Overview of prokaryotic cells

What are the two basic types of cells?

Prokaryotic cells and eukaryotic cells

What is a prokaryotic cell?

A simple usually unicellular cell that has no true nucleus and no membrane-bound organelles

What is an example of a prokaryotic organism?

Bacteria

What does unicellular mean?

Made of one cell

Do prokaryotic cells have a true nucleus?

No

Do prokaryotic cells have membrane-bound organelles?

No

Where is the main DNA of a prokaryotic cell found?

In the nucleoid region

What is the nucleoid?

The region of a prokaryotic cell containing its main DNA

What is the main difference between a nucleoid and a nucleus?

A nucleus is surrounded by a membrane while a nucleoid is not

What is an organelle?

A specialized structure inside a cell that performs a particular job

What form does the main bacterial chromosome usually have?

A single circular chromosome

What are plasmids?

Small extra pieces of DNA separate from the main bacterial chromosome

What does extra-chromosomal DNA mean?

DNA that exists separately from the main chromosome

What type of ribosomes do prokaryotic cells contain?

70S ribosomes

What important material is found in most bacterial cell walls?

Peptidoglycan

Why are prokaryotic cells clinically important?

Their structures contribute to infectious disease and provide important targets for antimicrobial therapy

What are the basic structures of a prokaryotic cell?

Plasma membrane + cytoplasm + 70S ribosomes + nucleoid + cell wall

What are the additional optional structures of prokaryotic cells?

Flagella + pili + capsule

What is the function of the plasma membrane?

It encloses the cell and regulates transport

What is the cytoplasm?

The material inside the cell that contains enzymes and metabolic components

What is metabolism?

The chemical reactions that keep a cell alive and functioning

What is the function of ribosomes?

Protein synthesis

What does protein synthesis mean?

Making proteins

What is the function of the nucleoid?

It contains the main circular bacterial DNA chromosome

What is the function of the bacterial cell wall?

It provides shape and protection

What is the function of flagella?

They enable motility

What does motility mean?

The ability to move

What are pili involved in?

Attachment and DNA transfer

What is the function of the capsule?

It provides protection and enhances virulence

What does virulence mean?

The ability of a microorganism to cause disease

What is the usual size of most prokaryotic cells?

About 1–10 µm

What does µm mean?

Micrometer

How large is Mycoplasma genitalium according to the lecture?

About 0.2 µm

How large can Thiomargarita namibiensis become according to the lecture?

Up to about 750 µm

What are the major bacterial shapes?

Cocci + bacilli + spiral forms + comma-shaped forms

What is a coccus?

A spherical or round bacterium

What is the plural of coccus?

Cocci

What is an example of cocci from the lecture?

Streptococcus

What is a bacillus?

A rod-shaped bacterium

What is the plural of bacillus?

Bacilli

What is an example of a bacillus from the lecture?

Lactobacillus

What is Vibrio shape?

Curved or comma-shaped

What is an example of a spiral form from the lecture?

Helicobacter

What is a spirillum?

A spiral-shaped bacterial form

What is a spirochete?

A long thin spiral-shaped bacterial form

What is a coccobacillus?

A short bacterial rod with a shape between a coccus and a bacillus

What does bacterial arrangement describe?

How bacterial cells are grouped together

What does diplo mean in bacterial arrangement?

Pair

What are diplococci?

Pairs of spherical bacteria

What does strepto mean in bacterial arrangement?

Chain

What are streptococci?

Chains of spherical bacteria

What are streptobacilli?

Chains of rod-shaped bacteria

What does staphylo mean in bacterial arrangement?

Cluster

What are staphylococci?

Clusters of spherical bacteria

What are sarcinae?

Bacteria arranged in packets

Why are bacterial size and shape and arrangement important?

They can provide the first clues for identifying a bacterium

How do prokaryotic cells generally compare in size with eukaryotic cells?

Prokaryotic cells are generally much smaller

What is the general size order from smallest to larger structures shown in the lecture?

