What substances are secreted? List the mechanisms bywhich these substances are transported.
What substances are secreted? List the mechanisms by
which these substances are transported.
The passage and movement of substances from one side to another side in a cell and gland is called secretion. The secretion process is different from the excretion process because excretion removes the waste material outside the body. The secretion can occur from a cell and from a gland of the body. Some vital functions are performed with the help of secretion.
The substances that are secreted by a cell or gland can be any type. A cell can secretions such as hydrogen, sodium, calcium, etc and many proteins are secreted by the endoplasmic reticulum and transported to the Golgi apparatus and to other target sites. The secretion from a gland is hormones that regulate many functions in the body. Enzymes are secreted by many cells and surfactants are released from the alveolar cell of the lungs. Neurotransmitters from neurons are secreted. Earwax is secreted by ceruminous glands. Some waste products are secreted from the body into the urine such as drugs and toxic substances.
These materials are transported from one side to another side through an active process, simple diffusion, and facilitated diffusion.
The plasma membrane is formed of lipids and it is semipermeable. It allows some specific molecules to pass through it. The lipid bilayer is a hydrophobic layer and allows the direct movements of some small and non-polar substances and ions such as water, urea, and glycerol, oxygen, and carbon dioxide.
The polar substances need to travel the membrane with the help of some transporters that are located into the plasma membrane.
The transportation can be active transport in which requirements of energy to transport and other is passive transport in which no energy is needed to move. ATP is used as energy. The passive transport happens along the concentration gradient( one side is concentration high and the other side has a low concentration of a particular substance) and active transport works against the concentration gradient.
In passive transport, simple diffusion occurs across the membrane without any membrane protein and facilitated diffusion with the help of membrane protein. Some ion channels help in the transport of ions across the membrane.
Active transport occurs through some ATPase transporter such as P- ATPase, V-ATPase, F-ATPase, and ABC transporters are used to transport some nutrient molecules.
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