Histo Lecture 3

Movement along concentration graident (high to low conc.); no ATP required

Direct passage through membrane

Utilizes membrane protein for import

Requires energy; typically moving against concentration gradient

Primary and Secondary

Lipid soluble molecules

e.g. Oxygen, carbon dioxide, alcohol

channel protein

• -Amount of substance availability
• -Lipid solubility of diffusing substance
• -Number and size of membrane opening (channels)
• -Velocity of kinetic motion of molecules (greater temp = faster diffusion)
• -Molecular weight - smaller particles move faster
• -Distance- shorter distance = faster diffusion

Carrier mediated diffusion

Carrier protein

• -No energy required
• -Conformational change in protein causes molecule to move through membrane
• -Molecule must be moving along concentration gradient

• Net movement of water along its concentration gradient
• (Requires semi-permeable membrane!)

Driving force for osmosis across a membrane

• -Directly related to solute concentrations of two fluids in compartments
• -Water tends to move from low to high solute concentration

Force that water transmits via its weight or via its flow through a vessel.

Tends to eualize with osmotic pressure to prevent too much loss/gain of water from cells/tissues

Transport of substances across cell membrane which require energy expenditure

Ions and large molecules (sugars & proteins)

Direct utilization of ATP as energy source

Energy comes from stored energy of ionic concentration gradient between intra/extracellular environments

Carrier proteins

-Important for maintaing voltage across the cell membrane

Both molecules required for binding to protein must be present for transport to occur

• Molecules are transported in opposite directions across the cell membrane.
• -Sodium potassium pump

Passage of material into a cell moving through cell membrane

• -Phagocytosis
• -Pinocytosis
• -Receptor Mediated Endocytosis

Uptake of particular material

Only "recognized" particles are engulfed

Uptake of soluble molecules (water)

Non-specific engulfment of molecules

Uptake of specific molecules using specific membrane proteins (clathrins)

Secreting proteins made by cell