bio chp. 5
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what is the cell membrane structure composed of
phospholipid bilayer (2 layers of phospholipids)
what does the cell membrane do?
serves as a barrier that seperates the inside from outside allows for the cell to control what passes in and out
what does the phospholipid bilayer contain?
proteins, glycoproteins, glycolipids and cholesterol
what is the fluid mosaic model?
describes cell membrane structure and is semi fluid
what are membrane proteins
functional components of membranes and perform various functions
what are membrane cholesterol?
it helps maintain optimum fluidity of cell membranes and helps stay not too fluid or too solid
glycolipid
lipid with a carbohydrate chain attached
glycoprotein
protein with a carbohydrate chain attached
what are the functions of cell surface carbohydrate chains (glycolipid and glycoproteins)?
function in cell-cell recognition (like an ID badge) helps protects proteins from damage
the cell membrane is _____ permeable
semi
what does the semipermeability allow for
to maintain its internal conditions separate from the environment by allowing: o Essential molecules to enter o Molecules needed inside the cell to remain o Waste products to exit o Maintenance of transmembrane gradients
what factors affect the ability of molecules to cross the membrane?
size, polarity, and charge
what is the membrane most permeable to?
small nonpolar molecules
what is the membrane least permeable to?
large and/or charged molecules
chemical gradient
concentration of solute is higher on one side than the other
electrochemical gradient
both a chemical gradient and an electrical gradient
what are the 3 ways molecules move across membranes as passive transport?
simple diffusion facilitated diffusion osmosis
what does passive transport mean?
a substance moves down a concentration gradient (high to low concentration) doesn’t require an energy input (no energy is expended)
simple diffusion
net movement of a substance from an area of high concentration to an area of low concentration (down a gradient)
facilitated diffusion
membrane transport proteins assist the movement of a substance from an area of high concentration to an area of low concentration
osmosis
the movement of solvent molecules across a semi permeable membrane from a dilute solution into a more concentrated solution
Tonicity
the relative solute concentration of one solution compared to another
Hypotonic
solute concentration is lower than another solution
Isotonic
solute concentration in equal to another solution