Download Prokaryotes vs. Eukaryotes

Prokaryotes vs. Eukaryotes
Process of Life
•
•
•
•
Growth (increase in size)
Reproduction
Responsiveness
_Metabolism___
Both prokaryotes and eukaryotes undergo these processes
Prokaryote
• Simple structure
• No nucleus
• Small; ~1.0 µm in
diameter
• One circular
chromosome, not in a
membrane
• No histones
• No _membrane___
bound organelles
• Peptidoglycan cell
walls
• Binary fission
• Comprised of bacteria
and archaea
Eukaryote
•
•
•
•
•
•
•
•
•
Complex Structure
Nucleus
Larger; 10-100 µm in diameter
Paired_ chromosomes, in
nuclear membrane
Histones
Organelles
Polysaccharide cell walls
Mitotic spindle__
Comprised of algae, protozoa,
fungi, animals, and plants
Comparing Prokaryotes and Eukaryotes
Figure 3.2ab
Comparing Prokaryotes and Eukaryotes
Figure 3.2ab
Prokaryotes
• Average size: 0.2 -1.0 µm × 2 - 8 µm
• Basic shapes:
Arrangements
External Structures of
Prokaryotic Cells
• Glycocalyx
• Flagella
• Fimbriae and Pili
Glycocalyx
• Gelatinous, sticky substance surrounding
the outside of the cell
• Composed of polysaccharides,
polypeptides, or both
• Two types
– Slime Layer
– Capsule
Slime Layer
• Loosely attached to
cell surface
• Thinner
• Water soluble
• Protects cells from
drying out
• Sticky layer that allows
prokaryotes to attach
to surfaces
Capsule
• Composed of organized
repeating units of organic
chemicals
• Thicker
• Firmly attached to cell
surface
• Protects cells from drying
out
• May prevent bacteria from
being recognized and
destroyed by host
Flagella
• Responsible for
movement
• Long, whiplike
structures that
extend beyond
surface of cell
Flagella Structure
• Composed of filament, hook, and basal body
• Flagellin protein (filament) arranged in chains
and forms helix around hollow core
• Base of filament inserts into hook
• Basal body anchors filament and hook to cell
wall by a rod and a series of either two or
four rings
• Filament capable of _rotating_ 360º
Motile Cells
• Rotate flagella to run or tumble
• Move toward or away from stimuli (taxis)
– Move toward food (+)
– Move away from harmful chemicals (-)
• Flagella proteins are H antigens
(e.g., E. coli O157:H7)
• Not all bacteria are motile
– Only those with a flagellum
• _Cocci_ do not have flagella
Motile Cells
Figure 4.9
Arrangements of Flagella
Monotrichous
Lophotrichous
Figure 3.6
Arrangements of Flagella
Amphitrichous
Peritrichous
Figure 3.6
Axial Filaments
• Endoflagella =
flagellum covered in a
sheath
• In spirochetes
• Anchored at one end
of a cell
• Rotation causes cell
to move
Figure 4.10a
Fimbriae and Pili
• Nonmotile extensions
• Fimbriae
– Sticky, proteinaceous, bristlelike projections
– Used by bacteria to adhere to one another, to
hosts, and to substances in environment
– May be hundreds per cell and are shorter than
flagella
– Serve an important function in biofilms
Fimbriae Versus Flagella
Figure 3.9
Pili
• Long hollow tubules composed of pilin
• Longer than fimbriae but shorter than flagella
• Bacteria typically only have one or two per
cell
• Join two bacterial cells and mediate the
transfer of DNA from one cell to another
(conjugation)
• Also known as conjugation pili or sex pili
Pilus Versus Fimbriae
Figure 3.10
Prokaryotic Cell Walls
• Provides structure and shape
• Protects cell from osmotic forces
• Assists some cells in attaching to other cells
or in eluding antimicrobial drugs
• Animal cells do not have cell walls
– target cell wall of bacteria with antibiotics
• Bacteria and archaea have different cell wall
chemistry
Bacterial Cell Walls
• Most have cell wall composed of
peptidoglycan_; a few lack a cell wall entirely
• Peptidoglycan composed of sugars, NAG and
NAM
• Chains of NAG and NAM attached to other
chains by tetrapeptide crossbridges
– Bridges may be covalently bonded to one another
– Bridges may be held together by short connecting
chains of amino acids
Peptidoglycan
• Polymer of disaccharide
N-acetylglucosamine (NAG) & N-acetylmuramic
acid (NAM)
• Linked by _____________
Figure 4.13a
Structure of Peptidoglycan
Bacterial Cell Walls
• Gram-Positive Cell Walls
– Relatively thick layer of peptidoglycan
– Contains unique polysaccharides called teichoic
acids
• Some covalently linked to lipids, forming lipoteichoic
acids that anchor _peptidoglycan_ to cell membrane
– Retains crystal violet dye in Gram staining
procedure; appear purple
– Acid-fast bacteria contain up to 60% mycolic
acid; helps cells survive dessication
Bacterial Cell Walls – Gram
positive
Figure 3.13a
Bacterial cell walls
• Gram-Negative Cell Walls
– Have only a thin layer of peptidoglycan
– Have a bilayer membrane composed of
phospholipids, channel proteins _(porins)_, and
lipopolysaccharide (LPS)
– May be impediment to the treatment of disease
– Following Gram staining procedure, cells appear
pink
Bacterial Cell Walls
