Prokaryotic and Eukaryotic Cells - MicroPara LectureP

Cell

Fundamental unit of any living organism because like the total organism it exhibits the basic characteristics of life

Prokaryotic

“pre-nucleus”

Prokaryotic

DNA is not enclosed within a membrane

Prokaryotic

DNA is one circular chromosome

Prokaryotic

Their DNA is not associated with histones

Prokaryotic

They lack membrane enclosed organelles

Prokaryotic

Their cell walls contain complex polysaccharide peptidoglycan

Murein

Peptidoglycan is also known as

Prokaryotic

They usually divide by binary fission

Nucleoid

• Lacks nuclear membrane and mitotic apparatus

• Contains DNA, 1mm long that can be in circular or linear forms

• Function: Replication; antibiotic resistance genes

• Composition: single circle of double stranded DNA

Cytoplasmic Structure

• Site of oxidative and transport enzymes; semi-permeable membrane

• Lipoprotein bilayer beneath cell wall

• Carotenoids

• Bacteriochlorophyll

• Phycobiliproteins

Photosynthetic pigments in Prokaryotes

Volution or Metachromatic granules

Storage of reserve materials

Cell Envelope

• Layers that surround the prokaryotic cells

• It protect the cell from degrading enzymes from Bdellovibrio bacteriovorus and from bacteriophages

• Maintenance of cell shape in archaebacteria

• Cell adhesion to host epidermal surfaces

S-layer

Os the outer most component of the cell envelope

Cytoplasmic membrane/inner membrane

• Selective permeability and transport of solutes

• Electron transport and oxidative phosphorylation in aerobic species

Cell wall

• Layers of cell envelope lying between the cell membrane and the capsule

• Composed mainly of peptidoglycan

N-acetylglucosamine and N-acetylmuramic acid

Peptidoglycans is made up of backbone composed of altering

Cell wall

• Provides osmotic protection

• Cell division

• Primer for its own biosynthesis

• Antigenic determinants

• Teichoic Acid

• Teichuronic Acid

Special components of Gram (+) cell walls

Teichoic and Teichuronic Acid

• 50% of dry CW and 10% of bacterial weight

• Water-soluble polymers containing ribitol or glycerol joined by phosphodiester linkage

• Carries amino acids or sugar constituent

• Lipoproteins

• Lipopolysaccharide (LPS)

• Periplasmic Space

• Double Membrane

Special components of Gram (-) cell walls

Lipoproteins

• The most abundant protein of Gram (-) organisms

• It stabilise the outer membrane and anchor it to the peptidoglycan layer

Lipopolysaccharides (LPS)

• Consist of polysaccharide core (O-antigen) and a Lipid-A (phosphorylated glucosamine disachharide + B-hydroxymyristic acid)

• Endotoxin of Gram (-) bacteria

Periplasmic Space

• The space between the inner and outer membrane occupying 20-40% of the cell volume

• It contains many hydrolytic enzymes including B-lactamases

Gram (+)

Thick cell walls

Gram (-)

Thin cell walls

capsule

• Extra cellular polymers forming a well-defined layer surrounding the cell

• Contribute to bacterial pathogenicity

Glycocalyx

Contributes to bacterial adherence

• Monotrichous

• Amphitrichous

• Lophotrichous

• Bilophotrichous

• Peritrichous

Arrangements of flagella

Monotrichous

Single polar flagellum

amphitrichous

Single or clusters of flagella at both poles

Lophotrichous

Single tuft of cluste of flagella at a pole

bilophotrichous

Two tufts or clusters of flagella at both poles

peritrichous

Single flagellum randomly distributed around the bacteria

Pili/Fimbriae

• Rigid appendages shorter and finer than flagella made of “pillins”

• Ordinary pili

• Sex pili

Types of Pili

endospores

• Resting cells that are highly resistant to dessication, heat and chemical agents

• Transformation

• Conjugation

• Transduction

Methods of DNA transfer

Transformation

• Genes are transferred from once bacterium to another as “naked” DNA in solution

• Example: Bacillus, Hemophilus, Neisseria, Acinetobacter, Streptococcus, Staphylococcus

Conjugation

• Direct cell-to-cell contact

Gram (+)

Uses a sticky substance (surface) in conjugation

Gram (-)

Uses sex pili in conjugation

Transduction

A process where bacterial DNA is transferred from a donor to a cell to a recipient cell by a bacteriophage/phage

Eukaryotic

“true nucleus”

histones

DNA of eukaryotes are associated with chromosomal proteins called

Algae

Cell wall of this organisms is composed of cellulose

Fungi

Cell wall is composed of chitin

chitin

Polysaccharide and a polymer of N-acetylglucosamine (NAG)

Yeast

Contains polysaccharide glycan and mannan

protozoa

Eukaryotes that does not have cell instead it has a flexible outer covering called pellicle

pellicle

Flexible outer covering of protozoa

Glycocalyx

• Layered material containing sticky carbohydrates

• Contribute to cell to cell recognition

Carbohydrates and sterols

Cytoplasmic membrane of eukaryotes contains

Carbohydrates (CHO)

Receptor site for cell-cell recognition

Sterols

Complex lipids (except in Mycoplasma cells)

Endocytosis

Segment of the plasma membrane surrounds a particle molecule, encloses it, and brings it into the cell

Cytosol

Fluid portion of the cytoplasm

Cytoplasmic streaming

Movement of cytoplasm from one part of the cell to other

Flagella

Few and ling in relation to the size of the cell

cilia

Numerous and short, resembling hairs

Nucleus

• Spherical or oval

• Contains DNA

Rough ER

• Continuos with nuclear membrane

• Usually unfolds into a series of flattened sacs

• Contains ribosomes

Smooth ER

• Extends from rough ER to form a network of membrane tubule

• Do not have ribosomes

Ribosomes

Protein synthesis

Golgi complex

• First step in protein pathway

Lysosomes

• Formed from Golgi complexes and look like membrane-enclosed spheres

• Digest bacteria

Vacuoles

• Space or cavity in the cytoplasm of a cell that is enclosed by tonoplast

• In plants, it takes up water to increase size and provides rigidity to leaves and stems

• Acts as a storage for proteins, organic acids, and inorganic ions

• Bring food into the cell by endocytosis

mitochondria

• Spherical or rod-shaped

• Powerhouse of the cell

chloroplasts

• Algae and green plants

• Contains both chlorophyll and enzyme required for the light gathering phase