Membranes and Membrane transport Flashcards
The cytosol of nearly all prokaryotes is surrounded by a phospholipid bilayer called
plasma mem .
What is phospholipid?
phosphate group, two FA chains, and a glycerol backbone.
this molecule is amphipathic ( has a polar and a non polar portion)
micelles can form with phospholipids
(bc they are the most thermodynamically stable conformation) and if enough are present ..liposomes
unlike eukaryotic membranes, prokaryotic plasma membranes usually do not have steroids like ?
cholesterol
instead some bacterial mem contain steroid like molecules called hapanoids
Membrane proteins act as ..
transporters receptors attachment sites identifiers adhesive proteins and enzymes some membrane proteins are attachment sites that anchor the cytoskeleton.
adhesion by one cell to another is accomplished by?
mem proteins
integral or intrinsic proteins are..?
amphipathic
what are the forces that hold the membrane together?
intermolecular forces ! the mem is therefore fluid . (parts can move laterally )
the model is described as a fluid mosaic model.
in eukaryotic membranes what moderates the mem fluidity?
cholesterol.
in prokaryotic membranes what reduces the fluidity?
hapanoids
what is the chemical concentration gradient?
pointing in the direction of lower concentration
what is the electrical concentration gradient?
where a positively charged particle will move.
what are two aspects of a compound that affect its semipermeability ?
size and polarity.
larger molecule - less permeable .
polarity- greater polarity (charge) = less permeable the mem is to the molecule
passive diffusion
molecules move through leakage channels across the mem due to random motion
transport or carrier proteins
facilitate the diffusion of specific molecules across the mem.
in order for a passage to be considered facilitated diffusion, diffusion must occur down the electro-chemical gradient.
active transport
movement of compound against its electrochemical gradient
expenditure of energy is needed.