Gram Negative
Figure 3.13b
LPS
• Union of lipid with sugar
• Also known as endotoxin
• Lipid portion known as lipid A
– Released from dead cells when cell
wall disintegrates
– May trigger fever, vasodilation,
inflammation, shock, and blood clotting
– Can be released when antimicrobial
drugs kill bacteria
Periplasmic Space
• Between outer membrane and cell membrane
– Contains peptidoglycan and periplasm
– Contains water, nutrients, and substances secreted
by the cell, such as digestive enzymes and proteins
involved in transport
Archael Cell Walls
• Do not have peptidoglycan
• Cell walls contain variety of specialized
polysaccharides and proteins
• Gram-positive archaea stain purple
• Gram-negative archaea stain pink
Prokaryotic Cytoplasmic
Membrane
• Phospholipid bilayer - composed of lipids
and associated proteins
• Proteins act as
– recognition proteins, enzymes, receptors,
carriers, or channels
– Integral proteins
– Peripheral proteins
– Glycoproteins
• Fluid mosaic model describes current
understanding of membrane structure
Phospholipid Bilayer of Cytoplasmic
Membrane
Figure 3.14
Cytoplasmic Membrane
Function
• Controls passage of substances into and out of
the cell; selectively permeable
• Functions in energy production
• Harvests light energy in photosynthetic
prokaryotes
Control of Substances Across
Cytoplasmic Membrane
• Naturally impermeable to most substances
• Proteins allow substances to cross
membrane
• Occurs by passive or active processes
• Maintains a concentration gradient and
electrical gradient; collectively known as
electrochemical gradient
– Chemicals concentrated on one side of the
membrane or the other
– Voltage exists across the membrane
Passive Processes of Transport
• Diffusion
• Facilitated Diffusion
• Osmosis
– Isotonic solution
– Hypertonic solution
– Hypotonic solution
• Active Transport
• Group Translocation
Movement Across Membranes
• Simple diffusion: Movement of a solute from an
area of high concentration to an area of low
concentration.
Movement Across Membranes
Facilitated diffusion: Solute combines with a
transporter protein in the membrane.
Figure 4.17
Movement Across Membranes
• Osmosis
– Movement of water
across a selectively
permeable membrane
from an area of high water
concentration to an area
of lower water
concentration.
Figure 4.18a
Figure 4.18c-e
Effects of Solutions on Organisms –
Osmotic Pressure
Figure 3.18
Movement Across Membranes
• Active transport of substances requires a
transporter protein and ATP.
• Group translocation of substances requires
a transporter protein and PEP.
– Substance chemically modified during transport
Cytoplasm of Prokaryotes
• Cytoplasm is the substance inside the
plasma membrane
– Cytosol is the liquid portion
Figure 4.6a, b
Nuclear Area
• Nuclear area (nucleoid)
Figure 4.6a, b
Ribosomes
Figure 4.6a
Ribosomes
Differ slightly in size from Eukaryotic ribosomal subunits
Streptomycin & gentamycin attach to 30S subunit
Erythromycin & Chloramphenicol attach to 50S subunit
Figure 4.19
Inclusions
• Metachromatic granules
(volutin)
• Polysaccharide granules
• Lipid inclusions
• Sulfur granules
• Carboxysomes
•Phosphate reserves
• Gas vacuoles
• Magnetosomes
•Protein covered cylinders
•Iron oxide
(destroys H2O2)
•Energy reserves
•Energy reserves
•Energy reserves
•Ribulose 1,5-diphosphate
carboxylase for CO2 fixation
Eukaryotic Cells
External Structures of Eukaryotic
Cells
• Glycocalyx
• Flagella
• Cilia
Glycocalyx
• Not as organized as prokaryotic capsules
• Helps anchor animal cells adhere to each
other
• Strengthens cell surface
• Provides protection against dehydration
• Function in cell-to-cell recognition and
communication
Flagella
• Shaft composed of tubulin arranged from
microtubules
• “9 + 2” arrangement of microtubules
• Filaments anchored to cell by basal body; no hook
• Basal body has “9 + 0” arrangement of
microtubules
• Originate inside the cell (not extensions outside
the cell)
• May be single or multiple
• Generally found at one pole of cell
• Do not rotate, but undulate rhythmically
Eukaryotic Flagella and Cilia
Figure 3.23
Flagella & Cilia
Eukaryotic Flagella and Cilia
Figure 3.23
Cilia
• Shorter and more numerous than
flagella
• Composed of tubulin in “9 + 2” and “9 +
0” arrangements
• Coordinated beating propels cells
through their environment
• Also used to move substances past the
surface of the cell
Eukaryotic Flagella and Cilia
Figure 3.23
Eukaryotic Cell Walls
• Fungi, algae, and plants have cell walls but
no glycocalyx
• Composed of various polysaccharides
– Cellulose found in plant cell walls
– Fungal cell walls composed of cellulose, chitin,
and/or glucomannan
– Algal cell walls composed of cellulose, agar,
carrageenan, silicates, algin, calcium carbonate,
or combination of these
What is not present in a eukaryotic cell wall?
