The Cell: Transport Mechanisms and Permeability

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Molecular Motion

Reflects the kinetic energy of molecules and is random and eratic.

Velocity of molecular movement

Is lower in larger molecules and increases with increasing temperature.

Sac containg 40% glucose suspended in distilled water.

Water diffused into the bag, and it gained mass.

Sac containing 40% glucose suspended in 40% glucose.

Had some concentration. Molecules were able to move equaly.

Sac containing 10%NaCL suspended in distilled water.

Salt ions and water could pass freely, gained 6 grams.

Sac containing 40% sucrose and congo red dye suspended in distilled water.

This was hypotonic. The bag swelled up and gained a little weight.

What single charcteristic of the differentially permeable membranes used in the labratory determines the substances that can pass through them?

The size of the pores.

In addition to the characteristic of small pores, what other factors influence the passage of substances through the living membranes?

The solubility in the lipid part of the membrane.

Diffusion

A movement of molecules from a region of higher concentration to a region of lower concentration.

Osmosis

The flow of water accross a differentially permeable membrane.

Simple Diffusion

The unassited diffusion of solutes through a differantially permeable membrane.

Filtration

Passive process by which water and solutes are forced through a membrane by fluid pressure.

Active Transport

Requires carrier protiens that combine specifically with the transported substance.

Phagocytosis

Parts of the plasma membrane and cytoplasm expand and flow around a bacteria/cell debris and engulf it.

Fluid-Phase Endocytosis

Cell membrane sinks beneath the material to form a small vesicle, which then pinches off into cell.

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