AP Biology- Unit 2.4-2.5 Cell Transport

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Selectively Permeable

a property of cell membranes that allows some substances to pass through, while others cannot

Phospholipid Bilayer

double layer of phospholipids that makes up plasma and organelle membranes

Integral Proteins

penetrate the hydrophobic core and often span the membrane

Peripheral Proteins

Bound to the inner or outer surfaces of the membrane and are easily separated from it.

Glycoproteins

proteins that have carbohydrates covalently bonded to them

Glycolipids

lipid that have carbohydrates covalently bonded to them

Passive Transport

transport that does not require the cell to expend energy (high to low concentration)

Active Transport

energy-requiring process where a substance moves against the concentration gradient (low to high concentration)

Diffusion

net movement of a substance down a concentration gradient (high to low)

Facilitated Diffusion

diffusion of solutes across a membrane, with the help of transport proteins

Osmosis

diffusion of water across a selectively permeable membrane

Hypertonic

solute concentration is greater than inside the cell, cell loses water; plant cells plasmolyze, animal cells crenate

Hypotonic

solute concentrations in less than inside the cell, cell gains water; animal cells lyse, plant cells have ideal turgor pressure

Isotonic

solute concentrations are the same on both sides of the membrane, cell does not gain or lose water; ideal condition for animal cells

Sodium-Potassium Pump

actively pumps Na+ ions out and K+ ions in, 3 Na leave for every 2 K that enter

Proton Pump

pumps (H+ ions) out of the cell, creating a proton gradient, protons diffuse back into the cell, which powers ATP production

Exocytosis

exporting macromolecules by fusion of vesicles with the plasma membrane

Endocytosis

importing macromolecules by forming vesicles derived from plasma membrane

Phagocytosis

part of the cell membrane engulfs large particles or entire cells (cell eating)

Pinocytosis

part of the cell membrane engulfs small dissolved substances or fluid droplets in vesicles (cell drinking)

Receptor-Mediated Endocytosis

importing of specific macromolecules by receptor proteins bind to a specific substance which triggers the inward budding of vesicles formed from coated pits

Ligands

molecule that binds to the specific receptor site on another molecule

Fluid Mosaic Model

states that the membrane is a fluid structure with a mosaic of various proteins embedded in it

Transport Proteins

allow passage of hydrophilic substances across the membrane

Concentration Gradient

a difference in concentration across a distance

Turgor Pressure

the pressure that is exerted on the inside of cell walls, caused by the movement of water into the cell

Aquaporins

facilitates the passage of water into a cell

plasmolysis

As a plant cell loses water, it shrivels, and its plasma membrane pulls away from the cell wall

cholesterol

A large, ring shaped lipid found in cell membranes. Its presence helps to maintain flexibility and fluidity in the membrane.

water potential

a measurement that combines the effects of solute concentration and pressure to predict the direction water will flow

solute potential

-iCRT, component of water potential which is proportional to its molarity

pressure potential

component of water potential which is the physical pressure on a solution