Cell TransportCell Transport

Maintaining BalanceMaintaining Balance• Homeostasis – process of

maintaining the cell’s internal environment

• Cannot tolerate great change• Boundary between cell and the

environment• What provides this?

Plasma MembranePlasma Membrane• Fluid Mosaic Model

• Selective Permeability

• Phospholipid bilayer

–Hydrophobic; Fatty Acid Tail –Polar Head; Hydrophilic

• Cholesterol – Provides stability

• Transport Proteins

• Carbohydrates

• Other Proteins– Cell recognition (immune

system)

Recall Following TermsRecall Following Terms• Solution

• Diffusion

• Concentration gradient

• Results in uniform concentration

OsmosisOsmosis• Cells try to reach equilibrium• Diffusion of water across a

selectively permeable membrane; 3 results– Isotonic– Hypertonic Tonicity– Hypotonic

IsotonicIsotonic

• Solute concentration of solution equal to that of cell

• No net water movement

HypertonicHypertonic• Solute concentration of solution

higher than cell • More dissolved particles outside

of cell than inside of cell • Hyper = more (think

hyperactive); Tonic = dissolved particles

• Water moves out of cell into solution

• Cell shrinks

HypotonicHypotonic• Solute concentration of solution

lower than cell • Less dissolved particles outside

of cell • Hypo = less, under (think

hypodermic, hypothermia); Tonic = dissolved particles

• Water moves into cell from solution

• Cell expands (and may burst)

Active vs. Passive Active vs. Passive • Active vs. Passive Transport• Passive requires no energy from

the cell• Active requires cells to use

energy, usually ATP

Passive TransportPassive Transport• Have to move with the

concentration gradient• Diffusion• Osmosis• Facilitated Diffusion- involves

use of transport proteins but still follow rule of diffusion

Active TransportActive Transport• Movement of materials against

concentration gradient• Transport proteins• Endocytosis – cell takes in

material• Exocytosis – expulsion or

secretion of materials from cell

Pinocytosis Pinocytosis PhagocytosisPhagocytosis