✭ biology past paper questions (flashcards, mixed)

• explain why large polar molecules cannot move through intact cell membranes

  they are too large to move through the cell membrane

  there are no carrier and channel proteins for large polar molecules to move through

  large polar molecules are polar and are repelled by fatty acid tails
• which of the molecules found in cell membranes have hydrophilic regions?

  phospholipids, channel proteins and cholesterol
• similarities between diffusion and active transport

  both move molecules through the phospholipid bilayer

  molecules can move through proteins in both diffusion and active transport
• differences between diffusion and active transport

  diffusion occurs DOWN a concentration gradient however active transport occurs AGAINST a concentration gradient

  diffusion is a passive process however active transport requires energy
• similarities between endocytosis and exocytosis

  both processes involve vesicles

  both processes involve energy from ATP
• differences between endocytosis and exocytosis

  exocytosis - involves molecules/substances leaving the cell

  endocytosis - involves molecules/substances entering the cell

  exocytosis - involves vesicles fusing with cell surface membrane

  endocytosis - formation of vesicles from the cell surface membrane