<span><span>anonymous </span> 3 years ago</span>Proteins are involved in almost all of the cell's functions. They can act as:
Transportation: they can transport hydrophobic molecules in blood for example
Regulation: protein hormones and enzymes
Receptor: can act as receptors on cell surface and in the subsequent signal transduction (G-protein for instance)
It is true that all proteins are made up of up to 20 amino acids, but there are several reasons for their diverse actions:
-One reason is the possible sequence and number of amino acids: Met-Ser-His is different from Met-His-Ser for example. Besides, you have different chain length, for a protein is made up of long chain of polypeptide (longer than 50-70 amino acids) and can have any of the 20 amino acids with repetition, so using simple probability, this can provide up to practically unlimited combination with proteins that have chains of thousands of amino acids.
-Another very crucial reason for the diversity of protein action is the conformation. A protein passes by at least 3 conformational stages before becoming mature. The straight amino acid chain is the primary structure of the protein that can never be active. Spatial modification of this primary structure results in a secondary structure, Helix or Beta-pleated sheets (or other coiling structure), that is also inactive. Further coiling and bending of the secondary structure produce a 3-dimentional conformation that is the active form of the protein. Moreover, many proteins can undergo further conformational rearrangement and combination with other protein sub-units producing a quaternary structure.
In humans, the placenta is essential to the embryo for RESPIRATION, NUTRITION AND EXCRETION.
The placenta refers to an organ in the uterus of pregnant mammals that is responsible for nourishing and maintaining the unborn baby through the umbilical cord. Th placenta has many functions but primarily it plays critical roles in the nutrition, respiration and excretion of the fetus. Its other functions include: production of hormones, production of immunity for the fetus for prevention from infections, etc. <span />
B is correct! Renewable and non
Answer:
Activated
Explanation:
In the presence of lactose, and in the absence of glucose, lactose will bind to a protein called a "repressor," deactivating it. Through this, RNA polymerase has a free way to synthesize the mRNA that will give enzymes for lactose degradation.
