Chapter 7 - Membrane Structure and Function

plasma membrane

the boundary that separates the living cell from its surroundings; exhibits selective permeability

cellular membranes

flexible structures composed of lipids and proteins; controls movement of substances in and out

phospholipids

amphipathic (has hydrophilic and hydrophobic regions)

protects perfect membrane fluidity (wedged between phospholipids)

cholesterol

determine most of the membrane’s specific functions

proteins

peripheral proteins

are bound to the membrane’s surface

integral proteins (transmembrane proteins)

penetrate the hydrophobic core

membrane carbohydrates

carbohydrates on the extracellular surface

membrane carbohydrates

covalently bound to lipids (glycolipids) and proteins (glycoproteins)

membrane carbohydrate

is important for cell to cell recognition because they vary among species, individuals, and cell types

plasma membranes are _____ permeable

selectively

can dissolve across the lipid bilayer

small and hydrophobic molecules

cannot cross the membrane easily

large and hydrophilic molecules

transport proteins

help hydrophilic substances cross the membrane

channel proteins

have a hydrophilic channel that certain molecules or ions can use as a tunnel

carrier proteins

bind to molecules and changes shape to shuttle them across the membrane

diffusion

molecules move to fill available space

diffusion of a substance across a biological membrane is

passive transport

osmosis

the diffusion of water across a selectively permeable membrane

water diffuses across a membrane from the region of _____ solute concentration to the region of _____ solute concentration

low; high

tonicity

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

isotonic solution

outside solute concentration is the same as the inside solute concentration (equilibrium/good for animals)

hypertonic solution

outside solute concentration is greater than that inside of the cell (bad for both plants and animals)

hypotonic solution

outside solute concentration is less than that inside the cell (good for plants)

osmoregulation

the control of solute concentrations and water balance depending on the environment

ion channels

facilitate the diffusion of ions

active transport

moves substances against their concentration gradients and requires energy

membrane potential

the voltage difference across a membrane

voltage

is created by differences in the distribution of positive and negative ions across a membrane

electrochemical gradient

the difference in ion concentration and electrical charge across a membrane.

electronic pump

a transport protein that generates voltages across a membrane

proton pump

the main electrogenic pump of plants, fungi, and bacteria

electrogenic pump

help create stored energy that can be used for cellular work

co-transport

the movement of one substance provides the energy or drives the movement of another

bulk movement happens through _____ and _____

exocytosis; endocytosis

exocytosis

transport vesicles migrate to the plasma membrane, fuse with it, and release their contents outside the cell

endocytosis

the cell takes in macromolecules by forming vesicles from the plasma membrane

phagocytosis, pinocytosis, and receptor-mediated endocytosis

three types of endocytosis

phagocytosis

a cell engulfs a particle in a vacuole

pinocytosis

molecules dissolved in droplets are taken up into tiny vesicles

receptor-mediated endocytosis

binding of ligands to receptors triggers vesicle formation