What makes endocytosis and exocytosis active transport mechanisms?
1) they happen through simple diffusion.
2) they involve taking a large molecule into the cell.
3) they require energy to change the cell membrane.
4) they involve the passage of molecules across the cell membrane.

After reading the paragraph below, answer the questions that follow. researchers have created a robot that has a very thin leg that is moved by cardiac (heart) cells contracting in unison. the robot, made of a polymer similar to that used in making contact lenses, is bathed in heart cells with supporting cells, which then attach to the robot and provide movement as they contract. all of the cardiac cells working together can cause the robot leg to move in a way that individual cells could not. this is an example of a. emergent properties of cells. b. energy flow through an ecosystem. c. adaptation. d. internal environment regulation.

Which of the following is not considered an appendage of the skin? nails glands follicles none of the above

What does natural resource management aim at ?