enzymes Flashcards
(14 cards)
What are enzymes (def)
Enzymes are proteins that function as biological catalysts that speed up the rate of chemical reactions by lowering the activation energy. Enzymes remain chemically unchanged at the end of the experiment.
how do enzymes catalyse chemical reactions
by lowering the activation energy
what is activation energy?
the energy needed to start a chemical reaction
enzymes either (…..) or (…..) complex substances
build up or break down
what are anabolic enzymes + egs
enzymes that build up or synthesise complex substances from simple substances
eg. amino acids being converted to proteins by special enzymes in the cytoplasm
what are catabolic reactions + some egs
enzymes that break down complex substances into simpler substances
“the cat broke down the house”
eg. digestive enzymes break down large and insoluble food molecules into smaller and soluble food molecules that can pass through the cell surface membrane and be absorbed by the cells
what is metabolism?
sum f all the chemical processes that occur within a living organism
describe the lock and key hypothesis
the enzyme reactions depend on the presence of active sites, which are highly specific three-dimensional shapes which the substrate molecules of a matching shape can fit and bind into, like how a key fits into a lock
list the characteristics of enzymes
- enzymes speed up chemical reactions by lowering the activation energy needed to start the reaction
- enzymes are highly specific in action
- enzymes are required in minute amounts and remain chemically unchanged at the end of a chemical reaction
- enzymes are affected by temperature
- enzymes are affected by pH
describe and explain at each stage how enzymes are affected by temperature
- at low temperatures, the enzyme activity is low. this is because the kinetic energy of both the substrate and enzyme are low, and the enzyme is less active/inactive. hence, the chances of the formation of enzyme-substrate complex is very low
- as the temperature increases, enzyme activity also increases. more kinetic energy causes a higher chance of the substrate and enzyme colliding to form enzyme-substrate complex. higher rate of enzyme substrate complex
- the optimum temperature is where the enzyme is most active. rate of reaction is at the highest as molecules have the highest kinetic energy, sand the highest rate of collision and formation of enzyme-substrate complex.
- the enzyme activity decreases rapidly. this is because at high temperatures, the protein-made enzymes’ peptide bonds are broken, and the three-dimensional shape of the active site is changed. less substrate can bind to the enzyme, and less enzyme-substrate complex is formed. enzyme is denaturing
- at extreme temperatures, the enzyme is fully denatures. there is no enzyme activity as the enzyme has lost its ability to catalyse the reaction. no substrate will bind to the enzyme as the active site is lost. no enzyme substrate complex, no break down of substrate
what is the optimum temperature for most human enzymes?
37 deg celcius
what is denaturation (def)
change in the three-dimensional structure of an enzyme or any soluble protein, cause by temperature or chemicals like acids and alkali
describe and explain how enzymes are affected by pH
- the optimum pH: enzyme is most active, rate of chemical reaction is at its highest. there is the highest rate of collision and enzyme-substrate complex
- as pH of solution becomes higher or lower: enzyme activity decreases rapidly but there is still reaction as the enzyme is not yet denatured
- at extreme pH: enzyme is denatures. the peptide bonds are broken within the enzyme, which changes its three-dimensional active site. lesser substrate can bind to the active site
what are the differences between the graph of enzymes/temp vs enzymes/pH
pH graphs are symmetrical in shape while temp graphs are not symmetrical in shape
pH graphs start and end with 0, while temp graphs only end with 0
