Download Prokaryotic and Eukaryotic Cell Structure

Prokaryotic and Eukaryotic
Cell Structure
And a Little Taxonomy too!
Taxonomy

The science of classification of living
organisms.
– So we can identify and understand relationships
between organisms.
Linnaean System

First developed by Carolus Linnaeus (1707-1778).
– Method of classifying things in a hierarchical structure
from most general to most similar.
– Binomial System (2 names)

Domain
– Kingdom (most general)
– Phylum or Division
–
Class
–
Order
–
Family
–
Genus
–
Species
Ex. Eschericia coli
or E. coli
Classification

Domains constitute a level of classification
above the kingdom.
 Domains are further subdivided into
kingdoms etc.
The 3 Domains

1. Archaea
2. Bacteria
3. Eukarya
- animals
- plants
- algae
- protozoa
- fungi
Prokaryotes
Eukaryotes
5 Kingdoms

Based on
similar
morphology,
geographic
distribution,
and if
multicellular,
the ability to
interbreed.
Bacteria
Bergey System

Another system for classifying Prokaryotes.
 Still use kingdom, division or phylum,
class, order, family, genus, species.
 Classification based on similar
morphological and biochemical
characteristics.
Eukaryotic and Prokaryotic Cells
 How
are they different and
how are they the same?
What Is a Cell?

It is the fundamental unit of all living
matter.
 Has all characteristics of life.
 Can live independently of other cells.
All Cells Have the Following:

Enzymes
– A protein that speeds up a chemical reaction.

DNA – deoxyribonucleic acid
– A large molecule that stores genetic information.

RNA – ribonucleic acid
– A large molecule involved in protein synthesis.

ATP – adenosine triphosphate
– The main energy currency of a cell.

Amino Acids
– Proteins are composed of basically the same 20 amino
acids.
Eukaryotic Cell Structure

Possess membrane-bound organelles.
 10-30µm in diameter.
 Eukaryote = “true nucleus”
– Their DNA is enclosed by a double membrane.
Eukaryotic Cell Structure

Cell Membrane
– Phospholipid (fatty chain with a phosphate) bi-
layer with different types of proteins
interspersed.
– Separates inside of cell from external
environment.
– It has selective permeability.

Only certain things can get in and out.
– Other organelle membranes are similar in
structure.
Cell Membrane
Eukaryotic Cell Structure

Nucleus
– Controls the functions of the cell (“the control
center).
– Nuclear membrane – surrounds nucleus.
– Nucleoplasm – gelatinous matrix.
– Chromosomes – linear DNA molecules and
proteins.
– Gene – specific DNA segment on the
chromosome that contains the information for
making a gene product, usually a protein.
– Nucleolus – where rRNA is made and is used
to make a structure called ribosomes.
Eukaryotic Cell Structure

Cytoplasm
– A semi-fluid, gelatinous, nutrient matrix.
– Contains storage granules and cell organelles.
– Most of cell’s metabolism occurs.
– Often called the cytosol.
Eukaryotic Cell Structure

Endoplasmic Reticulum (ER)
– An irregular maze of spaces enclosed by a
membrane.
– “Assembly Line”
– Rough ER


Contains ribosomes
Involved in making proteins
– Smooth ER
 Does not contain ribosomes
 Involved in lipid metabolism (fat storage)
Eukaryotic Cell Structure

Ribosomes
– Are important in protein synthesis.
– Are found in the Rough ER.
Eukaryotic Cell Structure
Eukaryotic Cell Structure

Golgi Complex
– “packaging plant.”
– Stacks of flattened, membranous sacs.
– Completes and packages newly formed proteins
and lipids.
– Packages them so that they are ready for
storage within the cell or outside of the cell.
Eukaryotic Cell Structure

Lysosomes
– “garbage disposal system”
– 1 µm diameter
– Contain lysozyme and other enzymes that break down
foreign material.
– Particles may enter cell by phagocytosis.
– Also involved in programmed cell death called
autolysis or apoptosis.

