BIOL 2112 Chapter Notes - Chapter 5: Macromolecule, Sickle-Cell Disease, Organic Compound
10 May 2018
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Lecture 7 – Proteins
Of the eight categories of protein, which is considered to be most important for the
emergence of the earliest life forms ~3.5 billion years ago? Enzymatic Proteins Describe
an amino acid monomer of a protein. In your description, include the -carbon, the
functional groups of the backbone, and the function of the R group. An amino acid is an
organic molecule with both an amino group and a carboxyl group. At the center of the
amino acid is an asymmetric carbon atom called the alpha (
) carbon. Its four different
partners are an amino group, a hydrogen atom, a carboxyl group, and a variable group
symbolized by R. The R group, also called the side chain, differs with each amino acid. In
the pH of a cell, the amino groups and carboxyl groups exist in ionized form. How do polar
and electrically charged amino acids differ from non-polar amino acids? Hydrophilic
Describe peptide bond formation between two amino acids. When two amino acids are
positioned so that the carboxyl group of one is adjacent to the amino group of the other,
they can become joined by a dehydration reaction, with the removal of a water molecule.
The resulting covalent bond is called a peptide bond. Repeated over and over, this process
yields a polypeptide, a polymer of many amino acids linked by peptide bonds. How does
polyerizatio establish the orietatio i.e. the ed groups of a protei? One end of
the polypeptide chain has a free amino group (the N-terminus of the polypeptide) while
the opposite end has a free carboxyl group (the C-terminus). The chemical nature of the
molecule as a whole is determined by the kind and sequence of the side chains which
determines how a polypeptide folds and thus its final shape and chemical characteristics.
When does a polypeptide become a protein? A functional protein is not just a
polypeptide chain, but one or more polypeptides precisely twisted, folded, and coiled into
a molecule of unique shape, which can be shown in several different types of models.
What ultimately determines the three-dimensional shape of a protein? The amino acid
sequence of each polypeptide determines the 3D structure the protein will have under
normal cellular conditions. What effect do hydrophobic amino acid side chains have on
protein folding? Where are stretches of hydrophobic amino acid residues normally
found in a globular protein? Hydrophobic amino acid side chains are nonpolar and do not
like to be exposed to the polar cellular environment so they naturally fold to the inside of
the protein. Describe the four levels of protein structure. For levels 2-4, include a
description of the chemical interactions that stabilize each structural level. Primary:
sequence of amino acids, dictates secondary and tertiary structure due to chemical nature
of backbone and side chain of amino acids along the peptide; Secondary: segments of
polypeptide chains repeatedly coiled or folded in patterns that contribute to the proteins
overall shape as a result of hydrogen bonds between the repeated constituents of the
polypeptide backbone, within backbone oxygen atoms have partial negative charge and
hydrogens attached to nitrogen have partial positive charge therefore hydrogen bonds
can form between these atoms; Tertiary: overall shape of a polypeptide resulting from
interactions between the sidechains of the various amino acids (hydrophobic interaction,
disulfide bridges, ionic bonds between charged groups, hydrogen bonds between polar
groups); Quaternary: two or more polypeptide chains aggregated into one functional
macromolecule resulting from aggregation of polypeptide subunits. Which levels of
protein structure are affected in Sickle-Cell Disease? Primary: substitution of one amino
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Document Summary
Carbon, the an amino acid monomer of a protein. In your description, include the functional groups of the backbone, and the function of the r group. An amino acid is an organic molecule with both an amino group and a carboxyl group. At the center of the amino acid is an asymmetric carbon atom called the alpha ( ) carbon. Its four different partners are an amino group, a hydrogen atom, a carboxyl group, and a variable group symbolized by r. the r group, also called the side chain, differs with each amino acid. In the ph of a cell, the amino groups and carboxyl groups exist in ionized form. Describe peptide bond formation between two amino acids. When two amino acids are positioned so that the carboxyl group of one is adjacent to the amino group of the other, they can become joined by a dehydration reaction, with the removal of a water molecule.
