instruction:
Given a scientific passage and an answer, generate a question for the given answer.
question:
Passage: The sodium-potassium pump is an active transport pump that exchanges sodium ions for potassium ions. Answer: potassium ions
answer:
The sodium-potassium pump is an active transport pump that exchanges sodium ions for what?

question:
Passage: Energy is a measure of the amount of or potential for movement in something. The total amount of energy in the universe is always the same. This symmetry is called a conservation law. Conservation of energy is one of five conservation laws that govern our universe. A group of things (we'll use the word system ) has a certain amount of energy. Energy can be added to a system; for instance, when chemical bonds in a burning log break, they release heat. Energy can be lost from a system; for instance, when a spacecraft "burns up" its energy of motion during re-entry, it loses energy and the surrounding atmosphere gains the lost energy. A closed system is one for which the total energy does not change, or is conserved . In this chapter, we will often consider closed systems, for which the total amount of energy stays the same, but transforms from one kind to another. The transfer of energy from one system to another is called Work . Work is equal to the amount of energy transferred in (positive work) or out (negative work) of a system. Work is equal to the distance the object is moved multiplied by the amount of force in the direction of its motion. The rate at which work is done is called Power . Answer: release heat
answer:
What happens when chemical bonds in a burning log break?

question:
Passage: When most people think of muscles, they think of the muscles that are visible just under the skin, particularly of the limbs. These are skeletal muscles, so-named because most of them move the skeleton. But there are two other types of muscle in the body, with distinctly different jobs. Cardiac muscle, found in the heart, is concerned with pumping blood through the circulatory system. Smooth muscle is concerned with various involuntary movements, such as having one's hair stand on end when cold or frightened, or moving food through the digestive system. This chapter will examine the structure and function of these three types of muscles. Answer: cardiac
answer:
What kind of muscle is found in the heart?