Eukaryotic Cell Membranes
• All eukaryotic cells have cell membrane
• Fluid mosaic of phospholipids and proteins
• Contains steroid lipids to help maintain
fluidity
• Controls movement into and out of cell
– Use diffusion, facilitated diffusion, osmosis, and
active transport
– Endocytosis
• Phagocytosis if solid substance
• Pinocytosis if liquid substance
– Exocytosis enables substances to be exported
from cell
Phagocytosis
Cytoplasm of Eukaryotes –
Nonmembranous Organelles
• Ribosomes
• Cytoskeleton
• Centrioles and Centrosome
Ribosomes
• Eukaryotic cells have two types of ribosomes
• 80S
– Composed of 60S and 40S subunits
– Membrane-bound
Attached to ER
– Free
In cytoplasm
• 70S
– In chloroplasts and mitochondria
Cytoskeleton
• Extensive
• Functions
– Provides basic shape
– Anchor organelles
– Cytoplasmic streaming and movement of
organelles
– Cell contraction
– Movement during endocytosis
– Amoeboid action (pseudopodia)
• Made up of microtubules, microfilaments,
and intermediate filaments
Centrioles and Centrosome
• Centrioles play a role in mitosis, cytokinesis,
and in formation of flagella and cilia
• Centrioles composed of “9 + 0” arrangement
of microtubules
• Centrosome – region of cytoplasm where
centrioles are found
Cytoplasm of Eukaryotes –
Membranous Organelles
•
•
•
•
Nucleus
Endoplasmic Reticulum
Golgi Body
Lysosomes, Peroxisomes, Vacuoles, and
Vesicles
• Mitochondria
• Chloroplasts
Nucleus
•
•
•
•
Often largest organelle in cell
Contains most of the cell’s DNA
Semi-liquid portion called nucleoplasm
One or more nucleoli
– RNA synthesized
• Chromatin – DNA associated with histones
• Double membrane bound
– two phospholipid bilayers – nuclear envelope
• Nuclear envelope contains nuclear pores
Nucleus
Endoplasmic Reticulum
• Continuous with the nuclear envelope
• Netlike arrangement of hollow tubules
• Functions
– Protein modification
– As transport system
• Two forms
– Smooth endoplasmic reticulum (SER) – plays
role in lipid synthesis
– Rough endoplasmic reticulum (RER) –
ribosomes attached to its outer surface; protein
modification
Rough and Smooth Endoplasmic Reticulum
Figure 3.32
Golgi Body
• Receives, processes, and
packages large molecules
for export from cell
• Protein modification and
trafficking
• Composed of flattened
hollow sacs surrounded
by phospholipid bilayer
Lysosomes, Peroxisomes,
Vacuoles, and Vesicles
• Vacuoles – store
chemicals within
cells
– Vesicles –
transport
chemicals within
cells
• Lysosomes contain catabolic
enzymes
• Peroxisomes contain enzymes
that degrade
poisonous wastes
Mitochondria
• Powerhouse of the cell
– Produce most of cell’s
ATP
• Double membrane
bound
• Interior matrix contains
– 70S ribosomes
– circular molecule of
DNA
Chloroplasts
• Used by algae and
plants for
photosynthesis
• Double membrane
bound
• Contain
– 70S ribosomes
– DNA
Prokaryote
• Simple structure
• No nucleus
• Small; ~1.0 µm in
diameter
• One circular
chromosome, not in a
membrane
• No histones
• No membrane bound
organelles
• Peptidoglycan cell walls
• Binary fission
• Comprised of bacteria
and archaea
Eukaryote
• Complex Structure
• Nucleus
• Larger; 10-100 µm in
diameter
• Paired chromosomes, in
nuclear membrane
• Histones
• Organelles
• Polysaccharide cell walls
• Mitotic spindle
• Comprised of algae,
protozoa, fungi, animals,
and plants
Endosymbiotic Theory
• Eukaryotes formed from phagocytosis of
small aerobic prokaryotes
– lost ability to exist independently
– Retained portion of DNA, ribosomes, and
cytoplasmic membranes
– Larger cell became dependent on for aerobic
ATP production
– Aerobic prokaryotes evolved into mitochondria
– Similar scenario for origin of chloroplasts
• Not universally accepted
Endosymbiotic
Theory
Figure 10.2
Prokaryotic membranes