Transport of substances into and out of cells

Transport of substances into and out of cells

Active Transport

• Active transport uses energy to move substances against a concentration gradient.
• This process enables cells to absorb ions from very dilute solutions.
• It is imperative for the uptake of glucose and amino acids.
• Substances are transported from a lower concentration to a region of higher concentration.

Osmosis

• Osmosis is the diffusion of water from a dilute to a concentrated solution through a partially permeable membrane.
• It is important in the transport of water and solutes across cell membranes.
• Osmosis assists in maintaining the correct balance of water in the body - too much or too little water in cells can be damaging.

Diffusion

• Diffusion is the passive movement of particles from an area of higher concentration to an area of lower concentration.
• Examples include the exchange of oxygen and carbon dioxide in the alveoli in the lungs, and the movement of digested food molecules from cells in the small intestine into the bloodstream.

Facilitated Diffusion

• In facilitated diffusion, substances move across cell membranes using protein channels or carrier proteins.
• It allows larger molecules such as glucose to be transported into cells.
• Like diffusion, it moves substances from an area of higher concentration to an area of lower concentration, but involves the use of membrane proteins.

Endocytosis and Exocytosis

• Endocytosis and exocytosis are used for transporting large particles into and out of a cell.
• In these processes, the cell membrane envelops the particle and forms a vesicle.
• Endocytosis involves the intake of materials, while exocytosis involves the expulsion of materials out of a cell. They are both energy-dependent processes.