Prokaryote Cell
Structure & Function
Cell Diagram: Mariana Ruiz, pub domain
1 m = 100 cm = 1,000mm = 1,000,000 µm = 1,000,000,000nm
1mm = 1000 µm = 1000000nm
1 µm = 1000nm
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
_____________________
_____________________
Diagrams:
Prokaryotic & Eukaryotic Cell, Mariana Ruiz
Prokaryotes
Binary Fission
Tell me about Prokaryotes…
Diagrams:
Prokaryotic Mariana Ruiz
Binary Fission, JW Schmidt
Prokaryotes
______________
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.
Prokaryotes
_______________
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.
Eukaryotic Cells
_________________
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.
Diagrams/Photos:
Fluorescent Cell: NIH, Pub Domain
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.
Diagrams:
Prokaryotic Cell, Mariana Ruiz
Membrane: NIST
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.
Prokaryotes – Cell Wall
Peptidoglycan is a huge polymer of interlocking chains of
identical peptidoglycan monomers.
Peptidoglycan
- Rigid mechanical support
- Freely permeable to solutes
Image:
Peptindoglycan Structure: NicolasGrandjean
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
Image:
Prokaryotic Cell, Mariana Ruiz
Gram +-, Julian Onions
Why are these differences
in cell wall structure so
important?
Images: Sources unknown
Prokaryotes - 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. Slime Layer
2. Capsule
STRUCTURE OF MICOBIAL CELLS
Prokaryotes - 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.
Streptococcus
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.
Staphylococcus
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.
STRUCTURE OF MICOBIAL CELLS
Prokaryotes - 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.
STRUCTURE OF PROKAROTIC CELLS
Prokaryotes - Glycocalyx
Bacterial Capsule and Meningococcal Infection
Meningococcal infection is caused by meningococcal
bacteria (Neisseria meningitidis).
Causes:
1.
meningococcal meningitis (infection of the
meninges/spinal cord)
2.
meningococcal septicaemia (blood poisoning).
Of the two forms, meningococcal septicaemia is the
most dangerous.
Meningococcal bacteria are the most common cause
of bacterial meningitis.
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.
Approximately 5% of people who suffer from
meningococcal meningitis will die.
http://www.meningitisuk.org/about-meningitis/bacterial-meningitis.htm
STRUCTURE OF PROKAROTIC CELLS