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Proteins differ from one another because the sequence of amino acids in the polypeptide chain differs from protein to protein. The sequence of amino acids in a given protein is determined by the order and type of nucleotides in its genetic code. [adinserter block="7"] Proteins may be simple or complRead more
Proteins differ from one another because the sequence of amino acids in the polypeptide chain differs from protein to protein. The sequence of amino acids in a given protein is determined by the order and type of nucleotides in its genetic code.
Proteins may be simple or complex. Some proteins are single polypeptides made of several hundred amino acids, whereas others have thousands of subunits—polypeptides that are themselves chains consisting of 20 to 100 amino acids.
Proteins with large numbers of subunits are often globular, spherical structures called oligomeric proteins.
Some oligomeric proteins have thousands of subunits. Many of these complex, multisubunit protein molecules are enzymes that catalyze a chemical reaction in one step and then split up into their component polypeptides to repeat the process when another molecule is available for catalysis.
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The metallic elements are solid at room temperature because they have a high energy level. Metals conduct heat and electricity well, which is one of the properties that makes them useful in construction. They also tend to be malleable, meaning they can easily be molded into products. All metallic coRead more
The metallic elements are solid at room temperature because they have a high energy level.
Metals conduct heat and electricity well, which is one of the properties that makes them useful in construction.
They also tend to be malleable, meaning they can easily be molded into products. All metallic compounds contain metals (such as iron, nickel, cobalt), and some contain other elements such as oxygen or sulfur.
The main reason that metals are solid at room temperature is that the electrons in the metal atoms can move freely around. This is called metallic bonding, and it allows for electrical conductivity.
The metallic bond also makes them malleable (i.e., capable of being bent into different shapes).
Other reasons that metals are solid at room temperature include the following: The atoms in a metal are tightly packed together.
During melting, heat is required to separate the atoms and rearrange them into new positions.
This requires energy because it takes work to push or pull objects apart. The added heat also makes the electrons move faster, which increases the metal’s energy level. Solid metals are very hard.
It takes a lot of heat to melt them, and even more, heat to evaporate them (that is, change from solid to gas).
These processes require a great deal of energy because they involve releasing heat that is stored in solid metal.
When a liquid is heated, the molecules move faster and their atoms become more spread out.
The opposite happens when they cool down; the molecules slow down and come closer together again to form solids.
In metallic compounds, there are so many electrons that it takes an enormous amount of energy to move them to a place where they can be absorbed by other atoms.
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