Question

Which of the following describes an example of molecular movement across a membrane

through active transport?
O Channel proteins bind with extracellular solutes and release them inside the cell.
O Hydrocarbons enter the cell by dissolving in the lipid bilayer of the membrane.
Proton pumps move hydrogen ions out of the cell against a concentration gradient.
O Vesicles carrying waste products fuse with the membrane during endocytosis.

Answer 1

The example of molecular movement across a membrane through active transport is proton pumps moving hydrogen ions out of the cell against a concentration gradient, which requires energy usually from ATP.

Step-by-step explanation:

An example of molecular movement across a membrane through active transport is when proton pumps move hydrogen ions out of the cell against a concentration gradient. Unlike passive transport, which allows molecules to move down the concentration gradient without the use of energy, active transport requires energy, commonly in the form of adenosine triphosphate (ATP). Proton pumps, such as those found in cellular membranes, work by using ATP to transport protons (hydrogen ions) across the membrane, creating a concentration gradient.

Channel proteins binding with extracellular solutes and releasing them inside the cell describe facilitated diffusion, hydrocarbons entering the cell by dissolving in the lipid bilayer of the membrane relate to passive diffusion, and vesicles carrying waste products fusing with the membrane during endocytosis is a form of vesicular transport, specifically exocytosis if it involves waste removal.

Answer 2

Step-by-step explanation:

The example of molecular movement across a membrane through active transport is:

Proton pumps move hydrogen ions out of the cell against a concentration gradient.

Active transport is a cellular process that requires energy (usually in the form of ATP) to move molecules or ions against their concentration gradient, i.e., from a region of lower concentration to a region of higher concentration. Proton pumps are a type of active transport protein found in cell membranes that move hydrogen ions (protons) out of the cell against their concentration gradient. This process is essential for maintaining the electrochemical gradient across the cell membrane and is involved in various cellular functions, including nutrient uptake and ATP synthesis.

The other options mentioned involve different mechanisms of membrane transport, but they are not examples of active transport. Channel proteins facilitate passive transport (option 1) by allowing solutes to move down their concentration gradient. Hydrocarbons dissolving in the lipid bilayer represent simple diffusion (option 2) which is also passive transport. Vesicles fusing with the membrane during endocytosis (option 4) represents a form of bulk transport and is not an example of active transport either.