Cell Classification and Characteristics

Cell Classification

• There are two main categories of cells: Prokaryot and Eukaryot.
• Prokaryot: "Pro" means before, and "karyon" means kernel or nucleus, referring to cells that lack a true nucleus.
• Eukaryot: "Eu" means true, and "karyon" means kernel or nucleus, referring to cells that have a true nucleus.

Characteristics of Living Cells

• 7 characteristics of living cells:
  • Removal of toxic materials and waste of metabolism
  • Excretion
  • Ability to produce offspring
  • Ability to sense and respond to stimuli
  • Consuming material from surrounding for growth and energy
  • Breaking down food to release energy
  • Increasing in number of cells

Microorganisms

• 5 major groups of microorganisms:
  • Bacteria
  • Fungi
  • Virus
  • Protozoa
  • Algae

Differences between Microorganisms and Other Living Organisms

• 5 key differences:
  • Size: Microorganisms are much smaller than other living organisms.
  • Complexity: Microorganisms are simpler in structure and complexity compared to other living organisms.
  • Reproduction: Microorganisms reproduce rapidly and can produce millions of offspring in a short period.
  • Diversity: Microorganisms are incredibly diverse and can survive in a wide range of environments.
  • Importance: Microorganisms play a vital role in several processes such as nutrient cycling, decomposition, fermentation, and digestion.

Nomenclature of Microorganisms

• Microorganisms are named according to the binomial system, introduced by Carl Linnaeus.
• The binomial system consists of a genus and species.
• Rules of nomenclature:
  • Use binary names
  • Capitalize the genus name
  • Italicize or underline the names of all taxa

Cell Components

• Gram-positive bacteria: contain teichoic acids, which are negatively charged and help regulate the cell wall's negative charge.
• Gram-negative bacteria: contain lipopolysaccharides, which function as a second membrane structure that protects the peptidoglycan.

Cell Wall Functions

• Act as an antigen
• Inhibit phagocytosis
• Give and maintain the shape of the cell
• Protect the cell against mechanical and osmotic stress
• Separate the interior of the cell from the outer environment
• Enable transport of substances in and out of the cell

Gram Positive vs Gram Negative Bacteria

• Gram-positive bacteria: thick cell wall, peptidoglycan 40-90%, no outer layer, flat surface, periplasmic space is absent.
• Gram-negative bacteria: thin cell wall, peptidoglycan 5-10%, outer layer-lipopolysaccharide, waving surface, periplasmic space is present.

Cell Membrane/Plasma Membrane

• Main components: phospholipid and proteins.
• Functions:
  • Regulate the passage of substances into and out of the cell
  • Agent for selective transport or uptake of material

External Structures

• Flagella: used for movement, arrangement can vary.
• Fimbriae: used for attachment of cell to a surface.
• Pili: used for bacteria conjugation involved in DNA transfer.
• Capsule/Slime Layer: protects the cell from desiccation, prevents phagocytosis, and helps in adhesion or attachment.

Overall Structure of Prokaryotic and Eukaryotic Cell

• Prokaryotic cell: lacks a true nucleus and has a single circular chromosome.
• Eukaryotic cell: has a true nucleus and linear chromosomes.

Flagella Arrangement

• There are four arrangements of flagella: monotrichous, lophotrichous, amphitrichous, and peritrichous.