micro bio day 3

Phospholipid Bilayer: The cell membrane is a phospholipid bilayer structure, often described by the fluid mosaic model.
- Fluid Nature: The phospholipids are not static; they move around slightly, similar to packed sardines in a can, which allows for fluidity.
- Mosaic Aspect: The membrane contains a variety of proteins (at least 200 different kinds), glycoproteins, glycolipids, and cholesterol, which contribute to its mosaic nature.

Ester and Ether Linkages: Differences in cell types.
- Bacterial Cells: Have ester linkages of fatty acids in their membranes.
- Archaeal Membranes: Characterized by ether linkages, which differ structurally from ester linkages.
- Lipid Monolayer: Some extremophiles (archaea adapted to high temperatures) feature a lipid monolayer that helps maintain cell integrity in extreme conditions.

Rigidity and Flexibility: Maintained through the presence of hopanoids (steroid-like molecules) in bacterial membranes.
Permeability: Membranes determine what materials can enter and exit the cell, which leads into the principle of movement of materials.

Diffusion: Movement from high concentration to low concentration; all molecules attempt to reach equilibrium.
- Experiment Example: Air freshener diffusing in a room demonstrates diffusion.
Osmosis: The specific diffusion of water across a membrane; the movement of water molecules occurs through channels called aquaporins.
- Molecule Requirements: Small, uncharged, and nonpolar molecules can diffuse directly through the membrane, while polar and charged molecules often need help.

Passive Transport: No energy required; materials move through ungated proteins (e.g., channel proteins) that are always open.
Active Transport: Requires energy input to move materials against their concentration gradient.
- Gated Proteins: These channels can open or close based on chemical signals from the environment, regulating material uptake.
- Sodium-Potassium Pump: For muscle contraction and maintaining cell potential, it uses ATP to transport sodium out and potassium in (3 sodium out, 2 potassium in; costs 1 ATP).

Group Translocation: A mechanism used by bacteria to actively transport substances while chemically modifying them upon entry.
- Example: Glucose is phosphorylated to glucose-6-phosphate, trapping it inside the cell.
ATP Binding Cassette (ABC) Transport: This method is often found in bacteria and requires energy to retrieve scarce materials from the environment.
- Mechanism: Binding proteins search for specific nutrients, bind to them, and then transport them to the cell membrane where they are brought into the cell, often requiring ATP for the process.

Peptidoglycan: A key structural component of bacterial cell walls, providing rigidity and protection.
- Composition: Made of two alternating sugars: N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM), each NAM has a tetrapeptide chain (four amino acids) attached.
- Gram Positive vs. Gram Negative:
  - Gram Positive: Thick peptidoglycan layer (20-80 nm) with teichoic and lipoteichoic acids.
  - Gram Negative: Thin peptidoglycan layer (2-10 nm), has an outer membrane, and a periplasmic space.