Active Transport

Active Transport via Membrane Proteins
• Active transport involves substances moving across a membrane against a concentration gradient, requiring energy (ATP) to move substances across a semi-permeable membrane.
• An example of active transport is in human nerve cells, where sodium ions are constantly transported out of the cell into the external fluid.

Pinocytosis
• Active uptake of large molecules from a solution requires energy.
• Particles are brought into the cell by invagination of the plasma membrane, forming and suspending them within small vesicles.
• Reversed pinocytosis occurs when small vesicles expel molecules to the outside of the cell.

Phagocytosis
• Cellular process of engulfing solid particles by the cell membrane to form an internal phagosome.
• Lysosomes may fuse with the food vacuole and empty digestive enzymes, digesting the food and absorbing it into the cell's cytoplasm.