Atoms → molecules → viruses → bacteria → organelles → eukaryotic cells

What are the three categories of bacterial cell structures?

Internal structures + cell envelope + external structures

What are the internal structures of bacteria listed in the lecture?

Cytoplasm + nucleoid + bacterial chromosome + plasmid + ribosomes + endospores + storage granules

What is the bacterial cell envelope?

The boundary structures that include the cell membrane and peptidoglycan cell wall and in Gram-negative bacteria an outer lipid membrane

Which bacteria have an outer lipid membrane according to the lecture?

Gram-negative bacteria

What are the external bacterial structures listed in the lecture?

Flagella + fimbriae + sex pilus + glycocalyx

What does bacterial ultrastructure mean?

The detailed structures that make up a bacterial cell

What structures are labeled in the bacterial ultrastructure diagram?

Capsule + cytoplasm + ribosomes + cell wall + plasma membrane + nucleoid containing DNA + plasmid + fimbriae + flagella + inclusion

What is an inclusion in a bacterial cell?

A structure containing stored material

Where is the bacterial cell wall located?

Outside the cell membrane

What may the bacterial cell wall directly contact?

The environment

What are the four major functions of the bacterial cell wall?

Protection + maintaining cell shape + maintaining osmotic integrity + playing an essential role in cell division

How does the cell wall protect bacteria?

It forms a strong outer layer that protects the cell

How does the cell wall affect bacterial shape?

It helps maintain the normal shape of the cell

What does osmotic integrity mean in relation to bacteria?

The ability of the cell to withstand changes in water movement and pressure

Why is the cell wall important for osmotic integrity?

It helps prevent damage when water movement changes pressure inside the cell

What role does the cell wall have in cell division?

It plays an essential role in the division process

What is peptidoglycan also called?

Murein

What is peptidoglycan?

A polymer of sugars and amino acids that forms a mesh-like layer outside the cell membrane of most bacteria

What is a polymer?

A large molecule made from repeating smaller units

Where is peptidoglycan located?

Outside the bacterial cell membrane where it forms the cell wall

What are the two alternating sugar residues in peptidoglycan?

NAG and NAM

What does NAG stand for?

N-acetylglucosamine

What does NAM stand for?

N-acetylmuramic acid

How are NAG and NAM arranged in peptidoglycan?

They alternate repeatedly in the glycan chain

What type of linkage connects the sugar residues in peptidoglycan?

β-(1→4) linkages

What are NAG and NAM structurally related to?

Glucose

How are the peptidoglycan subunits joined?

They are covalently joined to form glycan chains

What is a glycan chain?

A chain made from linked sugar units

What is the basic relationship between NAG and NAM and peptidoglycan?

NAG and NAM form repeating sugar chains that contribute to the peptidoglycan mesh

What is the basic structure of the cell membrane?

A lipid or phospholipid bilayer containing proteins

What does bilayer mean?

Two layers

What structures are shown in the cell membrane diagram?

Lipid bilayer + protein molecules + protein channels + carbohydrate chains

What membrane components are shown in the lecture?

Phospholipids + cholesterol + proteins + glycocalyx

What types of membrane proteins are shown in the lecture diagram?

Peripheral proteins and integral proteins

What is the fluid mosaic model?

A model describing the membrane as a flexible layer in which phospholipids and proteins can move and different components are scattered throughout

Why is the membrane called fluid?

Individual phospholipids and proteins can move around freely within the layer

Why is the membrane called mosaic?

Scattered protein molecules create a pattern like a mosaic

What is a simple way to remember the fluid mosaic model?

Fluid = movement within the membrane and mosaic = many different components arranged throughout it

What are the functions of the plasma membrane listed in the lecture?

Protective barrier + regulates transport + allows cell recognition + provides anchoring sites + provides enzyme binding sites + helps form interlocking surfaces + contains the cytoplasm

What does selectively permeable mean?

The membrane allows some substances to cross while restricting others

Why is the plasma membrane described as a protective barrier?

It separates the inside of the cell from the outside environment

What does the plasma membrane regulate?

Transport into and out of the cell