attachment, protection, and biofilm formation.

What is a capsule?

A tightly attached glycocalyx that helps protect the cell and promote attachment.

How does a capsule differ from a slime layer?

A capsule is tightly attached to the cell, while a slime layer is loosely attached.

What are the functions of the glycocalyx?

• Protection

• Attachment

• Biofilm formation

What is a biofilm?

A microbial community surrounded by an extracellular matrix that helps protect the cells.

Why are biofilms medically important?

They can colonize tissues and medical devices and can make infections difficult to treat.

What is the cell envelope?

The outer boundary of a bacterial cell, consisting mainly of the cell wall and cell membrane.

What is the bacterial cell wall?

A rigid structure surrounding the cell membrane that provides support and protection.

What is peptidoglycan?

A rigid mesh-like material that strengthens the bacterial cell wall.

What is the main difference between Gram-positive and Gram-negative cell walls?

Gram-positive bacteria have a thick peptidoglycan layer, while Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane.

What is found in a Gram-positive cell wall?

A thick peptidoglycan layer and teichoic acids.

What is found in a Gram-negative cell envelope?

An outer membrane, thin peptidoglycan layer, and cell membrane.

What is the periplasmic space?

The space between the inner membrane and outer membrane of Gram-negative bacteria.

Why do Gram-positive and Gram-negative bacteria stain differently?

Their cell envelopes have different structures and different amounts of peptidoglycan.

Why is the Gram stain important?

It separates bacteria into major groups and helps with bacterial identification and treatment decisions.

Who developed the Gram stain?

Hans Christian Gram.

What are acid-fast bacteria?

Bacteria with waxy, lipid-rich cell walls that resist decolorization by acid-alcohol.

What is an example of an acid-fast bacterium?

Mycobacterium tuberculosis.

What causes the acid-fast property?

Mycolic acid in the bacterial cell wall.

What is an example of a bacterium without a cell wall?

Mycoplasma.

Why can Mycoplasma survive without a cell wall?

Its cell membrane contains sterols that provide additional stability.

What is chemotaxis?

Movement toward or away from a chemical stimulus.

What is positive chemotaxis?

Movement toward a favorable chemical stimulus.

What is negative chemotaxis?

Movement away from an unfavorable or harmful chemical stimulus.

What is the function of bacterial ribosomes?

Protein synthesis.

Where are prokaryotic ribosomes located?

They are located in the cytoplasm.

What are bacterial endospores?

Dormant, highly resistant structures formed by some bacteria to survive harsh conditions.

Are endospores a form of bacterial reproduction?

No. Endospores are survival structures, not reproductive structures.

Why are endospores resistant to heat?

Their protective layers and dehydrated interior protect the DNA and other cellular components.

What conditions can endospores resist?

• Heat

• Drying

• Chemicals

• Radiation

• Other harsh environmental conditions

Which bacteria generally produce endospores?

Bacillus and Clostridium.

What is conjugation?

The direct transfer of genetic material from one bacterial cell to another.

What structure commonly helps bacteria perform conjugation?

A pilus.

What are plasmids?

Small circular DNA molecules that are separate from the bacterial chromosome.

What can plasmids carry?

Genes such as antibiotic-resistance genes.

Why are plasmids important?

They can provide useful traits and can be transferred between bacteria.

How do we identify bacteria?

By examining:

• Morphology

• Staining characteristics

• Biochemical reactions

• Physiology

• Serology

• Genetic or molecular characteristics

What is bacterial morphology?

The study of bacterial shape, size, and arrangement.

What is serology?

Identification based on reactions between antibodies and microbial antigens.

What are Koch's postulates?

Criteria used to establish that a specific microorganism causes a specific disease.

What is Koch's first postulate?

The suspected organism should be found in diseased hosts.

What is Koch's second postulate?

The organism should be isolated and grown in pure culture.

What is Koch's third postulate?

The isolated organism should cause the disease in a susceptible host.

What is Koch's fourth postulate?

The same organism should be recovered from the experimentally infected host.

What did Koch's postulates help demonstrate?

They helped demonstrate that specific microorganisms can cause specific diseases.