Cell Membrane Transport
Fluid Membrane Mosaic Model
Phospholipid Bilayer:
A layer encompassing the
cell membrane; controls
the transport of molecules
and maintains structure.
Proteins
Peripheral Membrane Proteins
A protein that is on the perimeter
of the bilayer; it can exist within
the cell or outside of it.
Used for signaling
For Structural Support of the Bilayer.
Carry out Enzyme functions
Synthesis Reactions
Destruction Reactions
Aid in Molecule Transfer
Integral Membrane Protein
A protein that exists inside
the bilayer; integrated in the cell.
Act as Entry and Exit routes for:
Ions
Nutrients
Waste Products
Drugs
Large Molecules such as DNA
Glycoproteins
Proteins attached to sugar.
Serve many important functions:
Protection
Glycoproteins allow skin cells
(epithelial cells) to attach to
each other; keep skin healthy.
Immune Response
White Blood cells attach to
Glycoproteins to travel along
the body
Trans-membrane Protein
A protein that spans the entire cell
membrane and is a gateway for
transporting substances across the
bilayer.
Contributes to Cell Membrane Structure
and Fluidity.
Regulates traffic of substances passing
in/out of the cell membrane.
Introduce immunological defense; provide
White Blood Cells
Steroid
Cholesterol
Prevents compression in the bilayer during colder temperatures.
Maintains membrane fluidity
Factors Affecting Fluidity
Temperature
Double Bonds
Length of fatty acid tails
Intramoleculaer forces of large molecules
Prevents movement in the bi-layer during warmer temperatures.
Carbohydrate Chains
Oligosaccaharides
Cell Recognition
Immune Response with White Blood Cells
Phospholipids
A lipid containing a Phosphate group;
amphophilic.
Three Fatty Acids
Hydrophobic Tails
Phosphate Group
Hydrophillic Head
Micelle
A lipid molecule.
helps absorb minerals, vitamins, and fats
Glycerol
Passive Transport
Allows for transport across the
cell membrane without the use
of energy
Moves down the gradient
Facilitated Diffusion
molecules move across the membrane
with help of membrane proteins.
A Channel Protein
allows specific molecules to pass through the membrane
some have gates and some remain open indefinitely
A Carrier Protein
open or close depending on physical or chemical stimulus
much slower transport than a channel protein
Diffusion
movement of molecules from an area of high concentration to an area of low concentration
factors affecting Diffusion
Concentration
require longer to diffuse completely
Temperature
temperature can increase energy or
reduce energy, thus, it can make it
a faster or slower process
Molecule size
the bigger the molecules, the longer it
takes to diffuse
Osmosis
Movement of H2O across biological membranes
Isotonic
the concentration of solute within the membrane is the same as outside the membrane; osmotic pressure is equal across the membrane.
Hypertonic
the concentration of solute is higher outside the cell than inside the cell.
Hypotonic
the concentration of solute is higher within the cell than outside the cell.
Active Transport
transports substances across the cell
membrane with the use of energy;
requires ATP for initialization.
Moves up the gradient
Vesicle (Bulk) Transport
Exocytosis
the process of substances moving from the interior to the exterior of the cell.
A vesicle carrying substances fuses with the cell membrane and releases it's contents outside the cell membrane.
Endocytosis
the process of substances moving from the exterior to the interior of the cell.
Substances are gathered and stored inside a vesicle once in contact with the cell membrane and travels to parts inside the cell.
Pinocytosis
the ingestion of fluid into a cell membrane
Phagocytosis
the ingestion of bacteria or other solid materials into the cell membrane
Secondary Active Transport
use ATP indirectly
get ATP from the concentration gradients that Proteins pumps already created
Protein Pumps
Uniport
Allows one molecule to pass in one direction
Symport
Allows two molecules pass through in one direction
Antiport
Allows two molecules to pass through in two directions
use energy of an ATP molecule to
move substances up the gradient
Sodium-Potassium Pump
moves sodium and potassium ions across the membrane
uses hydrolysis of ATP to harvest energy
for one unit expenditure of ATP molecule against the gradient:
the pump moves three sodium ions out
the pump keeps two potassium ions in
Calcium Pump
responsible for maintaining the electrochemical concentration Ca2+ at a steep slope across the gradient
moves calcium out off the cell membrane