Cellular Transport and Membrane

NOT JUST A BAG (controls what goes in and out)

Cell Envelop= barrier between cell and noncell (role of Phospholipids) which allow communication with extracellular media (role of proteins)

Major difference between procaryotes and eukaryotes cells

Barrier for most molecules
Allows cell to communicate with outside and other cells

Lipids (40%), Proteins (50%), Carbohydrates (10%)

Important for Immune system

Carbohydrates are alone or attached to proteins
(glycoproteins) to lipids (glycolipids)

Consist of 20-25 monosaccharide units

20-25 hydrophobic amino acids arranged in a alpha helix

Integral Proteins

proteins inside are hydrophobic
proteins exposed to cytoplasm or EXF are hydrophilic

Peripheral Proteins

found outside and inside surfaces of the membrane
(attached to integral protein or phospholipid)

Loosely attached!

Phospholipids; rotate, move latterly, flip-flop

Composition of endomembrane can change
upon the need of the cell

Gradient across the membrane

Varies on size and polarity

Small hydrophobic molecules CAN PASS

Gasses (O2,CO2,NO2) CAN PASS

Small polar molecules (H2O, ethanol C2H5OH) CAN SLOWLY PASS

A lot of (large) molecules need SPECIFIC TRANSPORTORS to pass membrane (proteins, amino acids, polysaccharides, DNA)

Transport, signalization, recognition

Dynamic, aqueous environment, attach site for ECM

Passive Transport, Active Transport, Bulk Transport

Stored, modified to make
macromolecules needed to
break down and produce
energy

Can exit, travel through vasculature system,
and enter or signal a different cell

Simple diffusion

Follow concentration gradient
(from high to low)

NO ENERGY needed

Allowed to move freely and
will achieve equilibrium

FOR WATER ONLY

Follow concentration gradient (high to low)

NO ENERGY NEEDED

Aided by proteins

NO ENERGY NEEDED

Require help of a membrane protein to pass

Cotransport (indirectly require ATP)

Involve carrier proteins and work AGAINST concentration gradient

Primary= uses direct source of energy
ion pumps important for cell membrane potential

Secondary = uses indirect source of energy,
CO2 transport (symporter or antiporter)

BOTH EXO and ENDOcytosis use the plasma membrane

Exocytosis

Used by secretory cells
(insulin release by pancreatic cells)

Used by neurons (neurotransmitters release)

Endocytosis

Phagocytosis = unicellular, immune cells

Pinocytosis= fluid intake (unicellular, intestinal cells)

Receptor Mediated Endocytosis = important for
cholesterol uptake

Aquaporins = facilitated transport of water
Ion-gated Channels = voltage gated

when the metabolism uses molecules in
order to transport to the correct location

stored, modified, to make
macromolecules needed to
break down and to produce
energy

Can exit, travel through vasculature
system, and enter or signal a
different cell