concentration gradient, using protein carriers driven by the expenditure of chemical energy is known as A facilitated transport. B active transport. C diffusion. D osmosis. E exocytosis.
Question 30 A type of transport of a solute across a membrane, up its concentration gradient, using protein carriers driven by the expenditure of chemical energy is known as A facilitated transport. B active transport. C diffusion. D osmosis. E exocytosis.
The Correct Answer and Explanation is:
Correct Answer: B) Active transport
Explanation:
Active transport is the process by which cells move substances across their plasma membrane against the concentration gradient, meaning from an area of lower concentration to an area of higher concentration. This movement is energetically unfavorable and therefore requires the input of energy. The energy for active transport typically comes from the hydrolysis of adenosine triphosphate (ATP), which provides the necessary power to move solutes across the membrane through specific transport proteins known as pumps or carriers.
A well-known example of active transport is the sodium-potassium pump. This transport protein moves three sodium ions out of the cell and two potassium ions into the cell against their respective concentration gradients. ATP is broken down during this process, and the released energy changes the shape of the protein, allowing ions to be transported in the desired direction.
Active transport is essential for maintaining important cellular functions. For example, it helps regulate internal concentrations of ions, nutrients, and waste products. It also plays a crucial role in nerve impulse transmission, muscle contraction, and nutrient absorption in the intestines.
Unlike facilitated diffusion or simple diffusion, active transport does not rely on passive movement. In diffusion and facilitated diffusion, substances move down their concentration gradients without energy use. Facilitated diffusion, however, involves the use of carrier proteins but still moves substances from high to low concentration.
Osmosis refers specifically to the movement of water across a semi-permeable membrane, and exocytosis is a process where vesicles fuse with the membrane to expel materials out of the cell.
In summary, when a solute is transported across a membrane up its concentration gradient using protein carriers and chemical energy, it is classified as active transport.
