enzymes

Question 1

what are enzymes?

Answer 1

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

Question 2

explain why enzymes lower activation energy?

Answer 2

• 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)

Question 3

explain the fact that enzymes catalyse digestion?

Answer 3

• 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

Question 4

explain building up of complex substances?

Answer 4

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)

Question 5

explain breaking down of complex substances?

Answer 5

catabolic reactions

• digestion of large, complex, insoluble food substances (starch –> glucose)
• breaking down of glucose, during cellular respiration to release energy

Question 6

describe enzyme names?

Answer 6

• ends with ‘ase’

- shows substance on which enzymes acts on

Question 7

describe classficiation?

Answer 7

• according to chemical reactions they catalyse
• hydrolases - hydrolytic reaction
• proteases that digest proteins
• lipases that digest lipids

Question 8

describe enzyme and reaction?

Answer 8

• digestion of carbohydrates : carbohydrase, catabolic reaction
• digestion of cellulose: cellulase, catabolic reaction
• synthesis of proteins : ribosome (ribozyme), anabolic reaction

Question 9

explain the process when enzymes are effects by temperature?

Answer 9

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

Question 10

explain the process when enzymes are affected by pH

Answer 10

• 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)