Card Set Information
What are six functions of proteins and give example
: hemoglobin binds to oxygen + transport
: myosin caises contraction o muscle fibres w/ actin
: insulin binds to receptors in plasma memb. o target cells causing them to remove glucose fr blood
: immunoglobin act as antibodies to inactivate/destroy foreign antigens
Explain significance of polar and non-polar amino acids (3)
controlling position of proteins in membranes
creating hydrophilic channels through membranes
specificity o active sites in enzyme
polar have hydrophilic r group, non polar opp
Explain non polar / polar AA for position o proteins in membranes
polar aa found on parts protein molecule tt protrude fr membrance b/c water exists there, in ECF and cytoplasm
non polar Aa found in parts o membrane proteins embedded in plasma membrane = keeps proteins embedded /stabilizes structure
polar aa create channels in transport proteins where hydrophilic substance can diffuse through P.M.
specificity o active sites in enzymes (polar/non polar aa)
If the amino acids in the active site of an enzyme are non-polar -> active site specific to non-polar substrates
if the active site = polar amino acids then the active site is specific to a polar substance
AA w/ postively charged r groups -> attract negatively charged substrate ions; vice versa
hydrophilic channels through membranes
polar aa on surface o proteins make them water soluble
non polar aa in centre = stabilize
non polar aa cause proteins to remain embedded in membranes
polar aa create channels which hydrophilic substances can dissolve
biological catalysts for chemical reactions
Are globular proteins (tertiary or quaternary structure)
Have active site where the specific
Influence stability of bonds in the reactants, can form bonds (anabolic)or break bonds
affected by temperature, pH,
lowers activation energy o chemical reaction
Region on the surface of an enzyme to which substrates bind
catalyzes a chemical reaction involving the substrates.
similarities lock and key model and induced fit model for enzyme activity
both involve quaternary/tertiary protein w/ an active site
lowering o activation energy in chemical reaction
product detaches fr active site after reaction
differences lock and key model and induced fit model for enzyme activity
: assumes active site and sub match exactly
: not exactly
: substrate fits exactly into active site
: induced after binding
: active site fits only one substrate
: several similar but different substrates can bind
lock and key model
assumes active site and sub match exactly, not other molec fit or attracted
enzyme lock, sub key
enzyme sub collide; sub binds
active site catalyzes chemical reaction
sub turns into product and detaches
induced fit model
until substrate binds, active site doesnt fit sub exactly
sub approaches active site w/ KMT
shape of active site changes as sub approaches and binds
then fits exactly
sub induces change in enzyme which weakens sub bonds -> product
detaches fr enzyme b/c doesnt fit active site anymore
several diff but similar sub can bind to one enzyme
structural change in protein that results in loss (usually permanent) of biological properties
caused by heat and pH
what four factors affect enzyme activity?
if plenty substrate available, increasing enzyme concentration increase reaction rate
direct positive correlation
if concentration enzyme fixed and conc. substrate increase, rate o reation will increase then level
enzyme becomes saturated as active sites filled
temperature effect on enzyme activity
higher temperatures increas rate o collision b/twn sub and enzyme
reaction rate increase
however few can tolerate temp above 50 - 60 degress cel
enzymes have optimal temp
above, heat denatures enzyme
pH on enzymes
all have optimum pH generally b/twn 6 and 8
extremes o pH reduce enzyme activity
both acids and bases denature enzymes
explain use o lactase in production o lactose free milk
example o industrial process depending on biotech
methods are huge and increasing economic importance
lactose naturally in milk, -> changed into glucose + galactose by lactase
people intolerant can't produce those enzymes;= diarrhea, cramps, bloating
can consume lactose free milk produced using lactase obtained fr yeast, naturally grows in milk
lactase extracted fr yeast, purified sold as immobilized enzyme
milk passed through column lactase, breaks down lactose = lactose free milk w/o lactase
lactase can be added as well
what do metabolic pathways consist of?
Metabolic pathways consist of chains and cycles of enzyme-catalysed reactions.
how do enzymes lower the activation energy of the chemical reactions that they catalyse?
Most reactions are exothermic
energy released by the new bonds formed is less than the activation energy.
Reactants of a chemical reaction need to gain energy (activation energy) before they can undergo the reaction.
needed to break bonds within the reactants.
substrate changed into transition state, diff fr trasition state during reaction when enzyme not involved
transition state w/ binding to active site has less energy and is how enzymes reduce activation energy
later stage in the reaction energy will be released as new bonds form.
competitive w/ ref to ex
: inhibiting molecule structurally similar to substrate binds to active site, competes w/ substrate binding
inhib folic acid synthesis in bacteria by prontosil
can be overcome by increasing substrate concentration, increases chance that sub binds to enzyme
non competitive inhibition and ex
: binds to enzyme, not active site, causes conformational change
change in active site -> reduces effectiveness or makes it unable to bind at all
does not compete directly for active site
sub cant prevent binding o inhibitor despite concentration so maximum enzyme activity rate lower than no inhibitor
ag+, cn- inhibit enzymes cytochrome oxidase (cellular resp) binds to -SH group, breaks disulfide linkages that hold tert. structure o enzyme
allosteric enzymes have two non-overlapping binding sites; one active, one allosteric site
molc behave like REVERSIBLE non competitive inhibitors
change enzymes shape and function by binding weakly to allosteric site; specific receptor site on enzyme molc remote fr active site
structure enzyme altered so substrate less likely to bind to active site
explain role control o metabolic pathways by end product inhibition and role o allosteric sites
metabolic pathways, product o last reaction inhibits enzyme that catalyses first reaction = end product inhibition, allosteric inhibitor
end product if amount large enough will bind to allost site shutting down pathway preventing creation o more end product
reversible,when end product lessens,detached enzyme returnes to original shape so active site can bind substrate again
regulates metabolism according to req o organism
negative feedback or feedback inhibition, stops or slows chemical reactions inside cell
e.g. surplus ATP = allosteric reg o one or more pathways involved in cellular resp by binding to phosphofructokinase
e.g. threonine binds to theronine dehydratase, end product isoleucine inhibits threonine dehydratase
Outline DNA nucleotide structure in terms of sugar (deoxyribose), base and phosphate, draw
DNA composed o subunits called nucleotides
circle phosphate group
pentagon sugar (deoxyribose)
rectangle nitrogenous base
Name four bases o DNA
Outline how DNA nucleotides are linked together by covalent bonds into a
A covalent bond forms between the sugar of one nucleotide with a phosphate group and the phosphate group of another nucleotide.
draw 3 rungs of DNA ladder with letters labelled, relative sizes and positions of deoxyribose should be accurate, hydrogen bonds
explain how DNA double helix is formed w/ complementary base pairing and hydrogen bonds
DNA is made up of two nucleotide strands.
connected together by covalent bonds within each strand.
sugar of one nucleotide forms a covalent bond with the phosphate group of another.
two strands themselves connected by hydrogen bonds.
hydrogen bonds found between the nitrogen bases of the two strands of nucleotides.
Adenine forms hydrogen bonds with thymine
Guanine forms hydrogen bonds with cytosine.
called complementary base pairing.
A nucleotide will only pair with another if it is “upside down”, therefore 1 strand runs opposite though parallel
Bonds between the strands creates a double helix shape that resembles a twisted ladder