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Globular Proteins (general properties (molecules are of a relatively…
Globular Proteins
general properties
molecules are of a relatively spherical shape
are soluble in water
have metabolic roles in organisms
Insulin
structure
made up of two polypeptide chains
one chain begins with an alpha-helix section
fold into a tertiary structure
the second ends of a beta-pleat
structure held by disulfide bonds
hydrophilic amino acids lay on the outside of the molecule
makes it soluble in water
function
binds to glycoprotein receptors on the outsides of muscle and fat cells
increases glucose uptake from the blood and consumption rate of glucose
Pepsin
function
an enzyme that digests proteins in the stomach
structure
consists of a single polypeptide chain
327 amino acids long
folds into a tertiary structure
contains more amino acids with an acidic R group than a basic R group
explains why it is more stable in the acidic environment of the stomach
tertiary structure held by hydrogen bonding and two disulfide bridges
Haemoglobin
structure
has a Quaternary structure
consists of four polypetides
two alpha-globin chains
two beta-globin chains
each has its own tertiary structure
interactions between these create the specific shape of the haemoglobin molcecule
shape held by various bonds including hydrogen bonds
has a haem group in the space just outside of each chain
haem group is a prosthetic group (non-protein that is part of the function of the protein)
contains an iron ion
conjugated protein as it has a prosthetic group
function
carries oxygen from the lungs to tissues
oxygen molecules in the lungs bind to the iron in the four haem groups
turns the haemoglobin from purple-red to bright red