Peroxisomes
– Membrane-bound vesicles that generate and break
down hydrogen peroxide (a dangerous and highly
reactive chemical).
– Used to break down lipids (fats) and destroy toxic
molecules.
Eukaryotic Cell Structure

Mitochondria
– “the power plant of the cell”
– 0.5 – 1 µm in diameter, 7 µm in length
– Where ATP (adenosine triphosphate) is
formed.

ATP is the energy currency of the cell.
– ATP is formed during a reaction called cellular
respiration.
– ATP is formed from our food sources.
Eukaryotic Cell Structure
Eukaryotic Cell Structure

Plastids
– Site of photosynthesis.
– Contain photosynthetic pigments.
 Photosynthesis – converting light energy into a
source of chemical energy for organism.
– Chloroplasts – type of plastid that contains
chlorophyll.

Chlorophyll – a green photosynthetic pigment.
Eukaryotic Cell Structure
- Plant Cell
micro.magnet.fsu.edu/cells/plants/plant
model.html
Eukaryotic Cell Structure

Cell Wall
– External structure that provides rigidity, shape,
and protection.
– May be composed of cellulose, pectin, lignin,
chitin, and some mineral salts.
– Usually simpler than prokaryotic cells.
Eukaryotic Cell Structure
Plant Cells
Cells stained green (DNA)
and red (keratin)
www.newworldencyclopedi
a.org/entry/Cell_(biology
Illustration by Robert Hooke (c.1665)
askabiologist.asu.edu/.../rhooke.html
Cell Walls
Cell Walls
Present
Absent
•Plants
•Animals
•Algae
•Protozoa
•Fungi
•Mycoplasma species
(type of bacteria)
•Most Bacteria
Eukaryotic Cell Structure

Flagella
– An organelle of movement.
– Long, thin structure that moves like a whip to propel
organism through liquid environment.
– Can be found in some species of protozoa,
spermatozoa, and algae.

Cilia
– Organelle of locomotion.
– Usually short, hair-like structures that beat in
coordinated, rhythmic movement.
– Can be found in some species of protozoa and types of
cells that line respiratory tract.
Eukaryotic Cell Structure
Euglena – sp. Protozoa. Notice
the flagella.
www.biologie.unierlangen.de/.../fotonm3_eng.htm
Paramecium – sp.
Protozoa. Notice the
cilia.
microbewiki.kenyon.edu/index.ph
p/Paramecium
Prokaryotic Cell Structure

More simple than eukaryotic cells.
 Can perform all functions necessary for life.
 Prokaryotes comprise all bacteria and
archaeans.
 Do NOT contain membrane-bound
organelles.
 Typical E. coli cell is about 1 µm wide and
2-3 µm long.
Prokaryotic Cell Structure

Bacterial Cell Wall
– Provides rigidity, strength, and protection.
– More complex than eukaryote cell walls.
– Composed of peptidoglycan (polymer of sugars and
amino acids)
– Gram-positive bacteria

Thick layer of peptidoglycan with some other molecules.
– Gram-negative bacteria

Thinner layer of peptidoglycan with an outer membrane
composed of lipid macromolecules.
– Genus Mycoplasma do not have cell walls.
– Archaens have cell walls but not composed of
peptidoglycan.
Prokaryotic Cell Structure

Cell Membrane
– Similar to eukaryotic cells.
– Contains proteins and phospholipids.
– Selectively permeable.
– It is very flexible and thin.
Prokaryotic Cell Structure

Glycocalyx
– Thick, slimy, gelatinous material produced by the cell
membrane and secreted outside the cell wall.
– Some bacteria have it.
– 2 types of glycocalyx

1. Slime Layer
– Is not highly organized or firmly attached to cell wall.
– Allows bacteria to glide or slide along surfaces.

