Proteins - AP Biology

The effect of a point mutation is not dependent on the amino acid—the amino acid's selection is entirely independent of its structure. The amino acid selection during translation depends only on the three base-pair codon read by the ribosome. For example, the start codon—AUG—recruits methionine. If a frameshift mutation lead to UGG as the codon instead, tryptophan would be recruited. No single amino acid is more likely to be incorporated after a point mutation.

Every amino acid has a central carbon with an amino terminus and a carboxyl terminus. There is also a hydrogen attached to the central carbon. The last substituent varies between amino acids and determines how the particular amino acid will be used in proteins. This variable group is known as the "R-group." Only one amino acid, alanine, has a methyl group attached in the "R-group" position.

The degeneracy of the genetic code is a major concept relating to protein synthesis. This concept states that each codon codes for a single amino acid, but that an amino acid can have more than one codon. If each three-base codon corresponded to a different amino acid, 64 amino acids would be produced in the body. Instead, most amino acids are coded for by multiple codons; for example, lysine corresponds to both AAA and AAG. This concept is especially important with regard to mutations. If an AAA codon undergoes a point mutation to become an AAG codon, the same amino acid will be produced, and the organism will be unharmed.

Peptide bonds are the uniquely named form of covalent bonds that hold together amino acids. These bonds are formed when the carboxylic acid of one amino acids reacts with the amino group of another amino acid. The result is a peptide polymer, known as a polypeptide, and a water molecule.

Glycosidic linkages are seen in sugars, and are used to bind monosaccharides. Hydrogen and ionic bonds are more general intermolecular forces. Hydrogen bonding helps shape the secondary and tertiary structure of proteins, but does not help in the formation of an amino acid chain.

Amino acids consist of an amine, a carboxylic acid, a hydrogen atom and a side chain (often simply referred to as an “R group”). Differences between these side chains are what differentiate amino acids from one another. These four components are bound to a central carbon atom, giving each amino acid a stereocenter. Amino acids form peptide bonds through condensation reactions between the carboxyl group of one residue and the amino group of another.

The amino acids, as denoted by the name, contain amino and carboxyl groups. Each amino acid has the amine group connected to a central carbon, which is then connected to a carboxyl group.

Amino acids may contain R-groups on the central carbon, and all amino acids have a specific R-group except for glycine, which is the simplest amino acid. Glycine is bound to an extra hydrogen atom in place of an R-group. Only methionine can start a protein structure; methionine is coded by the start codon on an mRNA sequence. Some amino acids are capable of forming alpha-helices, while others are capable of disrupting and breaking alpha-helices. Proline, for example, frequently disrupts this secondary structure. Each protein is coded by a specific sequence of amino acids; not all proteins will contain every amino acid.

The number of codons can be found by raising the number of nitrogenous bases to the power of the codon length. In the genetic code, there are four bases and codons are three bases in length.

If codons were four bases in length, then the number of possible bases would be raised to the fourth power.

Amino acids are compounds that make up proteins and polypeptide chains. They are made up of an amine group , a carboxylic acid group , and a variable side chain. The amine group is called the “N terminus” and the carboxylic acid group is called the “C terminus”. The N terminus of one amino acid and the C terminus of another amino acid can form a peptide bond through a condensation reaction.

Amino acids are the building blocks of proteins. The general structure of an amino acid consists of a carboxylic acid and an amine group bonded to a carbon that contains. The carbon contains an R group that varies depending on the amino acid.

The effects of point mutations vary by type. For example, leucine has 6 different codons. If the codon UUA is changed to UUG, the resulting amino acid inserted into the protein is not changed; it is still leucine. This is referred to as a silent mutation.

tRNA, or transfer RNA, is responsible for binding amino acids and delivering them to the ribosome during translation. tRNA binds amino acids with its anticodon. The anticodon is a sequence of 3 nucleotides that are complimentary to the codon of a specific amino acid. Anticodons can only bind to codons that are complementary in sequence; this ensures that the correct amino acids are chosen.

Cysteine is an amino acid that contain a sulfhydryl group . When two sulfhydryl groups come together and get oxidized they form a bond, which is referred to as a disulfide bond or a disulfide bridge.

Proteins are polymers of amino acids, which have an amino group, carboxyl group, and a side chain known as an R-group. Nucleotides make up DNA and RNA. Glucose is a carbohydrate monomer and make up starches, cellulose, and glycogen. Fatty acids are components of lipids.

Amino acids, which make up proteins, have an amino group, which contains nitrogen. Carbohydrates and lipids contain the elements carbon, hydrogen, and oxygen, but they do not contain nitrogen.

A nitrogenous base is a part of the DNA/RNA structure. They include adenine, guanine, cytosine, thymine, and/or uracil. All other answer choices are parts of amino acids.

Chaperonin is the enzyme responsible for folding nascent polypeptide chains into the correct and functional 3-dimensional structure. Lipase is an enzyme that breaks down lipids, or fats. Amylase breaks down starches and complex carbohydrates or sugars. Helicase helps unwind the DNA helix during replication, and topoisomerase II helps keep the DNA untangled and acts as adhesive during DNA repair or replication.

Primary structure revolves around the sequence of amino acids, while secondary structure is achieved through hydrogen bonds interacting along the backbone of the polypeptide. Tertiary structure is achieved through interactions between the various side chains of amino acids and is required for the protein to be functional. Quaternary structure involves the interaction of two or more polypeptide subunits, and adds efficiency to their ability to catalyze a reaction.

Proteins have four levels of structure: primary, secondary, tertiary, and quaternary. These refer to the types of binding and folding that occur in the molecule that cause it to take on a stable shape. Hydrogen bonds occur between parts of the molecule containing slightly positive hydrogen, and other parts that may be slightly negative (generally containing oxygen). These bonds stabilize the protein's secondary structure, allowing more complicated folding into tertiary and quaternary structures. Alpha-helices and beta-pleated sheets form the common secondary protein structures.

Primary structure is driven by peptide bonding, while tertiary structure is derived from disulfide bonds and hydrophobic interactions. Quaternary structure describes the congregation of multiple subunits driven by hydrophobic interaction and protein-mediated assembly.

The formation of -helices and -pleated sheets constitute the secondary structure of a protein. These conformations are reinforced by hydrogen bonds between the atoms in the polypeptide chain.

Primary structure is determined by peptide bonds, which link adjoining amino acids in sequence. Tertiary structure is determined by disulfide bonds between cysteine residues and hydrophobic interactions. Quaternary structure is determined by interactions between multiple subunits of a protein.