bio ch. 7, pt. 1

what can cellular membranes be equated to?

fluid mosaics of lipids and proteins

phospholipids are amphipathic molecules, meaning they contain what regions?

hydrophobic and hydrophilic regions

the hydrophilic tails of phospholipids are in what part of the membrane?

they are inside the membrane

the hydrophilic heads of phospholipids are exposed to what?

water on either side

the phospholipid membrane is a mosaic of what type of molecules?

protein molecules

membranes must be what to work properly?

fluid

membranes that have more unsaturated fatty acids are more…

fluid than those rich in saturated fatty acids

cholesterol has _____ affects on the membrane fluidity of animal cells

different

at warmer temperatures, what does cholesterol do to the movement of phospholipids?

restrains the movement

what are peripheral proteins?

they are bound to the surface of the membrane

what are integral proteins?

they penetrate the hydrophobic core

if integral proteins span the entire membrane what are they called?

a transmembrane protein

what do the hydrophobic regions of an integral protein consist of?

one or more stretches of non-polar amino acids, often coiled into alpha helixes

cell-surface membranes can carry out several functions, such as

transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, attachment to the cytoskeleton and extracellular matrix (ECM)

how do cells recognize each other?

they bind to molecules often containing carbohydrates on the extracellular surface of the plasma membrane

cell-cell recognition happens by using

carbohydrates

what does a cell have to do through the membrane?

a cell must exchange materials with its surroundings

what type of molecule can dissolve in the lipid bilayer and pass through the membrane rapidly?

a hydrophobic (non-polar) molecule

What type of molecules cannot just pass straight through the membrane?

hydrophilic molecules

what do proteins built into the membrane do?

they play key roles in regulating transport

transport proteins allow the passage of what type of substances across the membrane and are specific for the molecules they move?

hydrophilic substances

what is passive transport?

diffusion of a substance across a membrane with no energy investment

diffusion is

the tendency for molecules to spread out evenly into the space available

which way do substances diffuse?

down the concentration gradient

what is the concentration gradient?

the region along which the density of a chemical substance increases or decreases

diffusion takes what type of work?

no work

why is diffusion passive transport?

because it expends no energy for the cell to make it happen

osmosis is

the diffusion of water across a selectively permeable membrane

which way does water diffuse in osmosis?

across a membrane from a region of lower solute concentration to a region of higher solute concentration

what is tonicity?

the ability of surrounding solution to cause a cell to gain or lose water

what is an isotonic solution?

solute concentration is the same as the inside of the cell, there is no net water movement across the plasma membrane

what is a hypertonic solution?

solute concentration is greater than that inside the cell, the cell loses water

what is a hypotonic solution?

solute concentration is less than that inside the cell, the cell gains water

what is osmoregulation?

the control of the solute concentrations and water balance

what happens to cells without cell walls in hypertonic and hypotonic solutions during osmoregulation?

they will shrivel in a hypertonic solution and burst (lyse) in a hypotonic solution

what is facilitated diffusion?

transport proteins speed the passive movement of molecules across the plasma membrane

what is the purpose of a channel protein?

they provide corridors that allow a specific molecule or ion to cross the membrane

aquaporins facilitate what?

diffusion of water

ion channels facilitate the transport of what?

ions

ion channels are specialized types of what?

aquaporins (smaller)

what do carrier proteins undergo?

a subtle change in shape that translocates the solute-binding site across the membrane

what is the cause of carrier proteins changing shape?

chemical interactions and repulsions; not energy related

changes in shape for carrier proteins occur because of what?

the binding and release of the transported molecules