Proteins Flashcards
What are the monomers from which proteins are made?
Amino acids
Amino acids contain an amino group, NH2, a carboxyl group, COOH, and a variable R group.
How many different amino acids are there?
20
Each amino acid has a different R group that determines its chemical properties.
What type of bond joins amino acids together?
Peptide bonds
Peptide bonds are formed in condensation reactions.
What is a dipeptide?
A molecule containing two amino acids
Polypeptides contain three or more amino acids.
What determines the primary structure of a protein?
The linear sequence of amino acids
The primary structure is held together by peptide bonds.
What is the secondary structure of a protein characterized by?
Folding into an alpha helix or beta pleated sheet
The secondary structure is stabilized by hydrogen bonds.
What bonds are involved in the tertiary structure of a protein?
Hydrogen bonds, ionic bonds, and disulfide bridges
Ionic bonds form salt bridges between oppositely charged groups on the R groups.
What defines the quaternary structure of a protein?
The 3D arrangement of more than one polypeptide
Not all proteins have quaternary structure.
What are the characteristics of fibrous proteins?
Long parallel polypeptides, little tertiary/quaternary structure, insoluble, used for structural purposes
Fibrous proteins have occasional cross-linkages that form microfibres for tensile strength.
What are the characteristics of globular proteins?
Complex tertiary/quaternary structures, form colloids in water, various functions
Examples include hormones and antibodies.
What is collagen and its significance?
A fibrous protein with high tensile strength
Collagen is made up of three distinct α-chains forming a triple gamma helix, contributing to structures like bones and cartilage.
What is haemoglobin and its function?
A water-soluble globular protein that carries oxygen in the blood
Haemoglobin consists of four polypeptide chains and contains a haem group with Fe2+ ions.
Fill in the blank: A __________ contains two amino acids.
Dipeptide
True or False: All proteins have all four levels of structure.
False
Not all proteins exhibit quaternary structure.
