Transport of Molecules in a Cell

Terms to Know

• SOLUTE: refers to the substance that is to be dissolved (Salt, Sugar) • SOLVENT : responsible for dissolving the solute (Water) • SOLUTION : Solvent and solute after combining together • ECF : Extracellular Fluid. Surrounds all living cells • CONCENTRATION : mass of solute dissolved in the solvent • SEMI-PERMEABLE (SELECTIVELY-PERMEABLE) : a membrane that allows only some substances in or out

Selectively Permeable Membrane

Transportation of Molecules Passive Transport

•Movement of molecules across a semi-permeable membrane with the gradient 3 types: Osmosis,Diffusion + Facilitated Diffusion •Movement of molecules across a semi-permeable membrane with a protein

Active Transport

• Movement of molecules across a semi-permeable membrane against a concentration gradient with a protein • ENERGY required •NO ENERGY required

Diffusion

• Solute molecules moving from an area of high concentration to an area of low concentration • Random motion drives diffusion • Movement is based on kinetic energy (speed), charge, and mass of molecules • Equilibrium is reached when there is an even distribution of solute molecules 2 3 1 (water) 4

Equilibrium Reached Low Concentration High Concentration

Osmosis

• Diffusion of water through a semi-permeable membrane – Permeable to solvents (WATER), but not to large molecules – High [water] to low [water] [concentration] • Dissolved molecules (i.e. glucose, starch) are called solutes • REMEMBER: Water = solvent Glucose, Starch, Salt = solutes

Effect of Water on Cells

• Hypertonic Environment – High [solute], low [water] • Isotonic Environment – [water] = [solute] • Hypotonic Environment – High [water], low [solute]

Osmosis Sucrose will not move but water will

Dialysis Bag Experiment

• Dialysis Bag – Semi-permeable membrane – Water, glucose, & starch • What passes through the dialysis bag?

– Glucose (Benedict’s Test) – Starch (Iodine Solution) • Time Course Experiment – Every 10 minutes, measure the amount of glucose & starch present in the beaker Dialysis bag Glucose Iodine Starch

Osmosis in Living Cells

plasmolyzed flaccid Normal turgid Cellulose in cell wall

RED BLOOD CELLS

Osmosis in Plant Cells

Plasmolysis • Observe Elodea leaves via a wet mount of the sample  10% NaCl Hypertonic  Distilled water Hypotonic

Recall the Cell Membrane

Proteins in the Plasma (cell) Membrane

Proteins are Specific to certain Solutes

Active Transport

ENDOCYTOSIS

The general term for bringing bulk chemicals into a cell is

endocytosis

(endo = inside); the general term for bringing bulk chemicals

out of a cell

is

exocytosis

(exo=outside).

Moving material into the cell by endocytosis involves the pinching in of a portion of the cell membrane around the material to be transported into the cell. The pinched-in portion eventually breaks free from the cell membrane and forms a vesicle in the cytoplasm.

Homework

• Complete your Cheek Cell & Elodea Cell mini-lab • Study for your Microscope quiz • Answer questions on p.25 Q.1-19  Next topic: Cell cycle & cell division