proteins Flashcards
what is a protein?
a large and complex polymer molecule made up of long chains of amino acids.
what is proteins biological roles
(structural, catalytic, signalling, communological)
structural - muscle, skin, ligaments, hair
catalytic - all enzymes are proteins
signalling - many hormones & receptors are protein
communological - all antibodies are protein
what’s the structure of protein?
all have amino acid groups
all have carboxylic acid groups
all have a single hydrogen
they have a central carbon
what is the structure of amino acids?
every amino acid has a central carbon atom to which are attached to 4 different chemical bonds
amino acid group - NH2
carboxylic group
hydrogen atom
R side group
what is the function of a peptide bond?
amino acids monomers can combine to form a dipeptide.
the water is made by combining an -OH from the carboxylic group of another amino acid with a -H from the amino group of another amino acid.
the 2 amino acids then become linked by a new peptide bond between the carbon atom of 1 amino acid & the N atom of another
what is the primary structure of proteins?
many amino acids monomers can be joined together in a process of polymerisation. The order of amino acids in the polypeptide chain of covalent bonds
what is the secondary structure of proteins?
the sequence of amino acids causes parts of a protein molecules to bend into alpha helix shapes or folded into beta pleated sheets, held by hydrogen.
The linked amino acids that make up the polypeptide posses both -NH and -C= groups that have an overall -ve charge.
These 2 groups therefore form wax bonds called hydrogen bonds. This causes the long peptide chain to be twisted into a 3D shape (Alpha helix)
what is the tertiary structure of proteins?
the further folding of the secondary structure to form a 3D unique shape held in place by ionic, hydrogen, and disulphide bonds.
ionic bonds form between any carboxylic & amino groups that are not involved in forming peptide bonds
what is the quaternary structure of protein?
protein is made up of more than 1 polypeptide chain. they may also be non-protein groups associated with the molecules such as iron - containing haem group in haemoglobin.
although the 3D structure is important to show how a protein functions it is also the primary structure that determines the 3D shape in the first place.
test for protein
place sample in the test tube (solution) and add equal volume of NaOH solution at room temp.
add a few drops of dilute copper sulphate solution and mix gently.
+ve result give purple which indicates the peptide bonds
peptide bonds
an order of Amino acids
secondary structure - coiled into an alpha helix hydrogen on amino acid group and oxygen on carboxylic group of adjacent amino acid
tertiary - further folding
ionic bonds form between polar R groups
hydrophobic amino acids on the inside of the protein.
quaternary structure - not all include quaternary, more than 1 polypeptide chain & some prosthetic group same bond as tertiary.
structure of collagen
fibrous protein
is most common structural protein found in vertebrae
collagen is an insoluble
formed from 3 polypeptide chains closely held together by hydrogen bonds to form a triple helix
large size, long molecules, lack of OH groups
structure of haemoglobin
is a globular protein which is an oxygen carrying pigment found in vast quantities in red blood cells
4 oxygen molecules per haemoglobin molecules
what is enzyme action?
enzymes are biological catalysts they work by reducing the activation energy of a reaction. without the enzymes the reaction that happens wouldn’t be possible at normal body temperature
all enzymes are globular proteins and have regions called active sites the active site of an enzyme has a specific shape and allows the substrate to bind.
what is the induced fit model?
suggests that the shapes of the enzyme active site and its substrate aren’t complimentary but when the substrate enters the active site a conformational change occurs which induces a catalysis;
stage 1 - the substrate enters the enzymes active site forming an ES complex
stage 2 - the enzyme undergoes a conformational change which causes the conversion of substrate to product forming an EP complex.
stage 3 - the product is released from the enzymes active site.
