Which is afactor that deterrmines whether a molecule can cross a cell membrane

The nature(hydrophilic or hydrophobic) of the molecule to be transported across the membrane determines whether that molecule can cross the cell membrane or not.

Explanation:

Plasma membrane composed of lipid bilayer in which hydrophilic glycerol head groups of phospholipids in each monolayer are arranged oppositely with respect to each other whereas the nonpolar hydrophobic tail of both the monolayer faces each other.

     The plasma membrane only allow the hydrophobic or nonpolar molecules to pass through its phospholipid bilayer but resist the passage of hydrophilic molecules or polar molecules through it.

both anaerobic and aerobic respiration use glucose (or other carbohydrates), proteins and lipids to produce atp and nadh. cell uses those energy molecules, obtained from food and   breaks them down during the chemical reactions of respiration. in anaerobic respiration, nadh is regenerated to nad+ by enzymes lactate dehydrogenase (lactate is produced, e.g. in muscle cells) or by alcohol dehydrogenase where ethanol is produced (alcohol fermentation), while in aerobic respiration, electrons from nadh are deposited in the mitochondria to regenerate nad+ (electron transport chain. anaerobic respiration produces 2 atp per molecule of glucose compared to aerobic respiration where about 38 atp molecules are produced.