[1.6] proteins Flashcards
what are 10 functions of proteins?
and examples of each :D
- structure - collagen, keratin
- enzymes - amylase, catalase
- transport - haemoglobin
- hormones - insulin, glucagon
- receptors - rhodopsin
- antibodies - immunoglobulin
- blood clotting - thrombin, fibrin
- lubrication - glycoproteins in synovial fluid
- toxins - diptheria toxin
- antifreeze - glycoproteins in arctic flea
what elements are proteins made from?
- carbon, hydrogen, nitrogen, and oxygen
- they can also contain sulphur or phosphorus
what is the basic structure an amino acid?
- central carbon
- hydrogen atom
- side chain
- amine group
- carboxyl group
how many naturally occurring amino acids are there and how do they differ?
- there are 20 naturally occurring amino acids
- they have the same basic structure but with different R groups
how can R groups vary?
- size
- polarity
- charge - acid (+) or base (-) depending on H+ ion concentration
- this gives every amino acid different properties
how is a dipeptide formed?
- two amino acids are joined together during a condensation reaction to form a dipeptide
- the condensation reaction occurs between the carboxyl group (-COOH) and the amino group (-NH₂) on adjacent amino acids
- a molecule of water is released as one oxygen and two hydrogen atoms are removed from the amino acids
what is a peptide bond?
it is a covalent bond formed when two amino acids are joined together to form a dipeptide in a condensation reaction
how is a polypeptide formed?
when many amino acids are joined together in a series of condensation reactions
how is a protein formed?
when one or many polypeptide chains fold into a specific shape that allows it to perform a specific function
how can a dipeptide be broken down into two amino acids?
- through a hydrolysis reaction
- this required a molecule of water as one oxygen and two hydrogen atoms are added to the dipeptide
- this breaks the peptide bond, forming two amino acids
in what ways can polypeptides be broken down?
polypeptides can be broken down into amino acids by a series of hydrolysis reactions. this can happen in two ways:
O=O=O=O ➞ O=O=O + O ➞ O=O + O + O ➞ O + O + O + O
or
O=O=O=O ➞ O=O + O=O ➞ O + O + O + O
what is the primary structure of proteins?
a simple, linear chain of amino acids
what is the secondary structure of proteins?
bonds within the structure cause it to form either:
- an alpha helix or
- a beta pleated sheet
what causes the shape to change in the secondary structure?
hydrogen bonds form between the NH of one amino acid’s peptide bond and the C=O of another peptide bond
what is the tertiary structure of proteins?
- folded into a 3D shape
- the different R groups allow different bonds to form within it
> hydrogen bonds (weak)
> ionic bonds (medium)
> disulphide bonds in cysteine (strong)
what is the quaternary structure of proteins?
they are made of multiple polypeptide chains held together by bonds
what happens if you change the order of amino acids?
- proteins are made from amino acids
- a different protein is formed if the order of amino acids is changed
- the bonds form in different positions so the protein may become useless
what are primary bonds?
permanent forces of attraction which join together atoms/molecules to form larger molecules
what are the 3 types of primary bonds?
- glycosidic bond - links sugars
- peptide bond - links amino acids
- ester bond - attaches the alcohol with an acid (lipids)
why are secondary bonds important? (+ an example)
- essential for maintaining complex structures of biological molecules
- eg. hydrogen bonds
what are the properties of globular proteins? (4)
- compact
- roughly spherical
- soluble in water due to polar hydrophilic R groups on the outside
- non-polar hydrophobic R groups towards centre
examples of globular proteins and why are they important?
- eg. haemoglobin, immunoglobin, enzymes
- they have an important physiological role as they can be easily transported around organisms and are involved in metabolic reactions
what are the properties of fibrous proteins?
and examples
- little / no tertiary structure
- large number of hydrophobic R groups; insoluble
- limited number of AAs, sequence is highly repetitive
- very organised, strong structures
- eg. keratin, collagen
