enzymes Flashcards
what are enzymes?
biological catalysts that are commonly made of protein. They alter or speed up the rate of chemical reactions without themselves being chemically changed at the end of the reaction
- is a protein (has specific 3D structure)
- functions as biological catalyst
explain why enzymes lower activation energy?
- activation energy is energy needed to start a chemical reaction
glucose case study : - glucose is broken down during respiration to release energy
- enzymes lower actication energy required for reaction to take place
- cellular respiration can occur at normal body temperature (36.9 degrees celsius)
explain the fact that enzymes catalyse digestion?
- some food molecules are large, complex and insoluble in water (e.g. starch, proteins, fats)
- these molecules cannot diffuse across cell membrane
- have to be digested into smaller, simpler and soluble molecules in order to be absorbed into the cell (e.g. glucose, amino acids)
digestive enzymes :
- amylase (starch to maltose), in saliva
- maltase (maltose to glucose), small intestine
- pepsin (protein to polypeptides), stomach
- lipase (fats to fatty acids and glycerol), small intestine
explain building up of complex substances?
anabolic reactions
- condensation of amino acids to synthesize polypeptides
- condensation of fatty acids and glycerol to synthesize fats
- condensation of glucose to synthesize starch (plants)/ glycogen (animals)
explain breaking down of complex substances?
catabolic reactions
- digestion of large, complex, insoluble food substances (starch –> glucose)
- breaking down of glucose, during cellular respiration to release energy
describe enzyme names?
- ends with ‘ase’
- shows substance on which enzymes acts on
describe classficiation?
- according to chemical reactions they catalyse
- hydrolases - hydrolytic reaction
- proteases that digest proteins
- lipases that digest lipids
describe enzyme and reaction?
- digestion of carbohydrates : carbohydrase, catabolic reaction
- digestion of cellulose: cellulase, catabolic reaction
- synthesis of proteins : ribosome (ribozyme), anabolic reaction
explain the process when enzymes are effects by temperature?
Part A
- enzymes are inactive at low temperature
- kinetic energy is low at low temperature
- chances of substrate molecules colliding with enzymes are very low
Part B
- as temperature rises, enzyme activity increases
- increase in kinetic energy of molecules increases chance/frequency of effective collision between substrate and enzyme molecules
- this increases the rate of formation of enzyme-substrate complex to form products
Part C
- optimum temperature : rate of reaction is highest and enzymes are more active
- each enzyme has its own unique optimum temperature
- mostly 40-45 degrees celsius
Part D
- beyond optimum temperature, enzyme activity decreases rapidly until it reaches zero
- high temperature breaks weak hydrogen bonds within enzyme and changes 3D shape
- active sit loses original shape
- enzyme denatured
explain the process when enzymes are affected by pH
- each enzyme has its own unique optimum pH at which it is most active
- extreme changes in pH will cause the enzyme to denature and loses its function
- however, some enzymes can function optimally under extreme pHs (pepsin in stomach, pH 2-3)