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Lecture 4. Prokaryote Cell Structure & Function. Cell Diagram: Mariana Ruiz, pub domain. Size of Living Things. 1 m = 100 cm = 1,000mm = 1,000,000 µ m = 1,000,000,000nm 1mm = 1000 µ m = 1000000nm 1 µ m = 1000nm. Diagrams: http://www.cellsalive.com/howbig.htm.

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Lecture 4

Lecture 4

Prokaryote Cell

Structure & Function

Cell Diagram: Mariana Ruiz, pub domain

Size of living things
Size of Living Things

1 m = 100 cm = 1,000mm = 1,000,000 µm = 1,000,000,000nm

1mm = 1000 µm = 1000000nm

1 µm = 1000nm

Diagrams: http://www.cellsalive.com/howbig.htm

Lecture 4

The Cellular Level of Organization

Living things are constructed of cells.

Living things may be unicellular or multicellular.

Cell structure is diverse but all cells share common characteristics.

Cells are small so they can exchange materials with their surroundings.

Surface area relative to the volume decreases as size of cell increases.

- limits the size of cells

___________________ states:

1. All organisms are composed of one or more cells.

2. Cells are the basic unit of structure and function in organisms.

3. All cells come only from other cells.

Two basic types of cells
Two basic types of cells




Prokaryotic & Eukaryotic Cell, Mariana Ruiz


Binary Fission

Tell me about Prokaryotes…


Prokaryotic Mariana Ruiz

Binary Fission, JW Schmidt

Prokaryote genetics
Prokaryote Genetics


Region of cytoplasm where chromosomal DNA is located.

Usually a singular, circular chromosome


Small extra piece of chromosome/genetic material.

5 - 100 genes

Not critical to everyday functions.

Can provide genetic information to promote:

- Antibiotic resistance

- Virulence factors

(molecules produced by pathogen that specifically influence host's function to allow the pathogen to thrive)

- Promote conjugation

(transfer of genetic material between bacteria through cell-to-cell contact)




Also known as proto-plasm.

Gel-like matrix of water, enzymes, nutrients, wastes, and gases and contains cell structures.

Location of growth, metabolism, and replication.


Bacteria’s way of storing nutrients

Staining of some granules aids in identification




Found within cytoplasm or attached to plasma membrane.

What are they made of?

What do they do?

Composed of a small (30S) subunit and a large (50S) subunit.

Cell may contain thousands of ribosomes.


Cellular "scaffolding" or "skeleton" within the cytoplasm.

Major advance in prokaryotic cell biology in the last decade has been discovery of the prokaryotic cytoskeleton.

Previously thought to be a feature only of eukaryotic cells.

Eukaryotic Cells


Fluorescent Cell: NIH, Pub Domain

Prokaryotes plasma membrane
Prokaryotes- Plasma Membrane

Separates the cell from its environment.

Phospholipid molecules oriented so that hydrophilic (__________) heads directed outward and hydrophobic (__________) tails directed inward.

Proteins embedded in two layers of lipids (lipid bilayer).

___________________ to allow substances to pass into and out of the cell.


Prokaryotic Cell, Mariana Ruiz

Membrane: NIST

Prokaryotes plasma membrane as a barrier
Prokaryotes – Plasma Membrane as a Barrier

Primary function of plasma membrane →regulate movement of molecules entering or leaving cell.

Movement of molecules across plasma membrane requires energy.


Movement of molecules is passive if no energy sources of the cell are expended.

_____________ = when molecules move from a higher to a lower concentration.

What type of things might affect the rate of diffusion?

Diffusion Animation: biologycorner.com

Prokaryotes plasma membrane as a barrier1
Prokaryotes – Plasma Membrane as a Barrier


_____________ Diffusion

Proteins assist in diffusion of molecules across plasma membrane.

Movement only occurs in the presence of a concentration gradient.

Some molecules move across the membrane more quickly if diffusion is facilitated by a carrier molecule.


Facilitated diffusion, Mariana Ruiz

Prokaryotes plasma membrane as a barrier2
Prokaryotes – Plasma Membrane as a Barrier


Diffusion of ________ across the plasma membrane.

Environment surrounding cells may contain amounts of dissolved substances (solutes) that are…

equal to

less than

greater than

…those found within the cell.


__________: no net movement of water between cell and environment

__________: a higher concentration of solute.

__________: a lower concentration of solute.

Water will always move toward a hypertonic environment!!


Osmosis - www.scienceaid.co.uk/biology/plants/osmosis.html

Blood Cells: Mariana Ruiz

Prokaryotes plasma membrane as a barrier3
Prokaryotes – Plasma Membrane as a Barrier

_______________ TRANSPORT

How most molecules move across the plasma membrane.

Analogous to a pump moving water uphill.

Types of active transport are classified by type of energy used to drive molecules across membranes.

ATP Driven Active Transport

Energy from adenosine triphosphate (ATP) drives substances across the plasma membrane with the aid of carrier molecules.


Source unknown

Lecture 4

Prokaryotes – Cell Wall

  • Peptidoglycan is a huge polymer of interlocking chains of identical peptidoglycan monomers.

