Cell Membranes Flashcards
What do bilayered dynamic structures do
perform vital physiological roles
form boundaries between cells and their environments
regulate movement of molecules into and out of cells
What does the lipid part of the fluid mosaic model fo
barrier for water soluble molecules
contain membrane proteins
carbs attach to lipid or protein molecules
aqueous regions names
hydrophilic region (phosphate)
hydrophobic region (fatty acids)
Integral membrane proteins
have hydrophobic
regions of amino acids that
penetrate or entirely cross
the phospholipid bilayer.
Transmembrane proteins
have a specific orientation,
showing different “faces” on
the two sides of the
membrane
Peripheral membrane proteins
lack hydrophobic regions and are not embedded in the bilayer
Are proteins and lipids fixed
some can move around membrane
when proteins and lipids move
two cells fuse
single continous memrbane forms around both cells and membrane proteins distrubute evenly around the membrane
why are some proteins restricted in movement
anchored to components of the cytoskeleton or are trapped within regions of lipid rafts
causes unequal distrubution of proteins
what happes when proteins are unequally dsitributed
allow for specialization of certain regions of the cell membrane
describe how carbohydrates are composed in the membrane
cells have carbs on external surface
glycolipid
carb covalently bonded to protein = glycoprotein
What do plasma membrane glycoproteins enable
cells to be recognized by other cells and proteins
two types of binding between cells membranes
homotypic binding (same cell binds to eachother)
hetertypic binding
what forms between cells in a tissue
specialized cell junctions
three types of junctions
tight junctions
desmosomes
gap juncitons
Tight junctions
plasma membrane
link adjacent epithelial cells
1. restrict migration of membrane proteins and phospholipids from one region of the cell to another
2. Prevent substances moving through intercellular space
Desmosomes
spot welds on adjacent cells
have dense plaques that are attached to cytoplasmic fibers and membrane cell adhesion proteins
membrane cell adhesion proteins bind to proteins of adjacent cell
What are gap junctions
connections that facilitate communication between cells
made of connexons
What are connexons
span plasma membrane of two adjacent cells
made of connexins that snap together to generate a pore
faciliated diffusion is what
transport of polar molecules and ions in or out of the cell involving carrier and channel proteins
diffusion passive definition
proces of random movement towards the state of equilibrium
net movement directional
greater conc to lower until ewquilibrium is reached
what are diffusion rates determined b
temp, size of molecule, electrical charge of molecule and concentration gradient
lipid bilayer of simple diffusion
more lipid soluble = more rapid diffusion
except water
polar and charged do not pass across lipid bilayer
what is active transport
ions or molecules move against conc gradient across a membrane
requires atp
three types of proteins for active transport
uniport
symport
antiport
example of primary active transport
sodium potassium pumps
only cations use
wat are secondary active transport
uses atp to establish gradient
uses gradient to move substances
e.g. symport and antiport systems
difference between secondary and primary
primary = release energy as ions down gradient
secondary = against gradient
what is endocytosis
phagocytosis
pinocytosis
receptor-mediated endocytosis`
exocytosis
transports moecules out of cell from vesicles which fuse with membrane
what are pinocytosis
vescile formation
what are receptor mediated endocytosis
cells absorb SPECIFIC molecules by binding them to receptors on membrane
where are receptor proteins
exposed on outside of cell in coated pits
clathrin molecules form coat of the pits
Membranes functions
information processing
energy transformation = inner mitochondrial membrane converts energy of fuel to ATP, thylakoid of chloroplasts light energy
how are membranes dynamic
participate in numerous cellular processes
continually form, move and fuse
segments of membrane moves, changes structures and fuses with other membranes
each organelle modifies membrane to carry out specific functions
dynamic structure and activity
