bio ch 5

phospholipid bilayer

what is the framework of a membrane?

phospholipid bilayer

the basic framework of a biological membrane, consisting of. two layers of phospholipids.

hydrophilic

which region of the phospholipid bilayer faces water?

hydrophobic

which region of the phospholipid bilayer faces inward toward the membrane interior?

leaflet

half of a phospholipid bilayer

fluid-mosaic model

the accepted model of a biological membrane; its basic framework is the semifluid phospholipid bilayer with a mosaic of proteins

asymmetrical

the two leaflets are ______, with different amounts of each component

lipids, proteins, and carbohydrate

the membrane is considered a mosaic of what molecules?

lipids and proteins

the membrane resembles a fluid because ______ and _______ can move relative to each other within the membrane

transmembrane proteins

a protein that has one or more regions that are physically embedded in the hydrophobic interior of a membrane’s phospholipid bilayer

lipid-anchored proteins

a type of integral membrane protein that is attached to the membrane via a lipid molecule

integral membrane protein

a protein that cannot be released from the membrane unless the membrane is dissolved with an organic solvent or detergent

transmembrane and lipid-anchored proteins

what are the two types of integral membrane proteins?

peripheral membrane protein

a protein that is noncovalently bound to a region of an integral membrane protein that projects out from the membrane or noncovalently bound to the polar head group of a phospholipid

20-30%

what percent of all genes are estimated to encode transmembrane proteins?

transmembrane proteins

computer programs can be used to predict the number of that in an organism based on DNA sequence data of an organism’s genome?

cystic fibrosis

a lung disease caused by a problem with transmembrane proteins in membranes

function

what of many genes is unknown but study may provide a better understanding an better treatments for disease?

fluidity

a property if biological membranes in which individual molecules remain in close association yet have the ability to move rotationally or laterally within the plane of the membrane

semifluid

membranes are ____

long axes

lipids can rotate freely around their what?

membrane leaflet

lipids can move laterally within the what?

semifluid

a property of biological membranes in which the movement of membrane components occurs in two dimensions

flip-flop

which type of lipids from one leaflet to the opposite does not occur spontaneously?

ATP

flippase requires ___ to transport lipids between leaflets

lipid raft

in a membrane, a group of lipids, sometimes including associated proteins, that float together as a unit in a larger sea of lipids

length of phospholipid tails, double bonds, cholesterol

what are the three factors that affect fluidity?

length of phospholipid tails

shorter tails are less likely to interact, which makes the membrane more fluid

presence of double bonds

double bond creates a kink in the fatty acid tail, making it more difficult for neighboring tails to interact and making the bilayer more fluid

presence of cholesterol

cholesterol stabilizes membranes; effects vary depending on temperature

unsaturated

the property of certain lipids that contain one or more C=C double bonds

lipids

in eukaryotes, the cytosol and end-membrane system work together t synthesize what?

lipid exchange proteins

a protein that extracts a lipid from one membrane, diffuses it through the cell, and inserts the lipid into another membrane

flippase

phospholipids change leaflets with the help of what?

glycosylation

the covalent attachment of carbohydrates to a protein or lipid, producing a glycoprotein or glycolipid

glycolipid

a lipid that has a carbohydrate attached to it

glycoprotein

a protein that has a carbohydrate attached to it

cell surface recognition

glycolipids and glycoproteins ofter play a role in what?

n-linked glycosylation

attachment of carbohydrates to nitrogen atoms of asparagine side chain

o-linked glycosylation

addition of sugars to oxygen atoms of serine for threonine side chains

o-linked

which type of glycosylation occurs only in Golgi?

membrane transport

the movement of ions or molecules across a biological membrane

selective permeability

the property of membranes that allows the passage of certain ion or molecules but not others

passive transport

the diffusion of a solute across a membrane in a process that is energetically favorable and does not require an input of energy

simple and facilitated diffusion

which two types of membrane transport is passive transport?

simple diffusion

when a substance moves across a membrane from a region of higher concentration to a region of lower concentration, without a transport protein

facilitated diffusion

a mechanism of passive transport in which a transport protein provides a passageway for a substance to cross a membrane from an area of higher concentration to a lower concentration; uses the aid of a transport protein

active transport

the transport of a substance across a membrane from an area of low concentration to one of higher concentration with the aid of a transport protein; requires an input of energy

hydrophobic interior

the barrier to hydrophilic molecules or ions is due to what?

