The sodium-potassium ion exchange pump a) must reestablish ion concentrations after each action potential. b) transports sodium ions into the cell during depolarization. c) transports potassium ions out of the cell during repolarization. d) moves sodium and potassium opposite to the direction of their electrochemical gradients. e) depends on a hydrogen gradient for energy.

Moves sodium and potassium opposite to the direction of their electrochemical gradients. (Ans. D)

Explanation:

Sodium potassium pump: It is present in many plasma membrane of the cells. A protein which is present on the many cells is maintained the internal and external environment concentration by maintain internal concentration of potassium higher than outside and internal concentration of sodium lower than outside.

With the help of the ATP, moves sodium and potassium opposite to the direction of their electrochemical gradients. Two potassium ions are imported and three sodium ions are ejected in a cell, In a single pump cycle.

not sure if this what   you'r looking for would be percent composition

question#1

ans:

cell is the basic unit of organization of all living things. cells are often called the building block of life and it is the smallest unit of life. the study of cell is called cell biology. cell consists of cytoplasm enclosed within membrane, which contain bio-molecules such as proteins and nucleic acid.

two third of cell is water, which means that two-third of your whole body is water. the rest is the mixture of molecules, mainly proteins, lipids and carbohydrates.

question#2

ans:

organ:

an organ is a group of tissues specialized to form a functional unit. an example is the heart in animals.

organ system:

an organ system is a group of several organs whose functions are synchronized to release an effective action in a living organism. an example is digestive system.

question#3

different systems perform different function at tissue level. for example, the respiratory system facilitates breathing. in the alveoli tissue of the lungs, the exchange of oxygen and carbon dioxide molecules between the air and the bloodstream occurs by passive transport, so that oxygen is taken in and carbon dioxide and water are removed. different systems of the body carry out different functions. for example, your digestive system is responsible for taking in and processing food, while your respiratory system working with your circulatory system is responsible for taking up oxygen and getting rid of carbon dioxide.

question#4

different systems perform different function at tissue level. for example, the respiratory system facilitates breathing. in the alveoli tissue of the lungs, the exchange of oxygen and carbon dioxide molecules between the air and the bloodstream occurs by passive transport, so that oxygen is taken in and carbon dioxide and water are removed. different systems of the body carry out different functions. for example, your digestive system is responsible for taking in and processing food, while your respiratory system—working with your circulatory system is responsible for taking up oxygen and getting rid of carbon dioxide.

question#5

our body works because of the interactions that happen between organs and organ systems.  

for example:  

the heart to regulate blood flow throughout the body. the blood carries oxygen and nutrients to the cells and carries carbon dioxide and waste away from the cells. body systems work together in maintaining a constant internal environment. when this balance is disrupted, the body systems may not function properly, and human health can suffer.   you start to feel bad.