Researchers have identified a chemical in leeches that suppresses blood clotting. Why is this chemical important in leeches?

When you step from a hot street into an air-conditioned room, you feel cooler. Why does this change occur? 1. Heat is moving from a cold area (the room) to a hotter area (the street). 2. Heat leaves your body as it moves from a warm area (your body) to a colder area (the air in the room). 3. The motion energy used to walk into the room lowers your body temperature. 4. The motion energy used to walk into the room raises your body temperature.

How are the effects of paracrine signaling limited to an area near the signaling cells?

The body shown in cross section is a complete circular ring formed by revolving the cross-hatched area about the z-axis. Determine the surface area A and volume V of the body.

What is the mechanism by which C. scindens suppresses colonization by C. difficile?