2. Capsule
– Highly organized and firmly attached to cell wall.
– Chemical composition allows scientists to determine different
types of bacteria.
– Prevent bacteria from being phagocytized by phagocytic white
blood cells.
– Can attach bacteria to a wide array of surfaces.
Prokaryotic Cell Structure
diverge.hunter.cuny.edu/~weigang/Lecture-syll.
Prokaryotic Cell Structure

Prokaryotic Chromosome
– Single, long, supercoiled, circular DNA
–
–
–
–
–
molecule.
Embedded in cytoplasm.
Found in nuclear region of cell.
Does not have a nuclear membrane.
Contains all the information for carrying out
life processes.
Plasmids may also be found in prokaryotic
cells.
Prokaryotic Cell Structure

Plasmid
– Small, circular molecule of double-stranded
DNA.
– Not part of the chromosome.

Called extrachromosomal DNA.
– Found in the cytoplasm.
– May contain 10-100s genes.
– Number varies per cell.
Prokaryotic Cell Structure

Cytoplasm
– Semiliquid interior of cells.
– Consists of water, enzymes, dissolved oxygen
(in some bacteria), waste products, nutrients,
proteins, carbohydrates, and lipids.
– Everything necessary for its metabolic
functions.
Prokaryotic Cell Structure

Cytoplasmic Particles
– Ribosomes are found in the cytoplasm.
– They are important in protein synthesis.
– Some substances are stored in cytoplasmic
granules.


Such as starch, lipids, sulfur, or iron.
The type of substance stored depends on the species
of organism.
Prokaryotic Cell Structure
diverge.hunter.cuny.edu/~weigang/Lecture-syll.
Prokaryotic Cell Structure

Flagella
– A mechanism for
movement for some
bacteria.
– Bacteria can be
classified and
identified by the
arrangement of their
flagella.
– Nonflagellated
bacteria are usually
considered to be
nonmotile.

Although there are
exceptions.
Pseudomonas fluorescens –
aerobic soil bacteria.
www.scienceclarified.com/AsBi/Bacteria.html
Prokaryotic Cell Structure

Pili (Fimbriae)
– Not associated with motility.
– Thin, rigid, hair-like structure.
– Arise in cytoplasm and extend through the plasma
membrane, cell wall, and capsule (if present).
– 2 types of pili


1. Adhesins - allows bacteria to adhere to surfaces.
2. Sex pilus
– Allows for the transfer of genetic material through a process
called conjugation.
– One bacteria attaches its sex pilus to another cell and transfers its
genetic material to the other cell usually in the form of a plasmid.
Prokaryotic Cell Structure
Adhesin bacterial cell
with pili (fimbriae)
ultr23.vub.ac.be/.../fimbrialadhesio
n.html
Bacterial conjugation with sex
pilus.
www.cbs.dtu.dk/.../roanoke/genetics980309.html
Prokaryotic Cell Structure

Spores (Endospores)
– Bacterial spores called endospores.
– Usually found in 2 genera: Bacillus and Clostridium.
– Form through the process sporulation.

A copy of the chromosome and some cytoplasm is enclosed in
a thick protein coat.
– This occurs when moisture and nutrients are low.
– Endospores are resistant to heat, cold, drying, and most
chemicals.
– If adequate conditions are present, the endospore can
become an active bacteria.
Endospore

Clostridium difficil
forming an
endospore.
 Associated with
antibiotic related
diarrhea caused by
toxins produced
 Red structure is
endospore
forming.
www.chem.wayne.edu/feiggroup/research.htm
Prokaryotic Cell Reproduction

Binary Fission
– One parent cell splits to become 2 daughter
cells.
– This process produces a clone of the parent cell.
– During this process, its chromosome is
replicated in a process called DNA replication.
– Generation time

The time it takes one parent cell to become 2
identical daughter cells.
Binary Fission
www.uic.edu/.../bios100/lecturesf04am/lect06.htm
The End