  • Backbone of peptidoglycan molecule composed of two derivatives of glucose:

    • N-acetylglucosamine (NAG)

    • N-acetlymuramic acid (NAM)

  • NAG / NAM strands are connected by interpeptide bridges.


- Rigid mechanical support

- Freely permeable to solutes


Peptindoglycan Structure: NicolasGrandjean

Lecture 4

Prokaryotes - Cell Wall

From the peptidoglycan inwards all bacteria are very similar. Going further out, the bacterial world divides into two major classes (plus a couple of odd types). These are:

Gram-positive Gram-negative

Images: PHIL Public Health Image Library

Prokaryotes cell wall gram negative gram positive
Prokaryotes - Cell Wall: Gram-Negative & Gram-Positive


Prokaryotic Cell, Mariana Ruiz

Gram +-, Julian Onions

Why are these differences in cell wall structure so important
Why are these differences in cell wall structure so important?

Images: Sources unknown

Prokaryotes glycocalyx
Prokaryotes - important?Glycocalyx

Some bacteria have an additional layer outside of the cell wall called the glycocalyx.

This additional layer can come in one of two forms:

  • Slime Layer

  • Capsule


Prokaryotes glycocalyx1
Prokaryotes - important?Glycocalyx

Some bacteria have an additional layer outside of the cell wall called the glycocalyx.

This additional layer can come in one of two forms:

1. ______________________

glycoproteins loosely associated with the cell wall.

Slime layers cause bacteria to adhere to solid surfaces and help prevent the cell from drying out.


The slime layer of Gram+Streptococcus mutans allows it to accumulate on tooth enamel (yuck mouth and one of the causes of cavities).

Other bacteria in the mouth become trapped in the slime and form a biofilm & eventually a buildup of plaque.


The slime layer of Gram+Staphylococcus allows it to thrive in the salty, hypertonic environment of the skin.

Glycocalyces are not specific to Gram+ or Gram- bacteria, sometimes only some members of a certain species (strains) have a glycocalyx, whereas others don’t.


Prokaryotes glycocalyx2
Prokaryotes - important?Glycocalyx

2. ___________________

polysaccharides firmly attached to the cell wall.

Capsules adhere to solid surfaces and to nutrients in the environment.

Adhesive power of capsules is a major factor in the initiation of some bacterial diseases. Capsule also protect bacteria from being phagocitized by cells of the hosts immune system.


Prokaryotes glycocalyx3
Prokaryotes - important?Glycocalyx

Bacterial Capsule and Meningococcal Infection

Meningococcal infection is caused by meningococcal bacteria (Neisseria meningitidis).


  • meningococcal meningitis (infection of the meninges/spinal cord)

  • meningococcal septicaemia (blood poisoning).

    Of the two forms, meningococcal septicaemia is the most dangerous.

    Meningococcal bacteria are the most common cause of bacterial meningitis.

    Approximately 5% of people who suffer from meningococcal meningitis will die.

Meningococcal bacteria grow in pairs called diplococci often surrounded by a capsule coat. Over a million of these would fit on the head of a pin.



Prokaryotes endospores
Prokaryotes - important?Endospores

Dormant, tough, non-reproductive structure produced by small number of bacteria.

Primary function of endospores:



Resistant to radiation, desiccation, lysozyme, temperature, starvation, and chemical disinfectants.

Endospores commonly found in soil and water, where they may survive for long periods of time.

A stained preparation of Bacillus subtilis showing endospores as green and the vegetative cell as red


Stain: Jerry Keplinger, James H. Quillen College of Medicine

Procedure: Source link no longer works


Lecture 4
_____________________ important?

The most significant cause of pseudomembranous colitis

Severe infection of the colon, often happening after normal gut flora is eradicated by use of antibiotics. The C. difficile bacteria naturally resides in the body, but becomes overgrown.

C. difficile overgrowth is harmful because the bacterium releases toxins that cause:

* Bloating and constipation

* Diarrhea with abdominal pain

* Severe diarrhea with mucus and blood present in feces

* Body aches and severe abdominal pain caused from ulcerated intestines

  • Treatment includes specific anticlostridial antibiotics, e.g. metronidazole or vancomycin.

  • News story link: http://www.thesun.co.uk/sol/homepage/news/article860499.ece


Prokaryotes surface appendages
Prokaryotes – important?Surface Appendages

Some prokaryotes have distinct appendages that allow them to move about or adhere to solid surfaces.

Consist of delicate stands of proteins.


Long, thin extensions that allow some bacteria to move about freely in aqueous environments.

____________ (endoflagella)

Wind around bacteria, causing movement in waves.


Most Gram- bacteria have these short, fine appendages surrounding the cell. Gram+ bacteria don’t have.

No role in motility. Help bacteria adhere to solid

surfaces. Major factor in virulence.


Tubes that are longer than fimbriae, usually shorter than flagella. Use for movement, like grappling hooks, and also use conjugation pili (singular = pilus) to transfer plasmids.


Flagella: Mike Jones Wiki

Axial Filament: Indiana USchool of Med

EColi: Pub Library of Science

Neisseria gonorrhoeae
Neisseria gonorrhoeae important?

Gonorrhoeae one of the most communicable disease in the US.

125 cases per 100,000. Teens 15-19 yo 634 cases per 100,000. Young adults 20-25 460 per 100,000.