Proteins, Polysaccharides and Lipids Flashcards
(38 cards)
describe the alpha helix structure
rod-like, found in strong extensible proteins, stabilised by hydrogen bonds, CO of each amino acid is H-bonded to NH of amino acid four residues ahead in sequence
describe beta pleated sheets
zigzag chains, place several chains side by side, CO and NH groups align, H-bonding occurs, found in proteins where flexibility needed
what is parallel beta pleated sheets?
run in the same direction
what is anti-parallel beta pleated sheets?
chains run in opposite directions
describe a triple helix
collagen only, major component of connective tissues, very strong and water-insoluble fibres, three chains wound round each other, no H bonds, repeating structure
what are fibrous proteins?
insoluble and metabolically unreactive, structural proteins
what structures do fibrous proteins contribute to?
collagen, keratin, fibrin, elastin, myosin
describe globular proteins
spherical, backbone folds on itself, water-soluble compact structures, usually tertiary/quaternary structures
what is the function of myoglobin?
oxygen storage in muscle
what shape is myoglobin?
globular
what does the absence of a haem group in a myoglobin protein mean?
apoprotein, not as tightly folded
what is the function of haemoglobin?
oxygen transport
what is the structure of haemoglobin?
two pairs of polypeptide chains folded in a shape similar to myoglobin
comment on the haem groups of haemoglobin
four haem groups on the surface of the molecule in individual pockets
describe the interactions between the subunits of haemoglobin
each alpha subunit is in contact with both beta chains
name the different types of membrane proteins
peripheral, integral, channel and carrier
where does a peripheral membrane lie?
on the membrane surface
where do integral proteins lie?
within the lipid bilayer
what do channel proteins do?
form a channel in membranes and facilitate movement of small molecules across membrane
what do carrier proteins do?
bind to transported molecules
what do messenger proteins do?
allow cells to communicate with each other
what are the 3 modes of action of messenger proteins?
influence rate of synthesis of enzymes and other proteins, affect rate of enzymatic catalysis, alter permeability of cell membranes
what is the process of messenger sending with messenger proteins?
hormone binds receptor-message relayed to inside of cell-cascade of events-cellular action
what are example of messenger proteins?
HORMONES insulin, glucagon and human growth hormone
