proteins Flashcards
define amino acids
monomers of all amino acids and all amino acids have the same basic structure
define peptide bond
bond formed when two amino acids are joined together in a condensation reaction
what elements do all amino acids contain
C, H, O, N
what is the element that only three amino acids contain
sulfur
what are the four main biological roles of proteins
structural: make up most of the body’s tissues e.g. muscles hair skin and ligaments.
metabolic: all enzymes are proteins
signalling: many hormones and receptors are proteins
immunity: all antibodies are proteins
what is the general structure of an amino acid
an amino acid has an amino group (H2N), carboxyl group (CHO2) and an R group and a hydrogen (H) atom
what defines an amino acid
its R group
what type of bond are amino acids joined together by and what is it called
covalent bond called peptide bond.
what kind of reaction occurs when creating a peptide bond
condensation
what enzyme breaks down peptide bonds during digestion
protease
what are two amino acids called
dipeptide
what are more than two amino acids called
polypeptide
where does the peptide bond between two amino acids form
between the OH of carboxyl group and H of the amine group.
what does a protein consist of
one or more polypeptide chains folded into a specific 3D shape
what is the primary structure of a protein
sequence of amino acids
what is the secondary structure of a protein
the coiling or folding of an amino acid chain, which often arises as a result of hydrogen bonding on different parts of the chain
what are the two main formed of the secondary structure of a protein
helix and pleated sheet
what is the tertiary structure of a protein
the 3D shape of the protein molecule caused by interactions such as hydrogen bonding, ionic bonding, disulfide bridges, hydrophilic/phobic interactions
what is the quaternary structure of a protein
protein structure where a protein consists of more than one polypeptide chain e.g. insulin
in a chain of amino acids, what holds the helix secondary structure in shape
hydrogen bonds
where are H bonds are between in the helix of amino acids
the NH of one amino acids and the CO of another amino acid 4 places ahead of it in a chain
how do all the different bonds in tertiary structure work
hydrogen bonds between polar R groups and other polar R groups, hydroxyl, carboxyl and amine groups. ionic bonds between positively charged R groups. disulfide bridges between cysteine R groups. hydrophobic R groups bend towards the centre of the structure whereas hydrophilic R groups bend towards the water
what are the two main categories of three-dimensional tertiary and quaternary structures of protein
globular and fibrous
what are the characteristics of fibrous proteins
repetitive sequence of amino acids
insoluble
structural (collagen, keratin)
