Option A,
both limit movement of substances through the system
The sphincter muscle usually surrounds the openings in the body such as urethra, anus and performs the function of tightly closing the openings. When once the messages are received from the nervous system the sphincter relaxes and releases the material out of the opening during urination of excreting
The same is the function of valves in the circulatory system. They also prohibits the entry of blood from one chamber to other and then to the main circulatory system. The relaxes on receiving a signal from the brain and thus transfer blood from one chamber to the other.
B) small non-polar molecules. Small molecules can pass through the cell membrane through diffusion (does not require energy). The molecule being non-polar is an advantage because the tails of the phospholipid bilayer is hydrophobic (nonpolar), so it does not repel nonpolar molecules.
he correct answer is number one. A chromosome is composed of many genes. A chromosome is referred to as a DNA molecule in an organism's body, which consists of genetic materials. Chromosomes consists of numerous genes within them, in their nucleus and mitochondria, genes are found inside the Chromosomes itself
No, because “free” nitrogen is not combined with other kinds of atoms.
Most organisms can use nitrogen only once it has been "fixed" or combined with other elements to form nitrogen-containing compounds.
The cautions that can be given to the friend include the following:
Eating foods from different sources is very advantageous because it ensures that one gets all the necessary food nutrients that are needed for proper growth and development. Getting the necessary food nutrients on the other hand will boost one's immunity and enable one to develop resistance to diseases. Restricting one's food to a limited type of food is very bad and can have fatal consequences.
