6. Because they are embedded within the membrane, ion channels are examples of ________. receptor proteins integral proteins per
ipheral proteins glycoproteins 7. The diffusion of substances within a solution tends to move those substances ________ their ________ gradient. up; electrical up; electrochemical down; pressure down; concentration 8. Ion pumps and phagocytosis are both examples of ________. endocytosis passive transport active transport facilitated diffusion 9. Choose the answer that best completes the following analogy: Diffusion is to ________ as endocytosis is to ________. filtration; phagocytosis osmosis; pinocytosis solutes; fluid gradient; chemical energy
An integral protein is a protein that is permanently attached to a biological membrane. Some examples of integral membrane proteins include, for example, the insulin receptor, cell adhesion proteins (e.g., integrins), glucose permease, etc. Diffusion, also known as passive transport, refers to the process by which a substance/molecule tends to move from an area of high concentration to an area of low concentration. Moreover, osmosis is a type of diffusion by which a solvent (e.g., water) moves across a semipermeable membrane from a region of lower concentration to a region of higher concentration. Active transport refers to the movement of molecules/substances across a biological membrane against a concentration gradient. There are two types of active transport: primary active transport and secondary active transport. The primary active transport depends on a source of energy (e.g., ATP) for movement, whereas secondary active transport depends on electrochemical gradients to transport substances with the help of membrane transport proteins (i.e., cotransporters). Active transport involves ATP pumps that move ions into and out of the cell. Finally, endocytosis is the process by which cells absorb external material by engulfing them in transport vesicles, whereas pinocytosis refers to a type of endocytosis involving fluids that contain many solutes.