T1: Proteins Flashcards
how to draw protein
C in centre
H2N and COOH side branches
R group and hydrogen top and bottom
H2N amine group
COOH carboxyl group
R variable side chain
describe the overall structure of a protein
polymer of amino acids joined by peptide bonds formed by condensation
dipeptide
2 amino acids
polypeptide
3+ amino acids
peptide bond formation
OH removed from COOH
H removed from H2N
final peptide bond is C-N
primary structure of a protein
the sequence of amino acids in the polypeptide chain
linked by peptide bonds
determined by bases in DNA could change due to mutations
secondary structure of protein
folding of the polypeptide chain due to hydrogen bonding
forms alpha helices or beta pleated sheets
H bonds provide stability
tertiary structure of a protein
3D folding of the polypeptide chain due to hydrogen bonding and ionic and disulfide bonds
quaternary structure of protein
2 or more polypeptide chains held together by hydrogen, ionic and disulfide bonds
protein examples
a proteins shape determines its function
enzymes, antibodies, transport proteins, structural proteins
enzyme shape and functions
spherical and soluble so have roles in metabolism + larger protein synthesis
antibody shape and function
2 light and 2 heavy polypeptide chains with a variable region
found in blood and involved in the immune response
transport protein shape and function
transport molecules and ions across membranes e:g channel proteins
structural proteins shape and function
long polypeptide chains with cross links between them
e:g keratin (hair + nails) and collagen (tissue)
what is an enzyme?
a protein and a biological catalyst that lowers the activation energy of a reaction
describe the induced fit model of enzyme action (3)
before the reaction the active site is not complementary to the substrate
the shape of the active site changes as the substrate binds
distorting the bonds in substrate leading to reaction
why do enzymes have a specific active site?
the 3D shape of the enzyme depends on the tertiary structure of the protein which depends on the primary structure (order of amino acids)
how do enzymes and substrates work generally?
if enzyme is hydrolysing the substrate then fitting into the active site puts strain on the bonds so the substrate breaks easily
if the substrate is joining then the enzyme holds the molecules close reducing repulsion
how to measure the rate of an enzyme controlled reaction?
how fast the product is made (product-time graph)
how fast the substrate is hydrolysed (substrate conc and enzyme activity)
what are the 5 factors affecting enzyme activity?
temperature
pH
substrate concentration
enzyme concentration
inhibitors
how does temperate affect the rate of an enzyme controlled reaction?
more heat = more KE so a higher number of ESC’s formed
different enzymes have diff optimum temps, above which they denature stopping reaction
how does pH affect the rate of enzyme controlled reaction?
alters H bonds and ionic bonds holding the active site’s 3D shape
if too high or low the enzyme is denatured and the active site changes shape
how does substrate concentration affect the rate of an enzyme controlled reaction?
more substrate molecules = more collisions so more ESC’s formed
when all active sites are full, enzyme concentration becomes the limiting factor
how does enzyme concentration affect the rate of an enzyme controlled reaction?
more active sites are available so more ESC’s formed
increases rate until a saturation point where active sites are permanently occupied
define enzyme inhibitor
molecules that bind to the enzyme that they inhibit
can be competitive or non-competitive
how do competitive inhibitors work
they compete with the substrate molecules to bind to the active site, they block substrate so no reaction occurs
these can be overcome by using higher concentration of substrate
how do non competitive inhibitors work
bind to the enzyme (but not at the active site) and causes changes that alter the shape of the active site
these can resist a change in concentration of substrate because they don’t bind directly