Membrane Structure Fluid like Membrane #1 Phospholipid (#5) -creates bilayer of membrane.
Prokaryotic and Eukaryotic Cellular Structure · Prokaryotic Cell Membrane • Structure –...
Transcript of Prokaryotic and Eukaryotic Cellular Structure · Prokaryotic Cell Membrane • Structure –...
Prokaryotic and Eukaryotic Cellular Structure
Prokaryotic & Eukaryotic Cells: An Overview
Prokaryotes
Do not have membrane surrounding
their DNA
lack a nucleus
Lack various internal structures bound with phospholipid membranes
Are small, ~1.0 µm in diameter
Have a simple structure
Composed of bacteria and archaea
Prokaryotic & Eukaryotic Cells: An Overview
Eukaryotes
Have membrane surrounding their
DNA
Have a nucleus
Have internal membrane-bound
organelles
Are larger, 10-100 µm in diameter
Have more complex structure
Composed of algae, protozoa,
fungi, animals, and plants
Prokaryotic & Eukaryotic Cells: An Overview
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Prokaryotic Cell Membrane
• Structure
– Referred to as phospholipid bilayer; composed of lipids and associated proteins
– Approximately half composed of proteins that act as recognition proteins, enzymes, receptors, carriers, or channels
• Integral proteins
• Peripheral proteins
• Glycoproteins
– Fluid mosaic model describes current understanding of membrane structure
Cell Membrane
Membranes contain a
hydrophilic and
hydrophobic side
Composed of many
different types of
proteins
Proteins in the lipid
bilayer move freely
within the membrane
Cell Membrane
Thin pliable lipid and protein envelope
that defines a cell.
Phospholipid bilayer
Functions:
• Regulates nutrient and water
intake
• Regulates waste removal
• Site of prokaryotic respiration
• Site of prokaryotic flagella
attachment
• Involved in the distribution of
genetic material during binary
fission
Bacterial Appendages Flagella
Structures of locomotion
Originate in the plasma
membrane
In bacteria rotate like a
propellar
Many different
arrangements
External Structures of Prokaryotic Cells
• Flagella
– Are responsible for
movement
– Have long structures that
extend beyond cell surface
– Are not present on all
prokaryotes
External Structures of Prokaryotic Cells
Flagella
Structure Composed of filament, hook,
and basal body
Flagellin protein (filament) deposited in a helix at the lengthening tip
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 of integral proteins
Filament capable of rotating 360º
Bacterial Appendages Arrangements of Flagella
A. Monotrichous
B. Lophotrichous
C. Amphitrichous
D. Peritrichous
5. Mesosome
Mesosomes - invagination of the
plasma membrane that increases
the surfaces area of the plasma
membrane during binary fission.
The mesosome also serves as a
site for the attachment and
distribution of genetic material
during binary fission.
Inclusion Bodies
6. gas vacuoles - storage of metabolic gases such as methane or hydrogen
gas. The gas vacuoles help in the buoyancy of the cell and aids in it
motility.
7. ribosomes - responsible for the synthesis of proteins.
8. nucleoid material - the genetic material of bacteria, which usually is balled
up in the cell. During binary fission the nucleoid material unravels within the
cell in order to be copied and distributed to the daughter cells.
9. Plasmid - small fragments of self-replicating extrachromosomal DNA that
codes for the resistance to antibiotics or for the productions of a specific
metabolite, i.e. toxins, pigments. These plasmids may be transferred from
one bacterial cell to another by the F-pili.
Inclusion Bodies
9. Plasmid - small fragments of self-replicating extrachromosomal DNA that
codes for the resistance to antibiotics or for the productions of a specific
metabolite, i.e. toxins, pigments. These plasmids may be transferred from
one bacterial cell to another by the F-pili.
Intracellular Structures of Eukaryotic Organisms (organelles)
Membranous Organelles
Nucleus Often largest organelle in cell
Contains most of the cell’s DNA
Semi-liquid portion called nucleoplasm
One or more nucleoli present in nucleoplasm; RNA synthesized in nucleoli
Nucleoplasm contains chromatin – masses of DNA associated with histones
Surrounded by nuclear envelope – double membrane composed of two phospholipid bilayers
Nuclear envelope contains nuclear pores
Intracellular Structures of Eukaryotic Organisms (organelles)
Nucleus - double membraned
organelle that houses the genetic
material of cell.
Nuclear membrane contains
numerous pores through which
proteins and RNA can move.
Intracellular Structures of Eukaryotic Organisms (organelles)
Membranous Organelles
Endoplasmic reticulum
Netlike arrangement of flattened, hollow tubules continuous with nuclear envelope
Functions as transport system
Two forms
Smooth endoplasmic reticulum (SER) – plays role in lipid synthesis
Rough endoplasmic reticulum (RER) – ribosomes attached to its outer surface; transports proteins produced by ribosomes
Intracellular Structures of Eukaryotic Organisms (organelles)
Endoplasmic reticulum - network of
cytoplasmic membranes where
lipids and proteins are produced.
Smooth ER - synthesis of lipids
Rough ER - associated with
ribosomes and is responsible for
the synthesis of proteins.
.
Intracellular Structures of Eukaryotic Organisms (organelles)
Membranous Organelles
Golgi body
Receives, processes, and packages large molecules for export from cell
Packages molecules in secretory vesicles that fuse with cytoplasmic membrane
Composed of flattened hollow sacs surrounded by phospholipid bilayer
Not in all eukaryotic cells
Intracellular Structures of Eukaryotic Organisms (organelles)
Golgi apparatus (dictyosome) is
associated with the ER.
It modifies and packages the lipids
and proteins manufactured by the
ER and places them in vesicles for
cellular use.
Intracellular Structures of Eukaryotic Organisms (organelles)
• Membranous Organelles
– Lysosomes, peroxisomes,vacuoles,
and vesicles
• Store and transfer chemicals
within cells
• May store nutrients in cell
• Lysosomes contain catabolic
enzymes
• Peroxisomes contain enzymes
that degrade poisonous wastes
Intracellular Structures of Eukaryotic Organisms (organelles)
• Membranous
Organelles
– Mitochondria
• Have two membranes
composed of phospholipid
bilayer
• Produce most of cell’s
ATP
• Interior matrix contains
70S ribosomes and
circular molecule of DNA
Intracellular Structures of Eukaryotic Organisms (organelles)
mitochondria - involved in the
production of chemical energy in
the form of ATP.
Consist of convoluted inner
membrane and outer membrane.
Invaginations are called cristae and
contain enzymes used to synthesis
ATP.
All respiratory enzymes are located
in the inner membrane of the
mitochondria.
Cytoplasm of Eukaryotes
• Membranous
Organelles
– Chloroplasts
• Light-harvesting structures
found in photosynthetic
eukaryotes
• Have two phospholipid
bilayer membranes and
DNA
• Have 70S ribosomes
• Endosymbiotic Theory
– Eukaryotes formed from union of small aerobic prokaryotes with larger anaerobic prokaryotes
– smaller prokaryotes became internal parasites
• Parasites lost ability to exist independently; retained portion of DNA, ribosomes, and cytoplasmic membranes
• Larger cell became dependent on parasites for aerobic ATP production
• Aerobic prokaryotes evolved into mitochondria
• Similar scenario for origin of chloroplasts
– Not universally accepted
Cytoplasm of Eukaryotes
Cytoplasm of Eukaryotes
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Cytoplasm of Eukaryotes
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