C1.1 Enzymes + Metabolism SL

Question 1

define metabolic reactions

Answer 1

chemical reactions that keep us alive

Question 1

define anabolic reaction and give an example

Answer 1

reactions that build things up

e.g. combining monomers into polymers

e.g. condensation

Question 2

define catabolic reaction and give an example

Answer 2

reactions that break things down

e.g. digesting polymers into monomers

e.g. hydrolysis

Question 3

define enzymes

Answer 3

biological catalysts that are often used to speed up metabolic reactions

globular protein which acts as a catalyst for biochemical reactions

Question 4

active site’s shape is _____ to the substrate’s shape

Answer 4

COMPLEMENTARY

enzymes are specific to the substrate

Question 5

define catalyst

Answer 5

speeds up chemical reactions and will not be used up

Question 6

what is a substrate

Answer 6

reactant in biochemical reaction

Question 7

what is the induced-fit model

Answer 7

• some enzymes can catalyse multiple reactions
• as the substrate approaches the enzyme, it induces a conformational change in the active site - it changes shape to fit the substrate
• this stresses the substrate (weakens the bonds), reducing the activation energy of the reaction

Question 7

what is active site?

Answer 7

region on the surface of an enzyme to which substances bind and which catalyses the reaction

Question 7

what region of the amino acids attract substrate and active site of the enzyme

Answer 7

polar regions of amino acids attract substrate and active site of the enzyme

Question 7

under what conditions is a reaction catalysed and what happens after

Answer 7

once a substrate has been locked into the active site, the reaction is catalysed

the products are released and the enzyme is used again

Question 7

outline effect of increased temperature on rate of reaction

Answer 7

increase temperature → increase in kinetic energy → increase movement of substrates and enzymes → increase chance of successful collision → increase rate of reaction

Question 7

outline effect of increased enzyme concentration on rate of reaction

Answer 7

increase enzyme concentration → increase chance of successful collision → increase rate of reaction

Question 7

outline effect of increased substrate concentration on rate of reaction

Answer 7

increase substrate concentration → increase chance of successful collision → increase rate of reaction

Question 7

what is activation energy?

Answer 7

the amount of energy that must be put into a reaction to make it occur

Question 7

what is lactose intolerance

Answer 7

people are unable to produce the enzyme lactase in sufficient quantities

mutation that allowed continued production of lactase is not present in such people

Question 8

effect of temp on enzyme activity

Answer 8

• temp increase → rate of reaction increase ⇒ molecules have more energy, move faster and therefore collide and react more frequently
• above optimum temperature, further increase in temp leads to denaturation of the enzyme → active site is changed and so loses function
• thermophile: e.g. bacteria at deep-sea vents, an organism that is able to withstand much higher temperature before its enzymes denature
  • phile = like

Question 8

why does consumption of lactose cause diarrhea in lactose intolerant people?

Answer 8

• increase in lactose in the intestines → cannot be digested due to lack of lactase → bacteria in the intestine can use the lactose to reproduce → the increase in bacteria population causes water potential in the intestine to drop → blood has a higher water potential → water diffuses from the bloodstream into the small intestine using osmosis → diarrhoea occurs

Question 8

how to cope with lactose intolerance?

Answer 8

1) take lactase supplement

2) drink lactose-free milk

• add lactase to milk → lower quality and wasteful of lactase
• run milk through apparatus with immobilised lactase → use alginate beads, no enzyme in final product

Question 8

optimum pH of trypsin

Answer 8

8

Question 8

effect of pH on enzyme activity

Answer 8

• Enzymes only operate within a narrow range of pH values → optimum pH
• If deviation from the optimum pH, the hydrogen bonds between amino acids in the structure of the enzyme are broken
• this results in the loss of the shape of the active site of the enzyme, so it does not function
• usually a permanent change

Question 8

optimum pH of pepsin

Answer 8

2

Question 9

optimum pH of salivary amylase

Answer 9

7.2

Question 10

effect of substrate concentration on enzyme activity

Answer 10

• Increase substrate concentration → increase rate of reaction
• At optimum conc of substrate molecules, all active sites are full and working at maximum efficiency ⇒ plateau
  
  • limiting factor: enzyme concentration
  • enzymes are saturated
• any increase in the concentration beyond the optimum will have no added effect as there are no extra active sites to be used