Honors Biology Cellular Transport

Diffusion The net movement of particles from an area of high concentration to an area of low concentration

High concentrationLow concentration Equal distribution

Diffusion Movement goes with the concentration gradient –From areas of high concentration to areas of low concentration

Osmosis Diffusion of water through a selectively permeable membrane Goes with the concentration gradient

Osmosis Weak solution Strong solution WATER (Lots of water molecules) (Few water molecules)

Selectively permeable membrane Weak solution Strong solution Membrane allows water to pass but not solutes Solutions with equal concentrations

Osmosis Special terms for referring to strong or weak solutions

Osmosis –Isotonic: two solutions with equal concentrations of solutes

Osmosis Special terms for referring to strong or weak solutions –Isotonic: two solutions with equal concentrations of solutes –Hypertonic: solution with high concentration of solutes (strong solution)

Osmosis Special terms for referring to strong or weak solutions –Isotonic: two solutions with equal concentrations of solutes –Hypertonic: solution with high concentration of solutes (strong solution) –Hypotonic: solution with low concentration of solutes (weak solution)

Osmosis HypotonicHypertonic WATER

When does diffusion/osmosis stop? Never! When it reaches a homeostatic balance equal numbers of molecules are moving in both directions !

Turgor Pressure The pressure inside a cell Maintained via osmosis

Turgor Pressure Plasmolysis

Contractile Vacuoles Lysis

Cellular Transport Passive: goes with concentration gradient Active: goes against concentration gradient

Cellular Transport Passive Active Endo- and Exocytosis

Cellular Transport Passive –Simple diffusion through the lipid bilayer –Simple diffusion through an ion channel –Facilitated diffusion Active Endo- and Exocytosis

Passive Transport Simple diffusion through the lipid bilayer Simple diffusion through an ion channel Facilitated diffusion

Simple diffusion through the lipid bilayer Small, non-polar molecules –O 2 and CO 2 Osmosis Goes with concentration gradient

Passive Transport Simple diffusion through the lipid bilayer Simple diffusion through an ion channel Facilitated diffusion

Simple diffusion through an ion channel Ions are highly polar and cannot pass through the lipid bilayer Ions are critical to cell functioning –Na +, K +, Ca +, and Cl -

Simple diffusion through an ion channel Pass readily through a water-filled pore formed by an integral membrane protein

Simple diffusion through an ion channel Movement is bi-directional Channels are specialized for a single ion Goes with concentration gradient

Passive Transport Simple diffusion through the lipid bilayer Simple diffusion through an ion channel Facilitated diffusion

Facilitated Diffusion Diffusion is aided by a carrier protein (integral membrane protein)

Facilitated Diffusion Molecule to be transported physically binds to the carrier protein on one side of the membrane Protein undergoes a conformational change that does not require energy Molecule is released on the other side of the membrane

Facilitated Diffusion Molecule is attracted to a specific carrier protein

Facilitated Diffusion Molecule binds to carrier protein

Facilitated Diffusion Carrier protein undergoes conformational change and releases molecule on other side of membrane

Facilitated Diffusion Movement is bi-directional Carrier proteins are specialized for a single ion or molecule Goes with concentration gradient Passive process

Cellular Transport Passive Active Endo- and Exocytosis

Active Transport Similar to facilitated diffusion –Molecule to be transported physically binds to the carrier protein on one side of the membrane and is released on the other side of the membrane via a shape change of the protein

Active Transport Goes against concentration gradient Requires energy input from the cell

Active Transport

Bi-directional Carrier proteins are specialized to move a single substance

Active Transport Sodium-Potassium (Na-K) Pump Cotransport Countertransport Proton Pump (Next chapter)

Na + - K + Pump Cell needs low Na + and high K + relative to external environment Ions are “pumped” into and out of the cell via an integral membrane protein Na + concentration becomes form of stored energy for cotransport

Cotransport Na + is pumped into cell with concentration gradient Simultaneously sugar or amino acid is pumped into cell against concentration gradient

Countertransport Na + is pumped into cell with the concentration gradient Ca + or H + is pumped into cell against the concentration gradient

Cellular Transport Passive Active Endo- and Exocytosis

Used to move large amounts of materials into or out of a cell quickly Requires energy

Endocytosis Cell consumes large molecules or other cells Cytoskeleton extends plasma membrane outward toward particle, encircles the it, and contracts membrane back inwards, engulfing particle

Endocytosis 2 types –Phagocytosis –Pinocytosis

Endocytosis Phagocytosis: “Cell eating” –Cell takes in solid particles

Endocytosis Pinocytosis: “Cell drinking” –Cell takes in liquid materials

Exocytosis Cell excretes large wastes Mechanism for releasing hormones