3 Cells and Methods to Observe Them

cell envelope

surface layers of prokaryotic cell.

from inside out:

• cytoplasmic membrane: thin structure surrounding cytoplasm and defining cell boundary. serves as crucial permeability barrier

• cell wall

• capsule: a layer protecting cell and allow attachment to surfaces

  • often present in bacteria

  • rarely found in archaea

cytoplasm

Enclosed by the cell envelope, __ is a thick substance filled with nutrients, ribosomes, enzymes

• includes the organelles but the nucleus

• is the space between the chromosomes and the cellular membrane

cytosol

Fluid portion of the cytoplasm where a prokaryote’s chromosome can be found.

nucleoid

Gel-like region in the cytoplasm where the prokaryotic cell’s chromosome is found.

fluid mosaic model

Model that describes the dynamic nature of the cytoplasmic membrane

• phospholipid bilayer

  • hydrophilic heads faces/interacts with aqueous solutions

  • hydrophobic tails inward

    • why only:

    • gases → O₂, CO₂, N₂

    • small hydrophobic compounds

    • water (polar, but small enough)

    • can enter

• embedded with proteins that act like

  • selective gates → permeability barrier

  • sensors → transmits external environment info to inside of cell

  • enzymes → catalyze chemical reactions

  • constantly drift laterally in membrane

chemical

The general structure of bacterial and archaeal cells are the same (can be grouped as “prokaryotic” cells), but have several fundamental __ differences

• phospholipids in plasma can be monolayer in archaea

  • more stable under extreme conditions

• hydrophobic tails connected to hydrophilic heads via ether chemical linkage (instead of bacterial ester)

aquaporins

Pore-forming membrane proteins that facilitate water passage

simple diffusion

movement of solutes from a region of high concentration to one of low concentration until equilibrium is reached

dependent on the concentration gradient → greater conc. difference, higher rate of __.

how substances that can freely pass through the phospholipid bilayer pass through.

doesn’t involve transport proteins.

osmosis

diffusion of water across a selectively permeable membrane.

movement dependent on solute concentration across a membrane:

• from high water conc. to low water conc.

• from low solute conc. to high solute conc.

  • due to high solute conc. typically occurring from being nonpenetrating, i.e, POLAR or LARGE

such they have terms specific for non-penetrating solutes:

• hypotonic: less solutes outside cell; water goes inside

• hypertonic: more solutes outside cell; water goes outside

• isotonic: same solutes outside as inside

cell wall protects from lysing (bursting) in the hypotonic setting bacteria and archaea are usually found in

electron transport chain

Major difference between eukaryotes and prokaryotes is that:

eukaryotes use organelles for energy transformation

while prokaryotes utilize an __.

• protons are moved out of the cell; OH- remain inside

• creates an electrochemical gradient across membrane

• charged ions attract each other; stay close to membrane

• proton motive force: form of energy that the proton gradient acts as

  • energy of protons’ tendency to going back into cell is utilized to power active mechanisms