Types of proteins Flashcards
What are globular proteins?
compact, water soluble, roughly spheriica
form when tertiary structures form in such a way that the hydrophobic R-groups on the amino acids are kept away from the aqueous environment
hydrohpillic R-groups are on the outside of the proteins, this means the proteins are soluble in water.
solubility means it is essential in life
What is insulin?
It is a globular protein
Hormone involved in the regulation of blood glucose conc.
Hormones transported in the bloodstream so need to be soluble
They need precise shape to fit into specific receptors on cell surface membranes.
What are conjugated proteins?
Globular proteins that contain a non-protein component called a prosthetic groups.
different types of prosthetic groups, e.g. glycoproteins
What is haemoglobin
oxygen carrying pigment in cells
quaternary protein made from four polypeptides, two alpha and two beta subunits
each subunit contains a prosthetic haem group (Fe2+)
able to combine reversibly withan oxygen molecules
What is catalase?
an enzyme
quaternary protein contain four haem prostehtic group
the presecence of iron(II) allow catalase to interact with hydrogen peroxide and speed up its breakdown
hydrogen peroxide is a common byproduct of metabolism but is damaging to cells and cell components if allowed to accumulate
What are fibrous proteins?
long, insoluble molecules
due to the high proportion of amino acids with hydrophobic R-groups in their primary structures
they contain a limited range of amino acids, usually with small R-groups
the amino acid sequence in the primary structure is usually quite repetitive
this leads to very organised structures reflected in the roles fibrous proteins often have
What are the properties of fibrous proteins?
tend to make strong, long molecules which are not folded into complex 3d globular proteins
What is keratin?
group of fibrous proteins present in hair, skin and nails
contains a large propotion of the sulfur-containing amino acid, cysteine
results in many strong disulfide bonds, forming strong inflexible and insoluble materials
the degree of disulfide bonds determines its flexibility
causes the unpleasent smell when burnt
What is elastin?
a fibrous proteins found in elastic fibres (along with small protein fibres)
present in the walls of blood vessels and alveoli - they give them their flexibility to expand and retract when needed
What is collagen?
another fibrous protein
it is a connective tissue found in skin, tendons, ligaments and the nervous system
there are a number of different forms but are made up of three polypeptides wound together in a long, strong, rope-like structure
has flexibility
