transport across membranes Flashcards
why the FMM called fluid
the phospholipid molecules form double layer that are constantly moving around relative to one another , giving the membrane a fluid structure
why is the FMM called a mosaic
the protein are unevenly distrubed throughout the membrane so it is a mosaic
what’s within the cell membrane:
aqaporins
cholesterol
channel proteins
carrier proteins
enzymes
glycoproteins
phospholipids
receptor proteins
phospholipid function
-hydrophobic tails
-hydrophilic heads
-bilayer allows lipid-soluble molecules to pass through by simple diffusion
-prevents the passage of small polar molecules
cholesterol functions
decreases permeability and increases stability of the membrane
more cholesterol = less fluid
channel proteins functions
allow small molecules move across the membrane by facilitated diffusion
specific ions pass through specific channel proteins
carrier proteins function
transport of ions and large molecules
by facilitated diffusuon and active transport
receptor proteins functions
proteins act as specific receptors for complementary molecules eg. insulin to insulin receptor proteins
enzymes functions
complementary to substrates, form ESC
glycoproteins functions
carbs and proteins
outer surface of membrane
important in cell recognition, acts as antigens
produced in the golgi body
aquaporins functions
special channel proteins
specific to water
lots of aquaporins means permeable to water and carry out osmosis easily
diffusion definition
net movement of molecules from an area of higher concentration to a lower concentration across a partially permeable membrane
fick’s law
rate of diffusion= (surface area x concentration gradient)/ diffusion distance
factors affecting rate of diffusion
surface area
concentration gradient
diffusion distance
temperature
how does surface area affect the ROD
larger SA allows more space for molecules to pass through SO faster
how does temperature affect the ROD
increases kinetic energy SO faster
how does the concentration gradient affect the ROD
as concentration difference increases, ROD increases
how does diffusion distance affect ROD
shorter the distance, fewere membranes to cross SO molecules wil travel faster
facilitated diffusion definition
specific proteins aid specific molecules to pass through
is facilitated diffusion an active or passive process
passive
does not require ATP
when does facilitated diffusion plateau on a graph
when all the carrier proteins are saturated
number of proteins is a limiting factor
osmosis definition
net movement of water molecules from a high water potential to a lower water potential through a partially permeable membrane
Active transport definition
-transport of molecules against their concentration gradient
-low to high
-only uses carrier proteins
is active transport an active or passive process
it is active
requires ATP for a source of energy
Exocytosis
-use golgi vesicles to transport large quantities of molecules from inside the cell to outside the cell
-used to move enzymes and glycoproteins fro golgi apparatus to cell surface membrane
is exocytosis an active or passive process
active
it requires ATP to move the vesicles to the cell surface membrane and the vesicle fuse with the membrane
Endocytosis
cell surface membrane is pulled inwards to create a vesicle
any molecules nearby are enclosed into the vesicle
is endocytosis an active or passive process
active
requires ATP to create the vesicle and move the vesicle
Many different substances enter and leave a cell by crossing its cell surface membrane.
Describe how substances can cross a cell surface membrane.
- Small molecules pass via phospholipid bilayer
- Large molecules go through proteins via facilitated diffusion from high to low concentration
- Water moves by osmosis from higher water potential to lower water potential;
- Active transport is movement from low to high concentration against the concentration gradient;
- Active transport requires carrier proteins
- Active transport requires ATP
- NA+/glucose is
