Proteins have four levels of structure. Secondary structure involves the formation of alpha-helices and beta-sheets via hydrogen bonding between the amino acid backbone in the protein chain. 

Primary protein structure simply refers to the linear sequence of amino acid residues in the polypeptide chain. After initial folding of the backbone in secondary structure, functional groups of the amino acids interact to generate tertiary structure. Tertiary structure contains hydrogen bonding, hydrophobic interactions, and disulfide bridges. Some proteins then develop quaternary structure, when multiple polypeptide chains are joined as subunits to build a large protein complex. 

Proteins can be inhibited in numerous ways by different types of inhibitors. Competitive inhibitors will compete with substrate for the active site to block the protein from performing its function. If there is enough substrate and very little competitive inhibitor, proteins will perform their functions almost as if there were no competitive inhibitors.

In contrast, allosteric inhibitors bind to regions of the protein away from the active site, but change the shape of the active site such that substrate cannot bind. Since there is no direct competition, increasing substrate concentration cannot overcome allosteric inhibition. Non-competitive inhibition is a type of allosteric inhibition. Uncompetitive inhibition occurs when the inhibitor will only bind to the enzyme-substrate complex, locking the substrate in place and preventing other substrates from binding.

The active site on a protein is the area where a substrate can attach. This relationship is most often described using a metaphor of a lock and a key because each protein has an active site specific to one substrate much like a lock can only be opened by one key.

The key here is to know that if something binds the enzyme at a location other than the active site, the type of modification is defined as allosteric. The other words more generally describe things that can bind to receptors, enzymes, etc., but the best and most specific answer is "allosteric."

It is important to know that when exposed to high temperatures, all proteins become denatured, and lose their native shape/conformation.

This has nothing to do with the activation energy of the reaction (eliminating that answer). While some substrates may be degraded at high temperatures, the word "all" renders this answer incorrect, nor does this describe what happens to the enzyme. Covalent modificatinos can change enzymatic function, but do not have anything to do with higher temperature.

The correct answer is that the enzyme itself is denatured, thus changing the shape and the way the active site is shaped, resulting in an inability to efficiently bind its substrate. The structure of the enzyme is dictated by intermolecular forces, which are susceptible to interference from temperature changes (unlike covalent bonds).

Competitive inhibition is the only type of inhibition in which the inhibitor molecule directly binds the active site of the enzyme, thereby 'competing' with the actual substrate for location on the enzyme. The other choices involve binding elsewhere on the enzyme (non-competitive) or binding the enzyme-substrate complex but not an isolated enzyme (mixed), but none of them describe binding the active site except for competitive. 

Collagen is the most abundant protein in the human body. It adds great strength and flexibility to skin, tendons, and ligaments. These qualities are characteristic of structural proteins.

Globular proteins are generally rounded, protecting a nonpolar center from the aqueous environment around the protein. Most cytoplasmic proteins and enzymes are globular proteins. In contrast, fibrous proteins are generally elongated and designed for structural support; collagen is a fibrous protein, in addition to a structural protein. Integral proteins span the plasma membrane, often creating channels.

A peptide bond is formed between the carboxyl group and amino group of adjoining amino acids. The energy in proteins is released when peptide bonds are broken. Peptide bonds also determine the primary structure of proteins.

An ionic bond is formed when one element loses an electron and another element gains an electron. Ionic bonds most frequently form between metals and non-metals, and are not commonly seen in proteins.

A glycosidic bond is formed between a carbohydrate and another molecule. Glycosidic bonds can help form carbohydrate polymers, like glycogen, or link sugars to other groups, like in the DNA backbone.

An ester bond can be found in fatty acids, and contains a carbonyl group next to an ether linkage.

Proteins are classified into several categories based on where they perform their function. Peripheral membrane proteins span only one side of the lipid bilayer and thus have mobility. Unlike integral membrane proteins, which span the entire lipid bilayer, peripheral membrane proteins have the liberty of traveling from layer to layer as well as flip flop between the two bilayers.

Isomers are molecules that have the same molecular formula, but have different chemical structures. Isomerases are enzymes that are able to rearrange the structure of a molecule while keeping its chemical formula the same.