Categories: All - prokaryotes - bacteria - structures - cell

by Kohilavaani Ganesan 7 years ago

223

PROKARYOTES (EXTERNAL)

Prokaryotic cells are categorized by their structural differences, particularly in their cell walls. Gram-negative bacteria possess an outer membrane and a thin layer of peptidoglycan, while Gram-positive bacteria have a thicker peptidoglycan layer and contain teichoic acids.

PROKARYOTES (EXTERNAL)

PROKARYOTES (EXTERNAL)

ARCHAE

Pseudopeptidoglycan
Naturally resistant to lysozyme and penicillin

GRAM NEGATIVE

Lipopolysaccharide high content
Outer membrane present
Periplasmic space present
Thin layer of peptidoglycan and bonded to lipoproteins

CELL WALL

Functions : Prevent bacterial cells from rupturing and provide rigid platform
Gram Positive

Teichoic acid present

Thick peptidoglycan and smaller than the Gram Negative

Exoenzymes are secreted

Peptidoglycan composed of repeating dissacharide which is NAG and NAM
Composed of peptidoglycan known as murein

Structures external to the cell wall

Glycocalyx
Source of nutrients
Protection from phagocytosis
Of substance is unorganized and one loosely attached to the cell wall, it's a slime layer
If substance is organized and firmly attached to the cell wall is capsule
Made of sugars called extracellular polysaccharide
Flagella

Amphitrichous-one flagellum at each end of the cell

Peritrichous - Spread over entire surface of cell

Lophotrichous - cluster of flagella at one or both ends

Monotrichous- one flagellum

Motility and attachment to surface

Axial Filaments

Bundles of fibrils that arise at the ends of the cell beneath the outer sheath

Fimbriae and Pili

Transfer of DNA from one cell to another and called as sex pili

Can occur are the poles of the bacterial cell and evenly distributed

Shape is influenced by environmental conditions, age of culture and antibiotic pretreatment

BACTERIA

No fixed shape
Pleomorphic
Bacterial shape: Unusual - Star, Square, Triangular
Arrangement : Cocci : diplococci, staphylococci, and streptococci
3 basic shapes which is coccus, bacillus and spiral

Sizes: 0.2 to 2.0 micrometers in diameter and 2-8 micrometer in length

The prokaryotes are group of organisms that lack a cell nucleus