Cellular Transport and Membrane
Functions of Cellular Transport
Can exit, travel through vasculature
system, and enter or signal a
different cell
stored, modified, to make
macromolecules needed to
break down and to produce
energy
when the metabolism uses molecules in
order to transport to the correct location
Channel Proteins
Aquaporins = facilitated transport of water
Ion-gated Channels = voltage gated
Bulk Transport, Exocytosis, Endocytosis
Endocytosis
Receptor Mediated Endocytosis = important for
cholesterol uptake
Pinocytosis= fluid intake (unicellular, intestinal cells)
Phagocytosis = unicellular, immune cells
Exocytosis
Used by neurons (neurotransmitters release)
Used by secretory cells
(insulin release by pancreatic cells)
BOTH EXO and ENDOcytosis use the plasma membrane
Active Transport
Involve carrier proteins and work AGAINST concentration gradient
Secondary = uses indirect source of energy,
CO2 transport (symporter or antiporter)
Primary= uses direct source of energy
ion pumps important for cell membrane potential
Cotransport (indirectly require ATP)
Require help of a membrane protein to pass
Facilitated Transport
Aided by proteins
Osmosis
FOR WATER ONLY
NO ENERGY NEEDED
Follow concentration gradient (high to low)
Passive Transport
Simple diffusion
Allowed to move freely and
will achieve equilibrium
NO ENERGY needed
Follow concentration gradient
(from high to low)
Types of Cellular Transport
Passive Transport, Active Transport, Bulk Transport
Can exit, travel through vasculature system,
and enter or signal a different cell
Stored, modified to make
macromolecules needed to
break down and produce
energy
Embedded Proteins
Dynamic, aqueous environment, attach site for ECM
Transport, signalization, recognition
What Can Pass?
Varies on size and polarity
A lot of (large) molecules need SPECIFIC TRANSPORTORS to pass membrane (proteins, amino acids, polysaccharides, DNA)
Small polar molecules (H2O, ethanol C2H5OH) CAN SLOWLY PASS
Gasses (O2,CO2,NO2) CAN PASS
Small hydrophobic molecules CAN PASS
Membrane Fluidity
Gradient across the membrane
Composition of endomembrane can change
upon the need of the cell
Phospholipids; rotate, move latterly, flip-flop
Membrane Proteins
20-25 hydrophobic amino acids arranged in a alpha helix
Peripheral Proteins
Loosely attached!
found outside and inside surfaces of the membrane
(attached to integral protein or phospholipid)
Integral Proteins
proteins inside are hydrophobic
proteins exposed to cytoplasm or EXF are hydrophilic
Lipids (40%), Proteins (50%), Carbohydrates (10%)
Consist of 20-25 monosaccharide units
Carbohydrates are alone or attached to proteins
(glycoproteins) to lipids (glycolipids)
Important for Immune system
Functions of Membrane
Barrier for most molecules
Allows cell to communicate with outside and other cells
Major difference between procaryotes and eukaryotes cells
Cell Envelop= barrier between cell and noncell (role of Phospholipids) which allow communication with extracellular media (role of proteins)
NOT JUST A BAG (controls what goes in and out)
