both ethanol and glycine are small molecules of approximately equal molecular weight. However, ethanol is much more membrane permeable than glycine. What accounts for the large difference in membrane permeability between ethanol and glycine

Ethanol is a non polar molecule.Therefore it passes through the cells membrane easily by diffusion like other non polar like CO2 and water.However, glycine is an amino acid ( the simplest amino acid) a charged molecule /polar molecule/.it can not therefore pass through the bilayer by simple diffusion because of the phospholipid bi-layers. Therefore special transport proteins are needed for its passage across the cell membrane.

Example-GLYT 1 and 2 are the carrier proteins  specific for glycine transport across the membrane.

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Explanation:

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.