About proteins, amino acid structure, protein's structures and types

1. Chapter 2B

2.  Know the basic structure of an amino acid
 Understand the formation of polypeptides and proteins,
as amino acid monomers linked together by
condensation reactions to form peptide bonds
 Understand the significance of a protein’s primary
structure in determining its secondary structure, three-
dimensional structure and properties, and the types of
bond involved in its three-dimensional structure
 Know the molecular structure of a globular protein and
fibrous protein and understand how their properties
relate to their functions (including haemoglobin and
collagen)

3.  Proteins have many structures, resulting in a
wide range of functions
 Proteins account for more than 50% of the dry
mass of most cells
 Protein functions include structural support,
storage, transport, cellular communications,
movement, and defense against foreign
substances

5.  Proteins are a group of macromolecules made up
of many small monomer units called amino acids
joined together by condensation reactions.
 There are 20 naturally occurring amino acids.

9.  Amino acids join by a condensation reaction
between the amino group of one amino acid and
carboxyl group of another by peptide bond and
releasing a water molecule.
 Molecule which contains 2 amino acids = dipeptide
 If there are many amino acids=polypeptide
 A polypeptide forms a protein when the structure
of the chain changes by folding or coiling or
associates with other polypeptide chains.

11.  Peptide bond (covalent bond)-between
functional groups
 Hydrogen bond – between R groups or
functional groups
 Disulfide bond(covalent bond) –between R
groups
 Ionic bond – between R groups

13.  They are very important in the folding and coiling
of polypeptide chains.
 Hydrogen bonds break easily and reform if pH and
temperature conditions change.

14.  Forms when two cystein molecules are close
together and are strong bonds.
 Important for holding the folded polypeptide chains
in place.

15.  Can form between some of the strongly positive
and negative amino acid side chains and are strong
bonds

16.  A functional protein consists of one or more polypeptides
twisted, folded, and coiled into a unique shape
 The sequence of amino acids determines a protein’s three-
dimensional structure
 A protein’s structure determines its function

18.  The primary structure of a protein is its unique
sequence of amino acids
 Secondary structure, found in most proteins,
consists of coils and folds in the polypeptide chain
 Tertiary structure is determined by interactions
among various side chains (R groups)
 Quaternary structure results when a protein
consists of multiple polypeptide chains

20.  Primary structure, the
sequence of amino acids in a
protein, is like the order of
letters in a long word
 Primary structure is
determined by inherited
genetic information

21.  The coils and folds of secondary structure result
from hydrogen bonds between repeating
constituents of the polypeptide backbone
 Typical secondary structures are a coil called an 
helix and a folded structure called a  pleated
sheet

22.  Tertiary structure is
determined by
interactions between R
groups, rather than
interactions between
backbone constituents

23.  Quaternary structure results when two or
more polypeptide chains form one
macromolecule
 Collagen is a fibrous protein consisting of
three polypeptides coiled like a rope
 Hemoglobin is a globular protein consisting of
four polypeptides: two alpha and two beta
chains

25.  Change in temperature, pH or some chemicals can
cause the bonds to break, resulting in the loss of the
3D shape of the protein, known as denaturation.