Proteins and Enzymes

[blank_start]Primary Structure[blank_end] is the order (sequence) of the amino acids forming a protein chain. The amino acids are held together by [blank_start]peptide bonds[blank_end] and the chain is called a [blank_start]polypeptide[blank_end].

Secondary Structure refers to when the protein chain changes into a coil (called [blank_start]alpha helix[blank_end]), pleat (called [blank_start]beta sheet[blank_end]), or a [blank_start]random coil[blank_end]. These are formed by a [blank_start]hydrogen bond[blank_end].

Tertiary Structure is formed when there is an interaction between the [blank_start]R-groups[blank_end] of the amino acids within a single polypeptide chain.

The R-groups can form [blank_start]4[blank_end] types of bonds. [blank_start]Non-polar[blank_end] -> Hydrophobic Interaction [blank_start]Polar[blank_end] -> Hydrogen [blank_start]Acidic/Basic[blank_end] -> Ionic Bond [blank_start]Cysteine[blank_end] -> Disulfide Bridge *Exceptions 1. The amino acid cysteine is polar. However, it forms a disulfide bridge instead of a hydrogen bond. This is because it has a sulfur molecule. 2. Methionine also contains sulfur and is non-polar. It forms a hydrophobic interaction instead of a disulfide bridge.*

Polar amino acids usually have an N, F, or [blank_start]O[blank_end] in their R-groups. [blank_start]Cysteine[blank_end] is an exception. It is polar; however, it doesn't follow the common criteria. Another exception is [blank_start]Tryptophan[blank_end]. It has an N in its R-group, but it is non-polar as it has an equal pull on each side.

Non-polar amino acids have Cs and [blank_start]H[blank_end]s in their R-groups.

To tell whether an amino acid will form an [blank_start]ionic[blank_end] bond, the amino acid must be an acid or a base. An acid has a [blank_start]negative[blank_end] in its R-group, whereas a base has a [blank_start]positive[blank_end]. It is important to know that all acids and bases are [blank_start]polar[blank_end].

Which bond will the following amino acid form?

Which bond will the following amino acid form?

Which bond will the following amino acid form?

Which bond will the following amino acid form?

Some proteins stop after the [blank_start]tertiary[blank_end] structure. Some go on to the [blank_start]quaternary[blank_end] structure. In this structure, 2 or more [blank_start]polypeptide[blank_end] chains interact and for 3 dimensional structure.

Due to changes in pH levels, temperature, and other factors, proteins can often [blank_start]denature[blank_end]. This means that the bonds between the proteins break and the protein unravels. Some proteins are able to recover, others are not.

Enzymes are a type of [blank_start]protein[blank_end]. They help catalyze reactions. So, they help to [blank_start]speed up[blank_end] chemical reactions in the body. A [blank_start]substrate[blank_end] is the reactant that the enzyme acts on. The [blank_start]active site[blank_end] is the region on an enzyme where the substrate fits.

Which of these is an enzyme?