rate of diffusion

what depends on the chemistry of a solute and its concentration?

size, polarity, charge, concentration

what are the four factors accepting the rate of diffusion across membranes?

high permeability

what occurs with gases and small uncharged molecules?

moderate permeability

what occurs with water and urea?

low permeability

what occurs with polar organic molecules?

very low permeability

what occurs with ions, charged polar molecules, and large molecules?

transmembrane gradient

a situation in which the concentration of a solute is higher on one side of a membrane than on the other

electrochemical gradient

a dual gradient across a membrane, having both electrical and chemical components; determines the direction in which ions will move

osmosis

the movement of water across a membrane to balance solute concentrations

osmotic pressure

the tendency for water to move into any cell

isotonic

condition in which the solute concentrations on both sides of a plasma membrane are equal, which does not cause a cell to shrink or swell

hypertonic

when the concentration of solutes outside cell is higher and causes a cell to shrink due to osmosis of water outside the cell

hypotonic

when the concentration of solutes outside the cell is lower and causes a cell to swell due to the uptake of water via osmosis

plasmolysis

the shrinkage of algal or plant cytoplasm that occurs when the water leaves the cell by osmosis, with the result that the plasma membrane no longer presses on the cell wall

crenation

shrinkage of a cell in a hypertonic solution

osmotic lysis

swelling and bursting of a cell in a hypotonic solution

cell wall

what prevents major changes in a cell size

hypotonic to hypertonic

how does water move during osmosis?

turgor pressure

pushes plasma membrane against cell wall

hypotonic

freshwater protists survive in what type of environment?

contractile vacuoles

to prevent osmotic lysis, what takes up water and discharges it outside of the cell

cell volume

using vacuoles to remove excess water maintains a constant what?

channel

a transmembrane protein that forms an open passageway for the facilitated diffusion of ions or molecules across a membrane

transporters

a transmembrane protein that binds tp a solute and undergoes a conformational change to allow the movement of the solute across a membrane

channels and transporters

what are the two classes of transport proteins based on their type of movement?

gated

a property of many channels that allows them to open and close to control the movement of solutes across a membrane

lignands

an ion or molecule that binds to a protein, such as an enzyme, a receptor, or a channel

lignands

gated channels are controlled by binding of small molecules called what?

Peter agre

who first identified a protein that was abundant on bed blood cells, bladder, and kidney cells?

aquaporin

since it forms a channel that allows water to pass through the membrane, CHIP28 was renamed what?

uniporter

a transporter that binds a single ion or molecule and transports it across a membrane

symporter

a transporter that bonds two or more ions or molecules and transports them in the same direction across a membrane

antiporter

a transporter that bonds two or more ions or molecules and transports them in opposite directions

primary active transport

a type of transport that involves a pump that directly use energy to transport a solute against a gradient

secondary active transport

a type of membrane transport that involves the utilization of a pre-existing gradient to drive the active transport of another solute

pump

a transporter that directly couples its conformational changes to an energy source

electro generic pump

a pump that generates an electrical gradient across a membrane

exocytosis

a process in which material inside the cell is packaged into vesticles and excreted into the extracellular environment

endocytosis

a process in which the plasma membrane invaginates, or folds inward, to form a vesicle that brings substances or particles into the cell

receptor-mediates, pintocytosis, phagocytosis

what are the three types of endocytosis?

receptor-mediated endocytosis

a common type of endocytosis in which a receptor in the membrane is specific for a given cargo

pinocytosis

a type of endocytosis that involves the formation of membrane vesicles from the plasma membrane as a way for cells to internalize the extracellular fluid

phagocytosis

a type of endocytosis that involves the formation of a membrane vesicle, called a phagosome or phagocytes vacuole, which engulfs a particle

ATP

flippase requires … to transport lipids between leaflets

cholesterol

what controls fluidity in membranes?

stiffens

at higher temperatures, cholesterol … the membrane

fluid

freezing

at lower temperatures, cholesterol makes the membrane more … and prevents …

laterally

most lipids can move … within the membrane leaflet

ATP

what provides energy for cell function

ATP

adenosine triphosphate

ADP

adenosine diphosphate