enzymes Flashcards
enzymes def.
proteins that act as catalysts as they speed up chemical reactions without getting used up
extracellular enzymes def.
enzymes that are secreted out of the cell eg digestive enzymes
intracellular enzymes def.
work inside cells eg dna polymerase
types of enzymes:
anabolic
catabolic
anabolic enzymes def.
building molecules up eg DNA polymerase
catabolic enzymes def.
breaking molecules down eg amylase
enzyme model induced fit:
the enzyme active site forms in response to the substrate binding, but upon binding the substrate is able to move which puts the active site under strain. the strain is then able to elicit the energy that’s required for the reaction to occur by stabilising the transition state and not just the binding of the substrate
how do enzyme molecules work?
as enzymes are globular proteins they are soluble and have hydrophilic amino acids on their surface. the R groups of the amino acids in the active sites form bonds with the substrate molecules
what is starch broken into and by what enzymes and where?
first broken into disaccharide maltose by amylase (produced by salivary glands) then maltose broken down into glucose by maltase, occurring in small intestine
digestion of proteins:
proteins broken into peptides by trypsin, then again into amino acids by other proteases
- trypsin produced in pancreas and released into small intestine by pancreatic juice
what is the effect of the substrate concentration on rate of reaction?
- increasing substrate concentration increases rate of reaction because there are more collisions between active sites and substrate therefore more products are formed per unit of time.
- however there will come a substrate concentration at which any increase in substrate conc. will not increase the rate of reaction.
- this is because the number of active sites are now limiting the number of reactions and therefore the enzyme concentration is the limiting factor of reaction.
the effect of enzyme concentration on the rate of reaction
- more enzyme molecules = more active sites
- meaning the conversion of the substrate to the product is faster, therefore the reaction time decreases
- if you increase the enzyme concentration further, the extra enzyme molecules will have no role to play in the reaction as it has reached its maximum rate for the substrate volume
- the substrate volume is now a limiting factor unless you add more substrate, so it could bind to the enzyme increasing the rate again
the effect of temperature on enzyme catalysed rate of reaction
- as temp increases the rate of reaction increases as there’s more internal energy and therefore more successful collisions between the active site of the enzymes and the substrates
- therefore more products form - this continues up to the optimum temperature
- the optimum temperature gives the fastest rate of reaction. as the temp increases above the optimum temperature the rate of the reaction decreases rapidly and the enzyme becomes denatured.
explain the term ‘denatured’ with reference to enzymes.
when the active site of the enzyme changes shape and can therefore no longer fit into the substrate. hydrogen/ionic bonds between the R groups break so the tertiary structure breaks down.
the effect of pH on enzyme catalysed reaction
all enzymes have an optimum pH where the conc. of H+ ions and OH- allow all hydrogen bonds and ionic bonds to form correctly to hold the tertiary structure in place.
- however at pH above or below the optimum pH the concentration of H+ ions and OH- disrupt the ionic and hydrogen bonds between amino acid R groups, therefore the enzyme tertiary structure changes meaning the active site will no longer be complementary to the substrate therefore the rate of reaction decreases.
