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62 Cards in this Set

  • Front
  • Back

plasma membrane

theboundary that separates the living cell from its surroundings

selective permeability

plasma membrane trait allowingsome substances to cross it more easily than others

amphipathic

has a hydrophilic head region and ahydrophobic tail region

mostof the membrane’s specific functions

proteins determine:

peripheral proteins

bound to the surface of the membrane



integral proteins

penetratethe hydrophobic core

transmembrane proteins

Integralproteins that span the membrane

alpha helices

hydrophobicregions of an integral protein consist of one or more stretches ofnonpolaramino acids, often coiled into

1.Transport


2.Enzymaticactivity


3.Signaltransduction


4.Cell-cellrecognition


5.Intercellularjoining


6.Attachmentto the cytoskeleton and extracellular matrix (ECM)

functions of membrane proteins (6)

transport

enzymatic activity



signal transduction



cell- cell recognition



intercellular joiing



ECM

hydrophobic (non-polar)

___________ molecules,such as hydrocarbons, can dissolve in the lipid bilayer and pass through themembrane rapidly




ex. gases (O2, CO2),lipids, steroids

hydrophilic

___________ moleculesincluding ions and polar molecules do not cross the membrane easily

transport proteins

allowpassage of hydrophilic substances across the membrane

channel proteins

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

aquaporins

channelproteins that facilitate the passage of water

carrier proteins

bindto molecules and change shape to shuttle them across the membrane

diffusion

thetendency for molecules to spread out evenly into the available space

dynamic equilibrium

asmany molecules cross the membrane in one direction as in the other (no netmovement)

concentration gradient

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

down

Substancesdiffuse ______ their concentrationgradient, which requires no energy

passive transport

Thediffusion of a substance across a biological membrane if noenergy is expended by the cell to make it happen


-spontaneous, -deltaG


-molecules/ions become less organized

simple diffusion

themovement of gases (O2,CO2) and lipids through thephospholipid bilayer.

facilitated diffusion

Larger and more polar molecules andions cannot pass through the bilayer – requires help from membrane proteinsthrough the process of

-Channelproteins




-Aquaporins




-Ion channels




-carrier proteins



types of transport proteins used in facilitated diffusion

active trasport

movessubstances against their concentration gradients


-requires energy


-performed by carrier proteins embedded in membrane only


ex. Na-K pump

passive transport

active transport

membrane potential

thevoltage difference across a membrane

voltage

createdby differences in the distribution of positive and negative ions across amembrane

negative

Thenormal resting membrane potential of a human cell is _________.

electrochemical gradient

Twocombined forces drive the diffusion of ionsacross a membrane

electrical force

the effect of the membranepotential on the ion’s movement

chemical force

the ion’sconcentration gradient

electrogenic pump

atransport protein that generates voltage across a membrane


-ex. Na-K pump

proton pump

Themain electrogenic pump of plants, fungi, andbacteria

co-transport

whenactive transport of a solute indirectly drives transport of othersubstances

bulk transport

transport of largemolecules, such as polysaccharides and proteins to cross the membrane


-requires ATP

exocytosis

transportvesicles migrate to the membrane, fuse with it, and release their contentsoutside the cell


-used by hormone secretory cells


-moves a large number of molecules

endocytosis

thecell takes in macromolecules by forming vesicles from the plasma membrane

-Phagocytosis (“cellulareating”)


-Pinocytosis (“cellulardrinking”)


-Receptor-mediated endocytosis

Types of endocytosis (3)

phagocytosis

cellengulfs a particle in a vacuole. vacuole fuses with a lysosome and is broken down by digestive enzymes

pinocytosis

molecules dissolved in droplets are taken up when extracellular fluid is “gulped” into tiny vesicles




-Usually performed to take in H2O


-Non-specific

receptor-mediated endocytosis

binding of ligands to receptors triggers vesicle formation


-brings in large number of specific molecules


ex.human cells use this to take in cholesterol

ligand

any molecule that binds specifically to areceptor site of another molecule

hypercholesterolemia

inherited disease where LDL receptors aredefective, cholesterol not taken into cells, stays in blood

osmosis

thediffusion of water across a selectively permeable membrane

lower; higher

Waterdiffuses across a membrane from the region of _______ solute concentration to the region of _______ solute concentration until thesolute concentration is equal on both sides

tonicity

theability of a surrounding solution to cause a cell to gain or lose water


-Dependenton non-penetrating [solute] and membrane permeability

isotonic solution

Soluteconcentration is the same as that inside the cell; no net water movement across the plasmamembrane

hypertonic solution

Soluteconcentration is greater than that inside the cell; cell loses water

hypotonic solution

Soluteconcentration is less than that inside the cell; cell gains water

osmoregulation

thecontrol of solute concentrations and water balance; a necessary adaptationfor life in such environments

water balance

Cellwalls help maintain

turgid

Aplant cell in a hypotonic solution swells until the wall opposes uptake; thecell is now ______.

flaccid

If aplant cell and its surroundings are isotonic, there is no net movement of waterinto the cell;the cell becomes _________.

lose water

In ahypertonic environment, plant cells:

plasmolysis

In a hypertonic environment themembrane pulls away from the cell wall causing the plant to wilt, a usuallylethal effect called ________.