ch 7 membrane structure & function

plasma membrane:

boundary that seperates the living cell from its surroundings

what does the plasma membrane exhibit?

selective permeability

which membrane allows some substances to cross it more easily than others?

plasma

what are the functions of the plasma membrane?

defines cell shape, aids in cell recognition, exhibits attachment sites for signalling molecules & virusus

what are the major components of the plasma membrane?

lipids, proteins, and carbohydrates

lipids, proteins and carbohydrates are major components of what?

plasma membrane

fluid mosaic model:

membrane is a mosaic of protein molecules bobbing in fluid bilayer of phospholipids

the plasma membrane is a mosaic of what kind of molecules?

protein molecules

what fluid are the protein molecules inside the mosaic of protein model bobbing in?

fluid bylayer of phospholipids

membranes are not

locked ridgidly in place

what kind of interactions are membranes held together by?

weak interactions

what way can most lipids rapidly shift?

slideways or rotate

what way do most lipids rarely shift?

in a flip flop motion

what are some factors of the fluidity of membranes?

temperature and buffer

what happens as we incorporate temperature in the fluidity of the membrane?

as we incorporate temperature we incorporate fluidity and vice versa

what is a buffer for the fluidity of a membrane?

cholesterol

phospholipids are the what in membranes?

most abundant lipids in the membranes

amphiphathic molecules assemble into what?

a bilayer

a phospholipids structure is?

a hydrophilic head and two hydrophobic tails

what do proteins determine in the membrane?

the function

what are the two main types of proteins in the membrane?

integral and peripheral

integral membrane protein

permanetly imbedded within the lipid bilayer

what is a transmembrane?

when an integral membrane protein spans the membrane partially or fully

peripheral membrane protein

lossley or temperarily bound to the surface of the mambrane

where are membrane carbohydrates found?

in the exterior surface of the membrane

what are membrane carbs bonded to and how?

covalently bonded to lipids (glycolipids) or proteins (glycoproteins)

selectivie permeability

allows some susbstances to cross more easily than others

what happens if you wait a whille during selective permeability?

virtually any molecule will deffuse across the membrane

what is the ranking of he substances in order from easiest to hardest transverse in the membrane without assistance 

Small non polar 

Small polar molecules 

Large polar molecules 

Charges ions 

what is the easiest transverse in the membrane without assistance?

small non polar

what is the hardest transverse in the membrane without assistance?

charges ions

passive transport

movment of high molecules from an area of high concentration to low concentration

passitive transport requires?

no ATP/energy

what are the types of passive transport?

simple diffusion, facilitated diffusion, and osmosis

simpile diffusion

small, nonopolar molecules slip directly through the lipid layers on their own

how do you reach equilibrium in a simple diffusion

movement continues back and forth until both sides reach equilibrium

how much each molecule be evaluated in a simpiler diffusion?

independently

whar are the factors affecting the rate of diffusion?

concentratration gradient, temperature, size of molecules, and distance traveled

what is concentration gradient factor in simple diffusion?

higher gradient >faster diffusion

what is the temperature factor in simple diffusion?

higher temperature > faster diffusion

what is the size of molecules factor in simple diffusion?

smaller size > faster diffusion

what is the distance traveled factor in simple diffusion?

shorter distance > faster diffusion

facillitated diffusion

transport (transmembrane) proteins speed the passive diffusion of molecules across the membrane

what happens if all transport proteins are occupied?

the process becomes saturated and cannot proceed

types of transport proteins?

channles and carriers

what is a channel in facilitated diffusion?

hydrophillic tunnel through membrane (ion channels and aquaporins)

what are the carriers in the facillitated diffusion?

buindinh site for molecules and changes physical state (transfer is more specific and slower)

osmosis

passive diffusion of water across a membrane

what does osmosis do to the membrane

still moves down the concentration gradient and requires no energy

when does water stop moving?

when equilibrium is reached

tonicity of osmosis

ability of surrounding solutions to cause a cell to gaina/lose water

what direction does water always move during toxicity osmosis

towards the higher solute

what does the response of the cell do from osmosis depend on?

the cell type and external environment

isotonic solution:

equal solute concentration to the inside of the cell

hypertonic solution:

higher solute concentration than inside the cell

hypotonic solution:

lower solute concentration than inside the cell

active transport:

movement of molecules from low concentration to high concentration

what way does active transport move?

against the concentration gradient

active transport requires what?

ATP/energy

what kind of proteins does active transport include?

only carrier proteins

types of active transport:

primary, secondary, and bulk transport

primary active transport:

moves ions/molecules via direct use of ATP

how does primary active transport move ions?

based on concentration gradient (low to high)

primary active transport powers what?

secondary active transport

secondary active transport:

coupled transport of two or more molecules.ions via indrecr use of ATP

secondary active transport moves ions based on?

electrochemical gradient

electrochemical gradient:

combined concentration and electrical charge difference across a membrane

what happens when an ion/molecule is transported down its concentration gradient?

this provides the energy to pull the 2nd ion/molecule against its own gradient

types of secondary active transport:

symport and antiport

symport:

ions/molecules transported in the same direction across a membrane

anriport:

ions/molecules transported in different directions across a membrane

bulk transport:

process that moves large molecules, particles or large vol of fluids via vesicles

what way does bulk transport travel?

down or against the concentration gradient

what does bulk transport requires ATP to form?

vesticles that transport materials

categories of bulk transport

endocytosis and exocytosis

what does endocytosis do?

brings materials into the membrane through vesticle formation

what does excoytosis do?

sens materials out by merging vesticles with plasma membrane

phagocytosis:

cell “eats” large particles by extending pseudopodia and packaging into a vesticle to be digested or processed

what is pseudopodia?

temporary extensions of a cell that enable movement and the engulfing of materials

what might phagocytosis fuse with and why?

lysosomes for digestion

pinocytosis:

cell “drinks” extracellular fluid and any solutes contained w/in the fluid into a vesticle to be used for cellular processes

what happens to everything in the vicinity of pinocytosis?

it enters the vesticle

receptor-mediated:

cell takes in molecules that bing surface receptors into vesticles

what does receptor-mediated only target?

specific molecules that bind

exocytosis:

cell secretes molecules by the fusion of vesticles with the plasma membrane to release their contents externally

what is an example of exocytosis?

secretory cells in the pacreas release insulin into the bloodstream.

is diffusion active or passive?

passive

what material is being transported during diffusion?

small molecule weight material

is osmosis active or passive?

passive

what material is being transported during osmosis?

water

is facillitated transport active or passive?

passive

what materials are being transported during facillitated transport?

Mainly ions and large polar molecules (Na, K, Ca, glucose)

what materials are being transported during primary active transport?

Na, K, Ca

what materials are being transported during secondary active transport?

amino acids, lactose

is phagocytosis active or passive?

active

what materials are being transported during phagocytosis?

large molecules, whole cells and cellular structures

is pinocytosis active or passive?

active

what materials are being transported during pinocytosis?

small molecules and fluid

is receptor- mediated endocytosis active or passive?

active