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Functional Anatomy of Prokaryotic and Eukaryotic Cells

Prokaryotic Cells
Prokaryote : Greek word for “pre-nucleus”.

Size: 0.2 -1.0 µm  2 - 8 µm

Shape:
Morphological characteristics
introduction


introduction


introduction

Basic shapes

Spherical(cocci)
Rod- shaped
(bacilli)
Spiral
Spirochete
Vibrio (comma-shaped)


Unusual shapes
Star-shaped
Square or rectangular
introduction

• Most bacteria are monomorphic

• A few are pleomorphic
introduction

. Arrangements

Pairs: diplococci, diplobacilli
Clusters: staphylococci
Chains: streptococci, streptobacilli
introduction


introduction


introduction


Structure of prokaryotic cells

introduction

Outer cell layers

Glycocalyx
Cell wall
Plasma membrane

Cytoplasm

Nuclear material
Flagella
Fimbreae
Ribosomes

Glycocalyx

Outside cell wall
Usually sticky
Either
neatly organized called a capsule
Or unorganized & loose called a slime layer
Extracellular polysaccharide allows cell to attach
Protect bacteria from phagocytosis
introduction



introduction

Cell Wall

Prevents osmotic lysis
Made of peptidoglycan (in bacteria)
introduction

Peptidoglycan

Polymer of disaccharideN-acetylglucosamine (NAG) & N-acetylmuramic acid (NAM)
Linked by polypeptides
introduction

Gram positive Vs. Gram negative cell walls

introduction

• Thick peptidoglycan

• Teichoic acids
• Lack outer membrane
• No periplasmic space
• Thin peptidoglycan
• No teichoic acids
• Outer membrane
• Periplasmic space
introduction


Gram-Positive cell walls

Teichoic acids:
Lipoteichoic acid links to plasma membrane
Wall teichoic acid links to peptidoglycan
May regulate movement of cations
Polysaccharides provide antigenic variation
introduction

Gram-Negative Outer Membrane

Lipopolysaccharides, lipoproteins, phospholipids.
Lipopolysaccharide consists of two parts
Lipid A is an endotoxin.
O polysaccharide antigen, e.g., E. coli O157:H7.
Protection from phagocytes, complement, antibiotics
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Plasma Membrane

Phospholipid bilayer
Peripheral proteins
Integral proteins
Transmembrane proteins


introduction

Plasma Membrane

Selective permeability allows passage of some molecules
Enzymes for ATP production
Photosynthetic pigments on foldings called chromatophores or thylakoids

Damage to the membrane by alcohols, quaternary ammonium (detergents) and polymyxin antibiotics causes leakage of cell contents.

Movement Across Membranes

Simple diffusion: Movement of a solute from an area of high concentration to an area of low concentration.
Facilitative diffusion: Solute combines with a transporter protein in the membrane.
Osmosis
Active transport
introduction

Osmosis and osmotic pressure

introduction


Flagella

Outside cell wall
Made of chains of flagellin
Attached to a protein hook
Anchored to the wall and membrane by the basal body
introduction

Motile Cells

Move toward or away from stimuli (taxis)
Flagella proteins are H antigens (e.g., E. coli O157:H7)

Axial Filaments

Endoflagella
In spirochetes
Anchored at one end of a cell
Rotation causes cell to move
introduction




Fimbriae allow attachment
Pili are used to transfer DNA from one cell to another
introduction

• Fimbriae and Pili

Cytoplasm
Cytoplasm is the substance inside the plasma membrane
introduction

Ribosomes

introduction

Prokaryotic ribosome consists of two subunits:

• Small 30S subunit
• Large 50 S subunit.

Complete 70S ribosome


Nuclear Area
Nuclear area (nucleoid)
introduction


An area containing the genetic information. Unlike the eukaryotic cells, it is not surrounded by a membrane.

Eukaryotic Cells

Eukaryote : Greek word for “true nucleus”.

Cell Wall

Cell wall
Plants, algae, fungi.
Animal cells do not have a cell wall.
Plant and algae cells : mainly made of cellulose
Fungal cells: mainly made of chitin.

Flagella and Cilia

introduction


introduction



• Structure of flagellum
• Microtubules
• Tubulin
• 9 pairs + 2 arrangements

Plasma Membrane

Phospholipid bilayer
Peripheral proteins
Integral proteins
Transmembrane proteins
Sterols
Glycocalyx
• Carbohydrates extending from animal plasma membrane
• Bonded to proteins and lipids in membrane

Plasma Membrane: Functions

Selective permeability allows passage of some molecules
Simple diffusion
Facilitative diffusion
Osmosis
Active transport
Endocytosis
Phagocytosis: Pseudopods extend and engulf particles
Pinocytosis: Membrane folds inward bringing in fluid and dissolved substances


Eukaryotic Cell: Cytoplasm
Cytoplasm Inside to plasma membrane
membrane
Cytosol Fluid portion of cytoplasm
Cytoskeleton Microfilaments, intermediate filaments, microtubules
Cytoplasmic streaming Movement of cytoplasm throughout cell
Organelles
introduction

Membrane - bound structures within the cytoplasm

Organelles
Membrane-bound:
Nucleus Contains chromosomes
ER Transport network
Golgi complex Membrane formation and secretion
Lysosome Digestive enzymes
Vacuole Brings food into cells and provides support
Mitochondrion Cellular respiration
Chloroplast Photosynthesis
Peroxisome Oxidation of fatty acids; destroys H2O2


Nucleus
Figure 4.24
introduction

Endoplasmic Reticulum (ER)

introduction

Ribosomes

80S
Membrane-bound Attached to ER
Free In cytoplasm
70S
In chloroplasts and mitochondria

Golgi Complex

introduction

Lysosomes

introduction


Vacuoles

introduction

Mitochondrion

introduction

Chloroplast

introduction

Prokaryote Eukaryote

One circular chromosome, not in a membrane
No histones
No organelles
Peptidoglycan cell walls
Binary fission
• Paired chromosomes, in nuclear membrane
• Histones
• Organelles
• Polysaccharide cell walls
• Mitotic spindle



رفعت المحاضرة من قبل: Abduljabbar Al-Kazzaz
المشاهدات: لقد قام 41 عضواً و 439 زائراً بقراءة هذه المحاضرة








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