Bacterial Cell Structure Quiz

Bacterial Cell Structure

• The structure of a bacterial cell can be divided into four main components: external structure, cell envelope, internal structures, and endospore.

External Structure

• The external structure consists of a capsule, flagella, and pili.
• A capsule is a protective layer that helps bacteria resist phagocytosis and desiccation.
• Flagella are responsible for bacterial movement and chemotaxis.
• Pili are responsible for bacterial conjugation and DNA transfer.

Cell Envelope

• The cell envelope consists of a cell wall and a cytoplasmic membrane.
• The cell wall is a rigid structure that provides support and maintains the cell's shape.
• The major component of the bacterial cell wall is peptidoglycan (murein).
• Peptidoglycan is a polymer of disaccharides (glycan) cross-linked by short chains of identical amino acids (peptides).

Cell Wall Structure

• The cell wall of Gram-positive bacteria is thick and contains many layers of peptidoglycan and teichoic acids.
• The cell wall of Gram-negative bacteria is relatively thin and consists of a few layers of peptidoglycan surrounded by a second lipid membrane containing lipopolysaccharides and lipoproteins.

Functions of Cell Wall

• The cell wall determines the shape of the cell.
• It determines the staining reaction of the Gram stain.
• It plays an important role in cell division.
• It provides structural support and protects the cytoplasmic membrane.
• It provides osmotic protection and protects the cell from bursting in hypotonic solution.
• It protects the bacteria against the action of antibodies, antibiotics, and lysozyme.

Cell-Wall-Deficient Bacteria

• Some bacteria, such as Mycoplasma and L-form bacteria, lack a cell wall.
• These bacteria survive by living inside another host cell.
• They are not affected by antibiotic treatments that target cell wall synthesis.

Cytoplasmic Membrane

• The cytoplasmic membrane is a semi-permeable membrane that regulates the movement of molecules in and out of the cell.
• It is composed of proteins and phospholipids.
• It is osmotically sensitive and can be affected by changes in the concentration of solutes.

Functions of Cytoplasmic Membrane

• It maintains a constant environment within the cell by regulating the movement of molecules.
• It plays an important role in cell division.
• It contains cytochrome enzymes responsible for respiration and energy generation.
• It is involved in the excretion of hydrolytic exoenzymes that digest large food molecules.
• It is involved in the secretion of exotoxins.
• It contains chemotactic systems that attractants and repellents bind to specific receptors.

Mesosome

• Mesosomes are complex invaginations of the cytoplasmic membrane into the cytoplasm.
• They play a role in cell division.
• They increase the surface area of the cytoplasmic membrane, increasing the efficiency of permeability and active transport.
• They are the site for respiratory enzymes.