Which statement must be mentioned in explaining why amphipathic molecules line up at a water surface?

The right answer is polar group attract another one.

Amphipathic, amphiphilic and amphipolar, synonymous terms, denote a molecule (usually organic) carrying both a hydrophilic group (able to bind to water) and a hydrophobic group ("who does not like water").

These molecules are surfactants, in that they modify the surface tension between two media. The active components of detergents and soaps are amphipathic molecules, whose double solubility is exploited, in water (thanks to hydrophilic groups) and in fatty media (thanks to hydrophobic groups).

The membranes of living cells are made of two layers of molecules of this type (phospholipids).

The statement must be mentioned in explaining why amphipathic molecules line up at a water surface is polar group attract one another.

Amphipathic molecule are those which have both polar and non-polar part. Example phospholipids have both polar and non-polar parts  that is non-polar fatty acid tail and polar head.

Polar water molecule pull together , holding the polar parts of the amphipatic molecule and squeezing out the non-polar parts .That leave the non-polar parts in air .

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.

the correct answer is 2 and 4