Osmotic Pressure and Membrane Transport

Osmotic Pressure

Force associated with water movement by osmosis

Semipermeable Membrane

Allows selective molecule passage

Osmosis

Diffusion of water across a membrane

Osmolarity

Ability of a solution to induce water diffusion

Tonicity

Effect of a solution on cell volume

Buffer

Solute dampening the effect of added acid or base on pH changes

Metabolism

Sum of cellular metabolic pathways

Metabolic Pathways

Reactions converting substrates to products

Biomolecules

Carbohydrates, lipids, proteins, nucleic acids

Proteins

Cellular process mediators, cell structural contributors

Diffusion

- no energy is needed or released
- direction depends on concentration gradient

Membrane Potential

cell membranes are not at equilibrium

Facilitated Diffusion

- hydrophilic molecules
- protein transporter needed
no energy needed
depends on concentration gradient

Ion Channels

form pores

Conotoxin

Toxins from cone snails affecting ion channels

cells in hypertonic solution

cells shrink. water leaves the cell by osmosis

cells in hypotonic solution

cells swell. water enters the cell by osmosis

Isotonic

cells neither shrink or swell

buffers limit changes in pH changes

- important for cellular function
1.Allows cells to control pH
2.This in turn controls ionization of molecules
3.Which maintains weak bonding interactions based on charge

movement across membrane / membrane transport

diffusion, facilitated diffusion, active transport

rate of diffusion

Depends on concentration gradient, size of molecule (large vs small) (hydration shell- functional size), and charge and solubility. (all is the diffusion coefficient).

Permease

function like an enzyme:
- substrate binds to the protein
- binding initiates a conformational change
- substrate is released to the other side

Porins

Large channels allowing molecule diffusion

Active Transport

Energy required
protein transporter needed
molecules move from high to low concentration

Primary Active Transport

Uses exergonic reaction e.g. ATP

Secondary Active Transport

Uses energy from electrochemical gradient

Gradients

Affect chemical and some electrical balance

Electroneutral carriers

transport uncharged molecules or exchange an equal number of particles with the same charge

Electrogenic carriers

transfer a charge

Membrane Potential

Electrochemical gradient across cell membrane

membrane potential function

-Provide cell with energy for membrane transport
-Allow for changes in membrane potential used by cells in cell-to-cell signaling
-also important in osmotic movement of water in specific cell types

Passive Transport

No-energy movement along gradient

Endocytosis

Internalization of extracellular material

Exocytosis

Release of internal vesicles to extracellular space

Enzymes

Catalysts accelerating chemical reactions

Ribozymes

RNA molecules with catalytic properties

Coenzymes

Organic cofactors derived from vitamins

Inorganic Ion Cofactors

Copper, iron, magnesium, zinc aiding reactions

Affinity

Degree of attraction between a ligand and a molecule

Energy Storage

Cells store energy as reducing energy and high energy bonds

environmental effects on enzymes

enzyme activity is affected by temperature, ph, SALINITY, AND hydrostatic pressure

hypersomatic

solution with higher osmolarity

hyposomatic

solution with lower osmolarity

antiporter

molecules move in opposite directions

symporter

molecules move in the same direction