Cell Membranes and Transport Mechanisms

Nucleus

Stores DNA and RNA production

Ribosomes

protein synthesis

rough er

packaging proteins

smooth ER

stores lipids and calcium

golgi apperatus

post translational modifications

endosomes

sorting traficking

mitochondria

powerhouse of the cell and cell respiration

cytoskeleton

transport and motility

polar molecules

have positive and negative charged ends, surround with other polar molecules

nonpolar molecules

surround themselves with other nonpolar molecules

water is

polar

lipids are

non polar

What end of the phospholipid is polar

the head

what part of the phospholipid is nonpolar

the tailsw

what kind of molecules are lipids

amphipathic

what is the purpose of the phospholipid bilayer

separates the ECF from the ICF

what is membrane fluidity (fluid mosaic)

lateral movement within membrane because there are no chemical bonds between fatty acids

What does cholesterol do to membranes

decrease membrane fluidity

Function of plasma membranes

acts as selective barrier

help with communication

connect adjacent cells

anchor cells to extracellular matrix

how does plasma membrane act as selective barrier

regulate passage of substances into the cell

how does plasma membrane barrier play a role in communication

detects chemical signals from other cells

how does plasma membrane connect adjacent cells

by membrane junctions

two types of cell membrane proteins

integral or peripheral membrane proteins

Features of integral membrane proteins

• amphipathic

• embedded in bilayer

• strong hydrophobic int with membrane lipids

• transport molecules and cell communication

  • CALLED transmembrane proteins

Properties of peripheral membrane proteins

• polar DONT interact with tails

• attached to inner or outer surface

• weak polar interactions, easily detached

  • work in cell signaling and anchoring protiens

What effect do peripheral membrane proteins have on phospholipid bilayer

cell shape and motility

How are cells held together in tissues

by junctional complexes

desmosomes

junction held by plaques linking adjacent cells

tight junction

holds cell on matrix or connects very tightly

gap junction

allows signaling molecules to pass through physically connects the cytoplasm of adjacent cells

How do newly synthesized polar membrane proteins get to the surface or outside of the cell

they are packaged into vesicles in the golgi

Ligand

any molecules that is bound to a protein, usually binding is reversible

binding of ligand does what to protein

changes confrimation

Four charachteristics of ligand binding

specificity, affinity, saturation, concentation

specificty

biding site only fits specific messangers

affinity

the force of binding between messenger and receptor

saturation

the degree to which the receptors on a cell are fully occupied by a messenger

competition

different molecules with similar structure fight for the same binding site

High affinity meaning

need small amounts of ligand

high lignand conc means what to affinity

higher affinity

covalent modulation

covalent bonding of a charged chemical group to a protein or enzyme which causes conformational change to structure and function

allosteric modulation

protein with 2 oe more binding sites where a ligand binds noncovalently, altering the conformation and properties of another site

How can you increase acid concentration with plasma

increase plasma conc or increase binding site affinity

diffusion

movement of solute from high to low concentration without energy, driven by concentration gradient

what is flux

the amount of material crossing a surface in CM²/ time

Net flux

the difference between 2 fluxes

Once diffusion at equilibrium

net flux is zero

net flux is always

from a region of high conc to low conc

the larger the concentration gradient

the larger the net flux

Factors making larger flux

high temp

small molecular mass

larger available surface area

thin mediums

J= PA(Co-Ci)

J= flux

P= permiability constant

A- SA

Co-Co concentration outside - inside

Diffusion works best

over small distances like µM, or nM, cM is too big

Nonpolar substances and diffusion

diffuse rapidly in and out of cells

• o2, Co2, steroid hormones, anisthetics

ions and diffusion

charger, so can not diffuse → ion channels fo Na K and Ca, are selective

Ion channels go

from intracellular to extracelular

Ion channel gating

opening and closing of ion channels

types of ion channels

ligand gated

voltage gated

mechanically gated

ligand gated ion channel

open or close when moelcules bind to them

votlage gated ion channles

open and close when membrane potential changes

mechanically gates channels

open or close when membrane is stretched, recent discovery

Where is Na+ attracted

inside of cell due to their + charge and the intracellular fluids partial - charge

How to move insoluble moleucles into cell

mediated trasnport or vesicular trasnport

Mediated trasnport systems

use a carrier that is a transmembrane protein by using proteins that go through conformational changes follow ligand binding rules

flux in mediated transport system

variable, can be modified by concentration of ligand/ gradient, rate of transport, and number of transporters