Which of the following is the best description of active transport? - A protein pump in the cytosol pumps a molecule up it's concentration gradient by binding to it and changing shape.

- A protein pump embedded in the cell membrane pumps a molecule up it's concentration gradient by binding to it and changing shape. Active transport requires energy (ATP).

- A protein channel embedded in the cell membrane allows molecules to diffuse through it, down it's concentration gradient. No energy (ATP) is required.

- A protein pump embedded in the cell membrane pumps a molecule up it's concentration gradient. The protein pump does not bind to the molecule being transported and does not require energy.

i think it would be b. tissue because an organ system is a group of organs that work together to perform one or more functions. each does a particular job in the body, and is made up of certain tissues.

when the displaced particles are perpendicular to the direction the wave travels, is called a transverse wave, whereas in longitudinal wave the displace practices are parallel to the direction of the wave.

in the given image:

first image shows - longitudinal wave

second image shows - transverse wave

third image shows - longitudinal wave

fourth image shows - longitudinal wave

the solute can move "downhill," from regions of higher to lower concentration, relying on the specificity of the protein carrier to pass through the membrane. this process is called passive transport or facilitated diffusion, and does not require energy.