Chapter 3 - Biological molecules - proteins Flashcards
what are peptides
polymers made up of amino acids - proteins consist of one or more polypeptides arranged as a complex macromolecule
what elements do proteins contain
Hydrogen Nitrogen Oxygen and Carbon
what is the basic structure of an amino acid
central carbon and hydrogen
left - amine group (NHH)
right - carboxyl group (COOH)
down - R group (different in all amino acids)
how do amino acids join to form peptides
condensation reaction between one amine group and one carboxyl group to form a peptide bond forming a dipeptide
what is the primary structure of a polypeptide
the sequence in which amino acids are joined (peptide bonds)
what are the two secondary structures
alpha helixes or beta pleated sheets (hydrogen bonds)
what are the interactions in the tertiary structure
between r groups: hydrophobic/hydrophilic interactions (weak) hydrogen bonds (weakest) ionic bonds (strong) disulphide bridges (strongest) - covalent bonds between r groups containing sulphur
describe a quaternary structure
interaction between two or more individual proteins called subunits (same bonds as in the tertiary structure)
describe the quaternary structure of haemoglobin
made of two sets of identical subunits - two alpha and two beta subunits; each subunit contains a prosthetic haem group
what is the test for proteins
biuret test - peptide bonds form violet coloured complexes with copper ions in alkaline solutions
what are the two main protein groups
globular and fibrous
what are the features of globular proteins
compact, water soluble and usually roughly spherical - hydrophobic r groups are on the inside and hydrophilic r groups are on the outside
what type of protein is insulin
globular
what is a conjugated protein
globular proteins containing a prosthetic group (non-protein component)
what is a simple protein
a protein without prosthetic groups
what does the haem in haemoglobin do
the iron in it can reversibly combine with oxygen - it allows it to carry oxygen in the blood
what is the structure of catalase and what does it to
it is a quaternary protein containing four haem prosthetic groups. this allows catalase to breakdown hydrogen peroxide which is a by-product of metabolism
what is a the structure of a fibrous protein
long insoluble molecule (due to hydrophobic r-groups)
limited range of amino acid, usually with short r-groups
repetitive structure
give examples of fibrous proteins
keratin, elastin, collagen
where is keratin found and what is its structure
hair, skin and nails large proportion of sulphur containing amino acid - cysteine many disulfide bridges strong inflexible and insoluble (hair contains less bonds)
where is elastin found and what is its basic structure
in elastic fibres (walls of blood vessels and alveoli in lungs)
quaternary protein
where is collagen found and what is its structure
connective tissue found in skin, tendons, ligaments and the nervous system
three polypeptides wound together in a long strong rope-like structure
has flexibility
